Pore pressure prediction method and device

Abstract

The invention provides a pore pressure prediction method and device, and relates to the technical field of data processing. The method comprises the steps that according to the shale content, the total porosity and a preset fitting coefficient, the longitudinal wave speed of the rock when the effective pressure is zero is obtained through calculation; according to the longitudinal wave speed of the rock when the effective pressure is zero, the longitudinal wave speed when the micro-fracture is closed, the pressure when the soft hole in the rock is closed, the longitudinal wave speed of logging measurement, the first preset coefficient and the second preset coefficient, the actual effective pressure of the rock is obtained through calculation; and calculating the pore pressure according to the overlying rock pressure and the effective pressure of the actual rock. The device executes the method. According to the pore pressure prediction method and device provided by the embodiment of the invention, the pore pressure can be accurately predicted.

Description

Technical Field

[0001] The present invention relates to the technical field of data processing, and in particular to a pore pressure prediction method and device. Background Art

[0002] Pore ​​pressure prediction is widely used in all stages of oil and gas exploration, development, and engineering. In the geological exploration stage, pressure controls the generation, migration, accumulation, preservation, accumulation process, and distribution of oil and gas. Known pore pressure can be used for oil and gas detection and reserve confirmation; in the development stage, pressure directly provides energy for oil and gas migration. Known pore pressure can be used to determine the connectivity of inter-well reservoirs and optimize reservoir transformation; in the drilling stage, abnormally high pressure may cause blowouts, well wall instability, wellbore erosion, and drilling fluid circulation loss. Known pore pressure can be used to effectively prevent blowouts, stuck drill, and well leakage, and ensure the smooth progress of drilling operations. Therefore, using seismic data to accurately and comprehensively predict the pore pressure of complex porous reservoirs will help improve drilling and ensure drilling safety and economy.

[0003] Existing pore pressure prediction is based on effective stress theory and compaction theory, and adopts empirical models. These empirical models mainly consider the mechanical compaction of the formation and assume an obvious relationship between porosity and effective stress. Therefore, they are more suitable for rocks with developed primary pores. However, for rocks with dominant chemical compaction and developed secondary pores, the relationship between velocity and effective stress diverges and the correlation coefficient is small due to the extremely uneven distribution of porosity, saturation, permeability, pore structure, etc. within the formation. The prediction results of these models often deviate greatly from the actual drilling results.

[0004] The application conditions of existing pressure prediction models are relatively stringent. For example, the Eaton pressure model assumes that the longitudinal wave velocity is zero when the effective pressure is zero, while the Bowers pressure model assumes that the longitudinal wave velocity is 1500m / s when the effective pressure is zero. These assumptions are inconsistent with the actual rock velocity when the effective pressure is zero, and large errors are inevitable when applying these formulas for pressure prediction. Summary of the invention

[0005] In view of the problems in the prior art, an embodiment of the present invention provides a pore pressure prediction method and device, which can at least partially solve the problems in the prior art.

[0006] In one aspect, the present invention provides a pore pressure prediction method, comprising:

[0007] According to the shale content, total porosity and preset fitting coefficient, the longitudinal wave velocity of the rock when the effective pressure is zero is calculated;

[0008] The effective pressure of the actual rock is calculated based on the P-wave velocity of the rock when the effective pressure is zero, the P-wave velocity when the microcracks are closed, the pressure when the soft pores in the rock are closed, the P-wave velocity measured by well logging, the first preset coefficient and the second preset coefficient;

[0009] The pore pressure is calculated based on the overburden pressure and the effective pressure of the actual rock.

[0010] The method of calculating the longitudinal wave velocity of the rock when the effective pressure is zero according to the shale content, the total porosity and the preset fitting coefficient includes:

[0011] The longitudinal wave velocity of rock when the effective pressure is zero is calculated according to the following formula:

[0012]

[0013] in, is the longitudinal wave velocity of the rock when the effective pressure is zero, Vsh is the mud content, φ is the total porosity, d0, d1, d2 and d3 are all preset fitting coefficients.

[0014] The effective pressure of the actual rock is calculated based on the P-wave velocity of the rock when the effective pressure is zero, the P-wave velocity when the microcracks are closed, the pressure when the soft pores in the rock are closed, the P-wave velocity measured by well logging, the first preset coefficient and the second preset coefficient, including:

[0015] The effective pressure of the actual rock is calculated according to the following formula:

[0016]

[0017] Among them, P eff is the effective pressure of the actual rock, is the longitudinal wave velocity of the rock when the effective pressure is zero, is the longitudinal wave velocity when the microcrack is closed, P inf To make the soft pores in the rock close, is the longitudinal wave velocity measured by well logging, a is the first preset coefficient, and b is the second preset coefficient.

