CN110541703A - Method and system for determining well wall strengthening conditions and method and system for strengthening well wall - Google Patents
Method and system for determining well wall strengthening conditions and method and system for strengthening well wall Download PDFInfo
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Abstract
The invention relates to the field of drilling exploration, and discloses a method and a system for determining a well wall strengthening condition, and a method and a system for strengthening a well wall. The method for determining the well wall strengthening condition comprises the following steps: calculating the target temperature required to be cooled by the well wall and the crack opening distribution of cracks extending from the well wall to the stratum according to a well wall strengthening model and a preset pressure-bearing and thermo-fluid-solid coupling equation of the well wall; obtaining the temperature of the drilling fluid according to the target temperature to which the well wall needs to be cooled; and acquiring the particle size distribution of the reinforced material according to the crack opening distribution and the particle size matching criterion. On one hand, the invention can carry out quantitative characterization on the temperature of the drilling fluid and the particle size distribution of the reinforcing material required in the well wall reinforcing process, thereby realizing the fine control on the well wall reinforcing process; on the other hand, the influence of the filling of the reinforcing material on the stress around the well is enhanced by utilizing the thermal stress generated by the temperature change, so that the pressure bearing capacity of the well wall is improved.
Description
Technical Field
the invention relates to the field of drilling exploration, in particular to a method and a system for determining a well wall strengthening condition and a method and a system for strengthening a well wall.
Background
lost circulation is the phenomenon that under the action of pressure difference, drilling working fluid is leaked to a stratum through a crack. The lost circulation is one of the most serious underground complex conditions, not only can cause drilling fluid loss and pollution to a reservoir stratum, but also can cause a series of underground complex accidents such as well collapse and blowout, and the economic loss of the accidents to the global drilling industry is up to 20-30 billion dollars each year. In order to prevent the occurrence of lost circulation accidents and reduce the damage caused by lost circulation, the lost circulation treatment technology begins to develop from 'later-stage leaking stoppage' to 'earlier-stage prevention'. For example, the well wall strengthening technology is widely popularized and applied as an important leakage-proof technical measure, but the specific action mechanism of the well wall strengthening technology is not clear.
Currently, the well wall strengthening method commonly used is to empirically add a range of sizes of plugging agents for prevention while drilling. Because the opening of the formation fracture is difficult to accurately predict, the filling efficiency of the added plugging material while drilling is low, so that the method lacks quantitative construction parameters and is difficult to realize fine control on the implementation process of the well wall strengthening technology.
Disclosure of Invention
The invention aims to provide a method and a system for determining well wall strengthening conditions and a method and a system for strengthening the well wall, which can quantitatively represent the temperature of drilling fluid and the particle size distribution of strengthening materials required in the well wall strengthening process on one hand, thereby realizing the fine control of the well wall strengthening process; on the other hand, the influence of the filling of the reinforcing material on the stress around the well is enhanced by utilizing the thermal stress generated by the temperature change, so that the pressure bearing capacity of the well wall is improved.
In order to achieve the above object, the present invention provides, in one aspect, a method for determining a borehole wall strengthening condition, the method comprising: according to a well wall strengthening model and a preset pressure-bearing and thermo-fluid-solid coupling equation of the well wall, calculating a target temperature to which the well wall needs to be cooled and a crack opening of a crack extending from the well wall to a stratum; obtaining the temperature of the drilling fluid according to the target temperature to which the well wall needs to be cooled; and acquiring the particle size distribution of the reinforced material according to the crack opening distribution and the particle size matching criterion.
preferably, the calculating the target temperature to which the well wall needs to be cooled and the fracture opening distribution of the fracture extending from the well wall to the stratum comprises: calculating a first stress intensity factor of a crack tip after the well wall is filled with a reinforcing material according to the well wall reinforcing model and the preset pressure bearing of the well wall; calculating a second stress intensity factor of the crack tip according to the thermo-fluid-solid coupling equation and the preset pressure bearing and preset target temperature of the well wall; adjusting the preset target temperature of the well wall, and recalculating the second stress intensity factor of the fracture tip until the absolute value of the difference value between the calculated second stress intensity factor and the first stress intensity factor is less than or equal to a preset value; according to the preset target temperature of the well wall which is adjusted for the last time, the target temperature to which the well wall needs to be cooled is obtained; and acquiring the fracture opening distribution according to the displacement of the displacement field of the stratum at the fracture of the well wall, which is obtained by the thermo-fluid-solid coupling equation and the preset target temperature of the well wall adjusted at the last time.
preferably, the calculating a first stress intensity factor of the fracture tip after the borehole wall is filled with the strengthening material comprises: acquiring a first formula for calculating the first stress intensity factor according to the well wall strengthening model; and calculating the first stress intensity factor according to the first formula, the preset pressure bearing of the well wall, and the minimum horizontal ground stress and the maximum horizontal ground stress at the infinite distance from the well wall.
Preferably, the first formula for calculating the first stress intensity factor KIa is: KIa ═ F1+ F2. [2Pw- (σ H + σ H) ] + (F1+3F 3. (σ H- σ H) -2F4 · (Pw-P), where σ H is the minimum level of geostress at infinity from the borehole wall; σ H is the maximum horizontal ground stress at infinity from the borehole wall; p is the pore pressure of the formation; pw is the preset pressure bearing of the well wall; f1, F2, F3 and F4 are respectively a first integral function, a second integral function, a third integral function and a fourth integral function, wherein the first integral function F1, the second integral function F2, the third integral function F3 and the fourth integral function F4 are respectively obtained by the following formulas: wherein L is the distance between the crack tip and the center of the shaft, a is the crack length, R is the shaft radius, D is the distance between the position of the reinforcing material in the crack for plugging and bridging and the center of the shaft, and R is the distance between any point in the crack and the center of the shaft.
preferably, the calculating the second stress intensity factor of the fracture tip includes: calculating a displacement field of the stratum according to the thermo-fluid-solid coupling equation and the preset bearing pressure and the preset target temperature of the well wall; and calculating a second stress intensity factor of the fracture tip according to a J integral algorithm and the displacement field of the stratum.
