CN105003239A - Offshore fractured horizontal well post-fracture effectiveness evaluation method - Google Patents

Abstract

The present invention discloses an offshore fractured horizontal well post-fracture effectiveness evaluation method. The method comprises establishing a matrix linear flow equation; calculating an initial fracture half-fracture length and an initial fracture gap according to the established matrix linear flow equation; establishing a numerical model based on the calculated initial fracture half-fracture length and the initial fracture gap; and fitting a daily gas production and a cumulative gas production through numerical simulation based on the established numerical model, and adjusting the initial fracture half-fracture length and the initial fracture gap according to the fitting result, so as to realize complete fitting. Through the above technical scheme, an evaluation method which combines a horizontal well multiple fracture analytic model and a horizontal well multiple fracture numerical simulation is provided, and multiplicity of the numerical model can be avoided while the accuracy of an analytic solution can be raised.

Description

Effect evaluation method after marine pressure break horizontal well pressure

Technical field

The present invention relates to the technical field of production fluid from well, particularly, relate to the rear effect evaluation method of a kind of marine pressure break horizontal well pressure.

Background technology

Marine fracturing technique is the key of marine Low-permeability Gas Reservoirs success or not, and whether pressing crack construction reaches designing requirement direct relation pressure break well yield.But pressing crack construction to be evaluated accurately whether reach designing requirement and provide foundation for later stage production forecast, a set of perfect pressure Post-assessment Method just need be provided.How to address these problems, be that can the application of marine pressure break obtain successful key.

Begin one's study the eighties in 20th century fracturing yield increasing renovation technique of horizontal well both at home and abroad.The conventional means of asking for of fracture parameters of fractured horizontal wells have micro-seismic monitoring and net pressure matching reverse formation fracture parameter, microseismic is the nearly 20 years geophysics new technologies occurred, its Basic practice be by well or ground configuration wave detector to receive in crack initiation process produce small seismic events, by asking for the parameters such as microseism hypocentral location to the inverting of these events, but marine pressure break horizontal well cannot carry out layout wave detector, so microseismic cannot at sea be implemented; Net pressure matching is mainly by carrying out matching obtain fracture parameters to producing net pressure data in pressing crack construction, it is poor that the method obtains fracture parameters reliability, after pressure, well testing needs to carry out special Well Test Design, namely to carry out closing well, drive a well operation, and need special oil well test instruments, history matching for production adopts numerical simulation technology, it therefore can not be avoided to have multi-solution, therefore cannot obtain unique solution when inverting fracture parameters.

For the problems referred to above, in prior art, there is no good solution.

Summary of the invention

The object of this invention is to provide a kind of method, the method can avoid multiple cracking horizontal well numerical simulation to solve the multi-solution of fracture parameters, and the accuracy also making multiple cracking horizontal well analytic modell analytical model solve fracture parameters is improved.

To achieve these goals, the invention provides the rear effect evaluation method of a kind of marine pressure break horizontal well pressure, the method comprises: set up matrix linear flow equation; Incipient crack dummy joint length and initial kerf spacing is calculated according to set up matrix linear flow equation; Numerical model is set up based on the described incipient crack dummy joint length calculated and described initial kerf spacing; And based on set up numerical model, by numerical simulation, matching is carried out to daily output tolerance and cumulative gas production, and adjust the long and described initial kerf spacing of described incipient crack dummy joint to realize complete matching according to fitting result.

Further, the method also comprises: the flowing stage determining vertical lap seam horizontal gas well; And when determining that described flowing stage is the pseudo-linear stream stage, set up described matrix linear flow equation.

Further, the method comprises: determine described flowing stage according to gas reservoir pressure and gas reservoir differential of pressure curve; And when the slope of described gas reservoir differential of pressure curve is 0.5, determine that described flowing stage is the pseudo-linear stream stage.

Further, the matrix linear flow equation set up is:

$\frac{m\left(p_i\right)-m\left(p_{\mathrm{wf}}\right)}{q_g}=m_1\sqrt{t}$

Wherein m ₁for the pseudo-linear stream stage with t ^0.5slope of a curve.