[0018] The pore pressure is calculated based on the overburden pressure and the effective pressure of the actual rock, including:

[0019] The pore pressure is calculated according to the following formula:

[0020] P pore =P overburden -P eff

[0021] Among them, P pore is the pore pressure, Poverburden is the overburden pressure, P eff is the effective pressure of the actual rock.

[0022] Wherein, the pore pressure prediction method further includes:

[0023] Based on the dual-porosity rock physics model, soft pore and hard pore inversion is performed to obtain the longitudinal wave velocity when the microcracks are closed and the pressure when the soft pores in the rock are closed.

[0024] Wherein, obtaining the longitudinal wave velocity when the microcrack is closed includes:

[0025] The longitudinal wave velocity when microcracks are closed is calculated based on the bulk modulus of saturated rock when microcracks are closed, the density of saturated rock when microcracks are closed, and the shear modulus of dry rock skeleton when soft pores in the rock are closed.

[0026] The dry rock skeleton shear modulus when the soft pores in the rock are closed includes taking the porosity of the optimal hard pore as a calculation factor for calculating the dry rock skeleton shear modulus when the soft pores in the rock are closed;

[0027] The optimal hard hole porosity is the porosity of the hard hole when the error between the dry rock skeleton bulk modulus obtained according to actual measurement data and the dry rock skeleton bulk modulus estimated by the rock physics model is minimized.

[0028] Wherein, obtaining the pressure at which the soft pores in the rock are closed includes:

[0029] The porosity of the optimal soft pore is set to zero, and the pressure that closes the soft pores in the rock is calculated according to the following formula:

[0030]

[0031] Among them, P inf The pressure when the soft pores in the rock are closed, K m is the bulk modulus of the rock matrix of the actual measured data, G m is the shear modulus of the rock matrix, α c is the pore aspect ratio of the soft pores, σ m is the Poisson's ratio of the rock matrix.

[0032] In one aspect, the present invention provides a pore pressure prediction device, comprising:

[0033] The first calculation unit is used to calculate the longitudinal wave velocity of the rock when the effective pressure is zero according to the shale content, the total porosity and the preset fitting coefficient;

[0034] The second calculation unit is used to calculate the effective pressure of the actual rock according to the P-wave velocity of the rock when the effective pressure is zero, the P-wave velocity when the microcracks are closed, the pressure when the soft pores in the rock are closed, the P-wave velocity measured by well logging, the first preset coefficient and the second preset coefficient;

[0035] The third calculation unit is used to calculate the pore pressure according to the overburden stratum pressure and the effective pressure of the actual rock.

[0036] In another aspect, an embodiment of the present invention provides an electronic device, including: a processor, a memory, and a bus, wherein:

[0037] The processor and the memory communicate with each other via the bus;

[0038] The memory stores program instructions that can be executed by the processor, and the processor calls the program instructions to execute the following method:

[0039] According to the shale content, total porosity and preset fitting coefficient, the longitudinal wave velocity of the rock when the effective pressure is zero is calculated;

[0040] The effective pressure of the actual rock is calculated based on the P-wave velocity of the rock when the effective pressure is zero, the P-wave velocity when the microcracks are closed, the pressure when the soft pores in the rock are closed, the P-wave velocity measured by well logging, the first preset coefficient and the second preset coefficient;

[0041] The pore pressure is calculated based on the overburden pressure and the effective pressure of the actual rock.

[0042] An embodiment of the present invention provides a non-transitory computer-readable storage medium, including:

[0043] The non-transitory computer-readable storage medium stores computer instructions, which cause the computer to execute the following method:

[0044] According to the shale content, total porosity and preset fitting coefficient, the longitudinal wave velocity of the rock when the effective pressure is zero is calculated;

[0045] The effective pressure of the actual rock is calculated based on the P-wave velocity of the rock when the effective pressure is zero, the P-wave velocity when the microcracks are closed, the pressure when the soft pores in the rock are closed, the P-wave velocity measured by well logging, the first preset coefficient and the second preset coefficient;

[0046] The pore pressure is calculated based on the overburden pressure and the effective pressure of the actual rock.

[0047] The pore pressure prediction method and device provided in the embodiment of the present invention calculate the longitudinal wave velocity of the rock when the effective pressure is zero according to the mud content, the total porosity and the preset fitting coefficient; calculate the effective pressure of the actual rock according to the longitudinal wave velocity of the rock when the effective pressure is zero, the longitudinal wave velocity when the microcracks are closed, the pressure when the soft pores in the rock are closed, the longitudinal wave velocity measured by well logging, the first preset coefficient and the second preset coefficient; calculate the pore pressure according to the overburden pressure and the effective pressure of the actual rock, and can accurately predict the pore pressure. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0049] Figure 1 It is a flow chart of a pore pressure prediction method provided in one embodiment of the present invention.