preferably, the thermo-fluid-solid coupling equation comprises: the method comprises the following steps of (1) calculating a displacement field of the stratum correspondingly by using a stress balance equation, a fluid mass conservation equation and an energy balance equation: calculating the displacement field according to the stress balance equation, the preset bearing pressure and the preset target temperature of the well wall, the initial pore pressure of the stratum, the initial temperature of the stratum and the initial displacement of the stratum; calculating a pore pressure field of the stratum according to the fluid mass conservation equation, the preset pressure-bearing and preset target temperature of the well wall, the initial pore pressure of the stratum, the initial temperature of the stratum and the initial displacement of the stratum; calculating a temperature field of the stratum according to the energy balance equation, the preset bearing pressure and preset target temperature of the well wall, the initial pore pressure of the stratum, the initial temperature of the stratum and the initial displacement of the stratum; counting the iterative calculation process under the condition that the displacement field, the pore pressure field of the stratum and the temperature field of the stratum are obtained through calculation; and judging whether the count of the iterative computation process is equal to a preset number of times, and under the condition that the count of the iterative computation process is smaller than the preset number of times, continuing the iterative computation process by taking the displacement field, the pore pressure field and the temperature field of the stratum which are obtained through computation as initial values.
Preferably, the particle size matching criteria include: the particle size corresponding to the cumulative particle size distribution of the reinforcing materials with the first preset percentage is equal to the first preset crack opening degree; and the particle size corresponding to the cumulative particle size distribution of the reinforcing materials with the second preset percentage is equal to the second preset crack opening, wherein the first preset percentage is smaller than the second preset percentage, the first preset crack opening is smaller than the second preset crack opening, and the first preset crack opening and the second preset crack opening are related to the maximum crack opening in the crack opening distribution.
According to the technical scheme, the target temperature required to be cooled to the well wall and the crack opening distribution of cracks are calculated quantitatively creatively through the well wall strengthening model and the preset pressure-bearing and thermo-fluid-solid coupling equation of the well wall, then the temperature of the drilling fluid required to be pumped is obtained according to the target temperature required to be cooled to the well wall, the particle size distribution of the strengthening material required to be filled is obtained according to the crack opening distribution and particle size matching criterion, and the temperature of the drilling fluid required by the well wall strengthening process and the particle size distribution of the strengthening material can be quantitatively represented, so that the fine control of the well wall strengthening process can be realized, and an important foundation is laid for the well wall strengthening process.
In a second aspect, the present invention provides a system for determining a borehole wall strengthening condition, the system comprising: the calculating device is used for calculating the target temperature required to be cooled by the well wall and the crack opening distribution of the crack extending from the well wall to the stratum according to the well wall strengthening model and the preset pressure-bearing and thermo-fluid-solid coupling equation of the well wall; the temperature acquisition device is used for acquiring the temperature of the drilling fluid according to the target temperature to which the well wall needs to be cooled; and the particle size distribution acquisition device is used for acquiring the particle size distribution of the reinforced material according to the crack opening distribution and the particle size matching criterion.
For specific details and benefits of the system for determining borehole wall strengthening conditions provided by the present invention, reference may be made to the above description of the method for determining borehole wall strengthening conditions, and further description thereof will not be provided herein.
The invention provides a well wall strengthening method in a third aspect, which comprises the following steps: obtaining the temperature of the drilling fluid and the particle size distribution of the reinforcing material obtained by the method for determining the well wall reinforcing condition; pumping drilling fluid having the temperature; and filling a reinforcing material having the particle size distribution.
According to the technical scheme, the temperature of the drilling fluid and the particle size distribution of the reinforcing material obtained by the method for determining the well wall reinforcing condition are creatively obtained, then the required drilling fluid is pumped according to the obtained temperature, and the required reinforcing material is filled according to the obtained particle size distribution, so that the influence of the reinforcing material filling on the well circumferential stress is enhanced by utilizing the thermal stress generated by the temperature change, and the pressure bearing capacity of the well wall is improved.
The fourth aspect of the present invention provides a well wall strengthening system, comprising: the obtaining equipment is used for obtaining the temperature of the drilling fluid and the particle size distribution of the strengthening material obtained by the method for determining the well wall strengthening condition; a pumping device for pumping drilling fluid having said temperature; and a filling apparatus for filling the reinforcing material having the particle size distribution.
For the benefits of the borehole wall strengthening system provided by the present invention, reference may be made to the above description of the borehole wall strengthening method, which is not described herein again.
a fifth aspect of the present invention provides a machine-readable storage medium having instructions stored thereon for causing a machine to perform the method for determining a borehole wall strengthening condition or the borehole wall strengthening method.
Additional features and advantages of the invention will be set forth in the detailed description which follows.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:
FIG. 1 is a flow chart of a method for determining a borehole wall strengthening condition provided by an embodiment of the present invention;
FIG. 2 is a schematic illustration of a fracture provided by an embodiment of the present invention;
FIG. 3 is a flow chart of a method for calculating a target temperature to which a borehole wall is required to be cooled and a fracture opening profile according to an embodiment of the present invention;
FIG. 4 is a flow chart of calculating a first stress intensity factor for a fracture tip provided by an embodiment of the present invention;
FIG. 5 is a flow chart of calculating a second stress intensity factor for a fracture tip provided by an embodiment of the present invention;
FIG. 6 is a flow chart of calculating a displacement field of a formation provided by an embodiment of the present invention;
FIG. 7 is a flow chart of determining borehole wall strengthening conditions according to an embodiment of the present invention;
FIG. 8 is a prediction of the crack opening distribution provided by an embodiment of the present invention;
FIG. 9 is a graph illustrating a preferred particle size distribution of a reinforcement material according to particle size matching criteria, according to an embodiment of the present invention;
FIG. 10 is a block diagram of a system for determining borehole wall strengthening conditions provided by an embodiment of the present invention;
FIG. 11 is a flow chart of a method for borehole wall strengthening according to an embodiment of the present invention; and
FIG. 12 is a block diagram of a wellbore wall strengthening system provided by an embodiment of the present invention.
description of the reference numerals
10 calculating device 20 temperature acquisition device
30 particle size distribution acquisition device 40 acquisition equipment
50 pump-in apparatus 60 filling apparatus
Detailed Description
the following detailed description of embodiments of the invention refers to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.
