CN115434681B - Deep well and ultra-deep well fracturing sleeve protection method and operation flow - Google Patents
Deep well and ultra-deep well fracturing sleeve protection method and operation flow Download PDFInfo
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- CN115434681B CN115434681B CN202110625699.0A CN202110625699A CN115434681B CN 115434681 B CN115434681 B CN 115434681B CN 202110625699 A CN202110625699 A CN 202110625699A CN 115434681 B CN115434681 B CN 115434681B
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/25—Methods for stimulating production
- E21B43/26—Methods for stimulating production by forming crevices or fractures
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B47/00—Survey of boreholes or wells
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B47/00—Survey of boreholes or wells
- E21B47/06—Measuring temperature or pressure
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B49/00—Testing the nature of borehole walls; Formation testing; Methods or apparatus for obtaining samples of soil or well fluids, specially adapted to earth drilling or wells
Abstract
The invention provides a deep well and ultra-deep well fracturing sleeve protection method and an operation flow, and belongs to the technical field of petroleum exploitation. The method combines the block adjacent well pump stopping pressure gradient, the well test fracturing data and the fracturing construction parameters to calculate the maximum bearing pressure of the sleeve, combines the sleeve internal pressure resistance intensity and the wellhead bearing limit value to calculate the sleeve internal pressure resistance safety value, and finally obtains the annulus weighting protection liquid density. And (3) preparing the weight-increasing protective liquid according to the density of the weight-increasing protective liquid and the injection amount. And opening the sleeve valve, then opening the oil pipe valve, slowly injecting the weighted protection liquid from the oil pipe valve at a constant speed, adjusting the sleeve valve until the sleeve pressure is kept stable, switching into fracturing liquid after the injected liquid quantity reaches the design liquid quantity, jacking the weighted protection liquid in the oil pipe into an oil sleeve annulus, stopping displacement after the density of the liquid returned from the sleeve flank is equal to the density of the weighted protection liquid, and closing the sleeve valve. The invention can save packer materials and the running cost, and the process flow is simple and convenient to operate.
Description
Technical Field
The invention relates to the field of oil exploitation, in particular to a deep well and ultra-deep well fracturing sleeve protection method and an operation flow.
Background
Along with the continuous progress of oil and gas exploration technology, the exploration and development of deep and ultra-deep oil and gas reservoirs become the main development direction of future increased storage and production in a deep unconventional reservoir with the depth of 4500 m. At present, most of deep wells and ultra-deep well reservoirs are compact in rock property and poor in permeability, industrial oil gas flow is needed to be obtained through fracturing transformation, however, the technical problem that the construction pressure of a well head is too high is commonly existed in the field transformation process, part of the construction pressure even exceeds the bearing capacity and level of a sleeve, the sleeve is easy to damage, the integrity of a shaft is influenced, the transformation risk of the deep well reservoirs is greatly increased, and the construction success rate is reduced.
Because the compressive strength of the sleeve is far lower than that of the oil pipe, and once sand blockage cannot be removed circularly, an oil pipe fracturing transformation mode is generally adopted for high-pressure well fracturing construction of deep wells, ultra-deep wells and the like at present. The casing protection effect in the oil pipe fracturing process directly determines the success and failure of fracturing construction, so that the selection of a reasonable casing protection method is important for smooth fracturing construction. The sleeve protection method commonly adopted in the oil pipe fracturing process at present mainly comprises the following steps: and sealing the annular space of the oil jacket at the upper part of the target layer by adopting a packer, and carrying out idle preparation and pressing on the oil technical jacket. But both methods have poor applicability to deep well and ultra-deep well fracturing modification.
In the prior art, one of the common methods for protecting the casing in the oil pipe fracturing process is to seal the oil casing annulus at the upper part of the target layer by adopting a packer, so that the bearing of the casing is reduced, and the risks of expansion, deformation, fracture and the like of the casing are avoided. According to the K344 series packer acidizing fracturing string instruction, after the oil pipe is adopted to press and set the packer, the oil pipe discharge capacity can be increased to carry out fracturing construction, the annular pressure of the oil jacket below the packer is continuously increased along with the increase of the discharge capacity, the annular pressure of the oil jacket above the packer is lower in the fracturing process, and the pressure bearing of the free section of the upper oil layer sleeve is lower. After the fracturing construction is completed, pumping well flushing liquid into a sleeve gate to perform backwashing well flushing, lifting a pipe column after well killing to lift out a packer and a fracturing pipe column, and discharging into a production pipe column to start oil testing operation.
The method for sealing the annular space of the oil jacket at the upper part of the target layer by the packer can effectively protect the sleeve in the fracturing construction process, is generally suitable for fracturing construction of middle and shallow oil and gas wells, but has more defects in high-pressure well applications such as deep wells, ultra-deep wells and the like, and mainly comprises the following steps:
1) The packer cannot react to the sleeve pressure change in the fracturing process, and the judgment of the working condition of fracturing construction is affected.
2) Because high-pressure wells such as deep wells and ultra-deep wells are high in fracturing construction pressure, the packer is high in annular stress and easy to fail, and even the risk of breaking a fracturing string exists, the accurate positioning of a fracturing layer position and the fracturing construction safety are directly affected.