Further, described numerical model is the topographic map of mark crack location, crack dummy joint length and kerf spacing.

Further, described incipient crack dummy joint is calculated by following equation long:

$x_f=\frac{A_{\mathrm{cm}}}{4h{n}_f}$

Wherein, A _cmfor crack seam length direction section area, h is high for stitching, n _ffor seam number.

Further, described initial kerf spacing is calculated by following equation:

$x_s=\sqrt{\frac{32k{t}_e}{11455\mathrm{\φ}{u}_g{c}_t}}$

Wherein, t _efor the pseudo-linear stream stage is to the time of intending flex point place when quasi-stable state flowing changes, k is fractured interval matrix permeability, and φ is fractured interval degree of porosity, u _gfor gas viscosity coefficient, c _tfor fractured interval rock compressibility.

Pass through technique scheme, provide evaluation method horizontal well multiple cracking analytic modell analytical model and horizontal well multiple cracking numerical simulation combined, said method can avoid the multi-solution of digital-to-analogue can improve again the accuracy of analytic solutions, the method resolves Production development data tentatively to ask for fracture parameters, and recycling numerical simulation technology is verified the result obtained and revises.Because the method is the Production development data reverse formation fracture parameter utilizing producing well, the acquisition of creation data is comparatively simple, for the application at sea of the method is laid a good foundation.

Other features and advantages of the present invention are described in detail in detailed description of the invention part subsequently.

Accompanying drawing explanation

Accompanying drawing is used to provide a further understanding of the present invention, and forms a part for manual, is used from explanation the present invention, but is not construed as limiting the invention with detailed description of the invention one below.In the accompanying drawings:

Fig. 1 is effect evaluation method flow chart after the marine pressure break horizontal well pressure according to embodiment of the present invention;

Fig. 2 is the gas reservoir pressure of example and the log-log coordinate diagnosis curve of gas reservoir pressure derivative;

Fig. 3 is cumulative production according to embodiment of the present invention and the expert curve of time;

Fig. 4 is the numerical model that after the marine pressure break horizontal well pressure according to embodiment of the present invention, effect evaluation method builds; And

Fig. 5 is gas well daily output and the cumulative production matching diagram of example.

Detailed description of the invention

Below in conjunction with accompanying drawing, the specific embodiment of the present invention is described in detail.Should be understood that, detailed description of the invention described herein, only for instruction and explanation of the present invention, is not limited to the present invention.

Fig. 1 is effect evaluation method flow chart after the marine pressure break horizontal well pressure according to embodiment of the present invention.As shown in Figure 1, effect evaluation method after the marine pressure break horizontal well pressure of the one that embodiment of the present invention provides, the method comprises: S101, sets up matrix linear flow equation; S102, calculates incipient crack dummy joint length and initial kerf spacing according to set up matrix linear flow equation; S103, sets up numerical model based on the described incipient crack dummy joint length calculated and described initial kerf spacing; And S104, based on set up numerical model, by numerical simulation, matching is carried out to daily output tolerance and cumulative gas production, and adjust the long and described initial kerf spacing of described incipient crack dummy joint to realize complete matching according to fitting result.

Pass through technique scheme, provide evaluation method horizontal well multiple cracking analytic modell analytical model and horizontal well multiple cracking numerical simulation combined, said method can avoid the multi-solution of digital-to-analogue can improve again the accuracy of analytic solutions, the method resolves Production development data tentatively to ask for fracture parameters, and recycling numerical simulation technology is verified the result obtained and revises.Because the method is the Production development data reverse formation fracture parameter utilizing producing well, the acquisition of creation data is comparatively simple, for the application at sea of the method is laid a good foundation.

For vertical lap seam horizontal gas well, its flowing can be divided into double teacher:

(1) crack preserves the effective stage.When gas well drives a well, surface flow rate comes from the expansion preserving fluid in crack, and reservoir is not almost contributed, and this stage is called crack and preserves effect.

