Method and device for evaluating productivity of shale gas well in early stage and storage medium

Abstract

The invention provides a productivity evaluation method and device for a shale gas well in the early production stage and a storage medium, and the method comprises the steps: obtaining parameter types and corresponding parameter values of a drilled shale gas well in the early production stage, and carrying out the dimensionless processing of all parameters; a six-zone linear seepage model is established according to the variable flow conductivity of the main fracture, and the six-zone linear seepage model is solved to obtain the relation between the shale gas well dimensionless total gas production rate and the shale gas production time and the parameter type; the parameter values of the drilled shale gas well in the early production stage are input into the relation between the total gas production rate and the shale gas production time and the relation between the total gas production rate and the parameter types, and a rock gas well productivity evaluation chart is obtained; and evaluating the productivity of the shale gas well by using the obtained productivity evaluation chart of the shale gas well. The flow conductivity difference of different fracture networks is considered, and fine evaluation of the productivity of the shale gas well can be guided.

Description

Technical Field

[0001] The present invention belongs to the field of oil and gas field development, and in particular relates to a method, a device and a storage medium for evaluating the productivity of a shale gas well in the early stage of production. Background Art

[0002] With the advancement of exploration and development technology, shale gas, as a special unconventional gas reservoir, has become an important source of natural gas production and plays an important role in the current energy strategy. However, due to the special characteristics of its two major reservoir characteristics, shale gas reservoirs are difficult to mobilize and develop. Shale gas reservoirs have two main characteristics: the first characteristic is that the permeability and pore diameter of shale gas reservoirs are extremely low, with a permeability of less than 10 -3 , the porosity diameter is concentrated between 2 and 50 nm; the second characteristic is that there is a large amount of adsorbed gas in shale gas reservoirs. Shale gas is not only stored in the porous medium as free gas, but also up to 85% of the adsorbed gas is attached to the shale surface. The ultra-low porosity and ultra-low permeability make it difficult for reservoir fluids to flow, and the adsorption phenomenon seriously affects the migration of gas. Summary of the invention

[0003] In order to enrich the shale gas well productivity evaluation method to be applicable to more application scenarios, the present invention proposes a shale gas well productivity evaluation method in the early stage of production, comprising:

[0004] In a first aspect, an embodiment of the present invention provides a method for evaluating a productivity evaluation chart of an early-stage shale gas well, comprising:

[0005] Obtaining parameter types and corresponding parameter values ​​of the early production of the drilled shale gas well, wherein the parameter types include at least SRV parameters, wellbore parameters, gas physical property parameters, and reservoir parameters;

[0006] The fifth and sixth zones are added to the shale gas well reservoir, of which the fifth zone is the fracture limited conductivity zone and the sixth zone is the fracture unlimited conductivity zone;

[0007] The SRV parameters and the wellbore parameters are dimensionless by using the preset first rule to obtain dimensionless SRV parameters and dimensionless wellbore parameters;

[0008] According to the preset second rule, the gas physical property parameters and reservoir parameters are dimensionless, and the dimensionless adsorption analysis coefficient, the dimensionless diffusion coefficient, the fracture conductivity of the fifth zone, and the fracture conductivity of the sixth zone are obtained;

[0009] By using the dimensionless SRV parameter, the dimensionless wellbore reservoir parameter, the dimensionless adsorption analytical coefficient, the dimensionless diffusion coefficient, the fracture conductivity of the fifth zone, the fracture conductivity of the sixth zone and the linear seepage physical model of the six zones of the shale gas well, respectively establish linear seepage models of the six zones of the shale gas well;

[0010] The linear seepage model of six zones of shale gas wells is solved respectively, and the relationship between the dimensionless total gas production of shale gas wells and the shale gas production time and parameter type is obtained through the relationship between the constant production pressure degradation and the constant pressure flow solution;

[0011] Inputting the parameter values ​​of the drilled shale gas well in the early stage of production into the obtained relationship between the dimensionless total gas production of the shale gas well and the shale gas production time and parameter type, respectively, to obtain a shale gas well productivity evaluation chart;

[0012] The shale gas well productivity evaluation chart obtained is used to evaluate the shale gas well productivity.

[0013] Furthermore, the SRV parameters and the wellbore parameters are dimensionless by using the preset first rule to obtain dimensionless SRV parameters and dimensionless wellbore parameters, including:

[0014] The width of each SRV region is dimensionless to obtain the dimensionless width of each SRV region;

[0015] The non-SRV area width is non-dimensionalized to obtain the dimensionless non-SRV area width;

[0016] The SRV region length is non-dimensionalized to obtain the dimensionless SRV region length;

[0017] The non-SRV region length is non-dimensionalized to obtain the dimensionless non-SRV region length;

[0018] The crack width is non-dimensionalized to obtain the dimensionless crack width.

[0019] Furthermore, the dimensionless conversion of the fluid parameters and the reservoir parameters according to the preset second rule to obtain the dimensionless adsorption analysis coefficient, the dimensionless diffusion coefficient, the fracture conductivity of the fifth zone, and the fracture conductivity of the sixth zone includes:

[0020] The dimensionless adsorption analytical coefficient is obtained by presetting the first formula;

[0021] The fracture conductivity of the fifth zone is obtained by presetting the second formula:

[0022] The fracture conductivity of the sixth zone is obtained by presetting the third formula:

[0023] The dimensionless diffusion coefficient is obtained by presetting the fourth formula.

[0024] Furthermore, by using SRV parameters, wellbore parameters, gas physical property parameters, and reservoir parameters, combined with the preset seepage equations, boundary conditions, and fluid continuity conditions, the fourth zone seepage model, the third zone seepage model, the second zone seepage model, the first zone seepage model, the fifth zone seepage model, and the sixth zone seepage model are established in turn.

