Oil-gas exploration and development method based on electromagnetic method

Abstract

The invention discloses an oil-gas exploration and development method based on an electromagnetic method, and the method comprises the following steps: constructing a geoelectric model according to the data of well drilling, well logging, well logging and petroleum geology, and carrying out the computer automatic three-dimensional subdivision of the geoelectric model, and obtaining a three-dimensional resistivity data body; calculating a residual error between the three-dimensional resistivity data volume and a measured value, constructing a Jacobian matrix, calculating a resistivity parameter correction amount based on the Jacobian matrix and the residual error, and correcting the three-dimensional resistivity data volume based on the resistivity parameter correction amount to obtain a corrected data volume; and calculating a residual error between the corrected data volume and the measured value, obtaining a reservoir three-dimensional resistivity data volume when the residual error is smaller than a preset threshold value, obtaining a resistivity image based on the reservoir three-dimensional resistivity data volume, and developing the reservoir based on the resistivity image. The underground oil gas can be accurately explored for development.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas exploration, and in particular relates to an oil and gas exploration and development method based on electromagnetic method. Background Art

[0002] The principle of electromagnetic method is to use high-density transmitting system and receiving system to conduct electric field perspective of underground, and use the difference of earth resistivity to image. Under the condition that the resistivity of oil and gas reservoir is different from that of surrounding rock and formation, the resistivity change of reservoir is monitored, and the dynamic and static data such as drilling, logging, logging, geology, etc. are obtained through indoor data processing. The detection method is to place a power supply electrode A in the well and a return electrode B on the surface. In the process of the current emitted by electrode A flowing back from under the oil and gas reservoir to electrode B on the surface, the oil and gas reservoir has a significant impact on the flow direction of the current. The distribution of oil and gas reservoirs determines the distribution of underground current and the distribution of surface electric field. Reasonably design the transmitting system and receiving system to ensure that there are enough observation points on the ground and the potential anomaly values ​​collected are high enough. The ground potential measurement results are processed to obtain the underground resistivity distribution, and the correlation between resistivity and oil and gas reservoirs is used to determine the boundary of oil and gas reservoirs and the spatial distribution of oil and gas reservoirs.

[0003] However, there are many metal oil and water pipelines in oil fields, and the operations of oil production machinery such as pumping units, submersible pumps, screw pumps, and water injection operations have a great impact on the earth's electrical signals. Summary of the invention

[0004] In order to solve the above technical problems, the present invention proposes an oil and gas exploration and development method based on electromagnetic method to solve the problems existing in the above prior art.

[0005] To achieve the above object, the present invention provides an oil and gas exploration and development method based on electromagnetic method, comprising the following steps:

[0006] Constructing a geoelectric model based on drilling, logging, well logging and petroleum geological data, and performing computer-automatic three-dimensional segmentation on the geoelectric model to obtain a three-dimensional resistivity data volume;

[0007] Calculating the residual between the three-dimensional resistivity data volume and the measured value, constructing a Jacobian matrix, calculating a resistivity parameter correction based on the Jacobian matrix and the residual, and correcting the three-dimensional resistivity data volume based on the resistivity parameter correction to obtain a corrected data volume;

[0008] The residual between the corrected data volume and the measured value is calculated, and when the residual is less than a preset threshold, a three-dimensional resistivity data volume of the reservoir is obtained, and a resistivity image is obtained based on the three-dimensional resistivity data volume of the reservoir, and the reservoir is developed based on the resistivity image.

[0009] Preferably, the method for constructing a geoelectric model comprises: constructing a geoelectric model through point power supply theoretical potential and line power supply theoretical potential based on drilling, logging, well logging and petroleum geological data.

[0010] Preferably, the expression of the theoretical potential of the point power supply is:

[0011]

[0012] Where ρ represents the apparent resistivity of the formation, I represents the power supply current intensity, r represents the distance between the measuring point and the point source, r' represents the distance between the measuring point and the point source, and V represents the potential of the observation point.

[0013] Preferably, the expression of the theoretical potential of the line power supply is:

[0014]

[0015] Where, ρ represents the apparent resistivity of the formation; l1 and l2 represent the top and bottom burial depths of the power supply casing respectively; z p Indicates the buried depth of the measured point; r p Indicates the radial distance between the measuring point and the power supply line source; I indicates the power supply current intensity; V pA Represents the potential at the observation point.

