A method and apparatus for predicting pore pressure

Abstract

This invention provides a method and apparatus for predicting pore pressure, relating to the field of data processing technology. The method includes: calculating the P-wave velocity of rock when the effective pressure is zero based on clay content, total porosity, and preset fitting coefficients; calculating the actual effective pressure of the rock based on the P-wave velocity of the rock when the effective pressure is zero, the P-wave velocity at the closure of microfractures, the pressure at which soft pores in the rock close, the P-wave velocity measured by well logging, a first preset coefficient, and a second preset coefficient; and calculating the pore pressure based on the pressure of the overlying strata and the actual effective pressure of the rock. The apparatus performs the above method. The pore pressure prediction method and apparatus provided by this invention can accurately predict pore pressure.

Description

Technical Field

[0001] This invention relates to the field of data processing technology, and specifically to a method and apparatus for predicting pore pressure. Background Technology

[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, and reservoir formation processes of oil and gas, as well as their distribution. Known pore pressures can be used for oil and gas detection and reserve confirmation. In the development stage, pressure directly provides the energy for oil and gas migration; known pore pressures can be used to determine the connectivity of reservoirs between wells and optimize reservoir stimulation. In the drilling stage, abnormally high pressures can cause blowouts, wellbore instability, wellbore erosion, and drilling fluid circulation loss. Known pore pressures can be used to effectively prevent blowouts, stuck pipe, and lost circulation, ensuring smooth drilling operations. Therefore, accurately and comprehensively predicting pore pressures in complex pore reservoirs using seismic data helps improve drilling and ensures drilling safety and economy.

[0003] Existing pore pressure prediction methods are based on effective stress theory and compaction theory, and employ empirical models. These empirical models mainly consider the mechanical compaction of the formation and assume a clear relationship between porosity and effective stress. Therefore, they are more suitable for rocks with well-developed primary pores. However, for rocks where chemical compaction is dominant and secondary pores are well-developed, the extremely uneven distribution of porosity, saturation, permeability, and pore structure within the formation leads to a divergent relationship between velocity and effective stress, resulting in a small correlation coefficient. Consequently, the prediction results of these models often deviate significantly from actual drilling.

[0004] Existing pressure prediction models have rather stringent application conditions. For example, the Eaton pressure model assumes that the P-wave velocity is zero when the effective pressure is zero, while the Bowers pressure model assumes that the P-wave velocity is 1500 m / s when the effective pressure is zero. These assumptions do not match the actual velocity of rocks when the effective pressure is zero, and inevitably lead to large errors when applying these formulas for pressure prediction. Summary of the Invention

[0005] To address the problems in the prior art, embodiments of the present invention provide a pore pressure prediction method and apparatus, which can at least partially solve the problems existing in the prior art.

[0006] On one hand, this invention proposes a method for predicting pore pressure, comprising:

[0007] Based on the clay content, total porosity, and preset fitting coefficients, 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 longitudinal wave velocity of the rock when the effective pressure is zero, the longitudinal wave velocity when the micro-fractures close, the pressure that causes the soft pores in the rock to close, the longitudinal wave velocity measured by well logging, the first preset coefficient, and the second preset coefficient.

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

[0010] The step of calculating the longitudinal wave velocity of the rock when the effective pressure is zero, based on the clay content, total porosity, and preset fitting coefficients, includes:

[0011] The longitudinal wave velocity of the rock when the effective pressure is zero can be calculated using the following formula:

[0012]

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

[0014] The calculation of the actual rock effective pressure based on the P-wave velocity of the rock when the effective pressure is zero, the P-wave velocity when the microfracture closes, the pressure that causes the soft pores in the rock to close, the P-wave velocity measured by well logging, and the first and second preset coefficients includes:

[0015] The effective pressure of the actual rock can be calculated using the following formula:

[0016]

[0017] Among them, P eff For the effective pressure of actual rock, The longitudinal wave velocity of the rock when the effective pressure is zero. P is the longitudinal wave velocity when the microcrack closes. inf To ensure the pressure required to close soft pores in the rock, , where is the P-wave velocity measured in well logging, 'a' is the first preset coefficient, and 'b' is the second preset coefficient.