(2) the pseudo-linear stream stage.In the pseudo-linear stream stage, the fluid near crack in stratum flows to vertical fracture with linear flow pattern.Differential of pressure curve slope is 0.5.

(3) quasi-stable state flowing is intended.This stage is between pseudo-linear stream stage and compounded linear stream stage, the appearing as us and ask for SRV(and transform Domain Volume of this process) provide possibility, but when actual production, and all can there is this stage in the well of not all.The differential of pressure curve slope in this stage is 0.88.

(4) the compounded linear stream stage.In the compounded linear stream stage, fluid in formation, all vertical fractures and horizontal well act in the middle of stratum as Unified Global, and formation fluid flows to this system in linear flow mode.Pressure derivative line and pressure line are parallel to each other, and slope is close to 0.5.

(5) the pseudoradial flow stage.In the pseudoradial flow stage, the impact of pressure break horizontal well has involved whole gas-bearing formation, and now, the fluid in gas-bearing formation flows to whole system in the mode of radial flow.In reality test, could occur under the condition only having the testing time quite to grow.

Different matrix linear flow equations is had corresponding to different flowing stages.In the method for the invention, first can determining the flowing stage of vertical lap seam horizontal gas well, then when determining that described flowing stage is the pseudo-linear stream stage, setting up described matrix linear flow equation.

For the defining method of flowing stage, be described with reference to figure 2.As mentioned above, the manufacturing process of horizontal joint gas well through multiple flowing stage, may need to divide the creation data of gas well different time, determines the flowing stage residing for it before solving fracturing parameter, and this just needs to carry out Treatment Analysis to its creation data.In the method that embodiment of the present invention provides, described flowing stage can be determined according to gas reservoir pressure and gas reservoir differential of pressure curve.Wherein:

Gas reservoir pressure can be represented by following equation (1):

$m\left(\mathrm{RNP}\right)=\frac{m\left(p_i\right)-m\left(p_{\mathrm{wf}}\left(t\right)\right)}{q_g\left(t\right)}---\left(1\right)$

Wherein, p _ifor original formation pressure, p _wffor flowing bottomhole pressure (FBHP), q _gfor daily output tolerance.

Gas reservoir pressure derivative can be represented by following equation (2):

$m\left({\mathrm{RNP}}^{\′}\right)=\frac{\mathrm{dm}\left(\mathrm{RNP}\right)}{d\ln \left(t\right)}---\left(2\right)$

Wherein, p is bottom pressure, and Z is gas compressibility factor, and μ is gas viscosity coefficient.

M (RNP) and m (RNP ') curve can be made under log-log coordinate, as shown in Figure 2 according to above-mentioned equation (1) and (2).M (RNP) and m (RNP ') slope of a curve is utilized to divide fluidised form.

As shown in Figure 2, when the slope of described gas reservoir differential of pressure curve is 0.5, can determine that described flowing stage is the pseudo-linear stream stage.

It should be noted that, t _efor the pseudo-linear stream stage is to the time of intending flex point place when quasi-stable state flowing changes, can by the time point of the change (such as, being changed to about 0.88 from about 0.5) of the slope of gas reservoir differential of pressure curve.T in the embodiment shown in figure 2 _e=50 days.

When determining that flowing stage is the pseudo-linear stream stage, matrix linear flow equation can be set up, following equation (3):

$q=\frac{1}{2\mathrm{\π}\sqrt{\mathrm{\πt}}}\sqrt{\frac{\mathrm{\λ}}{3}}y---\left(3\right)$

Wherein, ye is crack dummy joint long (physical model), and Xe is horizontal wellbore length, and h is fracture height, and μ is gas viscosity coefficient.

