Method and device for predicting shale transformation area based on fracturing construction data

Abstract

The invention provides a method and device for predicting the shale transformation area based on fracturing construction data. The method comprises the steps that an obtaining module obtains wellhead pressure at different sampling moments from fracturing pump stopping to fracture closing in the fracturing construction data; first fracturing fluid filtration velocities corresponding to the wellhead pressures at the different sampling moments are determined on a pre-drawn wellhead pressure-filtration velocity curve, and first fracturing fluid filtration distances corresponding to the wellhead pressures at the different sampling moments are determined on a pre-drawn wellhead pressure-filtration distance curve; and predicting the shale transformation area according to the wellhead pressure, the first fracturing fluid filtration velocity and the first fracturing fluid filtration distance at different sampling moments. The device comprises a pressure acquisition module, a speed and distance acquisition module and a transformation area calculation module. According to the method, other monitoring equipment does not need to be adopted, the field operability is high, and the prediction result has important significance on analysis of the fracturing transformation effect and optimization of fracturing construction parameters.

Description

Technical Field

[0001] The present application belongs to the technical field of oil and gas reservoir development research, and specifically relates to a method and device for predicting shale transformation area based on fracturing construction data. Background Art

[0002] my country's shale reservoirs are of many types and their structures are relatively complex, which brings challenges to the design of volume fracturing transformation technology. For different shale blocks, the transformation effects of the same volume fracturing transformation technology generally vary greatly. At present, the transformation effect of volume fracturing wells is usually evaluated by means of microseismic monitoring, G function analysis, production profile testing, fracture inversion, etc. Since these monitoring or simulation methods are affected by multiple parameters such as formations and fracturing processes, the evaluation results sometimes have large deviations, and the monitoring methods also increase the transformation costs. The post-fracturing effect evaluation results are crucial for improving the fracturing process. For a mature shale block, it is often through a lot of fracturing practical experience to continuously explore the volume fracturing transformation parameters suitable for this block, and the cost and time are relatively high.

[0003] Analyzing reservoir characteristics and transformation effects through fracturing construction data is a relatively efficient method. At present, the most widely used method in shale reservoir fracturing is the G function analysis method, which obtains the closing pressure, complexity and other results of the reformed fractures through G function analysis. For unconventional reservoirs such as shale, the seepage area is crucial to the evaluation of post-fracturing production. At present, the method of inversion of fracturing data is mostly used to obtain the reservoir seepage area, that is, the fracture area of ​​fracturing reformation. However, the fracturing data inversion method is greatly affected by the geological parameters of the reservoir. For example, when the given filtration rate is small, the fracture creation efficiency of the fracturing fluid in the calculation result will be higher, and the reformed area will be much larger than the actual value. Especially for shale reservoirs with poor compaction effect and high permeability, the influence of filtration rate on the reformation efficiency is crucial. The formation filtration rate calculated by theory is subject to many constraints, such as fracturing fluid viscosity, formation pressure coefficient, formation porosity, formation heterogeneity, formation connectivity, etc., which have a great influence on the filtration of fracturing fluid in the formation. Therefore, the rational use of fracturing data to evaluate formation filtration rate and stimulated fracture area has important guiding significance for evaluating stimulation effects and optimizing stimulation parameters. Summary of the invention

[0004] Based on the above problems, the present application proposes a method and device for predicting shale transformation area based on fracturing construction data.

[0005] In the first aspect, the present application proposes a method for predicting shale transformation area based on fracturing construction data, comprising:

[0006] Obtain the wellhead pressure at different sampling times from fracturing pump stop to fracture closure in the fracturing construction data;

[0007] Determine the first fracturing fluid filtration rate corresponding to the wellhead pressures at different sampling times on a pre-drawn wellhead pressure-filtration rate curve, and determine the first fracturing fluid filtration distance corresponding to the wellhead pressures at different sampling times on a pre-drawn wellhead pressure-filtration distance curve;

[0008] The shale transformation area is predicted according to the wellhead pressure at different sampling times, the first fracturing fluid loss velocity, and the first fracturing fluid loss distance.

[0009] The process of drawing the wellhead pressure-filtration velocity curve and the wellhead pressure-filtration distance curve includes:

[0010] Obtain the wellhead pressure at different historical sampling times before formation rupture in the fracturing construction data;

[0011] Calculating the second fracturing fluid loss rate and the second fracturing fluid loss distance at different historical sampling times according to the wellhead pressures at different historical sampling times;

[0012] With the wellhead pressure as the x-axis and the fracturing fluid loss velocity as the y-axis, a wellhead pressure-loss velocity curve is obtained by plotting the wellhead pressure and the second fracturing fluid loss velocity at different historical sampling times;

[0013] With the wellhead pressure as the x-axis and the fracturing fluid loss distance as the y-axis, a wellhead pressure-loss distance curve is drawn based on the wellhead pressure and the second fracturing fluid loss distance at different historical sampling times.

[0014] The calculating, according to the wellhead pressures at different historical sampling moments, the second fracturing fluid loss velocity and the second fracturing fluid loss distance at different historical sampling moments comprises:

[0015] Calculate the bottom hole pressure at different historical sampling moments according to the wellhead pressure at different historical sampling moments;

[0016] The second fracturing fluid loss velocity and the second fracturing fluid loss distance at different historical sampling moments are calculated according to the difference between the bottom hole pressure and the formation pore pressure.

[0017] The method of calculating the bottom hole pressure at different historical sampling moments according to the wellhead pressure at different historical sampling moments includes:

[0018] Obtain the hydrostatic column pressure, friction along the way and throttling pressure of the orifice at different historical sampling moments before the formation breaks;

[0019] The bottom hole pressure at different historical sampling times before the formation rupture is calculated based on the wellhead pressure, hydrostatic column pressure, friction along the way, and hole throttling pressure at different historical sampling times before the formation rupture.