Before describing specific embodiments of the present invention, a brief introduction will be made to the main design concept of the present invention. For a target well, in order to improve the pressure-bearing capacity of the well wall of the target well (to a preset pressure-bearing capacity), a crack can be pressed open along a preset direction (such as a maximum horizontal stress direction) at a target temperature (low temperature), and finally the crack conforms to a certain crack opening distribution. Then, a reinforcing material with the particle size distribution matched with the crack opening distribution and cooling liquid with the temperature matched with the target temperature are selected to meet the reinforcing condition of the well wall, and further the reinforcing process of the well wall can be realized.
the fractures around the wellbore wall may occur naturally or be induced by the differential pressure between the pressure of the drilling fluid column and the pore pressure of the formation. FIG. 2 shows a schematic view of a wedge-shaped fracture extending from the borehole wall into the formation, the fracture having a length along the length of the fracture (indicated by arrow L); the direction perpendicular to the crack length direction is the crack opening direction (indicated by arrow W), and the width along the crack opening direction is the crack opening. Typically, the fracture length direction defines the fracture length origin at the borehole wall and the length at the fracture tip is the fracture total length, as shown in FIG. 2. The crack length can be preset in advance. Of course, the present invention is not limited to the wedge-shaped slits described above, and is also applicable to slits of any other shape.
FIG. 1 is a flow chart of a method for determining a borehole wall strengthening condition according to an embodiment of the present invention. As shown in fig. 1, the method for determining the borehole wall strengthening condition may comprise the following steps: step S101, calculating a target temperature required to be cooled by the well wall and crack opening distribution of cracks extending from the well wall to a stratum according to a well wall strengthening model and a preset pressure-bearing and thermo-fluid-solid coupling equation of the well wall; step S102, obtaining the temperature of the drilling fluid according to the target temperature to which the well wall needs to be cooled; and step S103, acquiring the particle size distribution of the reinforced material according to the crack opening distribution and the particle size matching criterion.
before step S101 is executed, well history data and core characteristic analysis results of a missing horizon of an adjacent well (or any area in a block where the target well is located) of the target well are collected and obtained, and are used to calculate rock mechanical parameters of the missing horizon, and a specific obtaining process is as follows.
For step S101, as shown in fig. 3, the process of calculating the target temperature to which the well wall needs to be cooled and the fracture opening of the fracture extending from the well wall to the formation respectively may include the following steps:
step S301, calculating a first stress intensity factor of the crack tip after the well wall is filled with the strengthening material according to the well wall strengthening model and the preset pressure bearing of the well wall.
specifically, for step S301, the process of calculating the first stress intensity factor may include the following steps, as shown in fig. 4.
Step S401, obtaining a first formula for calculating the first stress intensity factor according to the well wall strengthening model.
The first formula for calculating the first stress intensity factor KIa, which is derived from the borehole wall strengthening model, is:
K＝(F+F)·[2P-(σ+σ)]+(F+3F)·(σ-σ)-2F·(P-P) (1)
Wherein σ h is the minimum horizontal ground stress at infinity from the borehole wall; σ H is the maximum horizontal ground stress at infinity from the borehole wall; p is the pore pressure of the formation; pw is the preset pressure bearing of the well wall; f1, F2, F3 and F4 are the first integration function, the second integration function, the third integration function and the fourth integration function, respectively.
wherein the first integral function F1, the second integral function F2, the third integral function F3 and the fourth integral function F4 are mainly influenced by the geometry of the wellbore-fracture system, and can be respectively obtained by the following formulas: wherein L is the distance between the crack tip and the center of the shaft, a is the crack length, and R is the shaft radius; d is the distance from the position of the reinforcing material in the fracture for plugging and bridging to the center of the shaft, and r is the distance from any point in the fracture to the center of the shaft.
Step S402, calculating the first stress intensity factor according to the first formula, the preset pressure bearing of the well wall, and the minimum horizontal ground stress and the maximum horizontal ground stress at the infinite distance from the well wall.
the minimum level earth stress σ H and the maximum level earth stress σ H at infinity from the borehole wall can be obtained by the following equations (2) and (3), respectively:
wherein E is the elastic modulus; mu is Poisson's ratio; σ v is overburden pressure; α is the effective stress coefficient (Biot); p is the pore pressure of the formation; epsilon H is a maximum horizontal structural strain coefficient; ε h is the minimum horizontal formation strain coefficient.
for the elastic modulus E and the Poisson ratio mu, both can be measured by the triaxial compressive strength test of the rock. For overburden pressure σ v, it can be calculated by the following equation: σ v ═ GzdH, where Gz is overburden pressure gradient; h is the formation thickness. The effective stress coefficient α can be calculated by the following equation: wherein Kt is the bulk modulus of the pore medium; ks is the bulk modulus of the solid skeleton, and both can be measured by triaxial compressive strength experiments of rocks. The pore pressure P of the stratum can be calculated by a logarithmic linear curve of a well depth and a wave time difference method.
And substituting the minimum horizontal ground stress sigma H, the maximum horizontal ground stress sigma H and the preset pressure bearing Pw of the well wall into a formula (1) under the condition that the minimum horizontal ground stress sigma H and the maximum horizontal ground stress sigma H at the infinite distance from the well wall are obtained through calculation, and calculating a first stress intensity factor KIa.
And S302, calculating a second stress intensity factor of the crack tip according to the thermo-fluid-solid coupling equation and the preset pressure bearing and preset target temperature of the well wall.
for step S302, the process of calculating the second stress intensity factor of the fracture tip may include the following steps, as shown in FIG. 5.
and S501, calculating a displacement field of the stratum according to the thermo-fluid-solid coupling equation and the preset bearing pressure and the preset target temperature of the well wall.
wherein the thermo-fluid-solid coupling equation may include: stress balance equation, fluid mass conservation equation and energy balance equation.
Accordingly, for step S501, the process of calculating the displacement field of the formation may include the following steps, as shown in FIG. 6.
Step S601, calculating the displacement field according to the stress balance equation, the preset bearing pressure and the preset target temperature of the well wall, the initial pore pressure of the stratum, the initial temperature of the stratum and the initial displacement of the stratum.