[0018] The calculation of pore pressure based on the overlying strata pressure and the actual effective rock pressure includes:

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

[0020] P pore =P overburden -P eff

[0021] Among them, P pore For pore pressure, Poverburden For the pressure of the overlying strata, P eff This represents the effective pressure of the actual rock.

[0022] The pore pressure prediction method further includes:

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

[0024] The process of obtaining the longitudinal wave velocity when the microcrack closes includes:

[0025] The longitudinal wave velocity at the closure of microfractures is calculated based on the bulk modulus of saturated rock at the closure of microfractures, the density of saturated rock at the closure of microfractures, and the shear modulus of dry rock skeleton at the closure of soft pores in the rock.

[0026] Wherein, the dry rock skeleton shear modulus when the soft pores in the rock are closed includes the porosity of the optimal hard pore as a calculation factor for the dry rock skeleton shear modulus when the soft pores in the rock are closed.

[0027] The optimal porosity of hard pores is the porosity of hard pores that minimizes the error between the bulk modulus of the dry rock skeleton obtained from actual measurement data and the bulk modulus of the dry rock skeleton estimated by the rock physics model.

[0028] The method of obtaining the pressure that causes the soft pores in the rock to close includes:

[0029] Set the porosity of the optimal soft pore to zero, and calculate the pressure required to close the soft pore in the rock using the following formula:

[0030]

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

[0032] On one hand, the present invention proposes 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, based on the clay content, total porosity and preset fitting coefficients.

[0034] The second calculation unit is used to calculate the effective pressure of the actual rock based on the longitudinal wave velocity of the rock when the effective pressure is zero, the longitudinal wave velocity when the micro-fractures close, the pressure that causes the soft pores in the rock to close, the longitudinal 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 based on the pressure of the overlying strata and the effective pressure of the actual rock.

[0036] In another aspect, embodiments of the present invention provide 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 can execute the following methods by calling the program instructions:

[0039] Based on the clay content, total porosity, and preset fitting coefficients, 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 longitudinal wave velocity of the rock when the effective pressure is zero, the longitudinal wave velocity when the micro-fractures close, the pressure that causes the soft pores in the rock to close, the longitudinal wave velocity measured by well logging, the first preset coefficient, and the second preset coefficient.

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

[0042] This invention provides a non-transitory computer-readable storage medium, comprising:

[0043] The non-transitory computer-readable storage medium stores computer instructions that cause the computer to perform the following methods:

[0044] Based on the clay content, total porosity, and preset fitting coefficients, 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 longitudinal wave velocity of the rock when the effective pressure is zero, the longitudinal wave velocity when the micro-fractures close, the pressure that causes the soft pores in the rock to close, the longitudinal wave velocity measured by well logging, the first preset coefficient, and the second preset coefficient.

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

[0047] The pore pressure prediction method and apparatus provided in this invention calculate the longitudinal wave velocity of the rock when the effective pressure is zero based on the clay content, total porosity, and preset fitting coefficients; calculate the effective pressure of the actual rock based on the longitudinal wave velocity of the rock when the effective pressure is zero, the longitudinal wave velocity when microfractures close, the pressure that causes soft pores in the rock to close, the longitudinal wave velocity measured by well logging, and the first and second preset coefficients; and calculate the pore pressure based on the pressure of the overlying strata and the effective pressure of the actual rock, thus enabling accurate pore pressure prediction. Attached Figure Description

[0048] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings:

[0049] Figure 1 This is a schematic flowchart of a pore pressure prediction method provided in an embodiment of the present invention.

[0050] Figure 2 This is a schematic flowchart of a pore pressure prediction method provided in another embodiment of the present invention.

[0051] Figure 3 This is a schematic diagram illustrating the "three-point" effective pressure model provided in the embodiments of the present invention.

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

[0053] Figure 5 This is a schematic diagram of the physical structure of an electronic device provided in an embodiment of the present invention. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Here, the illustrative embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be arbitrarily combined with each other.

[0055] Figure 1 This is a schematic flowchart of a pore pressure prediction method provided in an embodiment of the present invention, as shown below. Figure 1 As shown, the pore pressure prediction method provided in this embodiment of the invention includes:

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

[0057] Step S2: Calculate the actual effective pressure of the rock based on the longitudinal wave velocity of the rock when the effective pressure is zero, the longitudinal wave velocity when the micro-fractures close, the pressure that causes the soft pores in the rock to close, the longitudinal 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 pressure of the overlying strata and the effective pressure of the actual rock.