[0020] The bottom hole pressure at different historical sampling times before the formation rupture is calculated based on the wellhead pressure, hydrostatic column pressure, friction along the way, and hole throttling pressure at different historical sampling times before the formation rupture. The calculation formula used is:

[0021] P 井底 =P 井口 -P 沿程 -P 孔眼 +P 液柱

[0022] Among them, P 井底 is the bottom hole pressure at different historical sampling times before formation rupture, P 井口 is the wellhead pressure P at different historical sampling times before formation rupture 沿程 is the friction along the way, P 沿程 =a1Q 1.8 α, a1 is the first fixed constant, Q is the pumping displacement, α is the fracturing fluid resistance reduction rate; P 孔眼 is the orifice throttling pressure, P 孔眼 =a2Q 2 , a2 is the second fixed constant, P 液柱 is the hydrostatic column pressure.

[0023] The calculating, according to the difference between the bottom hole pressure and the formation pore pressure, the second fracturing fluid loss velocity and the second fracturing fluid loss distance at different historical sampling times comprises:

[0024] According to the pumping displacement, the second fracturing fluid loss distance is obtained;

[0025] The second fracturing fluid loss rate is obtained according to the functional relationship between the first pressure difference, fracturing fluid viscosity, fracturing fluid loss distance and loss area; the first pressure difference is the difference between the bottom hole pressure and the formation pore pressure.

[0026] According to the pumping displacement, the second fracturing fluid loss distance is obtained, and the calculation formula is:

[0027]

[0028] Wherein, L(t) is the second fracturing fluid loss distance at time t, n is the total number of perforations, L1 is the hole length, and Q(t) is the pumping displacement at time t.

[0029] The functional relationship between the first pressure difference, fracturing fluid viscosity, fracturing fluid loss distance and loss area is expressed as:

[0030] v L (t)=f(μ,ΔP,L(t),A)

[0031] Among them, v L(t) is the second fracturing fluid loss rate, μ is the fracturing fluid viscosity, ΔP is the first pressure difference, L(t) is the fracturing fluid loss distance at time t, and A is the loss area. The loss area is a fixed value before the formation is broken.

[0032] The method of predicting the shale transformation area according to the wellhead pressure at different sampling times, the first fracturing fluid loss velocity, and the first fracturing fluid loss distance comprises:

[0033] Among the wellhead pressures at different sampling times from fracturing pump stop to fracture closure in the fracturing construction data, three groups of wellhead pressure data at specified time intervals are selected and recorded as the first wellhead pressure P1, the second wellhead pressure P2 and the third wellhead pressure P3, respectively. The sampling time of P1 is t1, the sampling time of P2 is t2, and the sampling time of P3 is t3;

[0034] Calculate the first wellhead pressure average value in the time period from t1 to t2 and the second wellhead pressure average value in the time period from t2 to t3 according to the three groups of wellhead pressure data;

[0035] The shale transformation area is obtained by the pre-established simultaneous equations of the first equation, the second equation, the third equation, and the fourth equation. The shale transformation area includes: the total filtration area A of the main fracture m and the total filtration area of ​​the branch seams A b ; The first equation represents the relationship between the first fracture volume reduction caused by fracture closure during the time period t1 to t2 and the first wellhead pressure P1, the second wellhead pressure P2, the rock flexibility and the total filtration area of ​​the main fracture; The second equation represents the relationship between the second fracture volume reduction caused by fracture closure during the time period t2 to t3 and the second wellhead pressure P2, the third wellhead pressure P3, the rock flexibility and the total filtration area of ​​the main fracture; The third equation represents the first filtration fluid volume V during the time period t1 to t2 L1 The average pressure of the first wellhead and the total filtration area of ​​the main fracture A m , Total filtration loss area of ​​branch seams A b , the relationship between the first fracturing fluid loss velocity and the first fracturing fluid loss distance; the fourth equation represents the second fluid loss volume V in the time period from t2 to t3 L2 The average pressure of the second wellhead and the total filtration area of ​​the main fracture A m , Total filtration loss area of ​​branch seams A b , the relationship between the first fracturing fluid loss velocity and the first fracturing fluid loss distance, wherein the first fracture volume reduction amount and the first fluid loss amount V in the time period from t1 to t2 are L1 The second fracture volume reduction is equal to the second fluid loss V during the time period from t2 to t3. L2 equal.

[0036] The first equation is:

[0037] ΔV1=c fm A m (P1-P2)

[0038] Where ΔV1 is the reduction in the first crack volume, c fm is the rock flexibility, A m is the total filtration area of ​​the main fracture, P1 is the first wellhead pressure, and P2 is the second wellhead pressure.

[0039] The second equation is:

[0040] ΔV2=c fm A m (P2-P3)

[0041] Where ΔV2 is the reduction in the volume of the second fracture, c fm is the rock flexibility, A m is the total filtration area of ​​the main fracture, P2 is the second wellhead pressure, and P3 is the third wellhead pressure.

[0042] The third equation is:

[0043]

[0044] Among them, A m is the total filtration area of ​​the main seam, v' L is the first fracturing fluid loss rate, is the average pressure of the first wellhead, L m is the first fracturing fluid loss distance, A b is the total filtration loss area of ​​the branch joint.

[0045] The fourth equation is:

[0046]

[0047] Among them, A m is the total filtration area of ​​the main seam, v' L is the first fracturing fluid loss rate, is the average pressure of the second wellhead, L m is the first fracturing fluid loss distance, A b is the total filtration loss area of ​​the branch joint.

[0048] In the second aspect, the present application proposes a device for predicting shale transformation area based on fracturing construction data, comprising:

[0049] A pressure acquisition module is used to obtain the wellhead pressure at different sampling times from fracturing pump stop to fracture closure in the fracturing construction data;

[0050] A speed and distance acquisition module, used to determine the first fracturing fluid loss velocity corresponding to the wellhead pressure at different sampling times on a pre-drawn wellhead pressure-loss velocity curve, and to determine the first fracturing fluid loss distance corresponding to the wellhead pressure at different sampling times on a pre-drawn wellhead pressure-loss distance curve;

[0051] The transformation area calculation module is used to predict the shale transformation area according to the wellhead pressure, the first fracturing fluid loss velocity, and the first fracturing fluid loss distance at different sampling times.