[0025] Furthermore, the parameter values ​​of the drilled shale gas well in the early stage of production are respectively input into the relationship between the dimensionless total gas production of the shale gas well and the shale gas production time and parameter type to obtain the dimensionless total gas production of multiple shale gas wells. The obtained dimensionless total gas production of the multiple shale gas wells are fitted to obtain a shale gas well productivity evaluation chart.

[0026] In a second aspect, accordingly, an embodiment of the present invention provides a shale gas well productivity evaluation device in the early stage of production, comprising:

[0027] A parameter acquisition module, used to obtain parameter types and corresponding parameter values ​​of the early production of the drilled shale gas well, wherein the parameter types include at least SRV parameters and wellbore parameters;

[0028] The module for establishing the seepage physical model is used to add the fifth and sixth zones to the shale gas well reservoir, where the fifth zone is the fracture limited conductivity zone and the sixth zone is the fracture unlimited conductivity zone;

[0029] A dimensionless conversion module, used for performing dimensionless conversion on the SRV parameters and the wellbore parameters by using a preset first rule to obtain dimensionless SRV parameters and dimensionless wellbore parameters;

[0030] A coefficient establishment module, used to obtain a dimensionless adsorption analytical coefficient, a dimensionless diffusion coefficient, a fracture conductivity of the fifth zone, and a fracture conductivity of the sixth zone according to a preset second rule;

[0031] A seepage model establishment module, used to establish linear seepage models of six zones of the shale gas well respectively through the dimensionless SRV parameter, the dimensionless wellbore reservoir parameter, the dimensionless adsorption analytical coefficient, the dimensionless diffusion coefficient, the fracture conductivity of the fifth zone, and the fracture conductivity of the sixth zone;

[0032] The model solving module is used to solve the linear seepage model of the six zones of the shale gas well respectively, and obtain the relationship between the dimensionless total gas production of the shale gas well and the shale gas production time and parameter type through the relationship between the constant production pressure degradation and the constant pressure flow solution;

[0033] A chart creation module, inputting the parameter values ​​of the drilled shale gas well in the early stage of production into the obtained relationship between the dimensionless total gas production of the shale gas well and the shale gas production time and parameter type, to obtain a shale gas well productivity evaluation chart;

[0034] The capacity evaluation module evaluates the capacity of the shale gas well using the obtained shale gas well capacity evaluation chart.

[0035] Based on the above technical solution, the beneficial effects of the present invention compared with the prior art are as follows:

[0036] The present invention establishes a method for evaluating the productivity of shale gas wells in the early stage of production. First, the parameter types and corresponding parameter values ​​of the drilled shale gas wells in the early stage of production are obtained, and each parameter is dimensionally processed; then, a six-zone linear seepage model is established according to the variable conductivity of the main fracture, and the linear seepage models of the six zones are solved to obtain the relationship between the dimensionless total gas production of the shale gas well and the shale gas production time and parameter type; the parameter values ​​of the drilled shale gas wells in the early stage of production are respectively input into the relationship between the total gas production and the shale gas production time and parameter type, and a shale gas well productivity evaluation chart is obtained; finally, the shale gas well productivity is evaluated using the obtained shale gas well productivity evaluation chart.

[0037] The present invention takes into account the differences in conductivity of different fracture networks, establishes a six-zone linear seepage model for shale gas, solves each zone after giving it specific boundary conditions, and draws a capacity prediction chart by bringing in the six-zone linear flow model with variable conductivity. The capacity of shale gas in each flow stage can be obtained by fitting the production history curve, thereby guiding the detailed evaluation of the capacity of shale gas wells. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0039] Figure 1 A schematic diagram of a method for generating a productivity evaluation chart for a shale gas well in the early stage of production provided by an embodiment of the present invention;

[0040] Figure 2 A schematic diagram of a six-zone linear seepage physical model provided by an embodiment of the present invention;

[0041] Figure 3 A schematic diagram of obtaining coefficients according to a preset second rule provided in an embodiment of the present invention;

[0042] Figure 4 A production capacity evaluation chart provided by an embodiment of the present invention;

[0043] Figure 5 A fitting result diagram of a well production data provided by an embodiment of the present invention;

[0044] Figure 6 It is a schematic diagram of cumulative production trend of different production allocations based on variable conductivity when implementing the present invention.

[0045] Figure 7A schematic diagram of a shale gas well productivity evaluation device for early production provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0046] Long horizontal section multi-stage fracturing technology has become the main method of shale gas fracturing. The formation of complex shale gas fracture network by volume fracturing is the key technology to improve the development effect of shale gas. To evaluate the effect of fracturing, it is necessary to establish a capacity model to evaluate its capacity. After years of research, the inventor found that compared with conventional gas wells, shale gas fracturing horizontal wells need to consider multiple migration mechanisms and interference between fracturing fractures. At present, whether it is the capacity evaluation method based on the fracture model of conventional fracturing wells or the capacity evaluation model proposed for the special properties of shale gas, there are certain limitations and defects: conventional fracturing well models are generally double-wing fractures, which do not consider adsorption and desorption phenomena and interference between fractures; shale gas capacity evaluation models are mostly capacity evaluation models that consider multiple migration mechanisms and fracture interference, and do not analyze the main fracture variable conductivity phenomenon. The main fracture formed by fracturing is conical, which leads to a large difference in the conductivity of the root and toe of the fracture, thereby causing a large error in the shale gas capacity evaluation result. After further research and development, the inventor made the present invention in order to accurately evaluate the capacity of shale gas wells.