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

[0060] Where, φ c For the porosity of soft pores, φ s Porosity of hard pores.

[0061] The calculation of the longitudinal wave velocity of the rock when the effective pressure is zero, based on the clay content, total porosity, and preset fitting coefficients, includes:

[0062] The longitudinal wave velocity of the rock when the effective pressure is zero can be calculated using the following formula:

[0063]

[0064] in, The longitudinal wave velocity of the rock is given by the effective pressure being zero, Vsh is the clay content, φ is the total porosity, and d0, d1, d2, and d3 are preset fitting coefficients that can be obtained by fitting the rock physical experimental data of the study area. The values ​​can be different for different study areas, and can be taken as d0 = 6.4353, d1 = -4.26732, d2 = -20.5315, and d3 = 0.00178541.

[0065] like Figure 2 As shown, prior to this step, the longitudinal wave velocity (corresponding to the soft pore closure velocity) when the microcrack closes and the pressure (corresponding to the soft pore closure pressure) that causes the soft pore in the rock to close can be calculated.

[0066] Specifically, based on the dual-porosity rock physics model, soft pores and hard pores are inverted to obtain the longitudinal wave velocity when the microcracks close and the pressure that causes the soft pores in the rock to close.

[0067] First, well logging and seismic data for the study area can be collected. Specifically, this can include pore pressure measured by well logging, P-wave and S-wave velocities and densities measured by well logging and seismic inversion, as well as data on clay content, porosity, and saturation.

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

[0069]

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

[0071] The bulk modulus of the dry rock skeleton estimated by the rock physics model is calculated using the following formula:

[0072]

[0073] in, Bulk modulus and P of dry rock skeleton estimated for rock physics model c The geometric factor of soft pores, P, used in calculating the bulk modulus of dry rock skeletons. 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 porosity of soft pores using optimization algorithms And the porosity of the optimal hard pore The bulk modulus of the dry rock skeleton obtained from the actual measurement data Bulk modulus of dry rock skeleton estimated by rock physics model The error between them is minimal.

[0075] Obtaining the pressure that causes the soft pores in the rock to close includes:

[0076] Set the porosity of the optimal soft pore to zero, and calculate the pressure required to close the soft pore in the rock using the following formula:

[0077]

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

[0079] Obtaining the longitudinal wave velocity when the microcrack closes includes:

[0080] The P-wave velocity at microfracture closure is calculated based on the bulk modulus of saturated rock at microfracture closure, the density of saturated rock at microfracture closure, and the dry rock skeleton shear modulus at microfracture closure. The P-wave velocity at microfracture closure is calculated using the following formula:

[0081]

[0082] in, The longitudinal wave velocity during microcrack closure, Let be the density of saturated rock when microfractures close. For a gas-water two-phase fluid, we have:

[0083]

[0084] ρ sat The density of saturated rock, ρ g For gas density, ρ w The density of the salt water is... The porosity is the optimal porosity for soft pores. The bulk modulus of saturated rock when microfractures close is expressed by the following formula:

[0085]

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

[0087] This is the dry rock skeleton shear modulus when the soft pores in the rock are closed. Q sThis is a geometric factor related to hard pores used in calculating the shear modulus of dry rock skeletons; it is a function of the pore aspect ratio.

[0088] The dry rock skeleton shear modulus when the soft pores in the rock are closed includes using the porosity of the optimal hard pores as a calculation factor for the dry rock skeleton shear modulus when the soft pores in the rock are closed; this can be referred to the above description and will not be repeated here.

[0089] The optimal porosity of hard pores is the porosity of hard pores that minimizes the error between the bulk modulus of the dry rock skeleton obtained from actual measurement data and the bulk modulus of the dry rock skeleton estimated by the rock physics model. Referring to the above description, further details are omitted.