[0052] In a third aspect, the present application proposes an electronic device, comprising: a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the method for predicting shale transformation area based on fracturing construction data is executed.

[0053] In a fourth aspect, the present application proposes a computer-readable storage medium storing executable instructions, which, when executed, enable a processor to execute the method for predicting shale transformation area based on fracturing construction data.

[0054] Beneficial effects:

[0055] The present application proposes a method and device for predicting shale transformation area based on fracturing construction data, determining the first fracturing fluid loss velocity corresponding to the wellhead pressure at different sampling times on a pre-drawn wellhead pressure-loss velocity curve, and determining the first fracturing fluid loss distance corresponding to the wellhead pressure at different sampling times on a pre-drawn wellhead pressure-loss distance curve; predicting the shale transformation area according to the wellhead pressure at different sampling times, the first fracturing fluid loss velocity, and the first fracturing fluid loss distance. This method does not require the use of other monitoring equipment, has strong on-site operability, and the prediction results are of great significance for analyzing the fracturing transformation effect and optimizing the fracturing construction parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 A flow chart of a method for predicting shale transformation area based on fracturing construction data according to an embodiment of the present application;

[0057] Figure 2 This is a principle block diagram of a device for predicting shale transformation area based on fracturing construction data according to an embodiment of the present application. DETAILED DESCRIPTION

[0058] The present disclosure is further described below in conjunction with the embodiments shown in the accompanying drawings.

[0059] At present, the transformation effect of volume fracturing wells is usually evaluated through microseismic monitoring, G function analysis, production profile testing, fracture inversion and other means. Since these monitoring or simulation methods are affected by multiple parameters such as formation and fracturing process, the evaluation results sometimes have large deviations, and the monitoring methods also increase the transformation cost. The post-fracturing effect evaluation results are crucial for improving the fracturing process. For a mature shale block, it is often necessary to continuously explore the volume fracturing transformation parameters suitable for this block through a large amount of fracturing practical experience, which is costly and time-consuming.

[0060] The present application proposes a method and device for calculating the fracturing transformation area of ​​shale reservoirs based on fracturing construction data. The core of the method is to obtain the wellhead pressure-filtration rate curve and the wellhead pressure-filtration distance curve through the fracturing construction data before the formation rupture, and bring the wellhead pressure at different sampling times from the fracturing pump stop to the crack closure into the above curves to obtain the corresponding fracturing fluid filtration rate and fracturing fluid filtration distance. Finally, the fracturing fluid filtration area, i.e., the shale transformation area, is obtained by solving the equation group in combination with the rock flexibility. The device of this embodiment does not need to use other monitoring equipment, has strong on-site operability, abandons the G function analysis method, and the prediction results are of great significance for analyzing the fracturing transformation effect and optimizing the fracturing construction parameters.

[0061] Example:

[0062] This embodiment proposes a method for predicting shale transformation area based on fracturing construction data, such as Figure 1 As shown, including:

[0063] Step S1: obtaining the wellhead pressure at different sampling times from fracturing pump stop to fracture closure in the fracturing construction data;

[0064] Step S2: determining the first fracturing fluid filtration rate corresponding to the wellhead pressures at different sampling times on a pre-drawn wellhead pressure-filtration rate curve, and determining the first fracturing fluid filtration distance corresponding to the wellhead pressures at different sampling times on a pre-drawn wellhead pressure-filtration distance curve;

[0065] Step S3: predicting the shale transformation area according to the wellhead pressure at different sampling times, the first fracturing fluid loss velocity, and the first fracturing fluid loss distance.

[0066] In this embodiment, the method of predicting the shale transformation area by the G function analysis method is abandoned. Instead, the wellhead pressure-filtration rate curve and the wellhead pressure-filtration distance curve are pre-drawn according to the wellhead pressure at different historical sampling times before the formation rupture in the fracturing construction data. The wellhead pressure obtained from the fracturing pump stop to the crack closure is respectively brought into the wellhead pressure-filtration rate curve and the wellhead pressure-filtration distance curve. The corresponding fracturing fluid filtration rate and fracturing fluid filtration distance are obtained, and the first fracturing fluid filtration rate and the first fracturing fluid filtration distance are used to obtain the predicted shale transformation area by establishing a set of equations to solve.

[0067] The drawing process of the wellhead pressure-filtration velocity curve and the wellhead pressure-filtration distance curve includes:

[0068] Step S101: obtaining the wellhead pressure at different historical sampling times before formation rupture in the fracturing construction data;

[0069] Step S102: Calculating the second fracturing fluid loss rate and the second fracturing fluid loss distance at different historical sampling times according to the wellhead pressures at different historical sampling times, including:

[0070] Step S102.1: Calculate the bottom hole pressure at different historical sampling times according to the wellhead pressure at different historical sampling times;

[0071] Specifically: the fracturing construction data records the wellhead pressure, and the filtration rate is related to the pressure difference (i.e. the difference between the well bottom pressure and the formation pore pressure). Therefore, when calculating the filtration rate (i.e. the fracturing fluid filtration rate), the bottom hole pressure must be calculated first. Before the formation is broken, the flow friction in the fracture is zero, and the bottom hole pressure P 井底 (i.e., the fluid pressure in the perforation cluster) is mainly affected by the wellhead pressure P 井口 、Friction resistance along the wellbore P 沿程 , hole throttling pressure P 孔眼 , Well static liquid column pressure P 液柱 According to the fracturing construction data and wellbore parameters, the bottom hole pressure can be obtained by the constructed calculation formula.

[0072] Step S102.2: Calculate the second fracturing fluid loss velocity and the second fracturing fluid loss distance at different historical sampling times according to the difference between the bottom hole pressure and the formation pore pressure.