[0047] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0048] Embodiment 1

[0049] The embodiment of the present invention provides a method for generating a production capacity evaluation chart of a shale gas well in the early stage of production, combining Figure 1 As shown, it includes steps S110 to S90:

[0050] Step S110, obtaining parameter types and corresponding parameter values ​​of the early stage of production of the drilled shale gas well, wherein the parameter types at least include SRV parameters, wellbore parameters, gas physical property parameters, reservoir parameters, and production time.

[0051] Specifically, SRV parameters refer to volumetric fracturing parameters. The parameters of the early production of drilled shale gas wells may include the number of horizontal sections, permeability of each section, gas compressibility coefficient, natural gas deviation factor, gas viscosity, porosity, original formation pressure, gas production, production time, fracture width, fracture half-length, fracture height, comprehensive reservoir compression coefficient, wellbore storage coefficient, etc.

[0052] Step S120, adding a fifth zone and a sixth zone to the shale gas well reservoir, wherein the fifth zone is a fracture limited conductivity zone, and the sixth zone is a fracture unlimited conductivity zone.

[0053] The main fracture formed by the fracturing of shale gas horizontal wells is conical from the root end to the finger end. The conductivity can be used to represent the physical change process, but the existing four-zone model does not consider the change of conductivity. In order to make up for the defects of the existing model, a six-zone linear seepage physical model considering the fracture variable conductivity is established.

[0054] Specifically, by considering the reservoir permeability and reservoir pressure after shale gas well fracturing, shale gas wells are divided into Figure 2 There are six areas shown, namely the first area (marked as 1), the second area (marked as 2), the third area (marked as 3), the fourth area (marked as 4), the fifth area (marked as 5), and the sixth area (marked as 6).

[0055] Step S130, using a preset first rule to non-dimensionalize the SRV parameters and the wellbore parameters to obtain dimensionless SRV parameters and dimensionless wellbore parameters.

[0056] Specifically, the width of each SRV region is dimensionless to obtain the dimensionless width of each SRV region, as shown in the following formula (1):

[0057] x 1D =x n,1 / y1 (1)

[0058] Among them, x 1D is the dimensionless width of each SRV region, x n,1 is the width of the nth SRV region, and y1 is the half-length of the crack.

[0059] The non-SRV area width is dimensionless, and the dimensionless non-SRV area width is obtained, as shown in the following formula (2):

[0060] x 2D =x n,2 / y1 (2)

[0061] Among them, x 1D is the dimensionless non-SRV region width, x n,1 is the width of the nth non-SRV area, and y1 is the half-length of the crack.

[0062] The dimensionless SRV region length is obtained by non-dimensionalizing the SRV region length, as shown in the following formula (3):

[0063] y D =y n,1 / y1 (3)

[0064] Among them, y D is the dimensionless SRV region length, y n,1 is the length of the nth SRV region, and y1 is the half-length of the crack.

[0065] The non-SRV region length is non-dimensionalized to obtain the dimensionless non-SRV region length, as shown in the following formula:

[0066] y 2D =y n,2 / y1 (4)

[0067] Among them, y 2D is the dimensionless non-SRV region length, y n,1 is the length of the nth non-SRV area, and y1 is the half-length of the crack.

[0068] The crack width is non-dimensionalized to obtain the dimensionless crack width, as shown in the following formula (5):

[0069] w D =w n / y1 (5)

[0070] Among them, w n is the crack width, and y1 is the crack half-length.

[0071] Step S140, non-dimensionalizing the gas physical property parameters and the reservoir parameters according to the preset second rule to obtain the dimensionless adsorption analysis coefficient, the dimensionless diffusion coefficient, the fracture conductivity of the fifth zone, and the fracture conductivity of the sixth zone.

[0072] Specifically, the fluid parameters and reservoir parameters are dimensionlessly converted according to the preset second rule to obtain the dimensionless adsorption analysis coefficient, the dimensionless diffusion coefficient, the fracture conductivity of the fifth zone, and the fracture conductivity of the sixth zone, such as Figure 3 As shown, it includes steps S1401 to S1404:

[0073] Step S1401, obtaining a dimensionless adsorption analytical coefficient by using a preset first formula.

[0074] The dimensionless adsorption analytical coefficient is obtained by the following first formula (6):

[0075]

[0076] Where γ is the dimensionless adsorption analytical coefficient, C t is the comprehensive compression coefficient, ρ gsc is the gas density under standard conditions; ρ g is the gas density, φ is the porosity, V L is the Langmuir volume, P L is the Langmuir pressure, P g is the gas pressure.

[0077] Step S1402, obtaining the fracture conductivity of the fifth zone by using a preset second formula.

[0078] The fracture conductivity of the fifth zone is obtained by the following second formula (7):

[0079]

[0080] Among them, F 5D,n is the fracture conductivity of the fifth zone of the nth segment, w n is the width of the nth crack, k n,5 is the permeability of the fifth zone of the nth segment, y1 is the half length of the fracture, k n,1 is the permeability of the first zone of the nth segment;

[0081] Step S1403, obtaining the fracture conductivity of the sixth zone by using a preset third formula.

[0082] The fracture conductivity of the sixth zone is obtained by the following third formula (8):

[0083]

[0084] Among them, F 6D,n is the fracture conductivity of the sixth zone in the nth segment, w n is the width of the nth crack, k n,6 is the permeability of the sixth zone of the nth segment, y1 is the half length of the fracture, k n,1 is the permeability of the first zone of the nth segment;

[0085] Step S1404: obtaining the dimensionless diffusion coefficient by using the preset fourth formula.