[0090] In step S2 above, the device calculates the actual effective pressure of the rock based on the P-wave velocity of the rock when the effective pressure is zero, the P-wave velocity when the microfracture closes, the pressure that causes the soft pores in the rock to close, the P-wave velocity measured by well logging, and a first preset coefficient and a second preset coefficient. The calculation of the actual effective pressure of the rock based on the P-wave velocity of the rock when the effective pressure is zero, the P-wave velocity when the microfracture closes, the pressure that causes the soft pores in the rock to close, the P-wave velocity measured by well logging, and the first and second preset coefficients includes:

[0091] The effective pressure of the actual rock is calculated using the following formula (corresponding to...). Figure 2 The "Three-Point" Effective Pressure Model in China:

[0092]

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

[0094] In step S3 above, the device calculates the pore pressure based on the pressure of the overlying strata and the effective pressure of the actual rock. The calculation of the pore pressure based on the pressure of the overlying strata and the effective pressure of the actual rock includes:

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

[0096] P pore =P overburden -P eff

[0097] Among them, P pore For pore pressure, P overburden For the pressure of the overlying strata, P eff This represents the effective pressure of the actual rock.

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

[0099] The first step is to collect P-wave and S-wave velocity data, as well as reservoir parameter data such as clay content, porosity, and saturation from well logging interpretation or seismic inversion within the work area. The second step is to apply a dual-porosity rock physics model to invert the soft and hard pore porosity of the rock from the seismic elastic parameters, and to calculate the pressure and corresponding P-wave velocity when the soft pores in the rock close using the closure pressure equation. The third step is to calculate the zero effective pressure velocity from the clay content and porosity of the rock using the zero effective pressure velocity model. Finally, the pore pressure is calculated using the "three-point" effective pressure model.

[0100] like Figure 3 As shown, the effective pressure model of the "three points" is explained as follows:

[0101] Figure 3 The point where the central pentagram is located is the effective pressure location to be determined. Figure 3 The points at the three arrows can be used to construct a triangle to establish the effective pressure model proposed in this invention. The parameters a and b in the model need to be obtained from the actual measured well site pressure data in the work area through regression.

[0102] Further, the calculation of the longitudinal wave velocity of the rock when the effective pressure is zero, based on the clay content, total porosity, and preset fitting coefficients, includes:

[0103] The longitudinal wave velocity of the rock when the effective pressure is zero can be calculated using the following formula:

[0104]

[0105] in, Vsh represents the longitudinal wave velocity of the rock when the effective pressure is zero, φ represents the clay content, d0, d1, d2, and d3 are all preset fitting coefficients. Refer to the above embodiments for further explanation; details will not be repeated here.

[0106] Further, the calculation of the actual rock effective pressure based on the P-wave velocity of the rock when the effective pressure is zero, the P-wave velocity when the microfracture closes, the pressure that causes the soft pores in the rock to close, the P-wave velocity measured by well logging, and the first and second preset coefficients includes:

[0107] The effective pressure of the actual rock can be calculated using the following formula:

[0108]

[0109] Among them, P eff For the effective pressure of actual rock, The longitudinal wave velocity of the rock when the effective pressure is zero. P is the longitudinal wave velocity when the microcrack closes. inf To ensure the pressure required to close soft pores in the rock, Here, 'a' represents the P-wave velocity measured in well logging, 'a' represents a first preset coefficient, and 'b' represents a second preset coefficient. The above embodiments can be referred to for further explanation, and will not be repeated here.

[0110] Furthermore, the calculation of pore pressure based on the overlying strata pressure and the actual effective rock pressure includes:

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

[0112] P pore =P overburden -P eff

[0113] Among them, P pore For pore pressure, P overburden For the pressure of the overlying strata, P eff This represents the effective pressure of the actual rock. Refer to the above embodiments for further explanation; details will not be repeated here.

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

[0115] Based on the dual-porosity rock physics model, the inversion of soft and hard pores is performed to obtain the longitudinal wave velocity when the microfractures close and the pressure that causes the soft pores in the rock to close. This can be referred to the above embodiments for explanation, and will not be repeated here.

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

[0117] The longitudinal wave velocity at the closure of microfractures is calculated based on the bulk modulus of saturated rock at the closure of microfractures, the density of saturated rock at the closure of microfractures, and the shear modulus of dry rock skeleton at the closure of soft pores in the rock. The above embodiments can be referred to for explanation, and will not be repeated here.

[0118] The dry rock skeleton shear modulus when the soft pores in the rock are closed includes using the porosity of the optimal hard pores as a calculation factor for the dry rock skeleton shear modulus when the soft pores in the rock are closed; this can be referred to the above embodiments for explanation, and will not be repeated here.