[0050] Figure 2 It is a flow chart of a pore pressure prediction method provided by another embodiment of the present invention.

[0051] Figure 3 It is a schematic diagram illustrating the “three-point” effective pressure model provided by an embodiment of the present invention.

[0052] Figure 4 It is a schematic diagram of the structure of a pore pressure prediction device provided in one embodiment of the present invention.

[0053] Figure 5 A schematic diagram of the physical structure of an electronic device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention more clear, the embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings. Here, the illustrative embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention. It should be noted that, in the absence of conflict, the embodiments in this application and the features in the embodiments can be combined with each other arbitrarily.

[0055] Figure 1 FIG. 1 is a flow chart of a pore pressure prediction method provided by an embodiment of the present invention. Figure 1 As shown, the pore pressure prediction method provided by the embodiment of the present invention includes:

[0056] Step S1: Calculate the longitudinal wave velocity of the rock when the effective pressure is zero according to the shale content, total porosity and preset fitting coefficient.

[0057] Step S2: Calculate the effective pressure of the actual rock based on the P-wave velocity of the rock when the effective pressure is zero, the P-wave velocity when the microcracks are closed, the pressure when the soft pores in the rock are closed, the P-wave velocity measured by well logging, the first preset coefficient and the second preset coefficient.

[0058] Step S3: Calculate the pore pressure based on the overburden pressure and the effective pressure of the actual rock.

[0059] In the above step S1, the device calculates the longitudinal wave velocity of the rock when the effective pressure is zero according to the shale content, total porosity and the preset fitting coefficient. The device can be a computer device for executing the method, for example, it can include a server. Total porosity φ = φ c +φ s ;

[0060] Among them, φ c is the porosity of the soft pores, φ s is the porosity of hard pores.

[0061] The method of calculating the longitudinal wave velocity of the rock when the effective pressure is zero according to the shale content, the total porosity and the preset fitting coefficient includes:

[0062] The longitudinal wave velocity of rock when the effective pressure is zero is calculated according to the following formula:

[0063]

[0064] in, is the longitudinal wave velocity of rock when the effective pressure is zero, Vsh is the mud content, φ is the total porosity, d0, d1, d2 and d3 are all preset fitting coefficients, which can be fitted using the rock physics experimental data of the study area. The values ​​may be different in different study areas, and can be taken as d0=6.4353, d1=-4.26732, d2=-20.5315, d3=0.00178541.

[0065] like Figure 2 As shown, before this step, the longitudinal wave velocity when the microcracks are closed (corresponding to the soft pore closing velocity) and the pressure when the soft pores in the rock are closed (corresponding to the soft pore closing pressure) can be calculated.

[0066] Specifically, soft pore and hard pore inversion is performed based on the dual-porosity rock physics model to obtain the longitudinal wave velocity when the microcracks are closed and the pressure when the soft pores in the rock are closed.

[0067] You can first collect logging and seismic data in the study area, which can include pore pressure measured by logging, longitudinal and shear wave velocities and density measured by logging and seismic inversion, as well as mud content, porosity and saturation data.

[0068] Based on the data collected above, the dry rock skeleton bulk modulus of the actual measured data is calculated using the following GASSMANN equation:

[0069]

[0070] in, is the bulk modulus of dry rock skeleton of actual measured data, K sat is the saturated rock bulk modulus of the actual measured data, K m is the rock matrix bulk modulus of the actual measured data, K f is the fluid modulus, for gas-water two-phase fluid Among them, K g is the bulk modulus of natural gas, K w is the bulk modulus of water, S w is the water saturation, φ is the total porosity, V P is the longitudinal wave velocity, V s is the shear wave velocity, ρ sat is the density of the fluid-saturated rock, K m The calculation method is related to the composition of the rock matrix. When there is only one mineral, such as quartz, the bulk modulus is the quartz bulk modulus. When the component is greater than 2, the conventional VRH average model can be used for calculation.

[0071] The dry rock skeleton bulk modulus estimated by the rock physics model was calculated according to the following formula:

[0072]

[0073] in, The dry rock skeleton bulk modulus, P, estimated by the rock physics model c is the geometric factor of soft pores used in calculating the bulk modulus of dry rock skeleton, P s The geometric factors of hard pores used in calculating the bulk modulus of dry rock skeletons are functions of the pore aspect ratio.