[0073] In the formation, the fracturing fluid loss is a function of the loss area A, fracturing fluid viscosity μ, pressure difference △P (i.e., the difference between the bottom hole pressure and the formation pore pressure), and loss distance L. During the multi-stage fracturing of shale gas, after the bridge plug is in place and before the fracture is initiated, all the fracturing fluid in this stage is used for loss. At this time, the fracturing fluid loss area is a constant, that is, the surface area of ​​the perforation cluster; the fracturing fluid is transmitted outward through the perforation cluster, and the loss distance can be calculated by the pore volume, the amount of pumped fluid, etc. The viscosity of the fracturing fluid is a parameter set in the construction. Therefore, the change in the loss rate can be obtained by calculating the pressure difference and loss distance at different displacement stages.

[0074] Step S103: With the wellhead pressure as the x-axis and the fracturing fluid loss velocity as the y-axis, a wellhead pressure-loss velocity curve is plotted based on the wellhead pressure and the second fracturing fluid loss velocity at different historical sampling times; with the wellhead pressure as the x-axis and the fracturing fluid loss distance as the y-axis, a wellhead pressure-loss distance curve is plotted based on the wellhead pressure and the second fracturing fluid loss distance at different historical sampling times.

[0075] Calculating the bottom hole pressure at different historical sampling times according to the wellhead pressure at different historical sampling times in step S102.1 includes:

[0076] Step S102.1.1: Obtain the hydrostatic column pressure, friction along the way and throttling pressure of the orifice at different historical sampling moments before the formation breaks;

[0077] Step S102.1.2: Based on the wellhead pressure, hydrostatic column pressure, friction along the way, and hole throttling pressure at different historical sampling times before the formation rupture, the bottom hole pressure at different historical sampling times before the formation rupture is calculated, and the calculation formula used is:

[0078] P 井底 =P 井口 -P 沿程 -P 孔眼 +P 液柱

[0079] Among them, P 井底 is the bottom hole pressure at different historical sampling times before formation rupture, P 井口 is the wellhead pressure P at different historical sampling times before formation rupture 沿程 is the friction along the way, P 沿程 =a1Q 1.8 α, a1 is the first fixed constant, Q is the pumping displacement, α is the fracturing fluid resistance reduction rate; P 孔眼 is the orifice throttling pressure, P 孔眼 =a2Q 2 , a2 is the second fixed constant, P 液柱 is the hydrostatic column pressure.

[0080] In step S102.2, according to the difference between the bottom hole pressure and the formation pore pressure, calculating the second fracturing fluid loss velocity and the second fracturing fluid loss distance at different historical sampling times includes:

[0081] Step S102.2.1: According to the pumping displacement, the second fracturing fluid loss distance is obtained, and the calculation formula is:

[0082]

[0083] Wherein, L(t) is the second fracturing fluid loss distance at time t, n is the total number of perforations, which is a constant, L1 is the hole length, which is a constant, and Q(t) is the pumping displacement at time t.

[0084] Among them, the pumping displacement Q(t) at time t is the amount of fluid loss when the fracture has not yet started, that is:

[0085] Q(t)=βv L (t)A

[0086] Where β is the perforation skin factor coefficient caused by perforation, which is a constant value; v L (t) is the second fracturing fluid loss velocity, which is the functional relationship between the first pressure difference, fracturing fluid viscosity, fracturing fluid loss distance and loss area.

[0087] Step S102.2.2: Obtain the second fracturing fluid loss rate according to the functional relationship between the first pressure difference, fracturing fluid viscosity, fracturing fluid loss distance and loss area; the first pressure difference is the difference between the bottom hole pressure and the formation pore pressure.

[0088] First, v L (t) can be expressed as:

[0089] v L (t)=f(μ,ΔP,t,A)

[0090] Where ΔP=P 井底 -P 孔隙 , that is, the first pressure difference, where P 孔隙 is the original formation pore pressure.

[0091] Before fracturing, the fracturing fluid avoids expanding outward along the hole. The time t has a corresponding relationship with the filtration distance L. By converting the time t and the filtration distance L, the filtration velocity v L Converted into a function of the filtration distance L:

[0092] After conversion, v L (t) can be expressed as: the functional relationship between the first pressure difference, fracturing fluid viscosity, fracturing fluid loss distance and loss area, the expression is:

[0093] v L (t)=f(μ,ΔP,L(t),A)

[0094] Among them, v L (t) is the second fracturing fluid loss rate, μ is the fracturing fluid viscosity, ΔP is the first pressure difference, L(t) is the fracturing fluid loss distance at time t, and A is the loss area. The loss area is a fixed value before the formation is broken.

[0095] In step S3, the general concept of predicting the shale transformation area is as follows: after the formation breaks, the cracks continue to expand far from the wellbore, and the filtration area continues to increase. However, the flow friction of the fracturing fluid and proppant in the cracks is affected by multiple factors such as the crack morphology, and the pressure in the cracks is nonlinearly distributed. Therefore, the filtration area cannot be accurately calculated at this stage. When the fracturing is completed (i.e., the pump is stopped), the fracturing fluid stops flowing. At this time, the fluid pressure in the crack is the same as the bottom hole pressure (the crack height is limited, and the influence of gravity is ignored), that is, the sum of the wellhead pressure and the static liquid column pressure in the wellbore. Due to the limited compressibility of the fracturing fluid, the compressibility of the fracturing fluid is ignored in the calculation. After stopping the pump, under the action of the bottom hole flow pressure, the liquid continues to filter out along the crack wall to the matrix rock, and the crack begins to slowly close. The reduction in the crack volume caused by the crack closure is equal to the total filtration. The shale transformation area can be obtained by calculating the filtration rate and filtration volume through the pressure change at the initial stage of crack closure.