[0119] The optimal porosity of hard pores is the porosity of hard pores that minimizes the error between the bulk modulus of the dry rock skeleton obtained from actual measurement data and the bulk modulus of the dry rock skeleton estimated by the rock physics model. This can be explained with reference to the above embodiments, and will not be repeated here.

[0120] Further, obtaining the pressure that causes the soft pores in the rock to close includes:

[0121] Set the porosity of the optimal soft pore to zero, and calculate the pressure required to close the soft pore in the rock using the following formula:

[0122]

[0123] Among them, P inf To ensure the pressure, K, when soft pores in the rock close, m The bulk modulus of the rock matrix and G are the actual measured data. m For the shear modulus of the rock matrix, α c The aspect ratio and σ of the soft pores m This represents the Poisson's ratio of the rock matrix. Refer to the above examples for further details; they will not be repeated here.

[0124] The pore pressure prediction method provided in this invention improves the accuracy of formation pressure prediction in complex porosity reservoirs. It calculates the soft pore closure pressure and rock velocity at zero pressure using a rock physics model. A pressure equation is constructed using a "triangle" formed by the soft pore closure point, the zero-pressure point, and the measurement point to predict reservoir pore pressure. This method fully considers the influence of soft and hard pore structures on rock P-wave velocity under varying effective pressure, making it more suitable for tight sandstone and carbonate reservoirs with highly developed secondary porosity. The method fully utilizes the variation of reservoir P-wave velocity with the porosity of soft pores, eliminating the need for formation compaction trend lines. This overcomes the problems of cumbersome calculations and the limitation of prediction accuracy by the compaction trend in classic empirical models such as Eaton.

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

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

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

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

[0129] Based on rock physics theory, this paper proposes for the first time to establish an equivalent pressure model by utilizing the variation characteristics of reservoir longitudinal wave velocity with soft pore porosity and pore pressure to predict pore pressure. Unlike conventional formation pressure prediction methods, this method does not require the use of formation compaction trend lines, thus overcoming the problems of cumbersome calculations and the limitation of prediction accuracy by the compaction trend in classic empirical models such as Eaton.

[0130] The pore pressure prediction method provided in this invention calculates the P-wave velocity of the rock when the effective pressure is zero based on the clay content, total porosity, and preset fitting coefficients; it calculates 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 microfractures close, the pressure that causes soft pores in the rock to close, the P-wave velocity measured by well logging, and the first and second preset coefficients; and it calculates the pore pressure based on the pressure of the overlying strata and the effective pressure of the actual rock, thus enabling accurate pore pressure prediction.

[0131] Figure 4 This is a schematic diagram of the pore pressure prediction device provided in an embodiment of the present invention, as shown below. Figure 4 As shown, the pore pressure prediction device provided in this embodiment of the 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 longitudinal wave velocity of the rock when the effective pressure is zero based on the clay content, total porosity and preset fitting coefficients; the second calculation unit 402 is used to calculate the effective pressure of the actual rock based on the longitudinal wave velocity of the rock when the effective pressure is zero, the longitudinal wave velocity when the microfractures close, the pressure that causes the soft pores in the rock to close, the longitudinal 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 based on the pressure of the overlying strata and the effective pressure of the actual rock.

[0133] Specifically, the first calculation unit 401 in the device is used to calculate the longitudinal wave velocity of the rock when the effective pressure is zero based on the clay content, total porosity and preset fitting coefficient; the second calculation unit 402 is used to calculate the effective pressure of the actual rock based on the longitudinal wave velocity of the rock when the effective pressure is zero, the longitudinal wave velocity when the microfracture closes, the pressure that causes the soft pores in the rock to close, the longitudinal 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 based on the pressure of the overlying strata and the effective pressure of the actual rock.

[0134] The pore pressure prediction device provided in this invention calculates the longitudinal wave velocity of the rock when the effective pressure is zero based on the clay content, total porosity, and preset fitting coefficients; it calculates the effective pressure of the actual rock based on the longitudinal wave velocity of the rock when the effective pressure is zero, the longitudinal wave velocity when microfractures close, the pressure that causes soft pores in the rock to close, the longitudinal wave velocity measured by well logging, the first preset coefficient, and the second preset coefficient; and it calculates the pore pressure based on the pressure of the overlying strata and the effective pressure of the actual rock, thus enabling accurate pore pressure prediction.