[0016] Preferably, the method for performing computer-automated three-dimensional segmentation comprises:

[0017] The boundary value expression of the potential v generated by a point current source is:

[0018]

[0019] The above equation is solved by the volume control method to obtain a three-dimensional resistivity data volume.

[0020] Preferably, the method for calculating the correction amount of the resistivity parameter includes: calculating the residual between the three-dimensional resistivity data body and the measured value, constructing a Jacobian matrix based on the electric field Green's equation, and calculating the correction amount of the resistivity parameter by solving a linear least squares equation based on the Jacobian matrix and the residual.

[0021] Preferably, the electric field Green's equation is expressed as:

[0022]

[0023] Where G is the half-space Green's function;

[0024] Preferably, the expression for calculating the resistivity parameter correction is:

[0025] (A T A+λCT C) ΔP=A T Δg

[0026] Where A is the Jacobian matrix, λ is the attenuation factor, C is the smoothing filter, ΔP is the parameter correction, and Δg is the residual vector.

[0027] Compared with the prior art, the present invention has the following advantages and technical effects:

[0028] The present invention discloses an oil and gas exploration and development method based on electromagnetic method, comprising the following steps: constructing a geoelectric model according to drilling, logging, well logging and petroleum geological data, performing computer automatic three-dimensional segmentation on the geoelectric model, and obtaining a three-dimensional resistivity data body; calculating the residual of the three-dimensional resistivity data body and the measured value, constructing a Jacobian matrix, calculating the resistivity parameter correction amount based on the Jacobian matrix and the residual, and correcting the three-dimensional resistivity data body based on the resistivity parameter correction amount to obtain a corrected data body; calculating the residual of the corrected data body and the measured value, obtaining a reservoir three-dimensional resistivity data body when the residual is less than a preset threshold, and obtaining a resistivity image based on the reservoir three-dimensional resistivity data body. The present invention can eliminate the interference of on-site operation machinery, thereby accurately exploring the underground oil and gas distribution and then developing it. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0030] Figure 1 is a flow chart of a method according to an embodiment of the present invention;

[0031] Figure 2 This is a diagram of electromagnetic detection results of Well XX according to an embodiment of the present invention;

[0032] Figure 3 This is a diagram showing the first detection result of the water well flooding effect according to an embodiment of the present invention;

[0033] Figure 4 This is a diagram showing the second test result of the water well flooding effect according to an embodiment of the present invention;

[0034] Figure 5 This is a gas storage test result diagram of an embodiment of the present invention;

[0035] Figure 6 This is a coal seam combustion goaf detection result diagram of an embodiment of the present invention;

[0036] Figure 7 This is an electrical profile diagram detected by electromagnetic method according to an embodiment of the present invention;

[0037] Figure 8This is a three-dimensional seismic profile diagram of an embodiment of the present invention. DETAILED DESCRIPTION

[0038] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0039] It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0040] Embodiment 1

[0041] like Figure 1 As shown, this embodiment provides an oil and gas exploration and development method based on electromagnetic method, comprising the following steps:

[0042] Constructing a geoelectric model based on drilling, logging, well logging and petroleum geological data, and performing computer-automatic three-dimensional segmentation on the geoelectric model to obtain a three-dimensional resistivity data volume;

[0043] Calculating the residual between the three-dimensional resistivity data volume and the measured value, constructing a Jacobian matrix, calculating a resistivity parameter correction based on the Jacobian matrix and the residual, and correcting the three-dimensional resistivity data volume based on the resistivity parameter correction to obtain a corrected data volume;

[0044] The residual between the corrected data volume and the measured value is calculated, and when the residual is less than a preset threshold, a three-dimensional resistivity data volume of the reservoir is obtained, and a resistivity image is obtained based on the three-dimensional resistivity data volume of the reservoir, and the reservoir is developed based on the resistivity image.

[0045] Furthermore, the method for constructing the geoelectric model includes: constructing the geoelectric model through the theoretical potential of the point supply source and the theoretical potential of the line supply source based on the drilling, logging, well logging and petroleum geological data.

[0046] Furthermore, the expression of the theoretical potential of the point power supply is:

[0047]

[0048] Where ρ represents the apparent resistivity of the formation, I represents the power supply current intensity, r represents the distance between the measuring point and the point source, r' represents the distance between the measuring point and the point source, and V represents the potential of the observation point.

[0049] Furthermore, the expression of the theoretical potential of the line power supply is:

[0050]

[0051] Where, ρ represents the apparent resistivity of the formation; l1 and l2 represent the top and bottom burial depths of the power supply casing respectively; z p Indicates the buried depth of the measured point; r p Indicates the radial distance between the measuring point and the power supply line source; I indicates the power supply current intensity; V pA Represents the potential at the observation point.