[0074] Determining the optimal soft pore porosity using an optimization algorithm and the porosity of the optimal hard pore The dry rock skeleton bulk modulus obtained from actual measured data Bulk modulus of dry rock skeleton estimated from rock physics model The error between them is minimal.

[0075] Obtaining the pressure at which the soft pores in the rock are closed includes:

[0076] The porosity of the optimal soft pore is set to zero, and the pressure that closes the soft pores in the rock is calculated according to the following formula:

[0077]

[0078] Among them, P inf The pressure when the soft pores in the rock are closed, K m is the bulk modulus of the rock matrix of the actual measured data, G m is the shear modulus of the rock matrix, α c is the pore aspect ratio of the soft pores, σ m is the Poisson's ratio of the rock matrix.

[0079] Obtaining the longitudinal wave velocity when the microcrack is closed, comprising:

[0080] The P-wave velocity when microcracks are closed is calculated based on the bulk modulus of saturated rock when microcracks are closed, the density of saturated rock when microcracks are closed, and the shear modulus of dry rock skeleton when soft pores in the rock are closed. The P-wave velocity when microcracks are closed is calculated according to the following formula:

[0081]

[0082] in, is the longitudinal wave velocity when the microcrack closes, is the density of saturated rock when microcracks are closed. For gas-water two-phase fluid, we have:

[0083]

[0084] ρ sat is the density of saturated rock, ρ g is the gas density, ρ w is the density of salt water, is the porosity of the optimal soft pores. is the bulk modulus of saturated rock when microcracks are closed, expressed according to the following formula:

[0085]

[0086] is the bulk modulus of the dry rock skeleton when the soft pores in the rock are closed.

[0087] It is the shear modulus of dry rock skeleton when the soft pores in the rock are closed. Q sA geometric factor related to hard pores used to calculate the shear modulus of the dry rock skeleton, which is a function of the pore aspect ratio.

[0088] Among them, the shear modulus of the dry rock skeleton when the soft pores in the rock are closed includes using the porosity of the optimal hard pores as a calculation factor for calculating the shear modulus of the dry rock skeleton when the soft pores in the rock are closed; please refer to the above description and no further details will be given.

[0089] The optimal hard hole porosity is the porosity of the hard hole when the error between the dry rock skeleton bulk modulus obtained according to the actual measurement data and the dry rock skeleton bulk modulus estimated by the rock physics model is minimized. Referring to the above description, no further details are given.

[0090] In the above step S2, the device calculates the effective pressure of the actual rock according to the longitudinal wave velocity of the rock when the effective pressure is zero, the longitudinal wave velocity when the microcracks are closed, the pressure when the soft pores in the rock are closed, the longitudinal wave velocity measured by well logging, the first preset coefficient and the second preset coefficient. The method of calculating the effective pressure of the actual rock according to the longitudinal wave velocity of the rock when the effective pressure is zero, the longitudinal wave velocity when the microcracks are closed, the pressure when the soft pores in the rock are closed, the longitudinal wave velocity measured by well logging, the first preset coefficient and the second preset coefficient includes:

[0091] The actual effective pressure of rock (corresponding to Figure 2 The "three-point" effective pressure model):

[0092]

[0093] Among them, P eff is the effective pressure of the actual rock, is the longitudinal wave velocity of the rock when the effective pressure is zero, is the longitudinal wave velocity when the microcrack is closed, P inf To make the soft pores in the rock close, is the P-wave velocity measured by well logging, a is the first preset coefficient, b is the second preset coefficient, and a and b can be obtained by fitting the pressure measurement points in the study area.

[0094] In the above step S3, the device calculates the pore pressure according to the overburden pressure and the actual effective pressure of the rock. The pore pressure is calculated according to the overburden pressure and the actual effective pressure of the rock, including:

[0095] The pore pressure is calculated according to the following formula:

[0096] P pore =P overburden -P eff

[0097] Among them, P pore is the pore pressure, P overburden is the overburden pressure, P eff is the effective pressure of the actual rock.

[0098] Combination Figure 2 The pore pressure prediction method provided by the embodiment of the present invention is described as follows:

[0099] The first step is to collect the P-wave and S-wave velocity data in the work area as well as reservoir parameter data such as mud content, porosity and saturation from logging interpretation or seismic inversion; the second step is to use the dual-porosity rock physics model to invert the soft pore and hard pore porosity of the rock from the seismic elastic parameters, and use the closing pressure equation to calculate the pressure and corresponding P-wave velocity when the soft pores in the rock are closed; the third step is to use the zero effective pressure velocity model to calculate the zero effective pressure velocity from the mud content and porosity of the rock; finally, the "three-point" effective pressure model is used to calculate the pore pressure.