[0135] Furthermore, the first computing unit 401 is specifically used for:

[0136] The longitudinal wave velocity of the rock when the effective pressure is zero can be calculated using the following formula:

[0137]

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

[0139] Furthermore, the second computing unit 402 is specifically used for:

[0140] The effective pressure of the actual rock can be calculated using the following formula:

[0141]

[0142] Among them, P eff For the effective pressure of actual rock, The longitudinal wave velocity of the rock when the effective pressure is zero. P is the longitudinal wave velocity when the microcrack closes. inf To ensure the pressure required to close soft pores in the rock, , where is the P-wave velocity measured in well logging, 'a' is the first preset coefficient, and 'b' is the second preset coefficient.

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

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

[0145] P pore =P overburden -P eff

[0146] Among them, P pore For pore pressure, P overburden For the pressure of the overlying strata, P eff This represents 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, the inversion of soft pores and hard pores is performed to obtain the longitudinal wave velocity when the microcracks close and the pressure that causes the soft pores in the rock to close.

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

[0150] The longitudinal wave velocity at the closure of microfractures is calculated based on the bulk modulus of saturated rock at the closure of microfractures, the density of saturated rock at the closure of microfractures, and the shear modulus of dry rock skeleton at the closure of soft pores in the rock.

[0151] Wherein, the dry rock skeleton shear modulus when the soft pores in the rock are closed includes the porosity of the optimal hard pore as a calculation factor for the dry rock skeleton shear modulus when the soft pores in the rock are closed.

[0152] The optimal porosity of hard pores is the porosity of hard pores that minimizes the error between the bulk modulus of the dry rock skeleton obtained from actual measurement data and the bulk modulus of the dry rock skeleton estimated by the rock physics model.

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

[0154] Set the porosity of the optimal soft pore to zero, and calculate the pressure required to close the soft pore in the rock using the following formula:

[0155]

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

[0157] The embodiments of the pore pressure prediction device provided in this invention can be used to execute the processing flow of the above-described method embodiments. Its functions will not be repeated here, but can be referred to the detailed description of the above-described method embodiments.

[0158] Figure 5 This is 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 501, a memory 502, and a bus 503;

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

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

[0161] Based on the clay content, total porosity, and preset fitting coefficients, 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 longitudinal wave velocity of the rock when the effective pressure is zero, the longitudinal wave velocity when the micro-fractures close, the pressure that causes the soft pores in the rock to close, the longitudinal wave velocity measured by well logging, the first preset coefficient, and the second preset coefficient.

[0163] The pore pressure is calculated based on the pressure of the overlying strata 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, and when the program instructions are executed by a computer, the computer can perform the methods provided in the above-described method embodiments, such as:

[0165] Based on the clay content, total porosity, and preset fitting coefficients, 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 longitudinal wave velocity of the rock when the effective pressure is zero, the longitudinal wave velocity when the micro-fractures close, the pressure that causes the soft pores in the rock to close, the longitudinal wave velocity measured by well logging, the first preset coefficient, and the second preset coefficient.

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

[0168] This embodiment provides a computer-readable storage medium storing a computer program that causes the computer to execute the methods provided in the above-described method embodiments, including, for example:

[0169] Based on the clay content, total porosity, and preset fitting coefficients, 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 longitudinal wave velocity of the rock when the effective pressure is zero, the longitudinal wave velocity when the micro-fractures close, the pressure that causes the soft pores in the rock to close, the longitudinal wave velocity measured by well logging, the first preset coefficient, and the second preset coefficient.

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

[0172] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied 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] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0174] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0175] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0176] In the description of this specification, the references to terms such as "an embodiment," "a specific embodiment," "some embodiments," "for example," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0177] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are 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 within the scope of protection of the present invention.