3) By adopting the method of sealing the annular space of the oil jacket on the upper part of the target layer by the packer, the well-killing operation is needed when the post-lifting pipe column is lifted out of the packer, the construction process is complex, and the later oil testing is not facilitated.
4) The underground packer is easy to be subjected to underground complex conditions such as clamping during the running, damage to a rubber cylinder, difficult deblocking, accidental opening of a backwashing valve and the like in field application, so that underground accidents are caused.
Another common practice in the prior art for protecting a casing in the oil pipe fracturing process is an oil technical casing annulus preparation pressing method. The ground pump truck is adopted to press the oil technical sleeve ring in an empty mode, so that expansion, deformation and fracture of a free section of the oil layer sleeve in the fracturing process are avoided. The method is simpler in field operation, but is not suitable for deep well and ultra-deep well fracturing construction, and the main reason is as follows: the deep well and the ultra-deep well are high in fracturing construction pressure, the air pressure requirement on the oil technology sleeve ring is high, when the bearing capacity of the sleeve is exceeded, the sleeve and the annular space of the technical sleeve are required to be further pressed to protect the technical sleeve, and at the moment, the site construction process is complex, and potential safety hazards such as overpressure, tubular column deformation and the like exist.
Disclosure of Invention
Aiming at the problem that the pressure of the sleeve is generally higher in the fracturing process of the oil pipe of the high-pressure well at present, the invention provides a deep well and ultra-deep well fracturing sleeve protecting method and an operating flow, wherein the maximum bearing pressure of the sleeve is calculated by combining the pressure gradient of the adjacent well pump stopping of a block, the fracturing data of the well test and the fracturing construction parameters, the internal pressure resistance safety value of the sleeve is calculated by combining the internal pressure resistance intensity of the sleeve and the pressure bearing limit value of a well mouth, and the reasonable annulus weighting protecting liquid density is calculated according to the pressure difference of the maximum bearing pressure and the internal pressure resistance safety value of the sleeve. According to the density of the weighted protection liquid and the injection liquid, the weight protection liquid is configured by 1:1.2 liquid preparation amount, a sleeve valve is opened before the weighted protection liquid is injected, so that the liquid in the oil pipe and the oil sleeve annulus can return to the ground, then the oil pipe valve is opened, and the configured weighted protection liquid is distributed at 0.8-1.0m from the oil pipe valve 3 And (3) slowly injecting at the speed of/min (keeping the bottom hole pressure less than or equal to the stratum fracture pressure), adjusting a sleeve valve until the sleeve pressure is kept stable, stopping injecting after the injected liquid quantity reaches the designed liquid quantity, switching the injected fracturing liquid to jack the weighted protection liquid in the oil pipe into an oil sleeve annulus, stopping displacing after the density of the returned liquid of the sleeve flank is equal to the density of the weighted protection liquid, closing the sleeve valve, and starting the fracturing construction operation. Compared with the method for sealing the upper oil sleeve annulus of the target layer by the packer, the method can save packer materials and running cost, has simple and convenient process flow operation, can judge the underground working condition of the fracturing process in time according to the real-time change of the casing pressure, provides a basis for dynamically adjusting the fracturing construction parameters, and guides the safe, economic and efficient reconstruction of deep well and ultra-deep well reservoirs.
The invention provides a deep well and ultra-deep well fracturing sleeve protection method, which comprises the following steps:
collecting reservoir physical properties, fracturing pipe columns and relevant parameters of fracturing construction, wherein the relevant parameters comprise depth of the middle part of a reservoir, tensile strength of rock, size of a sleeve, internal pressure resistance of the sleeve, wellhead bearing capacity, construction displacement and sand-liquid ratio, and closing pressure gradient or zone reservoir pump stopping pressure gradient obtained during testing fracturing;
obtaining the maximum bearing pressure of the casing according to the stratum fracture pressure, the liquid column pressure and the tube side friction resistance of the target interval;
according to the casing internal pressure resistance intensity of the well bore, combining the casing pressure resistance safety coefficient and wellhead pressure bearing capacity to obtain a casing internal pressure resistance safety value;
acquiring the density of the required weight-increasing protective liquid according to the pressure difference between the maximum bearing pressure of the sleeve and the internal pressure resistance safety value of the sleeve, and calculating the injection liquid amount;
and (3) determining the liquid preparation amount according to the injection amount in proportion, and injecting the weighted protection liquid with the volume being the liquid preparation amount into the oil pipe at a constant speed.