[0052] Furthermore, the method for performing computer-automated three-dimensional segmentation includes:

[0053] In a three-dimensional non-uniform medium with isotropic resistivity, the potential v generated by a point current source satisfies the boundary value problem:

[0054]

[0055] In the formula, Γ s and Γ ∞ - are the surface boundary and the underground infinite boundary of the study area Ω; n is the direction of the outer normal of the underground infinite boundary; r is the distance from the point current source A to the boundary; I is the supply current.

[0056] The control volume method is used to solve the above equations. From the perspective of computational mathematics theory, the control volume method, the finite element method, and the finite difference method can all be reduced to the weighted residual method. Compared with the finite element method, the control volume method is concise in theory and the derived formula has a clear physical meaning. In terms of calculation, the control volume method saves a lot of storage space and can be easily applied to three-dimensional space. Compared with the finite difference method, the control volume method has good numerical stability and good adaptability to strong nonlinear problems. Especially for very coarse grids, the control volume method can also obtain approximate physically real solutions. The biggest advantage of the control volume method is that the integral conservation of some physical quantities such as mass, momentum, and energy can be accurately satisfied in any set of control volumes, that is, in the entire computational domain; this feature exists for any number of grid nodes. Therefore, even the solution of the coarse grid still shows an accurate integral balance.

[0057] Calculate the numerical equations of the nodes in the earth's electric field:

[0058]

[0059] a P =a N +a S +a E +a W +a T +a B

[0060] Furthermore, the method for calculating the correction amount of the resistivity parameter includes: calculating the residual between the three-dimensional resistivity data body and the measured value, constructing a Jacobian matrix based on the electric field Green's equation, and calculating the correction amount of the resistivity parameter by solving a linear least squares equation based on the Jacobian matrix and the residual.

[0061] Specifically, according to Gauss's theorem

[0062]

[0063] And Green's formula:

[0064]

[0065] Starting from the electric field equation of isotropic inhomogeneous conducting medium

[0066]

[0067] The electric field Green's equation is obtained

[0068]

[0069]

[0070] where G is the half-space Green's function

[0071]

[0072] G| s＝s2 =0(r→∞)

[0073]

[0074] For a two-point current source with current intensities I and -I at rA and rB respectively,

[0075]

[0076] The nonlinear least squares method is used to repeatedly calculate the correction amount of the parameters through the following formula.

[0077] (A T A+λC T C) ΔP=A T Δg

[0078] Where A is the Jacobian matrix, λ is the attenuation factor, C is the smoothing filter, ΔP is the parameter correction, and Δg is the residual vector. The inversion is calculated in the following order: ① forward calculation, calculate the residual between the measured value and the calculated value; ② Jacobian matrix calculation; ③ solve the linear least squares equation and calculate the parameter correction; ④ repeat the calculations of ① to ② when the residual between the measured value and the calculated value does not meet the accuracy requirements.

[0079] The above method is implemented by the following equipment:

[0080] There are many metal oil and water pipe networks in the oil field. The oil extraction machinery operations such as pumping units, electric submersible pumps, screw pumps and water injection operations have great interference on the earth's electrical signals. Field operations require the identification and pickup of weak effective signals under the background of large interference. The WINTEL-PS100 digital high-precision earth electric field measuring instrument is used in field construction. The high-performance receiving and transmitting system controlled by CMDA sequence is adopted. The system transmits a group of wide-band random pulse square wave electric field signals each time. The frequency band ranges from ultra-low frequency square wave pulses to ultra-high frequency square wave pulses. The number of each group of pulse square waves and the duration of each pulse square wave are random. The receiver adopts the random coding weak signal detection technology, which greatly enhances the anti-interference ability of the receiver. The high-speed DSP digital processing chip is used for distributed real-time data processing. It has extremely high data processing speed and accuracy, so that a large number of complex measurement signals can be analyzed and processed in real time and calculated in a wide frequency range. The use of microcomputer control technology realizes the automatic acquisition, analysis and measurement of measurement signals, and all test results are displayed by the computer. All operations of the measurement system are controlled by an external microcomputer. The instrument system used for field measurement can be divided into three parts, namely the power supply part, the current sending part and the receiving part. The equipment types and performance parameters are described as follows:

[0081] (1) Power supply: The generator is a Yamaha EF6000 AC / DC generator with a maximum output current of 20 amperes and an output voltage of 110 volts and 220 volts.