Claims

1. A method of predicting pore pressure, characterized by, The method comprises the following steps: calculating the P-wave velocity of the rock when the effective pressure is zero according to the shale content, the total porosity and a preset fitting coefficient; 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 micro-fracture is closed, the pressure when the soft pores in the rock are closed, the P-wave velocity measured by logging, a first preset coefficient and a second preset coefficient; calculating the pore pressure according to the overburden pressure and the effective pressure of the actual rock; The method for calculating the P-wave velocity of the rock when the effective pressure is zero according to the shale content, the total porosity and a preset fitting coefficient comprises the following steps: The P-wave velocity of the rock when the effective pressure is zero is calculated according to the following formula: wherein, Vp0is the P-wave velocity of the rock when the effective pressure is zero, Vshis the shale content, φ is the total porosity, d0, d1, d2, and d3are preset fitting coefficients; The method for 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 micro-fracture is closed, the pressure when the soft pores in the rock are closed, the P-wave velocity measured by logging, a first preset coefficient and a second preset coefficient comprises the following steps: The effective pressure of the actual rock is calculated according to the following formula: wherein P eff is the effective pressure of the actual rock, is the P-wave velocity of the rock when the effective pressure is zero, is the P-wave velocity when the microfractures are closed, P inf is the pressure at which the soft pores in the rock are closed, is the P-wave velocity measured by logging, a is a first predetermined coefficient, and b is a second predetermined coefficient.

2. The pore pressure prediction method according to claim 1, characterized by, The method for calculating the pore pressure according to the overburden pressure and the effective pressure of the actual rock comprises the following steps: The pore pressure is calculated according to the following formula: P pore = P overburden - P eff where P pore is the pore pressure, P overburden is the overburden pressure, P eff is the effective stress of the actual rock.

3. The method of predicting pore pressure according to claim 1 or 2, characterized by, The method further comprises the following steps: performing soft pore and hard pore inversion based on a double-porosity rock physics model to obtain the P-wave velocity when the micro-fracture is closed and the pressure when the soft pores in the rock are closed.

4. The method of predicting pore pressure according to claim 3, wherein, The P-wave velocity when the micro-fracture is closed is obtained by the following steps: calculating the P-wave velocity when the micro-fracture is closed according to the bulk modulus of the saturated rock when the micro-fracture is closed, the density of the saturated rock when the micro-fracture is closed and the dry rock skeleton shear modulus when the soft pores in the rock are closed; The dry rock skeleton shear modulus when the soft pores in the rock are closed comprises 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 porosity of the optimal hard pore is the porosity of the hard pore that makes 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 the smallest.

5. The method of claim 3, wherein, The pressure when the soft pores in the rock are closed is obtained by the following steps: The pressure when the soft pores in the rock are closed is calculated according to the following formula by taking the porosity of the optimal soft pore as zero: where P inf is the pressure at which the soft pores in the rock close, K m is the bulk modulus of the rock matrix for the actual measured data, G m is the shear modulus of the rock matrix, a c is the aspect ratio of the soft pores, s m is the Poisson's ratio of the rock matrix.

6. A pore pressure prediction device characterized by comprising: The method comprises the following steps: The first calculation unit is configured to calculate the P-wave velocity of the rock when the effective pressure is zero according to the shale content, the total porosity and a preset fitting coefficient; The second calculation unit is configured 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 micro-fracture is closed, the pressure when the soft pores in the rock are closed, the P-wave velocity measured by logging, a first preset coefficient and a second preset coefficient; The third calculation unit is configured to calculate the pore pressure according to the overburden pressure and the effective pressure of the actual rock; The first calculation unit is specifically configured to calculate the P-wave velocity of the rock when the effective pressure is zero according to the following formula: The second calculation unit is specifically configured to calculate the effective pressure of the actual rock according to the following formula: wherein, Vp0is the P-wave velocity of the rock when the effective pressure is zero, Vshis the shale content, φ is the total porosity, d0, d1, d2, and d3are preset fitting coefficients; ​ ​ wherein P eff is the effective pressure of the actual rock, is the P-wave velocity of the rock when the effective pressure is zero, is the P-wave velocity when the microfractures are closed, P inf is the pressure at which the soft pores in the rock are closed, is the P-wave velocity measured by logging, a is a first predetermined coefficient, and b is a second predetermined coefficient.

7. An electronic device comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, The computer program is executed by the processor to implement the steps of the method of any one of claims 1 to 5.

8. A computer-readable storage medium having stored thereon a computer program, characterized in that, The computer program is executed by the processor to implement the steps of the method of any one of claims 1 to 5.

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