Preferably, the maximum bearing pressure of the bushing is obtained by the following formula:
P maximum bearing of sleeve ＝P Formation fracture pressure +P Tube side friction resistance -P Liquid column pressure ；
P Maximum bearing of sleeve The unit is MPa for the maximum bearing of the sleeve;
P tube side friction resistance The friction is the tube side friction, the unit is MPa, and the friction is obtained according to the following formula:
P tube side friction resistance ＝3451.2e -a ×Q 1.8 ×h Depth of middle part of reservoir of this well ；
Wherein, the liquid crystal display device comprises a liquid crystal display device,
h depth of middle part of reservoir of this well The depth of the middle part of the reservoir of the well is m;
a＝2.05-0.93/Q-0.0055C p -0.59；
q is construction displacement, the unit is m 3 /min；
C p Is sand-liquid ratio;
P liquid column pressure Is liquid column pressure, in MPa, obtained according to the formula:
P liquid column pressure ＝ρgh Depth of middle part of reservoir of this well ；
Wherein, the liquid crystal display device comprises a liquid crystal display device,
ρ is the density of the liquid column in kg/m 3 ；
g is gravity acceleration, and the unit is m/s 2 ；
P Formation fracture pressure MP for formation fracture pressurea, obtained according to the following formula;
P formation fracture pressure ＝P Predicting closure pressure +τ Tensile strength of ；
Wherein, the liquid crystal display device comprises a liquid crystal display device,
τ tensile strength of Tensile strength in MPa;
P predicting closure pressure In order to predict the closing pressure, the unit is MPa, and if the test fracturing is performed, the closing pressure is obtained according to the test fracturing data analysis;
if the test fracturing is not performed, obtaining according to the pump stopping pressure gradient of the adjacent well of the block by the following formula:
P predicting closure pressure ＝P Predicting pump down pressure -P Additional of +P Liquid column pressure ，
Wherein, the liquid crystal display device comprises a liquid crystal display device,
P additional of For additional pressure, the unit is MPa, and the value range is as follows: 3-8 MPa;
P liquid column pressure The liquid column pressure is expressed as MPa;
h depth of middle part of reservoir of this well The depth of the middle part of the reservoir of the well is m;
P predicting pump down pressure For predicting the pump down pressure, in MPa, the calculation is performed according to the following formula:
P predicting pump down pressure ＝μ Block adjacent well pump-down pressure gradient ×h Depth of middle part of reservoir of this well ；
μ Block adjacent well pump-down pressure gradient The pressure gradient of the adjacent well shut-in of the block is expressed in MPa/m, and is calculated according to the following formula:
wherein, the liquid crystal display device comprises a liquid crystal display device,
P pressure of stopping pump of adjacent well Stopping pumping pressure for an adjacent well, wherein the unit is MPa;
P hydrostatic column pressure in adjacent well The unit is MPa for hydrostatic column pressure of an adjacent well;
h adjacent well storageDepth of middle layer The depth of the middle part of the adjacent well reservoir is expressed as m.
Preferably, the casing internal pressure resistance safety value is obtained by the following formula:
P safety value against internal pressure ＝min(P 1 ，P 2 )；
Wherein, the liquid crystal display device comprises a liquid crystal display device,
P safety value against internal pressure Is an internal pressure resistant safety value, and the unit is MPa;
P internal pressure resistance of sleeve The internal pressure resistance strength of the sleeve is expressed in MPa;
to allow an anti-internal pressure safety factor, the minimum value is 1.2;
P 2 ＝P wellhead bearing ×80％；
P Wellhead bearing Bearing pressure for the wellhead, and the unit is MPa.
Preferably, the method for obtaining the required density of the weight-increasing protection liquid and the injection liquid according to the pressure difference between the maximum bearing pressure of the sleeve and the internal pressure-resistant safety value of the sleeve comprises the following steps:
acquiring a required pressure difference according to the maximum pressure bearing and internal pressure resistance safety value of the sleeve;
acquiring the density of the weight-added protective liquid according to the required pressure difference;
and obtaining the annular volume of the oil sleeve according to the sizes of the sleeve and the oil pipe, and obtaining the injection amount of the weighted protection liquid according to the annular volume of the oil sleeve.
Preferably, the required differential pressure is obtained according to the following formula:
P demand for ＝P Maximum bearing of sleeve -P Safety value of internal pressure resistance of sleeve ；
Wherein, the liquid crystal display device comprises a liquid crystal display device,
P demand for The unit is MPa for the pressure difference required;
P sleeve pipe is the mostLarge bearing pressure The unit is MPa for the maximum bearing of the sleeve;
P safety value of internal pressure resistance of sleeve Is the internal pressure resistant safety value of the sleeve, and the unit is MPa.
Preferably, the density ρ of the protective liquid is emphasized Weighting protective liquid The method is obtained according to the following formula:
wherein:
ρ weighting protective liquid To increase the density of the protective liquid, the unit is kg/m 3 ；
P Demand for The unit is MPa for the pressure difference required;
h depth of middle part of reservoir of this well The depth of the middle part of the reservoir of the well is m;
g is gravity acceleration, and the unit is m/s 2 。
Preferably, the amount of the added protecting liquid is obtained according to the following formula:
Q injection liquid amount ＝π((d Inside diameter of sleeve /2) 2 -(d External diameter of oil pipe /2) 2 )h Depth of middle part of reservoir of this well ；
Wherein:
Q injection liquid amount For the injection amount, the unit is m 3 ；
d Inside diameter of sleeve The diameter of the inner part of the sleeve is m;
d external diameter of oil pipe The unit is m, which is the outer diameter of the oil pipe;
h depth of middle part of reservoir of this well The depth of the middle part of the reservoir of the well is expressed as m.