[0100] like Figure 3 As shown in the figure, the “three-point” effective pressure model is explained as follows:

[0101] Figure 3 The point where the five-pointed star is located is the effective pressure position to be determined. Figure 3 The points at the three arrows can construct a triangle to establish the effective pressure model proposed in the present invention. The a and b parameters in the model need to be obtained by regression from the well site pressure point data actually measured in the work area.

[0102] Furthermore, the calculation of the longitudinal wave velocity of the rock when the effective pressure is zero according to the shale content, the total porosity and the preset fitting coefficient includes:

[0103] The longitudinal wave velocity of rock when the effective pressure is zero is calculated according to the following formula:

[0104]

[0105] in, is the longitudinal wave velocity of the rock when the effective pressure is zero, Vsh is the shale content, φ is the total porosity, d0, d1, d2 and d3 are all preset fitting coefficients. The above embodiments can be referred to for explanation and will not be repeated here.

[0106] Furthermore, the effective pressure of the actual rock is calculated based on the P-wave velocity of the rock when the effective pressure is zero, the P-wave velocity when the microcracks are closed, the pressure when the soft pores in the rock are closed, the P-wave velocity measured by well logging, the first preset coefficient and the second preset coefficient, including:

[0107] The effective pressure of the actual rock is calculated according to the following formula:

[0108]

[0109] Among them, P eff is the effective pressure of the actual rock, is the longitudinal wave velocity of the rock when the effective pressure is zero, is the longitudinal wave velocity when the microcrack is closed, P inf To make the soft pores in the rock close, is the P-wave velocity measured by well logging, a is the first preset coefficient, and b is the second preset coefficient. The above embodiments can be referred to for explanation and will not be described in detail.

[0110] Furthermore, the pore pressure is calculated based on the overburden pressure and the effective pressure of the actual rock, including:

[0111] The pore pressure is calculated according to the following formula:

[0112] P pore =P overburden -P eff

[0113] Among them, P pore is the pore pressure, P overburden is the overburden pressure, P eff is the effective pressure of the actual rock. Please refer to the above embodiment for explanation, which will not be described in detail.

[0114] Furthermore, the pore pressure prediction method further includes:

[0115] Based on the dual-porosity rock physics model, soft pore and hard pore inversion is performed to obtain the longitudinal wave velocity when the microcracks are closed and the pressure when the soft pores in the rock are closed. The above-mentioned embodiments can be referred to for explanation and will not be repeated here.

[0116] Further, obtaining the longitudinal wave velocity when the microcrack is closed includes:

[0117] The longitudinal wave velocity when the microcracks are closed is calculated based on the bulk modulus of the saturated rock when the microcracks are closed, the density of the saturated rock when the microcracks are closed, and the shear modulus of the dry rock skeleton when the soft pores in the rock are closed; the above-mentioned embodiments can be referred to for explanation and will not be repeated here.

[0118] Among them, the shear modulus of the dry rock skeleton when the soft pores in the rock are closed includes using the porosity of the optimal hard pores as a calculation factor for calculating the shear modulus of the dry rock skeleton when the soft pores in the rock are closed; the above-mentioned embodiment can be referred to for description and will not be repeated here.

[0119] The optimal hard hole porosity is the porosity of the hard hole when the error between the dry rock skeleton bulk modulus obtained according to actual measurement data and the dry rock skeleton bulk modulus estimated by the rock physics model is minimized. The above-mentioned embodiments can be referred to for explanation and will not be repeated here.

[0120] Further, obtaining the pressure at which the soft pores in the rock are closed includes:

[0121] The porosity of the optimal soft pore is set to zero, and the pressure that closes the soft pores in the rock is calculated according to the following formula:

[0122]

[0123] Among them, P inf The pressure when the soft pores in the rock are closed, K m is the bulk modulus of the rock matrix of the actual measured data, G m is the shear modulus of the rock matrix, α c is the pore aspect ratio of the soft pores, σ m is the Poisson's ratio of the rock matrix. Please refer to the above embodiments for explanation and will not repeat them here.

[0124] The pore pressure prediction method provided in the embodiment of the present invention is used to improve the prediction accuracy of formation pressure in complex porous reservoirs. The soft pore closing pressure and rock velocity at zero pressure are calculated through the rock physics model, and the pressure equation is constructed by the "triangle" composed of the soft pore closing point, the zero pressure point and the measurement point to realize the reservoir pore pressure prediction, which fully considers the influence of the soft and hard pore pore structure in the reservoir on the rock longitudinal wave velocity when the effective pressure changes, and is more suitable for dense sandstone and carbonate reservoirs with highly developed secondary pores. The method of the embodiment of the present invention makes full use of the change of the reservoir longitudinal wave velocity with the porosity of the soft pores in the pores, without the need to use the formation compaction trend line, and overcomes the problem that the calculation of the classic Eaton and other empirical models is cumbersome and the prediction accuracy is restricted by the accuracy of the compaction trend.