The stress balance equation is:
Wherein D is a stiffness matrix and u is a displacement vector; alpha is the effective stress coefficient; p is the pore pressure vector of the formation; α S is the thermal diffusion coefficient of the solid; t is the temperature vector of the formation.
The initial pore pressure, the initial temperature and the initial displacement of the stratum (namely the pore pressure, the temperature and the displacement of the stratum before the stratum is placed into the shaft) are used as initial conditions, the preset pressure bearing (fixed value) and the preset target temperature (variable) of the well wall are used as boundary conditions, and the displacement field of the stratum can be obtained by solving the equation (4).
Step S602, calculating a pore pressure field of the stratum according to the fluid mass conservation equation, the preset bearing pressure and the preset target temperature of the well wall, the initial pore pressure of the stratum, the initial temperature of the stratum and the initial displacement of the stratum.
The fluid mass conservation equation is as follows:
wherein u is a displacement vector; m is Biot modulus (M ═ 1/α); α f is the thermal diffusion coefficient of the fluid; phi is the porosity of the formation (which can be obtained by mercury intrusion experiments); k is the permeability coefficient of the formation (k ═ permeability of the formation/viscosity of the drilling fluid, permeability of the formation can be obtained by core displacement experiments); kT is the thermal permeability coefficient.
The pore pressure field of the formation can be obtained by solving the equation (5) with the initial pore pressure, the initial temperature and the initial displacement of the formation (i.e., the pore pressure, the temperature and the displacement of the formation before being placed in the wellbore) as initial conditions and the preset bearing pressure and the preset target temperature of the wellbore (which are the same as the preset target temperature in the step S601) as boundary conditions.
Step S603, calculating a temperature field of the stratum according to the energy balance equation, the preset pressure-bearing and preset target temperature of the well wall, the initial pore pressure of the stratum, the initial temperature of the stratum and the initial displacement of the stratum.
the energy balance equation is:
wherein ρ b is the average density of the rock; cb is the average specific heat capacity of the rock; λ b is the thermal conductivity of the pore medium.
The temperature field of the formation can be obtained by solving the equation (6) with the initial pore pressure, initial temperature and initial displacement of the formation (i.e., the pore pressure, temperature and displacement of the formation before being placed in the wellbore) as initial conditions and the preset bearing pressure and preset target temperature of the wellbore wall (which are the same as the preset target temperature in step S601) as boundary conditions.
And step S604, counting the iterative calculation process under the condition that the displacement field, the pore pressure field of the stratum and the temperature field of the stratum are obtained through calculation.
step S605, judging whether the count of the iterative computation process is equal to a preset number, and under the condition that the count of the iterative computation process is smaller than the preset number, continuing the iterative computation process by taking the displacement field, the pore pressure field and the temperature field of the stratum which are obtained through computation as initial values.
If the preset number of times is N0, when the count N of the iterative calculation process is less than N0, the displacement field, pore pressure field, and temperature field calculated in steps S601 to S603 are used as the initial displacement, initial pore pressure, and initial temperature of the entire formation, and steps S601 to S603 are re-executed. This iterative calculation process is then counted until the count of iterative calculation processes equals the preset number N0, at which point the resulting displacement field of the formation may be used to calculate a second stress intensity factor in step S502.
And S502, calculating a second stress intensity factor of the fracture tip according to a J integral algorithm and the displacement field of the stratum.
The formula of the J integral algorithm is as follows:
Wherein J is a J integral value; the gamma is an integral loop of the crack tip; w is the energy density; f is a tension vector; x refers to the direction of the x-axis in the analytical microcell.
the calculation formula of the energy density W is as follows: wherein, σ x, σ y and σ xy are respectively a positive stress component along the x direction, a positive stress component along the y direction and a shear stress component vertical to the x direction; and the epsilon x, the epsilon y and the epsilon xy are respectively a positive strain component along the x direction, a positive strain component along the y direction and a shear strain component vertical to the x direction, and the quantities can be obtained by calculating the displacement field of the stratum. The formula for the tension force F is: f ═ σ xnx + σ xyny, σ xynx + σ yny ], where nx and ny are unit vectors in the x and y directions, respectively.
substituting the displacement field of the stratum obtained in the step S601 into the formula (7), and calculating to obtain a J integral value J.
Substituting the J integral value J into equation (8) below can calculate a second intensity factor K2a,
Wherein E is the elastic modulus and mu is the Poisson's ratio.
Step S303, adjusting the preset target temperature of the well wall, and recalculating the second stress intensity factor of the fracture tip until the absolute value of the difference between the calculated second stress intensity factor and the first stress intensity factor is less than or equal to a preset value.
calculating an absolute value of a difference between the second stress intensity factor and the first stress intensity factor, and if the absolute value is greater than a preset value (e.g., 10-5), adjusting the preset target temperature; and repeating the step S302 to calculate the second stress intensity factor by using the adjusted preset target temperature until the absolute value of the difference between the calculated second stress intensity factor and the first stress intensity factor is less than or equal to the preset value (e.g., 10 "5). Then, in step S304 and step S305, the temperature field and the displacement field of the formation obtained in the process of calculating the second stress intensity factor for the last time may be used to obtain the target temperature to which the borehole wall needs to be cooled and the fracture opening distribution.
and S304, acquiring the target temperature to which the well wall needs to be cooled according to the preset target temperature of the well wall which is adjusted at the last time.
The target temperature to which the well wall needs to be cooled may be equal to the preset target temperature of the well wall which is adjusted for the last time or the temperature of the temperature field of the formation at the well wall which is obtained in the process of calculating the second stress intensity factor for the last time.
and S305, acquiring the fracture opening distribution according to the displacement field of the stratum, which is obtained by the thermo-fluid-solid coupling equation and the preset target temperature of the well wall adjusted at the last time.