The invention also provides a deep well and ultra-deep well fracturing casing protection operation flow, which adopts the deep well and ultra-deep well fracturing casing protection method and comprises the following operation steps:
acquiring the annular volume of the oil sleeve according to the size of the oil sleeve;
preparing a required weight-increasing protective liquid according to a preset proportion of the injection liquid;
before injection, opening a sleeve valve to enable oil pipe and oil sleeve annular liquid to return to the ground;
opening an oil pipe valve, and slowly injecting the prepared weighted protection liquid from the oil pipe at a constant speed v;
slowly adjusting the sleeve valve at a constant speed until the sleeve pressure is kept stable;
stopping injection after the injected liquid reaches the designed liquid amount;
switching and injecting fracturing fluid to jack the weighted protection fluid in the oil pipe into an oil sleeve annulus, and stopping displacement after the density of the fluid returned from the side wings of the sleeve is equal to that of the weighted protection fluid;
the sleeve valve is closed.
Preferably, the constant velocity v is in the range of 0.8-1.0m 3 And/min, during the period of injecting the weighted protection liquid, the bottom hole pressure is always kept to be less than or equal to the formation fracture pressure.
Preferably, the preset ratio is that the ratio of the injection liquid amount to the required weight-increasing protection liquid is 1:1.2.
Compared with the prior art, the invention has the following beneficial effects:
1. the protection method and the operation flow adopt an annulus weighting mode, so that a large amount of safe construction space can be reserved for protecting the oil pipe fracturing sleeve of the deep well and the ultra-deep well, the sleeve pressure change can be reflected in real time in the fracturing process, and a basis is provided for timely diagnosing the fracturing construction working condition and dynamically adjusting the fracturing construction parameters.
2. The construction procedure provided by the protection method and the operation flow of the invention is simple and convenient to operate, greatly reduces construction difficulty and risk, avoids the operation flows of well killing, pipe lifting and the like, and provides convenience for later oil testing operation.
3. The protection method of the invention has the advantages of less required parameters when the injection liquid amount is obtained, convenient calculation and simple operation, and compared with the method for sealing the upper oil sleeve annulus of the target layer by the packer, the packer material, the running cost and the construction time can be saved (the single well cost is saved by about 10 ten thousand yuan, the single well construction time is saved by about 3 hours), and the fracturing efficiency is improved by 25 percent as a whole. Therefore, the protection method and the operation flow of the invention can guide the safe, economical and efficient reconstruction of deep wells and ultra-deep wells, and provide reference significance for protecting the oil pipe fracturing sleeve of high-pressure wells such as land deep wells and ultra-deep wells.
4. The method comprises the steps of combining the pump stopping pressure gradient of the adjacent well of the block, the fracturing data of the test of the well and the fracturing construction parameters to obtain the maximum bearing pressure of the sleeve, calculating the internal pressure resisting safety value of the sleeve by combining the internal pressure resisting strength of the sleeve and the well mouth bearing limit value, and obtaining the reasonable annulus weighting protection liquid density according to the maximum bearing pressure of the sleeve and the pressure difference of the internal pressure resisting safety value so as to protect the fracturing sleeve.
Drawings
FIG. 1 is a schematic diagram of an upper oil casing annulus of a packer-seal purpose in the prior art.
Fig. 2 is a flow chart of a deep well and ultra-deep well fracturing casing protection method according to an embodiment of the invention.
FIG. 3 is a schematic illustration of an oil casing annulus weighting fluid protection casing according to one embodiment of the present invention.
FIG. 4 is a flow chart of the operation of the oil casing annulus weighting fluid protection casing according to one embodiment of the present invention.
Marked in the figure as:
1. an oil pipe valve; 2. a sleeve valve; 3. a surface layer sleeve; 4. oil technical sleeve annulus; 5. a technical sleeve; 6. a reservoir sleeve; 7. a packer; 8. an oil pipe; 9. the oil jacket annulus.
Detailed Description
The following describes the embodiments of the present invention in detail with reference to the drawings.
The invention provides a deep well and ultra-deep well fracturing sleeve protection method, which comprises the following steps:
collecting reservoir physical properties, fracturing pipe columns and relevant parameters of fracturing construction, wherein the relevant parameters comprise depth of the middle part of a reservoir, tensile strength of rock, size of a sleeve, internal pressure resistance of the sleeve, wellhead bearing capacity, construction displacement and sand-liquid ratio, and closing pressure gradient or zone reservoir pump stopping pressure gradient obtained during testing fracturing;
obtaining the maximum bearing pressure of the casing according to the stratum fracture pressure, the liquid column pressure and the tube side friction resistance of the target interval;
according to the casing internal pressure resistance intensity of the well bore, combining the casing pressure resistance safety coefficient and wellhead pressure bearing capacity to obtain a casing internal pressure resistance safety value;
acquiring the density of the required weight-increasing protective liquid according to the pressure difference between the maximum bearing pressure of the sleeve and the internal pressure resistance safety value of the sleeve, and calculating the injection liquid amount;
and (3) determining the liquid preparation amount according to the injection amount in proportion, and injecting the weighted protection liquid with the volume being the liquid preparation amount into the oil pipe at a constant speed.