[0125] The pore pressure prediction method provided in the embodiment of the present invention has the following main technical improvements:

[0126] One is to invert the porosity of soft pores and hard pores in rock pores from seismic elastic parameters based on the dual-porosity equivalent medium theory and Gassmann equation.

[0127] The second is to calculate the longitudinal wave velocity and closing pressure of the rock when the porosity of the soft pores in the rock pores is zero, that is, the microcracks are closed, and the velocity of the rock when the effective pressure is zero is calculated using the invented empirical formula. A triangle is constructed by "soft pore closure point, measurement point and zero pressure point", and then the pore pressure is calculated by the invented "three-point" effective pressure model.

[0128] The pore pressure prediction method provided by the embodiment of the present invention has the following advantages:

[0129] Based on rock physics theory, it is proposed for the first time to use the variation characteristics of reservoir longitudinal wave velocity with the soft pore porosity in the pores and the pore pressure to establish an equivalent pressure model to predict the pore pressure. In the implementation process, there is no need to use the formation compaction trend line like the conventional formation pressure prediction method, which overcomes the problems of cumbersome calculations of classic empirical models such as Eaton and the prediction accuracy being restricted by the accuracy of the compaction trend.

[0130] The pore pressure prediction method provided in the embodiment of the present invention calculates the longitudinal wave velocity of the rock when the effective pressure is zero according to the mud content, the total porosity and the preset fitting coefficient; calculates the effective pressure of the actual rock according to the longitudinal wave velocity of the rock when the effective pressure is zero, the longitudinal wave velocity when the microcracks are closed, the pressure when the soft pores in the rock are closed, the longitudinal wave velocity measured by well logging, the first preset coefficient and the second preset coefficient; calculates the pore pressure according to the overburden pressure and the effective pressure of the actual rock, and can accurately predict the pore pressure.

[0131] Figure 4 is a schematic diagram of the structure of a pore pressure prediction device provided by an embodiment of the present invention. Figure 4 As shown, the pore pressure prediction device provided by the embodiment of the present invention includes a first calculation unit 401, a second calculation unit 402 and a third calculation unit 403, wherein:

[0132] The first calculation unit 401 is used to calculate the P-wave velocity of the rock when the effective pressure is zero according to the mud content, the total porosity and the preset fitting coefficient; the second calculation unit 402 is used to calculate the effective pressure of the actual rock according to the P-wave velocity of the rock when the effective pressure is zero, the P-wave velocity when the microcracks are closed, the pressure when the soft pores in the rock are closed, the P-wave velocity measured by well logging, the first preset coefficient and the second preset coefficient; the third calculation unit 403 is used to calculate the pore pressure according to the overlying rock pressure and the effective pressure of the actual rock.

[0133] Specifically, the first calculation unit 401 in the device is used to calculate the P-wave velocity of the rock when the effective pressure is zero according to the mud content, the total porosity and the preset fitting coefficient; the second calculation unit 402 is used to calculate the effective pressure of the actual rock according to the P-wave velocity of the rock when the effective pressure is zero, the P-wave velocity when the microcracks are closed, the pressure when the soft pores in the rock are closed, the P-wave velocity measured by well logging, the first preset coefficient and the second preset coefficient; the third calculation unit 403 is used to calculate the pore pressure according to the overlying rock pressure and the effective pressure of the actual rock.

[0134] The pore pressure prediction device provided in the embodiment of the present invention calculates the longitudinal wave velocity of the rock when the effective pressure is zero according to the mud content, the total porosity and the preset fitting coefficient; calculates the effective pressure of the actual rock according to the longitudinal wave velocity of the rock when the effective pressure is zero, the longitudinal wave velocity when the microcracks are closed, the pressure when the soft pores in the rock are closed, the longitudinal wave velocity measured by well logging, the first preset coefficient and the second preset coefficient; calculates the pore pressure according to the overlying rock pressure and the effective pressure of the actual rock, and can accurately predict the pore pressure.

[0135] Furthermore, the first calculation unit 401 is specifically configured to:

[0136] The longitudinal wave velocity of rock when the effective pressure is zero is calculated according to the following formula:

[0137]

[0138] in, is the longitudinal wave velocity of the rock when the effective pressure is zero, Vsh is the mud content, φ is the total porosity, d0, d1, d2 and d3 are all preset fitting coefficients.