[0086] The dimensionless diffusion coefficient is obtained by the following fourth formula (9):

[0087]

[0088] Among them, n n,kD is the dimensionless diffusion coefficient, φ is the porosity, C t is the comprehensive compression coefficient, and N is the number of horizontal segments.

[0089] In practical applications, dimensionless parameters also include the following:

[0090] The dimensionless time is as follows:

[0091]

[0092] Where kn,1 is the SRV zone permeability; μ is the gas viscosity; and t is the production time.

[0093] The pseudo-pressure function is defined as formula (11):

[0094]

[0095] Where Z is the deviation factor and P is the pressure

[0096] The dimensionless pseudo-pressure is as follows:

[0097]

[0098] Tsc is the temperature under standard conditions; h is the fracture height; T is the shale gas reservoir temperature; psc is the pressure under standard conditions; Qsc is the gas production under standard conditions, is the original formation pressure, Create pressure for the transformation area.

[0099] Dimensionless wellbore storage coefficient (13):

[0100]

[0101] In the formula, C s is the wellbore storage coefficient; y w It is half the length of the horizontal well section.

[0102] Step S150, by using the dimensionless SRV parameter, the dimensionless wellbore reservoir parameter, the dimensionless adsorption analytical coefficient, the dimensionless diffusion coefficient, the fracture conductivity of the fifth zone, the fracture conductivity of the sixth zone and the linear seepage physical model of the six zones of the shale gas well, respectively establish linear seepage models for the six zones of the shale gas well.

[0103] Specifically, the fourth zone seepage model, the third zone seepage model, the second zone seepage model, the first zone seepage model, the fifth zone seepage model, and the sixth zone seepage model are established in sequence by using SRV parameters, wellbore parameters, gas physical property parameters, and reservoir parameters in combination with preset seepage equations, boundary conditions, and fluid continuity conditions. The assumptions that need to be considered in establishing the above models include at least the following: (1) the influence of gravity is ignored in the gas reservoir, (2) the flow in the gas reservoir is single-phase gas, (3) the fracturing fractures in the gas reservoir are perpendicular to the wellbore and symmetrical, (4) the conductivity of the root end and toe end of the main fracture is different, and (5) the model considers the adsorption and desorption phenomenon of shale.

[0104] Specifically, the seepage model of the fourth zone is established, including the seepage equation, boundary conditions and fluid continuity conditions, as shown below:

[0105] Seepage equation for the fourth zone:

[0106]

[0107] Boundary conditions:

[0108]

[0109] Fluid continuity conditions:

[0110]

[0111] in, is the pseudo pressure of the fourth zone, φ is the porosity, μ g is the gas viscosity, k4 is the permeability of the fourth zone, C t is the comprehensive compression coefficient, ρ gsc is the gas density under standard conditions, ρg is the gas density, V L is the Langmuir volume, P L is the Langmuir pressure, Pg is the gas pressure, y1 is the crack half-length, and y2 is the non-SRV area half-length;

[0112] The seepage model of the third zone is established, including the seepage equation, boundary conditions and fluid continuity conditions, as shown below:

[0113] The seepage equation of the third zone:

[0114]

[0115] Boundary conditions:

[0116]

[0117] Fluid continuity conditions:

[0118]

[0119] in, is the pseudo pressure of the third zone, φ is the porosity, μ g is the gas viscosity, k3 is the permeability of the third zone, C t is the comprehensive compression coefficient, ρ gsc is the gas density under standard conditions, ρg is the gas density, V L is the Langmuir volume, P L is the Langmuir pressure, Pg is the gas pressure, y1 is the crack half-length, and y2 is the non-SRV area half-length;

[0120] The seepage model of the second zone is established, including the seepage equation, boundary conditions and fluid continuity conditions, as shown below:

[0121] The seepage equation of the second zone:

[0122]

[0123] Boundary conditions:

[0124]

[0125] Fluid continuity conditions:

[0126]

[0127] in, is the pseudo pressure in the second zone, φ is the porosity, μ g is the gas viscosity, k2 is the permeability of the second zone, C t is the comprehensive compression coefficient, ρ gsc is the gas density under standard conditions, ρg is the gas density, V L is the Langmuir volume, P L is the Langmuir pressure, Pg is the gas pressure, x1 is the width of the SRV region, and x2 is the width of the SRV region and the non-SRV region;

[0128] The seepage model of the first zone is established, including the seepage equation, boundary conditions and fluid continuity conditions, as shown below:

[0129] The seepage equation of the first zone:

[0130]

[0131] Boundary conditions:

[0132]

[0133] Fluid continuity conditions:

[0134]

[0135] in, is the pseudo pressure in the first zone, φ is the porosity, μ g is the gas viscosity, k1 is the permeability of the first zone, C t is the comprehensive compression coefficient, ρ gsc is the gas density under standard conditions, ρg is the gas density, V L is the Langmuir volume, P L is the Langmuir pressure, Pg is the gas pressure, and w is the crack width;

[0136] The seepage model of the fifth zone (fracture finite conductivity) is established, including the seepage equation, boundary conditions and fluid continuity conditions, as shown below:

[0137] The seepage equation of the fifth zone:

[0138]

[0139] Boundary conditions:

[0140]

[0141] Fluid continuity conditions:

[0142]

[0143] in, is the pseudo pressure of the fifth zone, φ is the porosity, μ g is the gas viscosity, k5 is the permeability of the fifth zone, w is the crack width, x1 is the SRV zone width, and C5 is the comprehensive compressibility coefficient of the fifth zone;

[0144] The seepage model of the sixth zone (fracture infinite conductivity) is established, including the seepage equation, boundary conditions and fluid continuity conditions, as shown below:

[0145] Seepage equation for the sixth zone:

[0146]

[0147] Boundary conditions:

[0148]

[0149] Fluid continuity conditions:

[0150]

[0151] in, is the pseudo pressure of the sixth zone, φ is the porosity, μ g is the gas viscosity, k6 is the permeability of the sixth zone, w is the crack width, x1 is the SRV zone width, and C6 is the comprehensive compressibility coefficient of the sixth zone.