[0096] In step S3, the specific calculation process is as follows: predicting the shale transformation area according to the wellhead pressure, the first fracturing fluid loss velocity, and the first fracturing fluid loss distance at different sampling times includes:

[0097] Step S3.1: Among the wellhead pressures at different sampling times from the time when the fracturing pump is stopped to the time when the fracture is closed in the fracturing construction data, three groups of wellhead pressure data at a specified time interval are selected and recorded as the first wellhead pressure P1, the second wellhead pressure P2 and the third wellhead pressure P3, respectively, the sampling time of P1 is t1, the sampling time of P2 is t2, and the sampling time of P3 is t3;

[0098] Step S3.2: Calculate the first wellhead pressure average value in the time period from t1 to t2 and the second wellhead pressure average value in the time period from t2 to t3 according to the three sets of wellhead pressure data;

[0099] In this embodiment, before establishing the equation group to predict the shale transformation area, it is necessary to first select the pump stop data. From the time the pump is stopped during fracturing to the time the fracture is closed, three groups of pressure data P1, P2 and P3 with shorter time intervals are selected, that is, the specified time interval is less than the preset time interval, and the corresponding times are t1, t2, and t3, respectively. It is considered that the fracture loss rate is a constant value within this time interval, and the average value of the first wellhead pressure in the time period from t1 to t2 is calculated. and the average second wellhead pressure during the period from t2 to t3 In a short period of time, the fracturing fluid loss distance is also approximately a constant value, and the main fracture loss distance is taken as L m , L m Can be approximated as V 总 A is the total volume of liquid pumped into the fracturing process; m is the total filtration area of ​​the main seam; the filtration distance of the branch seam can be expressed as L m =bL b , where b is a constant, usually 0.5, L b is the branch seam filtration distance.

[0100] Step S3.3: Obtain the shale transformation area by using the pre-established simultaneous equations of the first equation, the second equation, the third equation, and the fourth equation. The shale transformation area includes: the total filtration area A of the main fracture m and the total filtration area of ​​the branch seams A b ; The first equation represents the relationship between the first fracture volume reduction caused by fracture closure during the time period t1 to t2 and the first wellhead pressure P1, the second wellhead pressure P2, the rock flexibility and the total filtration area of ​​the main fracture; The second equation represents the relationship between the second fracture volume reduction caused by fracture closure during the time period t2 to t3 and the second wellhead pressure P2, the third wellhead pressure P3, the rock flexibility and the total filtration area of ​​the main fracture; The third equation represents the first filtration fluid volume V during the time period t1 to t2 L1 The average pressure of the first wellhead and the total filtration area of ​​the main fracture A m , Total filtration loss area of ​​branch seams A b , the relationship between the first fracturing fluid loss velocity and the first fracturing fluid loss distance; the fourth equation represents the second fluid loss volume V in the time period from t2 to t3 L2 The average pressure of the second wellhead and the total filtration area of ​​the main fracture A m , Total filtration loss area of ​​branch seams A b , the relationship between the first fracturing fluid loss velocity and the first fracturing fluid loss distance, wherein the first fracture volume reduction amount and the first fluid loss amount V in the time period from t1 to t2 are L1 The second fracture volume reduction is equal to the second fluid loss V during the time period from t2 to t3. L2 equal.

[0101] The first equation is:

[0102] ΔV1=c fm A m (P1-P2)

[0103] Where ΔV1 is the reduction in the volume of the first crack, cfm is the rock flexibility, A m is the total filtration area of ​​the main fracture, P1 is the first wellhead pressure, and P2 is the second wellhead pressure.

[0104] The second equation is:

[0105] ΔV2=c fm A m (P2-P3)

[0106] Where ΔV2 is the reduction in the volume of the second fracture, c fm is the rock flexibility, A m is the total filtration area of ​​the main fracture, P2 is the second wellhead pressure, and P3 is the third wellhead pressure.

[0107] The third equation is:

[0108]

[0109] Among them, A m is the total filtration area of ​​the main seam, v' L is the first fracturing fluid loss rate, is the average pressure of the first wellhead, L m is the first fracturing fluid loss distance, A b is the total filtration loss area of ​​the branch joint.

[0110] The fourth equation is:

[0111]

[0112] Among them, A m is the total filtration area of ​​the main seam, v' L is the first fracturing fluid loss rate, is the average pressure of the second wellhead, L m is the first fracturing fluid loss distance, A b is the total filtration loss area of ​​the branch joint.

[0113] The first, second, third and fourth equations are combined into a system of equations and solved to obtain the total filtration area A of the main seam. m And the total filtration area of ​​the branch seam A b .

[0114] In order to describe the method proposed in this embodiment in more detail, a specific example is given to illustrate how to use the method of this embodiment in practical applications.

[0115] A shale gas horizontal well X has a vertical depth of 3800.00 m, a thickness of 30.00 m, and a Young's modulus of 40.1×10 3MPa, Poisson’s ratio 0.21, horizontal stress difference in two directions 10.5 MPa, rock matrix permeability 0.001×10 -3 um 2 , porosity 5.2%, original formation pressure 55.7MPa. Volume fracturing reformation single stage 4 clusters, each cluster perforation 10, hole diameter 10mm, hole depth 80cm; single stage injection fluid volume 3000.0m 3 , liquid viscosity 20mPa·s, liquid drag reduction rate 80%, construction displacement 20.0m 3 / min; when the formation is broken, the displacement is 16.0m 3 / min, fracture wellhead pressure 101.10MPa. The method for predicting shale transformation area based on fracturing construction data proposed in this embodiment is used for calculation. The specific implementation steps are as follows:

[0116] (1) Construction displacement 2.0m 3 / min, total liquid volume 60.3m 3 When the bridge plug is set, the sealing ball is in place and the pressure after setting is 70.0MPa. The displacement is increased step by step until the formation breaks, and the fracturing construction data of each stage is recorded, including: construction displacement, pressure data and injection fluid volume data.

[0117] (2) Calculate the total lateral area of ​​the perforated holes, that is, the filtration area before rupture is 1.0048m 2 .

