CN107575219B - Shale gas reservoir stratum fracture pressure gradient calculation method - Google Patents
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Abstract
The invention relates to a shale gas reservoir stratum fracture pressure gradient calculation method, which comprises the steps of collecting conventional well logging curve data of a whole well section, calculating rock skeleton density rho ma, determining stratum average porosity phi and fluid density rho w, collecting well logging curve data of depth, vertical depth, sound wave AC, density DEN and neutron CN L of a reservoir section of a shale gas well, calculating stratum average density through rho ═ 1-phi rho ma + phi rho w, determining a fracture pressure coefficient K ═ P0+ P1 AC + P2 DEN + P3 CN L by a fitting regression method, calculating a fracture pressure gradient of a reservoir stratum according to a formula FRAC K ═ and finally outputting a result, wherein the shale gas well is applied to 200 multiwellhead shale gas wells, the calculated fracture pressure gradient of the stratum is closer to the fracture pressure of the actual shale gas reservoir stratum, and the construction error is smaller than 15%.
Description
Technical Field
The invention relates to a method for calculating and determining shale reservoir stratum fracture pressure by utilizing conventional logging information, in particular to a shale gas reservoir stratum fracture pressure gradient calculation method.
Background
Shale gas is a novel clean energy source and an important unconventional natural gas resource. The development of shale gas needs to drill a horizontal well in a 'well factory' mode, and multi-section large-scale fracturing transformation needs to be carried out on a shale gas reservoir at the horizontal section of the horizontal well, so that the cost is high and the risk is high. The calculation or prediction precision of the shale gas reservoir stratum fracture gradient and stratum fracture pressure parameters is very important, and the reservoir transformation effect is directly influenced.
The traditional stratum fracture pressure gradient calculation methods mainly include an Eton method, a Mazis and Kelly method and a Crist man method. The methods are mainly formed during the sixties to the seventies of the last century, and solve the problems of calculating or predicting the fracture gradient and the fracture pressure parameters of the conventional reservoir stratum such as sandstone and carbonate rock.
Along with the discovery of the shale gas field in China and the expansion of the scale of shale gas exploration and development tests, the multi-section fracturing of the shale gas horizontal well has high cost and high risk, the requirements on the stratum fracture pressure gradient and the stratum fracture pressure calculation accuracy of the shale gas reservoir are higher and higher, the traditional stratum fracture pressure gradient calculation method is difficult to adapt to the production requirements, and the problem of large calculation error is more and more prominent.
Disclosure of Invention
The invention aims to provide a method for calculating the formation fracture pressure of a reliable shale gas reservoir by utilizing conventional logging curve data.
The invention aims to realize a shale gas reservoir stratum fracture pressure gradient calculation method, which comprises the following specific steps:
1) collecting conventional logging curve data of the whole well section, wherein the conventional logging curve data comprises natural gamma, neutron, density, sound wave and resistivity logging curves; calculating the density rho ma of a rock framework by using conventional logging curve data by adopting a weighted average method, and determining the average porosity phi of the stratum and the fluid density rho w by using the conventional logging curve data of the whole well section and core porosity analysis data of a regional exploratory well core-taking well;
the density rhoma dimension of the rock skeleton is g/cm3，
The average porosity of the formation phi dimension is a percentage,
the fluid density rho w dimension is g/cm3；
2) Collecting the logging curve data of the depth, the vertical depth, the acoustic wave AC, the density DEN and the neutron CN L of the reservoir section of the shale gas well;
density DEN dimension is g/cm3，
The acoustic wave AC dimension is μ s/m,
the neutron CN L dimension is a percentage,
3) calculating the average density rho of the stratum according to the density rho ma of the stratum rock skeleton, the porosity phi and the fluid density rho w obtained in the step 1):
ρ＝(1-Φ)*ρma+Φ*ρw；
the average density rho dimension of the stratum is g/cm3，
4) Determining a fracture pressure coefficient K, namely P0+ P1 AC + P2 + DEN + P3 CN L by a fitting regression method according to the sound wave, density DEN and neutron logging curve data of the shale reservoir interval collected in the step 2) and the fracture pressure of the fractured well in the region,
in the formula, P0-P3 are regional empirical coefficients and are related to the lithology of the stratum of the fracturing section, and the lithology of the stratum is related to a logging curve;
5) by the formula: calculating a formation fracture pressure gradient FRAC of the shale gas reservoir section according to the FRAC rho;
wherein the FPAC dimension of the shale reservoir stratum fracture pressure gradient is MPa/100m,
the average density rho dimension of the stratum is g/cm3，
6) And outputting a calculation result.