[0152] Step S160, respectively solve the linear seepage model of the six zones of the shale gas well, and obtain the relationship between the dimensionless total gas production of the shale gas well and the shale gas production time and parameter type through the relationship between the constant production pressure degradation and the constant pressure flow solution.

[0153] Specifically, it includes: firstly solving each area after giving preset boundary conditions;

[0154] Boundary conditions of the fourth zone:

[0155]

[0156] Solution of the fourth block equation:

[0157]

[0158] Boundary conditions of the third zone:

[0159]

[0160] Solution of the third region equation:

[0161]

[0162] Boundary conditions of the second zone:

[0163]

[0164] Solution of the second region equation:

[0165]

[0166] Boundary conditions of the first zone:

[0167]

[0168]

[0169] Solution of the first region equation:

[0170]

[0171] Boundary conditions of the fifth zone:

[0172]

[0173]

[0174] Solution of the fifth block equation:

[0175]

[0176] Solution of the sixth block equation:

[0177]

[0178] Then, by solving the relationship between constant production pressure degradation and constant pressure flow, the dimensionless gas production of a single fracture is obtained:

[0179]

[0180] Where s is the Laplace operator; by solving the relationship between the constant production pressure degradation and the constant pressure flow solution, the dimensionless flow rate of the single-stage hydraulic fracture i during constant pressure production is solved. The relevant calculation formula of the Laplace operator s is as follows:

[0181]

[0182]

[0183]

[0184]

[0185]

[0186]

[0187] Finally, according to the dimensionless gas production of the single-stage fracture, the dimensionless total gas production is obtained:

[0188]

[0189] Where N is the number of horizontal segments.

[0190] Step S170, inputting the parameter values ​​of the early stage of production of the drilled shale gas well into the relationship between the dimensionless total gas production of the shale gas well and the shale gas production time and parameter type, obtaining the dimensionless total gas production of multiple shale gas wells, fitting the obtained dimensionless total gas production of the multiple shale gas wells, and obtaining a shale gas well productivity evaluation chart.

[0191] Specifically, multiple parameter values ​​of the staged fracturing horizontal well are respectively input into the relationship between the dimensionless total gas production of the shale gas well and the shale gas production time and parameter type to obtain the dimensionless total gas production of multiple shale gas wells, and the obtained dimensionless total gas production of the multiple shale gas wells is fitted to obtain a shale gas well capacity evaluation chart, and the capacity evaluation chart is as follows: Figure 5 shown.

[0192] Step S180, evaluating the productivity of the shale gas well using the obtained shale gas well productivity evaluation chart.

[0193] Specifically, the production data is brought into the shale gas well capacity evaluation chart. By fitting the production data and the capacity prediction chart, it is possible to determine whether the current gas well is in the production stage based on the position of the production data on the capacity prediction chart, predict the subsequent direction of the curve, and obtain the capacity of shale gas in each flow stage.

[0194] In order to verify the content of the present invention, the inventors have conducted a large number of experiments, taking the productivity evaluation of a shale well in a certain place as an example: a shale gas fracturing horizontal well, the horizontal well length is 2000m, the number of fracturing stages is 21, the fracture width is 0.005m, the fracture half length is 10m, the fracture height is 0.005m, the well diameter is 0.108m, the reservoir thickness is 16m, the porosity is 6.02%, the natural gas relative density is 0.7, and the formation temperature is 130℃. The present invention uses the six-zone linear seepage physical model considering the variable conductivity to draw a typical well test curve Figure 5 , through the fitting results of production data Figure 6 , the capacity of each flow section can be obtained to evaluate the capacity. Figure 6 The example well fitting is in stage II, and the plate fitting effect is generally good. Figure 7It is the influence of different production allocation on cumulative production. It can be seen from the figure that contrary to the conventional understanding, the increase in cumulative production is not linearly related to the increase in production allocation. This is because the higher the production allocation, the greater the flow rate, the fluid will preferentially pass through the dominant channel (large conductivity), squeezing out the channel with low conductivity, resulting in a decrease in the overall cumulative production increase rate. Therefore, it is necessary to consider the variable conductivity of the main fracture in the actual production process.

[0195] The present invention establishes a method for evaluating the productivity of shale gas wells in the early stage of production. First, the parameter types and corresponding parameter values ​​of the drilled shale gas wells in the early stage of production are obtained, and each parameter is dimensionally processed; then, a six-zone linear seepage model is established according to the variable conductivity of the main fracture, and the linear seepage models of the six zones are solved to obtain the relationship between the dimensionless total gas production of the shale gas well and the shale gas production time and parameter type; the parameter values ​​of the drilled shale gas wells in the early stage of production are respectively input into the relationship between the total gas production and the shale gas production time and parameter type, and a shale gas well productivity evaluation chart is obtained; finally, the shale gas well productivity is evaluated using the obtained shale gas well productivity evaluation chart.

[0196] The present invention takes into account the differences in conductivity of different fracture networks, establishes a six-zone linear seepage model for shale gas, solves each zone after giving it specific boundary conditions, and draws a capacity prediction chart by bringing in the six-zone linear flow model with variable conductivity. The capacity of shale gas in each flow stage can be obtained by fitting the production history curve, thereby guiding the detailed evaluation of the capacity of shale gas wells.