According to one embodiment of the invention, the maximum bearing pressure of the bushing is obtained by the following formula:
P maximum bearing of sleeve ＝P Formation fracture pressure +P Tube side friction resistance -P Liquid column pressure ；
P Maximum bearing of sleeve The unit is MPa for the maximum bearing of the sleeve;
P tube side friction resistance The friction is the tube side friction, the unit is MPa, and the friction is obtained according to the following formula:
P tube side friction resistance ＝3451.2e -a ×Q 1.8 ×h Depth of middle part of reservoir of this well ；
Wherein, the liquid crystal display device comprises a liquid crystal display device,
h depth of middle part of reservoir of this well The depth of the middle part of the reservoir of the well is m;
a＝2.05-0.93/Q-0.0055C p -0.59；
q is construction displacement, the unit is m 3 /min；
C p Is sand-liquid ratio;
P liquid column pressure Is liquid column pressure, MPa, obtained according to the following formula:
P liquid column pressure ＝ρgh Depth of middle part of reservoir of this well ；
Wherein, the liquid crystal display device comprises a liquid crystal display device,
ρ is the density of the liquid column in kg/m 3 ；
g is gravity acceleration, and the unit is m/s 2 ；
P Formation fracture pressure For the formation fracture pressure to be high,the unit is MPa, and is obtained according to the following formula;
P formation fracture pressure ＝P Predicting closure pressure +τ Tensile strength of ；
Wherein, the liquid crystal display device comprises a liquid crystal display device,
τ tensile strength of Tensile strength in MPa;
P predicting closure pressure In order to predict the closing pressure, the unit is MPa, and if the test fracturing is performed, the closing pressure is obtained according to the test fracturing data analysis;
if the test fracturing is not performed, obtaining according to the pump stopping pressure gradient of the adjacent well of the block by the following formula:
P predicting closure pressure ＝P Predicting pump down pressure -P Additional of +P Liquid column pressure ，
Wherein, the liquid crystal display device comprises a liquid crystal display device,
P additional of For additional pressure, the unit is MPa, and the value range is as follows: 3-8 MPa;
P liquid column pressure The liquid column pressure is expressed in MPa:
ρ is the density of the liquid column in kg/m 3 ；
g is gravity acceleration, and the unit is m/s 2 ；
h Depth of middle part of reservoir of this well The depth of the middle part of the reservoir of the well is m;
P predicting pump down pressure For predicting the pump down pressure, in MPa, the calculation is performed according to the following formula:
P predicting pump down pressure ＝μ Block adjacent well pump-down pressure gradient ×h Depth of middle part of reservoir of this well ；
μ Block adjacent well pump-down pressure gradient The pressure gradient of the adjacent well shut-in of the block is expressed in MPa/m, and is calculated according to the following formula:
wherein, the liquid crystal display device comprises a liquid crystal display device,
P pressure of stopping pump of adjacent well The pump pressure is stopped for the adjacent well,the unit is MPa;
P hydrostatic column pressure in adjacent well The unit is MPa for hydrostatic column pressure of an adjacent well;
h depth of middle of adjacent well reservoir The depth of the middle part of the adjacent well reservoir is expressed as m.
According to one embodiment of the invention, the internal pressure safety value of the casing is obtained by the following formula:
P safety value against internal pressure ＝min(P 1 ，P 2 )；
Wherein, the liquid crystal display device comprises a liquid crystal display device,
P safety value against internal pressure Is an internal pressure resistant safety value, and the unit is MPa;
P internal pressure resistance of sleeve The internal pressure resistance strength of the sleeve is expressed in MPa;
to allow an anti-internal pressure safety factor, the minimum value is 1.2;
P 2 ＝P wellhead bearing ×80％；
P Wellhead bearing Bearing pressure for the wellhead, and the unit is MPa.
According to one embodiment of the invention, the method for obtaining the required density of the weight-gaining protection liquid and the injection liquid according to the pressure difference between the maximum bearing pressure of the sleeve and the internal pressure-resisting safety value of the sleeve comprises the following steps:
acquiring a required pressure difference according to the maximum pressure bearing and internal pressure resistance safety value of the sleeve;
acquiring the density of the weight-added protective liquid according to the required pressure difference;
and obtaining the annular volume of the oil sleeve according to the sizes of the sleeve and the oil pipe, and obtaining the injection amount of the weighted protection liquid according to the annular volume of the oil sleeve.
According to one embodiment of the invention, the required differential pressure is obtained according to the following formula:
P demand for ＝P Maximum bearing of sleeve -P Safety value of internal pressure resistance of sleeve ；
Wherein, the liquid crystal display device comprises a liquid crystal display device,
P demand for The unit is MPa for the pressure difference required;
P maximum bearing of sleeve The unit is MPa for the maximum bearing of the sleeve;
P safety value of internal pressure resistance of sleeve Is the internal pressure resistant safety value of the sleeve, and the unit is MPa.