The invention has applied more than 200 wells of the shale gas well in the Fuling shale gas field, the calculated stratum rupture pressure gradient is closer to the stratum rupture pressure gradient obtained by actual construction, and the error is less than 15 percent.
Drawings
FIG. 1 is a block diagram of the workflow of the present invention.
Detailed Description
Referring to fig. 1, the method comprises the following specific steps:
1) collecting conventional logging curve data of the whole well section, wherein the conventional logging curve data comprises logging curves such as natural gamma rays, neutrons, density, sound waves, resistivity and the like; calculating the density rho ma of the rock framework by using density logging curve data by adopting a weighted average method, and determining the average porosity phi of the stratum and the fluid density rho w by using conventional logging curve data of the whole well section and core porosity analysis data of a regional exploratory well core-taking well;
the density rhoma dimension of the rock skeleton is g/cm3，
The average porosity of the formation phi dimension is a percentage,
the fluid density rho w dimension is g/cm3。
Wherein the conventional well log data is data excluding bad well bores and unreliable data. The fluid density ρ w is generally 1.1. + -. 0.1g/cm3。
2) Collecting the logging curve data of the depth, the vertical depth, the acoustic wave AC, the density DEN and the neutron CN L of the reservoir section of the shale gas well;
density DEN dimension is g/cm3，
The acoustic wave AC dimension is μ s/m,
neutron CN L dimension is a percentage.
3) Calculating the average density rho of the stratum according to the density rho ma of the stratum rock skeleton, the porosity phi and the fluid density rho w obtained in the step 1):
ρ＝(1-Φ)*ρma+Φ*ρw；
the average density rho dimension of the stratum is g/cm3，
4) Determining a fracture pressure coefficient K, namely P0+ P1 AC + P2 + DEN + P3 CN L by a fitting regression method according to the sound wave, density DEN and neutron logging curve data of the shale reservoir interval collected in the step 2) and the fracture pressure of the fractured well in the region,
the fracture pressure coefficient is related to the lithology of the stratum of the fractured section, the lithology of the stratum is related to a logging curve, and the regional empirical coefficients P0-P3 can be determined by combining the data of the fractured wells with a data fitting method, so that the fracture pressure coefficient of the stratum is calculated.
5) By the formula: calculating a formation fracture pressure gradient FRAC of the shale gas reservoir section according to the FRAC rho;
wherein the FPAC dimension of the shale reservoir stratum fracture pressure gradient is MPa/100m,
the average density rho dimension of the stratum is g/cm3，
6) And outputting a calculation result.