[0197] Based on the same inventive concept, the present invention also provides a method for generating a productivity evaluation chart of an early-stage shale gas well, including the contents of steps S110-S170. For specific contents, refer to the productivity evaluation method of an early-stage shale gas well, which will not be described in detail here.

[0198] Embodiment 2

[0199] The embodiment of the present invention provides a shale gas well productivity evaluation device in the early stage of production, Figure 7 As shown, the device comprises:

[0200] The parameter acquisition module 201 is used to obtain the parameter types and corresponding parameter values ​​of the early production of the drilled shale gas well, and the parameter types at least include SRV parameters, wellbore parameters, gas physical property parameters, reservoir parameters, and production time.

[0201] The seepage physical model building module 202 is used to add a fifth zone and a sixth zone to the shale gas well reservoir, wherein the fifth zone is a fracture limited conductivity zone, and the sixth zone is a fracture unlimited conductivity zone.

[0202] The main fracture formed by the fracturing of shale gas horizontal wells is conical from the root end to the finger end. The conductivity can be used to represent the physical change process, but the existing four-zone model does not consider the change of conductivity. In order to make up for the defects of the existing model, a six-zone linear seepage physical model considering the fracture variable conductivity is established.

[0203] Specifically, by considering the reservoir permeability and reservoir pressure after shale gas well fracturing, shale gas wells are divided into Figure 3 There are six areas shown, namely the first area (marked as 1), the second area (marked as 2), the third area (marked as 3), the fourth area (marked as 4), the fifth area (marked as 5), and the sixth area (marked as 6).

[0204] The dimensionless conversion module 203 is used to perform dimensionless conversion on the SRV parameters and the wellbore parameters by using a preset first rule to obtain dimensionless SRV parameters and dimensionless wellbore parameters.

[0205] Specifically, the width of each SRV region is dimensionless to obtain the dimensionless width of each SRV region, as shown in the following formula:

[0206] x 1D =x n,1 / y1

[0207] Among them, x 1D is the dimensionless width of each SRV region, x n,1 is the width of the nth SRV region, and y1 is the half-length of the crack.

[0208] The non-SRV area width is dimensionless to obtain the dimensionless non-SRV area width, as shown in the following formula:

[0209] x 2D =x n,2 / y1

[0210] Among them, x 1D is the dimensionless non-SRV region width, x n,1 is the width of the nth non-SRV area, and y1 is the half-length of the crack.

[0211] The dimensionless SRV region length is obtained by non-dimensionalizing the SRV region length, as shown in the following formula:

[0212] y D =y n,1 / y1

[0213] Among them, y D is the dimensionless SRV region length, y n,1is the length of the nth SRV region, and y1 is the half length of the crack. The non-SRV region length is dimensionless, and the dimensionless non-SRV region length is obtained, as shown in the following formula:

[0214] y 2D =y n,2 / y1

[0215] Among them, y 2D is the dimensionless non-SRV region length, y n,1 is the length of the nth non-SRV area, and y1 is the half-length of the crack.

[0216] The crack width is non-dimensionalized to obtain the dimensionless crack width, as shown in the following formula:

[0217] w D =w n / y1

[0218] Among them, w n is the crack width, and y1 is the crack half-length.

[0219] The coefficient establishing module 204 is used to obtain the dimensionless adsorption analytical coefficient, the dimensionless diffusion coefficient, the fracture conductivity of the fifth zone, and the fracture conductivity of the sixth zone according to a preset second rule.

[0220] Specifically, the fluid parameters and reservoir parameters are dimensionlessly converted according to the preset second rule to obtain the dimensionless adsorption analysis coefficient, the dimensionless diffusion coefficient, the fracture conductivity of the fifth zone, and the fracture conductivity of the sixth zone, such as Figure 4 shown.

[0221] The seepage model establishment module 205 is used to establish linear seepage models of six zones of the shale gas well respectively through the dimensionless SRV parameter, the dimensionless wellbore reservoir parameter, the dimensionless adsorption analytical coefficient, the dimensionless diffusion coefficient, the fracture conductivity of the fifth zone, and the fracture conductivity of the sixth zone.

[0222] Specifically, the fourth zone seepage model, the third zone seepage model, the second zone seepage model, the first zone seepage model, the fifth zone seepage model, and the sixth zone seepage model are established in sequence by using SRV parameters, wellbore parameters, gas physical property parameters, and reservoir parameters in combination with preset seepage equations, boundary conditions, and fluid continuity conditions.

[0223] The model solving module 206 is used to solve the linear seepage model of the six zones of the shale gas well respectively, and obtain the relationship between the dimensionless total gas production of the shale gas well and the shale gas production time and parameter type through the relationship between the constant production pressure degradation and the constant pressure flow solution.

[0224] The chart creation module 207 is used to input the parameter values ​​of the drilled shale gas well in the early stage of production into the obtained relationship between the dimensionless total gas production of the shale gas well and the shale gas production time and parameter type, so as to obtain a shale gas well productivity evaluation chart.

[0225] Specifically, the parameter values ​​of the drilled shale gas well in the early stage of production are input into the relationship between the dimensionless total gas production of the shale gas well and the shale gas production time and parameter type, and the dimensionless total gas production of multiple shale gas wells is obtained. The dimensionless total gas production of the multiple shale gas wells obtained is fitted to obtain a shale gas well capacity evaluation chart.

[0226] The productivity evaluation module 208 is used to evaluate the productivity of the shale gas well using the shale gas well productivity evaluation chart.

[0227] The specific working process of the early-stage production shale gas well productivity evaluation device provided by the embodiment of the present invention is referred to in Example 1 and will not be repeated here.