According to one embodiment of the invention, the density ρ of the protective liquid is emphasized Weighting protective liquid The method is obtained according to the following formula:
wherein:
ρ weighting protective liquid To increase the density of the protective liquid, the unit is kg/m 3 ；
P Demand for The unit is MPa for the pressure difference required;
h depth of middle part of reservoir of this well The depth of the middle part of the reservoir of the well is m;
g is gravity acceleration, and the unit is m/s 2 。
According to one embodiment of the present invention, the amount of the added protecting liquid is obtained according to the following formula:
Q injection liquid amount ＝π((d Inside diameter of sleeve /2) 2 -(d External diameter of oil pipe /2) 2 )h Depth of middle part of reservoir of this well ；
Wherein:
Q injection liquid amount For the injection amount, the unit is m 3 ；
d Inside diameter of sleeve The diameter of the inner part of the sleeve is m;
d external diameter of oil pipe The unit is m, which is the outer diameter of the oil pipe;
h depth of middle part of reservoir of this well The depth of the middle part of the reservoir of the well is expressed as m.
The invention also provides a deep well and ultra-deep well fracturing casing protection operation flow, which adopts the deep well and ultra-deep well fracturing casing protection method and comprises the following operation steps:
acquiring the annular volume of the oil sleeve according to the size of the oil sleeve;
preparing a required weight-increasing protective liquid according to a preset proportion of the injection liquid;
before injection, opening a sleeve valve to enable oil pipe and oil sleeve annular liquid to return to the ground;
opening an oil pipe valve, and slowly injecting the prepared weighted protection liquid from the oil pipe at a constant speed v;
slowly adjusting the sleeve valve at a constant speed until the sleeve pressure is kept stable;
stopping injection after the injected liquid reaches the designed liquid amount;
switching and injecting fracturing fluid to jack the weighted protection fluid in the oil pipe into an oil sleeve annulus, and stopping displacement after the density of the fluid returned from the side wings of the sleeve is equal to that of the weighted protection fluid;
and closing the sleeve valve and starting the fracturing construction operation.
According to one embodiment of the invention, the constant velocity v takes a value in the range of 0.8-1.0m 3 And/min, during the period of injecting the weighted protection liquid, the bottom hole pressure is always kept to be less than or equal to the formation fracture pressure.
According to one embodiment of the invention, the predetermined ratio is such that the ratio of the amount of injection to the desired weight protection liquid is 1:1.2.
Example 1
The method for protecting the fracturing sleeve of the deep well and the ultra-deep well is described in detail below by taking a certain oil field south-edge deep exploratory well Gao Quan well as an example.
1) Collecting required key parameter values: h is a Depth of middle part of reservoir of this well 6055m, τ Tensile strength of 8.0-10.0 MPa, 9.0MPa; by 7 5 8' tieback sleeve, 15.11mm wall thickness, steel grade TP140V, internal pressure resistance strength 125.2MPa, wellhead bearing 140MPa, construction discharge capacity 4.5m 3 And/min, sand-liquid ratio is 0.05, and the fracturing is tested by the well to obtain a closed fracturing gradient of 0.023MPa/m.
2) The maximum bearing pressure of the sleeve is obtained according to the following formula:
P maximum bearing of sleeve ＝P Formation fracture pressure +P Tube side friction resistance -P Liquid column pressure ；
P Predicting closure pressure : according to the test fracturing closing pressure gradient, predicting a closing pressure of 140.0MPa;
calculation of P Formation fracture pressure ：149.0MPa，P Liquid column pressure ：60.0MPa，P Tube side friction resistance ：28.0MPa
Finally obtain P Maximum bearing of sleeve ＝117.0MPa
3) The internal pressure resistance safety value is obtained according to the following formula:
P safety value against internal pressure ＝min(P 1 ，P 2 )；
Wherein, the liquid crystal display device comprises a liquid crystal display device,
P 2 ＝P wellhead bearing ×80％＝112.0MPa；
Finally obtaining the internal pressure resistant safety value P Safety value against internal pressure ＝104.3MPa。
4) Obtaining the density rho of the weight-increasing protective liquid Weighting protective liquid ：
Obtaining a required pressure difference P according to the maximum pressure bearing and internal pressure resistance safety value Demand for ；P Demand for ＝12.7MPa；
Acquiring the density rho of the weighted protection liquid according to the pressure difference of the demand Weighting protective liquid ；
Final acquisition of ρ Weighting protective liquid ＝1.2g/cm 3
Acquiring the annular volume of the oil sleeve according to the size of the oil sleeve, and acquiring the injection quantity Q of the weighted protection liquid according to the annular volume of the oil sleeve Injection liquid amount 。
Calculating the injection liquid amount according to the internal diameter= 81.74mm of the sleeve and the external diameter= 46.23mm of the oil pipe to obtain Q Injection liquid amount ＝86.4m 3 ；
And (3) determining the liquid preparation amount according to the injection amount in proportion, and injecting the weighted protection liquid with the volume being the liquid preparation amount into the oil pipe at a constant speed.