Above-mentioned equation is set up under double porosity model, can rewrite it, obtains the equation being applicable to only have matrix flow.After rewriting, the equation (4) for matrix linear flow can be expressed as:

$\frac{m\left(p_i\right)-m\left(p_{\mathrm{wf}}\right)}{q_g}=m_1\sqrt{t}---\left(4\right)$

Wherein m ₁represent the linear flow stage with t ^0.5slope of a curve, can by setting up expert curve to m ₁ask for.Such as, by the expert curve of cumulative production (longitudinal axis) as shown in Figure 3 with the time (transverse axis), m can be obtained ₁=323.45Mpa ²day ^0.5cp ^-1(10 ⁴m ³) ^-1.Long and the initial kerf spacing of incipient crack dummy joint can be calculated establishing according to set up matrix linear flow equation, as follows:

The long X of described incipient crack dummy joint can be calculated by following equation (5) _f:

$x_f=\frac{A_{\mathrm{cm}}}{4h{n}_f}---\left(5\right)$

Wherein, A _cmfor crack seam length direction section area, h is seam high (or being called Effective thickness of formation), n _ffor seam number.

Described initial kerf spacing Xs can be calculated by following equation:

$x_s=\sqrt{\frac{32k{t}_e}{11455\mathrm{\φ}{u}_g{c}_t}}---\left(6\right)$

Wherein, t _efor the pseudo-linear stream stage is to the time of intending flex point place when quasi-stable state flowing changes, k is fractured interval matrix permeability, and φ is fractured interval degree of porosity, u _gfor gas viscosity coefficient (be same parameters with μ), c _tfor fractured interval rock compressibility.

Parameter A in above-mentioned equation _cmcan be asked for by following equation (7):

$A_{\mathrm{cm}}=f_{\mathrm{CP}}\frac{463.6T}{\sqrt{{\left(\mathrm{\φ\μ}{c}_{t}k\right)}_m}}\frac{1}{m_1}---\left(7\right)$

Wherein, $D_D=\frac{m\left(p_i\right)-m\left(p_{\mathrm{wf}}\right)}{m\left(p_i\right)},f_{\mathrm{CP}}=1-0.0852D_D-0.0857D_D^2$

In above-mentioned equation, T is fractured interval temperature, and k is fractured interval matrix permeability, c _tfor fractured interval rock compressibility, φ is fractured interval degree of porosity, and x _ffor crack dummy joint long (be same parameters with ye).

Corresponding to above-mentioned embodiment, fluid and the formation parameter of the citing of employing are as shown in table 1.

Table 1

Parameter	Value
		Original formation pressure/MPa	24
Depth of stratum/m	3300
		Horizontal section length/m	820
System compressibility c t/MPa -1	2.2×10 -4
		Matrix porosity φ	0.09
Gas viscosity u g/mPa·s	0.019
		Reservoir temperature T/ DEG C	104
Effective thickness of formation h/m	20
		Number of Fractures n f	4
Matrix permeability k/mD	0.01

In the embodiment provided above, after determining that flowing stage is the pseudo-linear stream stage, method provided by the invention can be utilized to ask for the long X of crack dummy joint by the equation provided _fwith kerf spacing X _s, as the basic data setting up numerical model.The long X of incipient crack dummy joint can be obtained _f=150m, and kerf spacing X _s=195 meters.Then can according to the long X of incipient crack dummy joint calculated _fand kerf spacing X _stopographic map marks, obtains the topographic map that mark has crack location, crack dummy joint length and kerf spacing, i.e. numerical model (as shown in Figure 4, in this model, the angle of crack and pit shaft is 90 °, and namely this crack is raphe transection).

Fig. 5 is gas well daily output and the cumulative production matching diagram of example.As shown in Figure 5, after establishing numerical model, matching can be carried out to daily output tolerance and cumulative gas production by numerical simulation, and adjust the long and described initial kerf spacing of described incipient crack dummy joint according to fitting result, final when simulated by data model to daily output tolerance and/or cumulative gas production identical with the daily output tolerance obtained in actual production and/or cumulative gas production time realize complete matching.Crack dummy joint length and kerf spacing accurately can be obtained through over-fitting.