[0228] Based on the same inventive concept, an embodiment of the present invention further discloses a computer-readable storage medium, in which instructions are stored. When the instructions are executed on a terminal, the terminal executes steps S110-S180 in the first embodiment.

[0229] In the above detailed description, various features are grouped together in a single embodiment to simplify the disclosure. This method of disclosure should not be interpreted as reflecting an intention that the embodiments of the claimed subject matter require more features than are clearly stated in each claim. On the contrary, as reflected in the appended claims, the invention is in a state of having less than all the features of the disclosed individual embodiments. Therefore, the appended claims are hereby expressly incorporated into the detailed description, with each claim standing on its own as a separate preferred embodiment of the invention.

[0230] The above description includes examples of one or more embodiments. Of course, it is not possible to describe all possible combinations of components or methods for the purpose of describing the above embodiments, but it should be recognized by those skilled in the art that the various embodiments may be further combined and arranged. Therefore, the embodiments described herein are intended to cover all such changes, modifications and variations that fall within the scope of protection of the appended claims. In addition, with respect to the term "comprising" used in the specification or claims, the word is encompassed in a manner similar to the term "including", as explained by "including," used as a transitional word in the claims. In addition, any term "or" used in the specification of the claims is intended to mean "non-exclusive or".

Claims

1. A method for evaluating the productivity of shale gas wells in the early stage of production, characterized in that: include: Obtaining parameter types and corresponding parameter values ​​of the early stage of production of the drilled shale gas well, wherein the parameter types at least include SRV parameters, wellbore parameters, gas physical property parameters, reservoir parameters, and production time; The fifth and sixth zones are added to the shale gas well reservoir, of which the fifth zone is the fracture limited conductivity zone and the sixth zone is the fracture unlimited conductivity zone; The SRV parameters and the wellbore parameters are dimensionless by using the preset first rule to obtain dimensionless SRV parameters and dimensionless wellbore parameters; According to the preset second rule, the gas physical property parameters and reservoir parameters are dimensionless, and the dimensionless adsorption analysis coefficient, the dimensionless diffusion coefficient, the fracture conductivity of the fifth zone, and the fracture conductivity of the sixth zone are obtained; Establishing linear seepage models of six zones of the shale gas well respectively by using the dimensionless SRV parameter, the dimensionless wellbore reservoir parameter, the dimensionless adsorption analytical coefficient, the dimensionless diffusion coefficient, the fracture conductivity of the fifth zone, and the fracture conductivity of the sixth zone; The linear seepage model of six zones of shale gas wells is solved respectively, and the relationship between the dimensionless total gas production of shale gas wells and the shale gas production time and parameter type is obtained through the relationship between the constant production pressure degradation and the constant pressure flow solution; Inputting the parameter values ​​of the drilled shale gas well in the early stage of production into the obtained relationship between the dimensionless total gas production of the shale gas well and the shale gas production time and parameter type, respectively, to obtain a shale gas well productivity evaluation chart; The shale gas well productivity evaluation chart obtained is used to evaluate the shale gas well productivity.

2. The method according to claim 1, characterized in that The method of converting the SRV parameters and the wellbore parameters into dimensionless parameters by using the preset first rule to obtain dimensionless SRV parameters and dimensionless wellbore parameters includes: The width of each SRV region is dimensionless to obtain the dimensionless width of each SRV region; The non-SRV area width is non-dimensionalized to obtain the dimensionless non-SRV area width; The SRV region length is non-dimensionalized to obtain the dimensionless SRV region length; The non-SRV region length is non-dimensionalized to obtain the dimensionless non-SRV region length; The crack width is non-dimensionalized to obtain the dimensionless crack width.

3. The method according to claim 1, characterized in that The step of converting the fluid parameters and the reservoir parameters into dimensionless values ​​according to the preset second rule to obtain the dimensionless adsorption analysis coefficient, the dimensionless diffusion coefficient, the fracture conductivity of the fifth zone, and the fracture conductivity of the sixth zone includes: The dimensionless adsorption analytical coefficient is obtained by presetting the first formula; The fracture conductivity of the fifth zone is obtained by presetting the second formula; The fracture conductivity of the sixth zone is obtained by presetting the third formula; The dimensionless diffusion coefficient is obtained by presetting the fourth formula.

4. The method according to claim 3, characterized in that The preset first formula is: Where γ is the dimensionless adsorption analytical coefficient, C t is the comprehensive compression coefficient, ρ gsc is the gas density under standard conditions; ρ g is the gas density, φ is the porosity, V L is the Langmuir volume, P L is the Langmuir pressure, P g is the gas pressure.

5. The method according to claim 3, characterized in that The preset second formula is: Among them, F 5D,n is the fracture conductivity of the fifth zone of the nth segment, w n is the width of the nth crack, k n,5 is the permeability of the fifth zone of the nth segment, y1 is the half length of the fracture, k n,1 is the permeability of the first zone of the nth segment.

6. The method according to claim 3, characterized in that The preset third formula is: Among them, F 6D,n is the fracture conductivity of the sixth zone in the nth segment, w n is the width of the nth crack, k n,6 is the permeability of the sixth zone of the nth segment, y1 is the half length of the fracture, k n,1 is the permeability of the first zone of the nth segment.

7. The method according to claim 3, characterized in that The preset fourth formula is: Among them, n n,kD is the dimensionless diffusion coefficient, φ is the porosity, C t is the comprehensive compression coefficient, and N is the number of horizontal segments.