Example 2
The density ρ of the weighted protection liquid determined according to the protection method in embodiment 1 of the present invention Weighting protective liquid Injection liquid amount Q Injection liquid amount 104m is obtained according to the proportion of 1:1.2 3 Liquid preparation, at 104m 3 The density of the weight-added protection liquid required by the liquid preparation amount configuration is ρ Weighting protective liquid ＝1.2g/cm 3 Weighting the protective liquid; the injection speed is 0.8-1.0m 3 /min；
Opening a sleeve valve 2 before filling the weighting protection liquid;
enabling liquid in the oil pipe and the oil sleeve annulus to return to the ground;
then opening the oil pipe valve 1;
will be configured ρ Weighting protective liquid ＝1.2g/cm 3 From tubing at 0.8-1.0m 3 Slow injection at a rate of/min;
slowly adjusting the sleeve valve 2 at a constant speed until the sleeve pressure is stable;
the amount of liquid to be injected reaches 86.4m 3 Stopping injection;
switching injection fracturing fluid to jack the weighted protection fluid in the oil pipe into an oil sleeve annulus, and stopping displacement after the wellhead returns out of the weighted protection fluid;
and closing the sleeve valve 2 and starting the fracturing construction operation.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention are included in the protection scope of the present invention.
Claims (10)
1. The deep well and ultra-deep well fracturing casing protection method is characterized by comprising the following steps of:
collecting reservoir physical properties, fracturing pipe columns and relevant parameters of fracturing construction, wherein the relevant parameters comprise depth of the middle part of a reservoir, tensile strength of rock, size of a sleeve, internal pressure resistance of the sleeve, wellhead bearing capacity, construction displacement and sand-liquid ratio, and closing pressure gradient or zone reservoir pump stopping pressure gradient obtained during testing fracturing;
obtaining the maximum bearing pressure of the casing according to the stratum fracture pressure, the liquid column pressure and the tube side friction resistance of the target interval;
according to the casing internal pressure resistance intensity of the well bore, combining the casing pressure resistance safety coefficient and wellhead pressure bearing capacity to obtain a casing internal pressure resistance safety value;
acquiring the density of the required weight-increasing protective liquid according to the pressure difference between the maximum bearing pressure of the sleeve and the internal pressure resistance safety value of the sleeve, and calculating the injection liquid amount;
and (3) determining the liquid preparation amount according to the injection amount in proportion, and injecting the weighted protection liquid with the volume being the liquid preparation amount into the oil pipe at a constant speed.
2. The method for protecting a fracturing sleeve of a deep well and an ultra-deep well according to claim 1, wherein the maximum bearing pressure of the sleeve is obtained by the following formula:
P maximum bearing of sleeve ＝P Formation fracture pressure +P Tube side friction resistance -P Liquid column pressure ；
Wherein, the liquid crystal display device comprises a liquid crystal display device,
P maximum bearing of sleeve The unit is MPa for the maximum bearing of the sleeve;
P tube side friction resistance The friction is the tube side friction, the unit is MPa, and the friction is obtained according to the following formula:
P tube side friction resistance ＝3451.2e -a ×Q 1.8 ×h Depth of middle part of reservoir of this well ；
Wherein, the liquid crystal display device comprises a liquid crystal display device,
h depth of middle part of reservoir of this well The depth of the middle part of the reservoir of the well is m;
a＝2.05-0.93/Q-0.0055C p -0.59；
q is construction displacement, the unit is m 3 /min；
C p Is sand-liquid ratio;
P liquid column pressure Is liquid column pressure, in MPa, obtained according to the formula:
P liquid column pressure ＝ρgh Depth of middle part of reservoir of this well ；
Wherein, the liquid crystal display device comprises a liquid crystal display device,
ρ is the density of the liquid column in kg/m 3 ；
g is gravity acceleration, and the unit is m/s 2 ；
P Formation fracture pressure The fracture pressure of the stratum is expressed in MPa, and is obtained according to the following formula;
P formation fracture pressure ＝P Predicting closure pressure +τ Tensile strength of ；
Wherein, the liquid crystal display device comprises a liquid crystal display device,
τ tensile strength of Tensile strength in MPa;
P predicting closure pressure In order to predict the closing pressure, the unit is MPa, and if the test fracturing is performed, the closing pressure is obtained according to the test fracturing data analysis;
if the test fracturing is not performed, obtaining according to the pump stopping pressure gradient of the adjacent well of the block by the following formula:
P predicting closure pressure ＝P Predicting pump down pressure -P Additional of +P Liquid column pressure ，
Wherein, the liquid crystal display device comprises a liquid crystal display device,
P additional of For additional pressure, the unit is MPa, and the value range is as follows: 3-8 MPa;
P liquid column pressure The liquid column pressure is expressed in MPa:
P predicting pump down pressure For predicting the pump down pressure, in MPa, the calculation is performed according to the following formula:
P predicting pump down pressure ＝μ Block adjacent well pump-down pressure gradient ×h Depth of middle part of reservoir of this well ；
μ Block adjacent well pump-down pressure gradient The pressure gradient of the adjacent well shut-in of the block is expressed in MPa/m, and is calculated according to the following formula:
wherein, the liquid crystal display device comprises a liquid crystal display device,
P pressure of stopping pump of adjacent well Stopping pumping pressure for an adjacent well, wherein the unit is MPa;
P hydrostatic column pressure in adjacent well The unit is MPa for hydrostatic column pressure of an adjacent well;
h depth of middle of adjacent well reservoir The depth of the middle part of the adjacent well reservoir is expressed as m.