[0118] (3) According to the wellhead pressure at different historical sampling times before the formation rupture in the fracturing construction data, the second fracturing fluid loss rate and the second fracturing fluid loss distance at different historical sampling times are calculated. The results are shown in Table 1:

[0119] Table 1 Relationship between formation filtration rate and injection parameters

[0120]

[0121] According to Table 1, with the wellhead pressure as the x-axis and the fracturing fluid loss velocity as the y-axis, the wellhead pressure and the second fracturing fluid loss velocity at different historical sampling times are plotted to obtain the wellhead pressure-loss velocity curve; with the wellhead pressure as the x-axis and the fracturing fluid loss distance as the y-axis, the wellhead pressure and the second fracturing fluid loss distance at different historical sampling times are plotted to obtain the wellhead pressure-loss distance curve.

[0122] (4) When the total liquid volume injected is 3000m 3 The pump is stopped at this time, and the pressure when the pump is stopped is 78.2MPa.

[0123] (5) According to the G function analysis method, it is determined whether the main fracture begins to close. (In this example, the G function analysis method is only used to determine whether the main fracture begins to close, but is not used to calculate the shale improvement area). 24 minutes after the pump is stopped, the main fracture begins to close.

[0124] (6) The wellhead pressure data points were selected at 4 min, 5 min, and 6 min after the pump was stopped and before the fracture closed. The wellhead pressures were 72.1 MPa, 70.8 MPa, and 70.0 MPa, respectively.

[0125] (7) The wellhead pressure data corresponding to the selected point is found in the wellhead pressure-filtration rate curve and the wellhead pressure-filtration distance curve as the first fracturing fluid filtration rate and the first fracturing fluid filtration distance.

[0126] (8) The first, second, third and fourth equations are combined into a system of equations and solved to obtain the total filtration area of ​​the main fracture of this section of fracturing: 9.68×10 4 m 2 And the total filtration area of ​​the branch seam A b The main seam area is 4.39×10 4 m 2 .

[0127] This embodiment proposes a method for predicting shale transformation area based on fracturing construction data. First, the acquisition module obtains the wellhead pressure at different sampling times from the fracturing pump stop to the crack closure in the fracturing construction data; secondly, the first fracturing fluid loss rate corresponding to the wellhead pressure at different sampling times is determined on the pre-drawn wellhead pressure-loss rate curve, and the first fracturing fluid loss distance corresponding to the wellhead pressure at different sampling times is determined on the pre-drawn wellhead pressure-loss distance curve; finally, according to the wellhead pressure at different sampling times, the first fracturing fluid loss rate, and the first fracturing fluid loss distance, the shale transformation area is predicted. And examples are used to further prove that the method proposed in this embodiment can be effectively used in the actual fracturing process. This method does not require the use of other monitoring equipment, has strong on-site operability, and abandons the G function analysis method. The prediction results are of great significance for analyzing the fracturing transformation effect and optimizing the fracturing construction parameters.

[0128] Embodiment 2:

[0129] This embodiment proposes a device for predicting shale transformation area based on fracturing construction data, such as Figure 2 As shown, it includes: a pressure acquisition module, a speed and distance acquisition module, and a transformation area calculation module;

[0130] The pressure acquisition module is connected to the speed and distance acquisition module, and the speed and distance acquisition module is connected to the transformation area calculation module;

[0131] A pressure acquisition module is used to obtain the wellhead pressure at different sampling times from fracturing pump stop to fracture closure in the fracturing construction data;

[0132] A speed and distance acquisition module, used to determine the first fracturing fluid loss velocity corresponding to the wellhead pressure at different sampling times on a pre-drawn wellhead pressure-loss velocity curve, and to determine the first fracturing fluid loss distance corresponding to the wellhead pressure at different sampling times on a pre-drawn wellhead pressure-loss distance curve;

[0133] The transformation area calculation module is used to predict the shale transformation area according to the wellhead pressure, the first fracturing fluid loss velocity, and the first fracturing fluid loss distance at different sampling times.

[0134] The speed and distance acquisition module includes a pressure acquisition unit, a speed and distance calculation unit, and a curve drawing unit;

[0135] The pressure acquisition unit is connected to the speed and distance calculation unit, and the speed and distance calculation unit is connected to the curve drawing unit;

[0136] The force acquisition unit is used to acquire the wellhead pressure at different historical sampling moments before the formation rupture in the fracturing construction data;

[0137] The speed and distance calculation unit is used to calculate the second fracturing fluid loss speed and the second fracturing fluid loss distance at different historical sampling moments according to the wellhead pressures at different historical sampling moments;

[0138] The curve drawing unit is used to draw a wellhead pressure-filtration rate curve based on the wellhead pressure and the second fracturing fluid filtration rate at different historical sampling moments with the wellhead pressure as the x-axis and the fracturing fluid filtration rate as the y-axis; and to draw a wellhead pressure-filtration distance curve based on the wellhead pressure and the second fracturing fluid filtration distance at different historical sampling moments with the wellhead pressure as the x-axis and the fracturing fluid filtration distance as the y-axis.

[0139] This embodiment proposes a device for predicting shale transformation area based on fracturing construction data. First, a pressure acquisition module is used to obtain the wellhead pressure at different sampling times from the fracturing pump stop to the crack closure in the fracturing construction data; secondly, a speed and distance acquisition module is used to determine the first fracturing fluid loss velocity corresponding to the wellhead pressure at different sampling times on a pre-drawn wellhead pressure-loss velocity curve, and the first fracturing fluid loss distance corresponding to the wellhead pressure at different sampling times is determined on a pre-drawn wellhead pressure-loss distance curve; finally, a transformation area calculation module is used to predict the shale transformation area according to the wellhead pressure at different sampling times, the first fracturing fluid loss velocity, and the first fracturing fluid loss distance. The device of this embodiment does not need to use other monitoring equipment, has strong on-site operability, and abandons the G function analysis method. The prediction results are of great significance for analyzing the fracturing transformation effect and optimizing the fracturing construction parameters.

[0140] Embodiment 3:

[0141] This embodiment provides an electronic device, including: a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the method for predicting shale transformation area based on fracturing construction data is executed.