The maximum fracture opening in the fracture opening distribution may be equal to the displacement of the displacement field of the formation at the well wall obtained in the last calculation of the second stress intensity factor.
in step S102, since a certain heat exchange occurs between the external environment and the cooling fluid, and when the borehole wall is cooled by the cooling fluid with the temperature T, the final borehole wall temperature may be slightly higher than T, so that the influence caused by the heat exchange effect can be compensated by a smaller preset temperature adjustment. The obtaining the temperature of the drilling fluid may include: and solving the difference between the target temperature to which the well wall needs to be cooled and the preset adjusting temperature, and taking the solved difference as the temperature of the drilling fluid. Of course, the preset regulation temperature can be determined according to actual conditions and is generally very small (can be 0).
The invention adopts the low-temperature fracturing effect of the drilling fluid to reduce the fracture pressure of the stratum, so that the stratum can be pressed to open the fracture by lower pumping pressure, after the well wall strengthening material is filled, when the temperature of the stratum is recovered to the original temperature, the thermal stress generated by the thermal expansion of stratum rocks increases the fracture closing stress, thereby enhancing the strengthening effect of the filling particles on the pressure-bearing capacity of the periphery of the well.
For step S103, obtaining the particle size distribution of the reinforcing material may include:
The self-made plugging instrument is used for researching the particle size matching rule of cracks with different opening degrees, and the following particle size matching criteria can be obtained: the particle size corresponding to the cumulative particle size distribution of the reinforcing materials with the first preset percentage is equal to the first preset crack opening degree; and the particle size corresponding to the cumulative particle size distribution of the reinforcing materials with the second preset percentage is equal to the second preset crack opening, wherein the first preset percentage is smaller than the second preset percentage, the first preset crack opening is smaller than the second preset crack opening, and the first preset crack opening and the second preset crack opening are related to the maximum crack opening in the crack opening distribution.
the cumulative particle size distribution is a percentage of the total mass of particles having a particle diameter smaller than a predetermined particle diameter in a unit volume of the reinforcing material. The cumulative fracture opening distribution referred to below is a percentage of the fracture volume smaller than a predetermined opening in the fracture opening distribution to the entire fracture volume. The cumulative particle size distribution of the selected reinforcing material needs to be matched with the cumulative crack opening distribution of the cracks, so that the well wall can be reinforced.
specifically, the particle size matching criterion may be: d50 ═ 3/10Wf and D90 ═ 6/5Wf, where D50 refers to the particle size corresponding to the cumulative particle size distribution of 50% of the reinforcing material; d90 indicates the particle size corresponding to the cumulative particle size distribution of 90% of the reinforcing material; wf is the maximum crack opening, accordingly 3/10Wf is the first preset crack opening and 6/5Wf is the second preset crack opening. Therefore, the particle size corresponding to the cumulative particle size distribution of the reinforcing material can be ensured not to be too small or too large, and the particle size distribution of the reinforcing material can be determined more accurately.
The specific situation of the cumulative fracture opening distribution of the fracture and the maximum fracture opening Wf can be obtained according to the fracture opening distribution, and the particle size distribution of the reinforced material obtained by combining the particle size matching criterion needs to meet the requirements that D50 is 3/10Wf and D90 is 6/5 Wf. Then, the reinforcing material having the above particle size distribution can be obtained. The specific process can be seen in detail in the description of fig. 8 below.
according to the method, the process of solving the fracture opening distribution according to the parameters such as the thermal fluid-solid coupling equation, the rock mechanical parameters of the stratum, the rheological property of the drilling fluid and the like is a process of solving a numerical solution, and the solving result is not accurate, so that the method firstly utilizes a well wall strengthening model to obtain an accurate analytic solution, then utilizes the thermal fluid-solid coupling equation to obtain the numerical solution, and adjusts the target preset temperature for multiple times until the error between the numerical solution and the analytic solution is small enough, and determines the target preset temperature which is adjusted at the last time as the target to be cooled by the well wall and the corresponding displacement field of the stratum as the fracture opening distribution, so that the well wall strengthening condition can be accurately predicted.
in particular, as shown in FIG. 7, the process of determining the borehole wall strengthening conditions is explained and illustrated in its entirety.
The process of determining the borehole wall strengthening condition may include the steps of:
Step S701, well history data and core analysis are obtained.
Step S702, calculating a first stress intensity factor SIF1 according to the well wall strengthening model and the preset pressure bearing of the well wall.
and S703, solving a second stress intensity factor SIF2 according to the thermo-hydro-mechanical coupling equation, the preset bearing pressure of the well wall and the preset target temperature.
Step S704, judging whether | SIF2-SIF1| <10-5, if yes, executing step S705; otherwise, adjusting the preset target temperature of the well wall and executing the step S703.
Step S705, according to the preset target temperature and the thermo-hydro-mechanical coupling equation adjusted at the last time, the target temperature to which the well wall needs to be cooled and the crack opening distribution are obtained.
According to well history data and coring measurement results of a leakage layer of an adjacent well (or any region in the block), the problem of well leakage is easy to occur in a deep water block, and the elastic modulus of a rock in a leakage layer section is 14GPa, the Poisson ratio is 0.2, the formation porosity is 0.2, the formation permeability is 10.8mD, the formation pore pressure is 12.41MPa, the drilling fluid column pressure in the leakage layer section is 25MPa, the pressure bearing capacity needs to be improved to 27.58MPa, the formation temperature is 394K, the formation thermal diffusivity is 3 x 10 < -4 > K < -1 >, the formation specific heat capacity is 4181J/(kg < -K), the formation thermal conductivity is 1.3W/(m < -K >), the formation thermal permeability is 2.1 x 10 < -11 > m2 >/(. s < -K >), and the viscosity of the drilling fluid is 20 mPas < -s >.
According to the pressure-bearing capacity required by the well wall, calculating to obtain a stress intensity factor required by the crack tip to be-1.53 MPa-m 1/2; the temperature to which the well wall needs to be cooled is 293K and the crack opening degree distribution is obtained through iterative calculation of a thermo-fluid-structure coupling formula, as shown in FIG. 8.