The present invention is described in detail below with reference to specific examples. (the embodiment is preferably written as before)
Example one: JY2-3 well for certain gas field
1) Collecting conventional well logging curve data (including acoustic, density and neutron curves) of the whole well section of the well, and calculating the average skeleton density rho ma of the rock to be 2.67g/cm by adopting a weighted average method and using the density well logging curve data3Determining the average porosity phi of the stratum to be 0.05 and the fluid density rho w to be 1.05g/cm by utilizing the conventional logging curve data of the whole well section and the core porosity analysis data of the regional exploratory well core-taking well3；
2) Determining the shale gas reservoir well section to be 2980.0-4490.0m vertical depth to be 2448.0-2521.0m, and collecting the sonic, density and neutron logging curve data of the shale reservoir section;
3) passing ρ ═ (1- Φ) × ρ ma + Φ ρ w; calculating the average density rho of the stratum to be 2.589g/cm3；
4) Determining a fracture pressure coefficient K (a regional empirical coefficient related to regional formations) through fracture section sound wave, density and neutron logging curve data, and calculating a fracture pressure coefficient according to a formula (AC is sound wave, DEN is density, CN L is neutron, and P0-P3 are constants), wherein K is P0+ P1 AC + P2 DEN + P3 CN L. by performing fitting analysis on fracture data of the 4000 residual sections of the multi-well in the Fuling area 260, P1 is-0.004274867, P2 is-0.046441009, P3 is 0.004972802, P0 is 2.019452937, and the average K value of the fracture sections is 0.977.
5) By the formula: calculating the fracture pressure gradient of the stratum of the fracturing section to be 2.537 and the average fracture pressure to be 63.06MPa according to the FRAC (Kx rho);
6) and outputting the fracture pressure gradient and the fracture pressure calculation result according to the user requirement.
The method is used for calculating the shale gas layer stratum fracture pressure of the JY2-3 well 2980.0-4490.0m well section to be 63.06MPa, well completion fracturing construction is carried out, the average stratum fracture pressure of the 20 sections of the well is 63.48MPa in actual measurement, the error is less than 10%, the calculation results of the 20 sections of the well are very close, and the initial unobstructed flow daily natural gas yield is about 116.39 × 104m3And the fracturing reconstruction effect is obvious.
As can be seen from example 1, the stratum fracture pressure gradient and the stratum fracture pressure calculated by the method are close to the actual measurement result, the error is less than 10%, the method meets the requirements of site construction, and the method has high application value.
Example two: JY13-2 well for certain shale gas field
The JY13-2 well is a long horizontal section horizontal well, the horizontal section of the gas reservoir is 2630-4078m, the vertical depth of the gas reservoir is 2330.0-2412.0m, and the horizontal section passes through the gas reservoir.
1) Collecting conventional well logging curve data (including acoustic, density and neutron curves) of the whole well section of the well, and calculating the average skeleton density rho ma of the rock to be 2.67g/cm by adopting a weighted average method and using the density well logging curve data3Determining the average porosity phi of the stratum to be 0.05 and the fluid density rho w to be 1.05g/cm by utilizing the conventional logging curve data of the whole well section and the core porosity analysis data of the regional exploratory well core-taking well3；
2) Determining the shale gas reservoir well section to be 2630-4078m and the vertical depth to be 2332.0-2412.0m, and collecting the data of the sonic wave, the density and the neutron logging curve of the shale reservoir section;
3) passing ρ ═ (1- Φ) × ρ ma + Φ ρ w; calculating the average density rho of the stratum to be 2.589g/cm3；
4) Determining a fracture pressure coefficient K (a regional empirical coefficient related to regional formations) through fracture section acoustic wave, density and neutron logging curve data, calculating a fracture pressure coefficient by using a formula (AC is an acoustic wave, DEN is density, CN L is neutron, and P0-P3 are constants), wherein K is P0+ P1 AC + P2 DEN + P3 CN L, performing fitting analysis on fracture data of the 4000 residual sections of the multi-well in the Fuling area 260, obtaining P1-0.004274867 by using a fitting regression method, P2 is-0.046441009, P3 is 0.004972802, P0 is 2.019452937, and calculating the average K value of the fracture section is 1.036;
5) by the formula: calculating the fracture pressure gradient of the stratum of the fracturing section to be 2.137 and the average fracture pressure to be 64.2MPa according to the FRAC rho;
6) and outputting the fracture pressure gradient and the fracture pressure calculation result according to the user requirement.