[0142] The electronic device may be a mobile phone, a computer or a tablet computer, etc., including a memory and a processor, wherein a computer program is stored in the memory, and when the computer program is executed by the processor, the method for predicting shale transformation area based on fracturing construction data as described in the embodiment is implemented. It is understood that the electronic device may also include an input / output (I / O) interface and a communication component.

[0143] The processor is used to execute all or part of the steps in the method for predicting shale transformation area based on fracturing construction data as described in the above embodiment. The memory is used to store various types of data, which may include instructions of any application or method in the electronic device, as well as data related to the application.

[0144] The processor can be an application specific integrated circuit (ASIC), a digital signal processor (DSP), a programmable logic device (PLD), a field programmable gate array (FPGA), a controller, a microcontroller, a microprocessor or other electronic components, and is used to execute the method for predicting shale transformation area based on fracturing construction data described in the above embodiment.

[0145] Embodiment 4:

[0146] This embodiment provides a computer-readable storage medium storing executable instructions, which, when executed, enable a processor to execute the method for predicting shale transformation area based on fracturing construction data.

[0147] If implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium.

[0148] Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes a number of instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the method for predicting shale transformation area based on fracturing construction data described in each embodiment of the present application.

[0149] The aforementioned storage media include: flash memory, hard disk, multimedia card, card-type memory (for example, SD (Secure Digital Memory Card) or DX (Memory Data Register, MDR abbreviation, memory data register) memory, etc.), random access memory (RAM), static random access memory (SRAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), programmable read-only memory (PROM), magnetic memory, disk, CD, server, APP (Application, abbreviation of application software) application mall and other media that can store program verification codes, on which a computer program is stored. When the computer program is executed by a processor, the various steps of the method for predicting shale transformation area based on fracturing construction data described above can be implemented.

[0150] The various embodiments in the present disclosure are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0151] The protection scope of the present disclosure is not limited to the above-mentioned embodiments. Obviously, those skilled in the art can make various changes and modifications to the present disclosure without departing from the scope and spirit of the present disclosure. If these changes and modifications fall within the scope of the claims of the present disclosure and their equivalents, the intention of the present disclosure also includes these changes and modifications.

Claims

1. A method for predicting shale transformation area based on fracturing construction data, characterized in that: The method comprises: Obtain the wellhead pressure at different sampling times from fracturing pump stop to fracture closure in the fracturing construction data; Determine the first fracturing fluid filtration rate corresponding to the wellhead pressures at different sampling times on a pre-drawn wellhead pressure-filtration rate curve, and determine the first fracturing fluid filtration distance corresponding to the wellhead pressures at different sampling times on a pre-drawn wellhead pressure-filtration distance curve; The shale transformation area is predicted according to the wellhead pressure at different sampling times, the first fracturing fluid loss velocity, and the first fracturing fluid loss distance.

2. The method for predicting shale transformation area based on fracturing construction data according to claim 1, characterized in that: The process of drawing the wellhead pressure-filtration velocity curve and the wellhead pressure-filtration distance curve includes: Obtain the wellhead pressure at different historical sampling times before formation rupture in the fracturing construction data; Calculating the second fracturing fluid loss rate and the second fracturing fluid loss distance at different historical sampling times according to the wellhead pressures at different historical sampling times; With the wellhead pressure as the x-axis and the fracturing fluid loss velocity as the y-axis, a wellhead pressure-loss velocity curve is obtained by plotting the wellhead pressure and the second fracturing fluid loss velocity at different historical sampling times; With the wellhead pressure as the x-axis and the fracturing fluid loss distance as the y-axis, a wellhead pressure-loss distance curve is drawn based on the wellhead pressure and the second fracturing fluid loss distance at different historical sampling times.

3. The method for predicting shale transformation area based on fracturing construction data according to claim 2, characterized in that: The calculating, according to the wellhead pressures at different historical sampling moments, the second fracturing fluid loss velocity and the second fracturing fluid loss distance at different historical sampling moments comprises: Calculate the bottom hole pressure at different historical sampling moments according to the wellhead pressure at different historical sampling moments; The second fracturing fluid loss velocity and the second fracturing fluid loss distance at different historical sampling moments are calculated according to the difference between the bottom hole pressure and the formation pore pressure.

4. The method for predicting shale transformation area based on fracturing construction data according to claim 3, characterized in that: The method of calculating the bottom hole pressure at different historical sampling moments according to the wellhead pressure at different historical sampling moments includes: Obtain the hydrostatic column pressure, friction along the way and throttling pressure of the orifice at different historical sampling moments before the formation breaks; The bottom hole pressure at different historical sampling times before the formation rupture is calculated based on the wellhead pressure, hydrostatic column pressure, friction along the way, and hole throttling pressure at different historical sampling times before the formation rupture.

5. The method for predicting shale transformation area based on fracturing construction data according to claim 4, characterized in that: The bottom hole pressure at different historical sampling times before the formation rupture is calculated based on the wellhead pressure, hydrostatic column pressure, friction along the way, and hole throttling pressure at different historical sampling times before the formation rupture. The calculation formula used is: P 井底 =P 井口 -P 沿程 -P 孔眼 +P 液柱 Among them, P 井底 is the bottom hole pressure at different historical sampling times before formation rupture, P 井口 is the wellhead pressure P at different historical sampling times before formation rupture 沿程 is the friction along the way, P 沿程 =a1Q 1.8 α, a1 is the first fixed constant, Q is the pumping displacement, α is the fracturing fluid resistance reduction rate; P 孔眼 is the orifice throttling pressure, P 孔眼 =a2Q 2 , a2 is the second fixed constant, P 液柱 is the hydrostatic column pressure.