Specifically, according to the crack opening distribution shown in fig. 8, on the one hand, the maximum crack opening Wf of 0.25mm can be obtained; on the other hand, the cumulative fracture opening distribution Dk ═ S (L)/S (0) (where k is an arbitrary value from 0 to 100, S (L) is the cumulative fracture opening at the fracture length L, and S (0) is the cumulative fracture opening at the fracture length origin), for example, the fracture opening corresponding to the fracture length of 53mm is 0.2mm, and the cumulative fracture opening corresponding to the fracture opening of 0.2mm is the shaded area S (53mm) shown in fig. 8 (the calculation process of the shaded area is not the important description of the present invention, and is not described here again), and Dk1 ═ S (53mm)/S (0). Thus, the fracture lengths L1 and L2 corresponding to D50 and D90 can be obtained from the cumulative fracture opening distribution Dk of the fractures. Then, the broken line shown in fig. 9 can be obtained from the two coordinates, and the particle size distribution of the reinforcing material that can be preferably obtained by matching (solid line shown in fig. 9) can be obtained.
In conclusion, the method and the device have the advantages that the target temperature and the crack opening degree which need to be cooled to the well wall are calculated quantitatively through the well wall strengthening model and the preset pressure-bearing and thermo-fluid-solid coupling equation of the well wall creatively, then the temperature of the drilling fluid which needs to be pumped is obtained according to the target temperature which needs to be cooled to the well wall, the particle size distribution of the strengthening material which needs to be filled is obtained according to the crack opening degree and the particle size matching criterion, and the particle size distribution of the drilling fluid and the particle size distribution of the strengthening material which need to be filled in the well wall strengthening process can be characterized quantitatively, so that the refined control of the well wall strengthening process can be realized, and an.
Correspondingly, the embodiment of the invention also provides a system for determining the well wall strengthening condition. As shown in fig. 10, the system may include: the calculating device 10 is used for calculating the target temperature required to be cooled to the well wall and the crack opening degree of the well wall according to the well wall strengthening model and the preset pressure-bearing and thermo-hydraulic-solid coupling equation of the well wall; the temperature obtaining device 20 is used for obtaining the temperature of the drilling fluid according to the target temperature to which the well wall needs to be cooled; and a particle size distribution obtaining device 30 for obtaining the particle size distribution of the reinforcing material according to the crack opening degree of the well wall and the particle size matching criterion.
preferably, the computing device comprises: the first stress intensity factor calculation module is used for calculating a first stress intensity factor of the crack tip after the well wall is filled with the strengthening material according to the well wall strengthening model and the preset pressure bearing of the well wall; the second stress intensity factor calculation module is used for calculating a second stress intensity factor of the crack tip according to the thermo-fluid-solid coupling equation and the preset bearing pressure and the preset target temperature of the well wall; the adjusting module is used for adjusting the preset target temperature of the well wall, recalculating the second stress intensity factor of the crack tip until the absolute value of the difference value between the calculated second stress intensity factor and the first stress intensity factor is less than or equal to a preset value, and obtaining the target temperature to which the well wall needs to be cooled and the crack opening degree of the well wall; the target temperature obtaining module is used for obtaining the target temperature to which the well wall needs to be cooled according to the preset target temperature of the well wall which is adjusted at the last time; and the fracture opening obtaining module is used for obtaining the fracture opening of the well wall according to the displacement of the displacement field of the stratum at the fracture of the well wall, which is obtained by the thermo-fluid-solid coupling equation and the preset target temperature of the well wall adjusted at the last time.
Preferably, the first stress intensity factor calculating module includes: the acquiring unit is used for acquiring a first formula for calculating the first stress intensity factor according to the well wall strengthening model; and the first stress intensity factor calculation unit is used for calculating the first stress intensity factor according to the first formula, the preset pressure bearing of the well wall, and the minimum horizontal ground stress and the maximum horizontal ground stress at the infinite distance from the well wall.
preferably, the second stress intensity factor calculating module includes: the displacement field calculation unit is used for calculating the displacement field of the stratum according to the thermo-fluid-solid coupling equation and the preset bearing pressure and the preset target temperature of the well wall; and the second stress intensity factor calculation unit is used for calculating a second stress intensity factor of the fracture tip according to a J integral algorithm and the displacement field of the stratum.
Preferably, the thermo-fluid-solid coupling equation comprises: the stress balance equation, the fluid mass conservation equation and the energy balance equation are correspondingly calculated by the displacement field calculation unit, and the displacement field calculation unit comprises: the displacement field calculator is used for calculating the displacement field according to the stress balance equation, the preset bearing pressure and preset target temperature of the well wall, the initial pore pressure of the stratum, the initial temperature of the stratum and the initial displacement of the stratum; the pore pressure field calculator is used for calculating the pore pressure field of the stratum according to the fluid mass conservation equation, the preset bearing pressure and preset target temperature of the well wall, the initial pore pressure of the stratum, the initial temperature of the stratum and the initial displacement of the stratum; the temperature field calculator is used for calculating the temperature field of the stratum according to the energy balance equation, the preset bearing pressure and the preset target temperature of the well wall, the initial pore pressure of the stratum, the initial temperature of the stratum and the initial displacement of the stratum; and a counter for counting the iterative computation process under the condition that the displacement field, the pore pressure field of the stratum and the temperature field of the stratum are obtained through computation; and the judger is used for judging whether the count of the iterative calculation process is equal to a preset number of times or not, and inputting the displacement field, the pore pressure field of the stratum and the temperature field which are obtained by calculation as initial values into the displacement field calculator, the pore pressure field calculator and the temperature field calculator to continue the iterative calculation process under the condition that the count of the iterative calculation process is smaller than the preset number of times.
For specific details and benefits of the system for determining borehole wall strengthening conditions provided by the present invention, reference may be made to the above description of the method for determining borehole wall strengthening conditions, and further description thereof will not be provided herein.
Correspondingly, the invention also provides a well wall strengthening method, as shown in fig. 11, the well wall strengthening method may include the following steps: step S1101, obtaining the temperature of the drilling fluid and the particle size distribution of the reinforcing material obtained according to the method for determining the well wall reinforcing condition; step S1102, pumping the drilling fluid having the temperature; and a step S1103 of filling the reinforcing material having the particle size distribution.
wherein the reinforcing material may be calcium carbonate particles. Compared with the injected chemical materials (water-absorbing resin, chemical gel, delayed expansion plugging agent and the like) in the prior art, the calcium carbonate particles can not cause unrecoverable damage to the reservoir. In addition, compared with the method for forming pressure isolation of the crack tip by adopting chemical materials such as water-absorbent resin, chemical gel, delayed expansion plugging agent and the like in the prior art, the well wall strengthening method provided by the invention is simple to operate and low in cost.