8. The method according to claim 1, characterized in that The linear seepage models of six zones of the shale gas well are established respectively by using the dimensionless SRV parameter, the dimensionless wellbore reservoir parameter, the dimensionless adsorption analytical coefficient, the dimensionless diffusion coefficient, the fracture conductivity of the fifth zone, and the fracture conductivity of the sixth zone, including: Using SRV parameters, wellbore parameters, gas physical property parameters, and reservoir parameters, combined with the preset seepage equations, boundary conditions, and fluid continuity conditions, the fourth zone seepage model, the third zone seepage model, the second zone seepage model, the first zone seepage model, the fifth zone seepage model, and the sixth zone seepage model are established in turn.

9. The method according to claim 1, characterized in that The parameter values ​​of the drilled shale gas well in the early stage of production are respectively input into the obtained relationship between the dimensionless total gas production of the shale gas well and the shale gas production time and parameter type, and a shale gas well productivity evaluation chart is obtained, including: The parameter values ​​of the drilled shale gas well in the early stage of production are respectively input into the obtained relationship between the dimensionless total gas production of the shale gas well and the shale gas production time and parameter type to obtain the dimensionless total gas production of multiple shale gas wells. The obtained dimensionless total gas production of the multiple shale gas wells is fitted to obtain a shale gas well productivity evaluation chart.

10. The method according to claim 9, characterized in that The linear seepage models of the six zones of the shale gas well are solved respectively, and the relationship between the dimensionless total gas production of the shale gas well and the shale gas production time and parameter type is obtained through the relationship between the constant production pressure degradation and the constant pressure flow solution, including: Each zone is solved after given preset boundary conditions; By solving the relationship between constant production pressure degradation and constant pressure flow, the dimensionless gas production of a single fracture is obtained: Where S is the Laplace operator, is the dimensionless gas production of a single-stage fracture; According to the dimensionless gas production of the single-stage fracture, the dimensionless total gas production is obtained: Where N is the number of horizontal segments.

11. A method for generating a productivity evaluation chart for shale gas wells in the early stage of production, characterized in that: include: Obtaining parameter types and corresponding parameter values ​​of the early production of the drilled shale gas well, wherein the parameter types include at least SRV parameters, wellbore parameters, gas physical property parameters, and reservoir parameters; The fifth and sixth zones are added to the shale gas well reservoir, of which the fifth zone is the fracture limited conductivity zone and the sixth zone is the fracture unlimited conductivity zone; The SRV parameters and the wellbore parameters are dimensionless by using the preset first rule to obtain dimensionless SRV parameters and dimensionless wellbore parameters; According to the preset second rule, the gas physical property parameters and reservoir parameters are dimensionless, and the dimensionless adsorption analysis coefficient, the dimensionless diffusion coefficient, the fracture conductivity of the fifth zone, and the fracture conductivity of the sixth zone are obtained; By using the dimensionless SRV parameter, the dimensionless wellbore reservoir parameter, the dimensionless adsorption analytical coefficient, the dimensionless diffusion coefficient, the fracture conductivity of the fifth zone, the fracture conductivity of the sixth zone and the linear seepage physical model of the six zones of the shale gas well, respectively establish linear seepage models of the six zones of the shale gas well; The linear seepage model of the six zones of the shale gas well is transformed according to a preset third rule to obtain a first relationship, wherein the first relationship is used to describe the relationship between the shale gas bottom pressure and the shale gas production time and parameter type; The first relational expression is transformed according to a preset fourth rule to obtain a second relational expression, wherein the second relational expression is used to describe the relationship between the dimensionless total gas production of the shale gas well and the shale gas production time and parameter type; The parameter values ​​of the drilled shale gas wells in the early stage of production are respectively input into the second relational expression to obtain the dimensionless total gas production of multiple shale gas wells, and the dimensionless total gas production of the multiple shale gas wells obtained is fitted to obtain a shale gas well productivity evaluation chart.

12. A shale gas well productivity evaluation device in the early stage of production, characterized in that: include: A parameter acquisition module is used to obtain the parameter types and corresponding parameter values ​​of the early production of the drilled shale gas well, wherein the parameter types at least include SRV parameters, wellbore parameters, gas physical property parameters, reservoir parameters, and production time; The module for establishing the seepage physical model adds the fifth and sixth zones to the shale gas well reservoir, where the fifth zone is the fracture limited conductivity zone and the sixth zone is the fracture unlimited conductivity zone; The dimensionless module is used to dimensionlessly transform the SRV parameters and wellbore parameters according to the preset first rule to obtain dimensionless SRV parameters and dimensionless wellbore parameters; and to dimensionlessly transform the gas physical property parameters and reservoir parameters according to the preset second rule to obtain dimensionless adsorption analytical coefficient, dimensionless diffusion coefficient, fracture conductivity of the fifth zone, and fracture conductivity of the sixth zone; A seepage model establishment module, used to establish linear seepage models of six zones of the shale gas well respectively through the dimensionless SRV parameter, the dimensionless wellbore reservoir parameter, the dimensionless adsorption analytical coefficient, the dimensionless diffusion coefficient, the fracture conductivity of the fifth zone, and the fracture conductivity of the sixth zone; The model solving module is used to solve the linear seepage model of the six zones of the shale gas well respectively, and obtain the relationship between the dimensionless total gas production of the shale gas well and the shale gas production time and parameter type through the relationship between the constant production pressure degradation and the constant pressure flow solution; A chart creation module, inputting the parameter values ​​of the drilled shale gas well in the early stage of production into the obtained relationship between the dimensionless total gas production of the shale gas well and the shale gas production time and parameter type, to obtain a shale gas well productivity evaluation chart; The capacity evaluation module evaluates the capacity of the shale gas well using the obtained shale gas well capacity evaluation chart.

13. A computer-readable storage medium, in which instructions are stored. When the instructions are executed on a terminal, the terminal executes the method for evaluating the productivity of an early-stage shale gas well as described in any one of claims 1 to 10.

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