[0082] (2) The current transmitter that supplies power to the underground through the casing converts the AC voltage input by the generator into a wide-band random pulse square wave signal output. The current stabilization accuracy is within ±1%, the frequency stability is 0.01%, the maximum output current amplitude is 20 amperes, and the output signal waveform frequency band ranges from ultra-low frequency random coded square wave pulses to ultra-high frequency random coded square wave pulses.

[0083] (3) IPRF-2 random code receiver, which receives the primary electric field signal of the earth at different positions on the ground corresponding to the transmission frequency, with a resolution of 1μv and a potential measurement accuracy within 1%.

[0084] The above method was tested.

[0085] The electromagnetic detection results of Well XX are as follows: Figure 2 As shown;

[0086] The monitoring results of water well flooding effect are as follows: Figure 3-4 As shown;

[0087] Gas storage inspection Figure 5 As shown;

[0088] Coal seam combustion goaf detection Figure 6 As shown;

[0089] The results of marine electromagnetic detection of oil and gas are as follows Figure 7-8 shown.

[0090] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for oil and gas exploration and development based on electromagnetic method, characterized in that: The following steps are involved: Constructing a geoelectric model based on drilling, logging, well logging and petroleum geological data, and performing computer-automatic three-dimensional segmentation on the geoelectric model to obtain a three-dimensional resistivity data volume; Calculating the residual between the three-dimensional resistivity data volume and the measured value, constructing a Jacobian matrix, calculating a resistivity parameter correction based on the Jacobian matrix and the residual, and correcting the three-dimensional resistivity data volume based on the resistivity parameter correction to obtain a corrected data volume; The residual between the corrected data volume and the measured value is calculated, and when the residual is less than a preset threshold, a three-dimensional resistivity data volume of the reservoir is obtained, and a resistivity image is obtained based on the three-dimensional resistivity data volume of the reservoir, and the reservoir is developed based on the resistivity image.

2. The electromagnetic oil and gas exploration and development method according to claim 1, characterized in that: The method for constructing a geoelectric model comprises: constructing a geoelectric model through a point power supply theoretical potential and a line power supply theoretical potential based on drilling, well logging, well logging and petroleum geological data.

3. The electromagnetic oil and gas exploration and development method according to claim 2, characterized in that: The expression of the theoretical potential of the point power supply is: Where ρ represents the apparent resistivity of the formation, I represents the power supply current intensity, r represents the distance between the measuring point and the point source, r' represents the distance between the measuring point and the point source, and V represents the potential of the observation point.

4. The electromagnetic oil and gas exploration and development method according to claim 2, characterized in that: The expression of the theoretical potential of the line power supply is: Where, ρ represents the apparent resistivity of the formation; l1 and l2 represent the top and bottom burial depths of the power supply casing respectively; z p Indicates the buried depth of the measured point; r p Indicates the radial distance between the measuring point and the power supply line source; I indicates the power supply current intensity; V pA Represents the potential at the observation point.

5. The electromagnetic oil and gas exploration and development method according to claim 1, characterized in that: The method for performing computer-automatic three-dimensional segmentation comprises: The boundary value expression of the potential v generated by a point current source is: In the formula, Γ s and Γ ∞ are the surface boundary and the infinitely far underground boundary of the study area Ω, respectively; n represents the direction of the outer normal of the infinitely far underground boundary, r represents the distance from the point current source A to the boundary; I represents the power supply current intensity; The above equation is solved by the volume control method to obtain a three-dimensional resistivity data volume.

6. The electromagnetic oil and gas exploration and development method according to claim 1, characterized in that: The method for calculating the resistivity parameter correction includes: calculating the residual between the three-dimensional resistivity data body and the measured value, constructing a Jacobian matrix based on the electric field Green's equation, and calculating the resistivity parameter correction by solving a linear least squares equation based on the Jacobian matrix and the residual.

7. The electromagnetic oil and gas exploration and development method according to claim 6, characterized in that: The electric field Green's equation expression is: Where G is the half-space Green's function; 8. The electromagnetic oil and gas exploration and development method according to claim 6, characterized in that: The expression for calculating the resistivity parameter correction is: (A T A+λC T C)ΔP=A T Δg Where A is the Jacobian matrix, λ is the attenuation factor, C is the smoothing filter, ΔP is the parameter correction, and Δg is the residual vector.

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