In conclusion, the temperature of the drilling fluid and the particle size distribution of the reinforcing material obtained by the method for determining the well wall reinforcing condition are creatively obtained, then the required drilling fluid is pumped according to the obtained temperature, and the required reinforcing material is filled according to the obtained particle size distribution, so that the influence of the filling of the reinforcing material on the well wall stress is enhanced by utilizing the thermal stress generated by the temperature change, and the pressure bearing capacity of the well wall is improved.
accordingly, the present invention also provides a well wall strengthening system, as shown in fig. 12, the well wall strengthening system may include: the obtaining device 40 is used for obtaining the temperature of the drilling fluid and the particle size distribution of the strengthening materials obtained by the method for determining the well wall strengthening conditions; a pumping device 50 for pumping drilling fluid having said temperature; and a filling device 60 for filling the reinforcing material having the particle size distribution.
For the benefits of the borehole wall strengthening system provided by the present invention, reference may be made to the above description of the borehole wall strengthening method, which is not described herein again.
Accordingly, the present invention also provides a machine-readable storage medium having stored thereon instructions for causing a machine to perform the method for determining a borehole wall strengthening condition or the borehole wall strengthening method.
The machine-readable storage medium includes, but is not limited to, Phase Change Random Access Memory (PRAM, also known as RCM/PCRAM), Static Random Access Memory (SRAM), Dynamic Random Access Memory (DRAM), other types of Random Access Memory (RAM), Read Only Memory (ROM), Electrically Erasable Programmable Read Only Memory (EEPROM), Flash Memory (Flash Memory) or other Memory technology, compact disc read only Memory (CD-ROM), Digital Versatile Disc (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, and various media capable of storing program code.
the preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications can be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.
It should be noted that the various features described in the above embodiments may be combined in any suitable manner without departing from the scope of the invention. The invention is not described in detail in order to avoid unnecessary repetition.
In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.
Claims (15)
1. a method for determining a borehole wall strengthening condition, the method comprising:
Calculating the target temperature required to be cooled by the well wall and the crack opening distribution of cracks extending from the well wall to the stratum according to a well wall strengthening model and a preset pressure-bearing and thermo-fluid-solid coupling equation of the well wall;
Obtaining the temperature of the drilling fluid according to the target temperature to which the well wall needs to be cooled; and
And acquiring the particle size distribution of the reinforced material according to the crack opening distribution and the particle size matching criterion.
2. The method for determining the borehole wall strengthening condition as recited in claim 1, wherein the calculating the target temperature to which the borehole wall is required to cool and the fracture opening profile of the fracture extending from the borehole wall into the formation comprises:
Calculating a first stress intensity factor of a crack tip after the well wall is filled with a reinforcing material according to the well wall reinforcing model and the preset pressure bearing of the well wall;
Calculating a second stress intensity factor of the crack tip according to the thermo-fluid-solid coupling equation and the preset pressure bearing and preset target temperature of the well wall;
Adjusting the preset target temperature of the well wall, and recalculating the second stress intensity factor of the fracture tip until the absolute value of the difference between the calculated second stress intensity factor and the first stress intensity factor is less than or equal to a preset value;
according to the preset target temperature of the well wall which is adjusted for the last time, the target temperature to which the well wall needs to be cooled is obtained; and
And acquiring the fracture opening distribution according to the displacement field of the stratum, which is obtained by the thermo-fluid-solid coupling equation and the preset target temperature of the well wall adjusted at the last time.
3. The method for determining the borehole wall strengthening condition as recited in claim 2, wherein the calculating a first stress intensity factor for the fracture tip after the borehole wall is filled with the strengthening material comprises:
acquiring a first formula for calculating the first stress intensity factor according to the well wall strengthening model; and
and calculating the first stress intensity factor according to the first formula, the preset pressure bearing of the well wall, and the minimum horizontal ground stress and the maximum horizontal ground stress at the infinite distance from the well wall.
4. The method for determining the borehole wall strengthening condition as recited in claim 3, wherein the first formula for calculating the first stress intensity factor KIa is: KIa (F1+ F2. [2Pw- (σ H + σ H) ] + (F1+3F 3. (σ H- σ H) -2F 4. (Pw-P),
wherein σ h is the minimum horizontal ground stress at infinity from the borehole wall; σ H is the maximum horizontal ground stress at infinity from the borehole wall; p is the pore pressure of the formation; pw is the preset pressure bearing of the well wall; f1, F2, F3 and F4 are respectively a first integration function, a second integration function, a third integration function and a fourth integration function,
Wherein the first integral function F1, the second integral function F2, the third integral function F3 and the fourth integral function F4 are respectively obtained by the following formulas: wherein L is the distance between the crack tip and the center of the shaft, a is the crack length, R is the shaft radius, D is the distance between the position of the reinforcing material in the crack for plugging and bridging and the center of the shaft, and R is the distance between any point in the crack and the center of the shaft.
5. The method for determining the borehole wall strengthening condition as defined in claim 2, wherein calculating the second stress intensity factor for the fracture tip comprises:
Calculating a displacement field of the stratum according to the thermo-fluid-solid coupling equation and the preset bearing pressure and the preset target temperature of the well wall; and
And calculating a second stress intensity factor of the fracture tip according to a J integral algorithm and the displacement field of the stratum.
6. the method for determining the borehole wall strengthening condition according to claim 5, wherein the thermo-hydro-mechanical coupling equation comprises: a stress balance equation, a fluid mass conservation equation and an energy balance equation,
Accordingly, the calculating the displacement field of the formation comprises:
Calculating the displacement field according to the stress balance equation, the preset bearing pressure and the preset target temperature of the well wall, the initial pore pressure of the stratum, the initial temperature of the stratum and the initial displacement of the stratum;
Calculating a pore pressure field of the stratum according to the fluid mass conservation equation, the preset pressure-bearing and preset target temperature of the well wall, the initial pore pressure of the stratum, the initial temperature of the stratum and the initial displacement of the stratum;
Calculating a temperature field of the stratum according to the energy balance equation, the preset bearing pressure and preset target temperature of the well wall, the initial pore pressure of the stratum, the initial temperature of the stratum and the initial displacement of the stratum;
counting the iterative calculation process under the condition that the displacement field, the pore pressure field of the stratum and the temperature field of the stratum are obtained through calculation; and
and judging whether the count of the iterative computation process is equal to a preset number of times, and under the condition that the count of the iterative computation process is smaller than the preset number of times, continuing the iterative computation process by taking the displacement field, the pore pressure field and the temperature field of the stratum which are obtained by computation as initial values.