6. The method for predicting shale transformation area based on fracturing construction data according to claim 3, characterized in that: The calculating, according to the difference between the bottom hole pressure and the formation pore pressure, the second fracturing fluid loss velocity and the second fracturing fluid loss distance at different historical sampling times comprises: According to the pumping displacement, the second fracturing fluid loss distance is obtained; The second fracturing fluid loss rate is obtained according to the functional relationship between the first pressure difference, fracturing fluid viscosity, fracturing fluid loss distance and loss area; the first pressure difference is the difference between the bottom hole pressure and the formation pore pressure.

7. The method for predicting shale transformation area based on fracturing construction data according to claim 6, characterized in that: According to the pumping displacement, the second fracturing fluid loss distance is obtained, and the calculation formula is: Wherein, L(t) is the second fracturing fluid loss distance at time t, n is the total number of perforations, L1 is the hole length, and Q(t) is the pumping displacement at time t.

8. The method for predicting shale transformation area based on fracturing construction data according to claim 6, characterized in that: The functional relationship between the first pressure difference, fracturing fluid viscosity, fracturing fluid loss distance and loss area is expressed as: v L (t)=f(μ,ΔP,L(t),A) Among them, v L (t) is the second fracturing fluid loss rate, μ is the fracturing fluid viscosity, ΔP is the first pressure difference, L(t) is the fracturing fluid loss distance at time t, and A is the loss area. The loss area is a fixed value before the formation is broken.

9. The method for predicting shale transformation area based on fracturing construction data according to claim 1, characterized in that: The method of predicting the shale transformation area according to the wellhead pressure at different sampling times, the first fracturing fluid loss velocity, and the first fracturing fluid loss distance comprises: Among the wellhead pressures at different sampling times from fracturing pump stop to fracture closure in the fracturing construction data, three groups of wellhead pressure data at specified time intervals are selected and recorded as the first wellhead pressure P1, the second wellhead pressure P2 and the third wellhead pressure P3, respectively. The sampling time of P1 is t1, the sampling time of P2 is t2, and the sampling time of P3 is t3; Calculate the first wellhead pressure average value in the time period from t1 to t2 and the second wellhead pressure average value in the time period from t2 to t3 according to the three groups of wellhead pressure data; The shale transformation area is obtained by the pre-established simultaneous equations of the first equation, the second equation, the third equation, and the fourth equation. The shale transformation area includes: the total filtration area A of the main fracture m and the total filtration area of ​​the branch seams A b ; The first equation represents the relationship between the first fracture volume reduction caused by fracture closure during the time period t1 to t2 and the first wellhead pressure P1, the second wellhead pressure P2, the rock flexibility and the total filtration area of ​​the main fracture; The second equation represents the relationship between the second fracture volume reduction caused by fracture closure during the time period t2 to t3 and the second wellhead pressure P2, the third wellhead pressure P3, the rock flexibility and the total filtration area of ​​the main fracture; The third equation represents the first filtration fluid volume V during the time period t1 to t2 L1 The average pressure of the first wellhead and the total filtration area of ​​the main fracture A m , Total filtration loss area of ​​branch seams A b , the relationship between the first fracturing fluid loss velocity and the first fracturing fluid loss distance; the fourth equation represents the second fluid loss volume V in the time period from t2 to t3 L2 The average pressure of the second wellhead and the total filtration area of ​​the main fracture A m , Total filtration loss area of ​​branch seams A b , the relationship between the first fracturing fluid loss velocity and the first fracturing fluid loss distance, wherein the first fracture volume reduction amount and the first fluid loss amount V in the time period from t1 to t2 are L1 The second fracture volume reduction is equal to the second fluid loss V during the time period from t2 to t3. L2 equal.

10. The method for predicting shale transformation area based on fracturing construction data according to claim 9, characterized in that: The first equation is: ΔV1=c fm A m (P1-P2) Where ΔV1 is the reduction in the volume of the first crack, c fm is the rock flexibility, A m is the total filtration area of ​​the main fracture, P1 is the first wellhead pressure, and P2 is the second wellhead pressure.

11. The method for predicting shale transformation area based on fracturing construction data according to claim 9, characterized in that: The second equation is: ΔV2=c fm A m (P2-P3) Where ΔV2 is the reduction in the volume of the second fracture, c fm is the rock flexibility, A m is the total filtration area of ​​the main fracture, P2 is the second wellhead pressure, and P3 is the third wellhead pressure.

12. The method for predicting shale transformation area based on fracturing construction data according to claim 9, characterized in that: The third equation is: Among them, A m is the total filtration area of ​​the main seam, v' L is the first fracturing fluid loss rate, is the average pressure of the first wellhead, L m is the first fracturing fluid loss distance, A b is the total filtration loss area of ​​the branch joint.

13. The method for predicting shale transformation area based on fracturing construction data according to claim 9, characterized in that: The fourth equation is: Among them, A m is the total filtration area of ​​the main seam, v' L is the first fracturing fluid loss rate, is the average pressure of the second wellhead, L m is the first fracturing fluid loss distance, A b is the total filtration loss area of ​​the branch joint.

14. A device for predicting shale transformation area based on fracturing construction data, characterized in that: include: A pressure acquisition module is used to obtain the wellhead pressure at different sampling times from fracturing pump stop to fracture closure in the fracturing construction data; A speed and distance acquisition module, used to determine the first fracturing fluid loss velocity corresponding to the wellhead pressure at different sampling times on a pre-drawn wellhead pressure-loss velocity curve, and to determine the first fracturing fluid loss distance corresponding to the wellhead pressure at different sampling times on a pre-drawn wellhead pressure-loss distance curve; The transformation area calculation module is used to predict the shale transformation area according to the wellhead pressure, the first fracturing fluid loss velocity, and the first fracturing fluid loss distance at different sampling times.

15. An electronic device, characterized in that: include: A memory and a processor, wherein a computer program is stored in the memory, and when the computer program is executed by the processor, the method for predicting shale transformation area based on fracturing construction data according to any one of claims 1 to 13 is executed.

16. A computer-readable storage medium, characterized in that: It stores executable instructions, which, when executed, enable the processor to execute the method for predicting shale transformation area based on fracturing construction data as described in any one of claims 1-13.

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