The average fracture pressure of the shale gas layer stratum of the horizontal segment of the JY13-2 well 2630-4078m calculated by the method is 64.2 MPa. Completing well and fracturing operation, constructing in 18 sections, actually measuring the average fracture pressure of the stratum to be 60.0MPa, and generating natural gas about 1 day without resistance flow in the initial stage11.02×104m3And the fracturing reconstruction effect is obvious.
As can be seen from example 1, the stratum fracture pressure gradient and the stratum fracture pressure calculated by the method are close to the actual measurement result, the error is less than 10%, and the fracturing construction effect is guided to be good.
Claims (3)
1. The shale gas reservoir stratum fracture pressure gradient calculation method is characterized by comprising the following steps of: the method comprises the following specific steps:
1) collecting conventional logging curve data of the whole well section, wherein the conventional logging curve data comprises natural gamma, neutron, density, sound wave and resistivity logging curves; calculating the density rho ma of a rock framework by using conventional logging curve data by adopting a weighted average method, and determining the average porosity phi of the stratum and the fluid density rho w by using the conventional logging curve data of the whole well section and core porosity analysis data of a regional exploratory well core-taking well;
the density rhoma dimension of the rock skeleton is g/cm3，
The average porosity of the formation phi dimension is a percentage,
the fluid density rho w dimension is g/cm3；
2) Collecting the logging curve data of the depth, the vertical depth, the acoustic wave AC, the density DEN and the neutron CN L of the reservoir section of the shale gas well;
density DEN dimension is g/cm3，
The acoustic wave AC dimension is μ s/m,
the neutron CN L dimension is a percentage,
3) calculating the average density rho of the stratum according to the density rho ma of the stratum rock skeleton, the porosity phi and the fluid density rho w obtained in the step 1):
ρ＝(1-Φ)*ρma+Φ*ρw,
the average density rho dimension of the stratum is g/cm3；
4) Determining a fracture pressure coefficient K, namely P0+ P1 AC + P2 + DEN + P3 CN L by a fitting regression method according to the sound wave, density DEN and neutron logging curve data of the shale reservoir interval collected in the step 2) and the fracture pressure of the fractured well in the region,
in the formula, P0-P3 are regional empirical coefficients and are related to the lithology of the stratum of the fracturing section, and the lithology of the stratum is related to a logging curve;
5) by the formula: calculating a formation fracture pressure gradient FRAC of the shale gas reservoir section according to the FRAC rho;
wherein the FPAC dimension of the shale reservoir stratum fracture pressure gradient is MPa/100m,
the average density rho dimension of the stratum is g/cm3；
6) And outputting a calculation result.
2. The shale gas reservoir formation fracture pressure gradient calculation method of claim 1, wherein: and (3) the conventional logging curve data in the step 1) is data excluding bad well bores and unreliable data.
3. The shale gas reservoir formation fracture pressure gradient calculation method of claim 1, wherein: the fluid density rho is 1.1 +/-0.1 g/cm3。
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| CN108708715A (en) * | 2018-05-02 | 2018-10-26 | 中石化石油工程技术服务有限公司 | The survey logging method of fast prediction shale gas-bearing formation formation fracture pressure gradient |
| CN108801538B (en) * | 2018-06-15 | 2020-10-30 | 中国石油大学(华东) | Method for calculating pressure attenuation gradient |
| CN110469321B (en) * | 2019-08-05 | 2023-03-24 | 中国石油化工股份有限公司 | Logging method for determining stratum fracture pressure gradient |
| CN110410069B (en) * | 2019-08-15 | 2022-08-19 | 中石化石油工程技术服务有限公司 | Shale gas horizontal well stratum fracture pressure gradient logging prediction method |
| CN113550740A (en) * | 2020-04-24 | 2021-10-26 | 中国石油化工股份有限公司 | Method for realizing continuous calculation of longitudinal pressure gradient of single well |
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