7. The method for determining borehole wall strengthening conditions according to claim 1, wherein the particle size matching criteria comprises: the particle size corresponding to the cumulative particle size distribution of the reinforcing materials with the first preset percentage is equal to the first preset crack opening degree; and the particle size corresponding to the cumulative particle size distribution of the second predetermined percentage of the enhanced particle sizes is equal to the second predetermined fracture opening,
the first preset percentage is smaller than the second preset percentage, the first preset crack opening is smaller than the second preset crack opening, and the first preset crack opening and the second preset crack opening are related to the maximum crack opening in the crack opening distribution.
8. a system for determining a borehole wall strengthening condition, the system comprising:
the calculating device is used for calculating the target temperature required to be cooled by the well wall and the crack opening of the crack extending from the well wall to the stratum according to the well wall strengthening model and the preset pressure-bearing and thermo-fluid-solid coupling equation of the well wall;
The temperature acquisition device is used for acquiring the temperature of the drilling fluid according to the target temperature to which the well wall needs to be cooled; and
And the particle size distribution obtaining device is used for obtaining the particle size distribution of the reinforced material according to the crack opening distribution and the particle size matching criterion.
9. The system for determining a borehole wall strengthening condition according to claim 8, wherein the computing device comprises:
the first stress intensity factor calculation module is used for calculating a first stress intensity factor of the crack tip after the well wall is filled with the strengthening material according to the well wall strengthening model and the preset pressure bearing of the well wall;
The second stress intensity factor calculation module is used for calculating a second stress intensity factor of the crack tip according to the thermo-fluid-solid coupling equation and the preset bearing pressure and the preset target temperature of the well wall;
The adjusting module is used for adjusting the preset target temperature of the well wall and recalculating the second stress intensity factor of the fracture tip until the absolute value of the difference value between the calculated second stress intensity factor and the first stress intensity factor is less than or equal to a preset value;
The target temperature obtaining module is used for obtaining the target temperature to which the well wall needs to be cooled according to the preset target temperature of the well wall which is adjusted at the last time; and
And the fracture opening acquisition module is used for acquiring the fracture opening distribution according to the displacement of the displacement field of the stratum at the fracture of the well wall, which is obtained by the thermo-fluid-solid coupling equation and the preset target temperature of the well wall adjusted at the last time.
10. The system for determining a borehole wall strengthening condition according to claim 9, wherein the first stress intensity factor calculation module comprises:
The acquiring unit is used for acquiring a first formula for calculating the first stress intensity factor according to the well wall strengthening model; and
And the first stress intensity factor calculation unit is used for calculating the first stress intensity factor according to the first formula, the preset pressure bearing of the well wall, and the minimum horizontal ground stress and the maximum horizontal ground stress at the infinite distance from the well wall.
11. The system for determining a borehole wall strengthening condition according to claim 9, wherein the second stress intensity factor calculation module comprises:
The displacement field calculation unit is used for calculating the displacement field of the stratum according to the thermo-fluid-solid coupling equation and the preset bearing pressure and the preset target temperature of the well wall; and
And the second stress intensity factor calculation unit is used for calculating a second stress intensity factor of the fracture tip according to a J integral algorithm and the displacement field of the stratum.
12. the system for determining a borehole wall strengthening condition according to claim 11, wherein the thermo-hydro-mechanical coupling equation comprises: a stress balance equation, a fluid mass conservation equation and an energy balance equation,
Accordingly, the displacement field calculation unit comprises:
The displacement field calculator is used for calculating the displacement field according to the stress balance equation, the preset bearing pressure and preset target temperature of the well wall, the initial pore pressure of the stratum, the initial temperature of the stratum and the initial displacement of the stratum;
The pore pressure field calculator is used for calculating the pore pressure field of the stratum according to the fluid mass conservation equation, the preset bearing pressure and preset target temperature of the well wall, the initial pore pressure of the stratum, the initial temperature of the stratum and the initial displacement of the stratum;
the temperature field calculator is used for calculating the temperature field of the stratum according to the energy balance equation, the preset bearing pressure and the preset target temperature of the well wall, the initial pore pressure of the stratum, the initial temperature of the stratum and the initial displacement of the stratum; and
The counter is used for counting the iterative calculation process under the condition that the displacement field, the pore pressure field of the stratum and the temperature field of the stratum are obtained through calculation;
And the judger is used for judging whether the count of the iterative calculation process is equal to a preset number of times or not, and inputting the displacement field, the pore pressure field of the stratum and the temperature field which are obtained by calculation as initial values into the displacement field calculator, the pore pressure field calculator and the temperature field calculator to continue the iterative calculation process under the condition that the count of the iterative calculation process is smaller than the preset number of times.
13. A well wall strengthening method is characterized by comprising the following steps:
obtaining the temperature of the drilling fluid and the particle size distribution of the reinforcing material obtained by the method for determining the borehole wall reinforcing conditions according to any one of claims 1-7;
pumping drilling fluid having the temperature; and
the reinforcing material having the particle size distribution is filled.
14. A wellbore strengthening system, comprising:
an acquisition device for acquiring the temperature of the drilling fluid and the particle size distribution of the reinforcing material obtained by the method for determining the borehole wall reinforcing condition according to any one of claims 1 to 7;
A pumping device for pumping drilling fluid having said temperature; and
and the filling equipment is used for filling the reinforcing material with the particle size distribution.
15. A machine-readable storage medium having instructions stored thereon for causing a machine to perform the method for determining a borehole wall strengthening condition of any one of the preceding claims 1-7 or the method for borehole wall strengthening of claim 13.
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