3. The deep well and ultra-deep well fracturing casing protection method according to claim 1, wherein the casing internal pressure resistance safety value is obtained by the following formula:
P safety value against internal pressure ＝min(P 1 ，P 2 )；
Wherein, the liquid crystal display device comprises a liquid crystal display device,
P safety value against internal pressure Is an internal pressure resistant safety value, and the unit is MPa;
P internal pressure resistance of sleeve The internal pressure resistance strength of the sleeve is expressed in MPa;
to allow an anti-internal pressure safety factor, the minimum value is 1.2;
P 2 ＝P wellhead bearing ×80％；
P Wellhead bearing Bearing pressure for the wellhead and MPa.
4. The method for protecting a fracturing casing of a deep well or an ultra-deep well according to claim 1, wherein the step of obtaining the required density of the weighted protection fluid and the injection fluid according to the pressure difference between the maximum bearing pressure of the casing and the internal pressure-resistant safety value of the casing comprises the following steps:
acquiring a required pressure difference according to the maximum pressure bearing and internal pressure resistance safety value of the sleeve;
acquiring the density of the weight-added protective liquid according to the required pressure difference;
and obtaining the annular volume of the oil sleeve according to the sizes of the sleeve and the oil pipe, and obtaining the injection amount of the weighted protection liquid according to the annular volume of the oil sleeve.
5. The method for protecting a fracturing casing of a deep well or an ultra-deep well according to claim 4, wherein the required pressure difference is obtained according to the following formula:
P demand for ＝P Maximum bearing of sleeve -P Safety value of internal pressure resistance of sleeve ；
Wherein, the liquid crystal display device comprises a liquid crystal display device,
P demand for The unit is MPa for the pressure difference required;
P maximum bearing of sleeve The unit is MPa for the maximum bearing of the sleeve;
P safety value of internal pressure resistance of sleeve Is the internal pressure resistant safety value of the sleeve, and the unit is MPa.
6. The method for protecting a fracturing sleeve of a deep well and an ultra-deep well according to claim 4, wherein the density ρ of the protecting liquid is increased Weighting protective liquid The method is obtained according to the following formula:
wherein:
ρ weighting protective liquid To increase the density of the protective liquid, the unit is kg/m 3 ；
P Demand for The unit is MPa for the pressure difference required;
h depth of middle part of reservoir of this well The depth of the middle part of the reservoir of the well is m;
g is gravity acceleration, and the unit is m/s 2 。
7. The method for protecting a fracturing casing of a deep well and an ultra-deep well according to claim 4, wherein the amount of the added protecting fluid is obtained according to the following formula:
Q injection liquid amount ＝π((d Inside diameter of sleeve /2) 2 -(d External diameter of oil pipe /2) 2 )h Depth of middle part of reservoir of this well ；
Wherein:
Q injection liquid amount For the injection amount, the unit is m 3 ；
d Inside diameter of sleeve The diameter of the inner part of the sleeve is m;
d external diameter of oil pipe The unit is m, which is the outer diameter of the oil pipe;
h depth of middle part of reservoir of this well The depth of the middle part of the reservoir of the well is expressed as m.
8. A deep well and ultra-deep well fracturing casing protection operation flow, which is characterized in that the method of claim 1 is adopted, and comprises the following operation steps:
acquiring the annular volume of the oil sleeve according to the size of the oil sleeve;
preparing a weight-increasing protective liquid with the volume being the liquid preparation amount according to the preset proportion of the injection liquid amount;
before injection, opening a sleeve valve to enable oil pipe and oil sleeve annular liquid to return to the ground;
opening an oil pipe valve, and slowly injecting the prepared weighted protection liquid from the oil pipe at a constant speed v;
slowly adjusting the sleeve valve at a constant speed until the sleeve pressure is kept stable;
stopping injection after the injected liquid reaches the designed liquid amount;
switching and injecting fracturing fluid, pushing the weighted protection fluid in the oil pipe into an oil sleeve annulus, and stopping displacement after the density of the returned fluid of the sleeve flank is equal to that of the weighted protection fluid;
the sleeve valve is closed.
9. The deep well and ultra-deep well fracturing casing protection operation procedure according to claim 8, wherein the constant velocity v takes a value in the range of 0.8-1.0m 3 And/min, always keeping the bottom hole pressure less than or equal to the formation fracture pressure during the period of injecting the weighted protection liquid。
10. The flow of claim 8, wherein the predetermined ratio is a ratio of injection fluid to backup fluid of 1:1.2.
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| WO2004038164A2 (en) * | 2002-09-12 | 2004-05-06 | M-I L.L.C. | Remediation treatment of sustained casing pressures (scp) in wells with top down surface injection of fluids and additives |
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| CN104265215A (en) * | 2014-09-25 | 2015-01-07 | 西南石油大学 | Method for reducing kill casing pressure by using well site reserve mud |
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