[0139] Further, the second calculating unit 402 is specifically used for:

[0140] The effective pressure of the actual rock is calculated according to the following formula:

[0141]

[0142] Among them, P eff is the effective pressure of the actual rock, is the longitudinal wave velocity of the rock when the effective pressure is zero, is the longitudinal wave velocity when the microcrack is closed, P inf To make the soft pores in the rock close, is the longitudinal wave velocity measured by well logging, a is the first preset coefficient, and b is the second preset coefficient.

[0143] Furthermore, the third calculation unit 403 is specifically used for:

[0144] The pore pressure is calculated according to the following formula:

[0145] P pore =P overburden -P eff

[0146] Among them, P pore is the pore pressure, P overburden is the overburden pressure, P eff is the effective pressure of the actual rock.

[0147] Furthermore, the pore pressure prediction device is also used for:

[0148] Based on the dual-porosity rock physics model, soft pore and hard pore inversion is performed to obtain the longitudinal wave velocity when the microcracks are closed and the pressure when the soft pores in the rock are closed.

[0149] Furthermore, the pore pressure prediction device is also specifically used for:

[0150] The longitudinal wave velocity when microcracks are closed is calculated based on the bulk modulus of saturated rock when microcracks are closed, the density of saturated rock when microcracks are closed, and the shear modulus of dry rock skeleton when soft pores in the rock are closed.

[0151] The dry rock skeleton shear modulus when the soft pores in the rock are closed includes taking the porosity of the optimal hard pore as a calculation factor for calculating the dry rock skeleton shear modulus when the soft pores in the rock are closed;

[0152] The optimal hard hole porosity is the porosity of the hard hole when the error between the dry rock skeleton bulk modulus obtained according to actual measurement data and the dry rock skeleton bulk modulus estimated by the rock physics model is minimized.

[0153] Furthermore, the pore pressure prediction device is also specifically used for:

[0154] The porosity of the optimal soft pore is set to zero, and the pressure that closes the soft pores in the rock is calculated according to the following formula:

[0155]

[0156] Among them, P inf The pressure when the soft pores in the rock are closed, K m is the bulk modulus of the rock matrix of the actual measured data, G m is the shear modulus of the rock matrix, α c is the pore aspect ratio of the soft pores, σ m is the Poisson's ratio of the rock matrix.

[0157] The embodiment of the pore pressure prediction device provided in the embodiment of the present invention can be specifically used to execute the processing flow of the above-mentioned method embodiments. Its functions are not repeated here, and reference can be made to the detailed description of the above-mentioned method embodiments.

[0158] Figure 5 A schematic diagram of the physical structure of an electronic device provided in an embodiment of the present invention, such as Figure 5 As shown, the electronic device includes: a processor (processor) 501, a memory (memory) 502 and a bus 503;

[0159] The processor 501 and the memory 502 communicate with each other via a bus 503;

[0160] The processor 501 is used to call the program instructions in the memory 502 to execute the methods provided by the above method embodiments, for example, including:

[0161] According to the shale content, total porosity and preset fitting coefficient, the longitudinal wave velocity of the rock when the effective pressure is zero is calculated;

[0162] The effective pressure of the actual rock is calculated based on the P-wave velocity of the rock when the effective pressure is zero, the P-wave velocity when the microcracks are closed, the pressure when the soft pores in the rock are closed, the P-wave velocity measured by well logging, the first preset coefficient and the second preset coefficient;

[0163] The pore pressure is calculated based on the overburden pressure and the effective pressure of the actual rock.

[0164] This embodiment discloses a computer program product, which includes a computer program stored on a non-transitory computer-readable storage medium. The computer program includes program instructions. When the program instructions are executed by a computer, the computer can perform the methods provided by the above method embodiments, for example, including:

[0165] According to the shale content, total porosity and preset fitting coefficient, the longitudinal wave velocity of the rock when the effective pressure is zero is calculated;

[0166] The effective pressure of the actual rock is calculated based on the P-wave velocity of the rock when the effective pressure is zero, the P-wave velocity when the microcracks are closed, the pressure when the soft pores in the rock are closed, the P-wave velocity measured by well logging, the first preset coefficient and the second preset coefficient;

[0167] The pore pressure is calculated based on the overburden pressure and the effective pressure of the actual rock.

[0168] This embodiment provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, wherein the computer program enables the computer to execute the methods provided by the above method embodiments, for example, including:

[0169] According to the shale content, total porosity and preset fitting coefficient, the longitudinal wave velocity of the rock when the effective pressure is zero is calculated;

[0170] The effective pressure of the actual rock is calculated based on the P-wave velocity of the rock when the effective pressure is zero, the P-wave velocity when the microcracks are closed, the pressure when the soft pores in the rock are closed, the P-wave velocity measured by well logging, the first preset coefficient and the second preset coefficient;

[0171] The pore pressure is calculated based on the overburden pressure and the effective pressure of the actual rock.