By the method that embodiment of the present invention provides, first one group of fracture parameters (incipient crack dummy joint length and initial kerf spacing) is obtained by analytic method, then this fracture parameters is utilized to carry out setting up numerical model, numerical simulation technology is utilized to verify the fracture parameters that analytic method obtains, if this parameter energy matching production history preferably, then this parameter be required by the fracture parameters got, if not, then can finely tune it when numerical simulation, such as with unit length (0.5m, 1m, 2m, 5m etc.) respectively increasing or decreasing is carried out to incipient crack dummy joint length and initial kerf spacing.The normative reference of fine setting can be take fitting degree as benchmark.So both the parameter that analytic method obtains is revised, also mitigate the workload of numerical simulation history matching.When realizing complete matching, and kerf spacing long through over-fitting revised crack dummy joint can be exported as evaluation result.

Below the preferred embodiment of the present invention is described in detail by reference to the accompanying drawings; but; the present invention is not limited to the detail in above-mentioned embodiment; within the scope of technical conceive of the present invention; can carry out multiple simple variant to technical scheme of the present invention, these simple variant all belong to protection scope of the present invention.

It should be noted that in addition, each the concrete technical characteristic described in above-mentioned detailed description of the invention, in reconcilable situation, can be combined by any suitable mode.In order to avoid unnecessary repetition, the present invention illustrates no longer separately to various possible combination.

In addition, also can be combined between various different embodiment of the present invention, as long as it is without prejudice to thought of the present invention, it should be considered as content disclosed in this invention equally.

Claims (7)

1. an effect evaluation method after marine pressure break horizontal well pressure, it is characterized in that, the method comprises:

Set up matrix linear flow equation;

Incipient crack dummy joint length and initial kerf spacing is calculated according to set up matrix linear flow equation;

Numerical model is set up based on the described incipient crack dummy joint length calculated and described initial kerf spacing; And

Based on set up numerical model, by numerical simulation, matching is carried out to daily output tolerance and cumulative gas production, and adjust the long and described initial kerf spacing of described incipient crack dummy joint to realize complete matching according to fitting result.

2. effect evaluation method after marine pressure break horizontal well pressure according to claim 1, it is characterized in that, the method also comprises:

Determine the flowing stage of vertical lap seam horizontal gas well; And

When determining that described flowing stage is the pseudo-linear stream stage, set up described matrix linear flow equation.

3. effect evaluation method after marine pressure break horizontal well pressure according to claim 2, it is characterized in that, the method comprises:

Described flowing stage is determined according to gas reservoir pressure and gas reservoir differential of pressure curve; And

When the slope of described gas reservoir differential of pressure curve is 0.5, determine that described flowing stage is the pseudo-linear stream stage.

4. effect evaluation method after marine pressure break horizontal well pressure according to claim 2, it is characterized in that, the matrix linear flow equation set up is:

$\frac{m\left(p_i\right)-m\left(p_{\mathrm{wf}}\right)}{q_g}=m_1\sqrt{t}$

Wherein m ₁for the pseudo-linear stream stage with t ^0.5slope of a curve.

5. effect evaluation method after marine pressure break horizontal well pressure according to claim 1, is characterized in that, described numerical model is the topographic map of mark crack location, crack dummy joint length and kerf spacing.

6. effect evaluation method after marine pressure break horizontal well pressure according to claim 1, is characterized in that, calculate described incipient crack dummy joint long by following equation:

$x_f=\frac{A_{\mathrm{cm}}}{4h{n}_f}$

Wherein, A _cmfor crack seam length direction section area, h is high for stitching, n _ffor seam number.

7. effect evaluation method after marine pressure break horizontal well pressure according to claim 1, is characterized in that, calculate described initial kerf spacing by following equation:

$x_s=\sqrt{\frac{32k{t}_e}{11455\mathrm{\φ}{u}_g{c}_t}}$

Wherein, t _efor the pseudo-linear stream stage is to the time of intending flex point place when quasi-stable state flowing changes, k is fractured interval matrix permeability, and φ is fractured interval degree of porosity, u _gfor gas viscosity coefficient, c _tfor fractured interval rock compressibility.