[0172] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0173] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0174] These computer program instructions may also be stored in a computer readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture including an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0175] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0176] In the description of this specification, the description with reference to the terms "one embodiment", "a specific embodiment", "some embodiments", "for example", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0177] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A pore pressure prediction method, characterized in that: include: According to the shale content, total porosity and preset fitting coefficient, the longitudinal wave velocity of the rock when the effective pressure is zero is calculated; The effective pressure of the actual rock is calculated based on the P-wave velocity of the rock when the effective pressure is zero, the P-wave velocity when the microcracks are closed, the pressure when the soft pores in the rock are closed, the P-wave velocity measured by well logging, the first preset coefficient and the second preset coefficient; The pore pressure is calculated based on the overburden pressure and the effective pressure of the actual rock.

2. The pore pressure prediction method according to claim 1, characterized in that: The method of calculating the longitudinal wave velocity of the rock when the effective pressure is zero according to the shale content, the total porosity and the preset fitting coefficient includes: The longitudinal wave velocity of rock when the effective pressure is zero is calculated according to the following formula: in, is the longitudinal wave velocity of the rock when the effective pressure is zero, Vsh is the mud content, φ is the total porosity, d0, d1, d2 and d3 are all preset fitting coefficients.

3. The pore pressure prediction method according to claim 1, characterized in that: The method of calculating the effective pressure of the actual rock according to the P-wave velocity of the rock when the effective pressure is zero, the P-wave velocity when the microcracks are closed, the pressure when the soft pores in the rock are closed, the P-wave velocity measured by well logging, the first preset coefficient and the second preset coefficient comprises: The effective pressure of the actual rock is calculated according to the following formula: Among them, P eff is the effective pressure of the actual rock, is the longitudinal wave velocity of the rock when the effective pressure is zero, is the longitudinal wave velocity when the microcrack is closed, P inf To make the soft pores in the rock close, is the longitudinal wave velocity measured by well logging, a is the first preset coefficient, and b is the second preset coefficient.

4. The pore pressure prediction method according to claim 1, characterized in that: The pore pressure is calculated based on the overburden pressure and the effective pressure of the actual rock, including: The pore pressure is calculated according to the following formula: P pore =P overburden -P eff Among them, P pore is the pore pressure, P overburden is the overburden pressure, P eff is the effective pressure of the actual rock.

5. The pore pressure prediction method according to any one of claims 1 to 4, characterized in that: The pore pressure prediction method further comprises: Based on the dual-porosity rock physics model, soft pore and hard pore inversion is performed to obtain the longitudinal wave velocity when the microcracks are closed and the pressure when the soft pores in the rock are closed.

6. The pore pressure prediction method according to claim 5, characterized in that: Obtaining the longitudinal wave velocity when the microcrack is closed, comprising: The longitudinal wave velocity when microcracks are closed is calculated based on the bulk modulus of saturated rock when microcracks are closed, the density of saturated rock when microcracks are closed, and the shear modulus of dry rock skeleton when soft pores in the rock are closed. The dry rock skeleton shear modulus when the soft pores in the rock are closed includes taking the porosity of the optimal hard pore as a calculation factor for calculating the dry rock skeleton shear modulus when the soft pores in the rock are closed; The optimal hard hole porosity is the porosity of the hard hole when the error between the dry rock skeleton bulk modulus obtained according to actual measurement data and the dry rock skeleton bulk modulus estimated by the rock physics model is minimized.

7. The pore pressure prediction method according to claim 5, characterized in that: Obtaining the pressure at which the soft pores in the rock are closed includes: The porosity of the optimal soft pore is set to zero, and the pressure that closes the soft pores in the rock is calculated according to the following formula: Among them, P inf The pressure when the soft pores in the rock are closed, K m is the bulk modulus of the rock matrix of the actual measured data, G m is the shear modulus of the rock matrix, α c is the pore aspect ratio of the soft pores, σ m is the Poisson's ratio of the rock matrix.

8. A pore pressure prediction device, characterized in that: include: The first calculation unit is used to calculate the longitudinal wave velocity of the rock when the effective pressure is zero according to the shale content, the total porosity and the preset fitting coefficient; The second calculation unit is used to calculate the effective pressure of the actual rock according to the P-wave velocity of the rock when the effective pressure is zero, the P-wave velocity when the microcracks are closed, the pressure when the soft pores in the rock are closed, the P-wave velocity measured by well logging, the first preset coefficient and the second preset coefficient; The third calculation unit is used to calculate the pore pressure according to the overburden stratum pressure and the effective pressure of the actual rock.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

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