CN115898368A - A Method for Extracting Anisotropic Resistivity of Horizontal Well Shale Oil Reservoir - Google Patents

Abstract

The invention discloses a method for extracting the anisotropic resistivity of a horizontal well shale oil reservoir, comprising: obtaining adjacent well information, and horizontal well array induction logging N sub-arrays and synthesized apparent resistivity curves; Sub-array curves and measured GR curves are used to divide the formation interface of horizontal wells; interpretation models are established to construct layered isotropic processing model M ₁ and homogeneous anisotropic processing model M ₂ ; the ith sub-array curve is inverted to obtain formation resistance and take it as the initial value of the next long source spacing sub-array; invert the apparent resistivity curves of each sub-array in turn to obtain the corresponding formation resistivity profile; for the jth formation, use the model M ₂ to invert The anisotropic resistivity R _hj and R _vj of the current layer; cycle to obtain the anisotropic resistivity of each formation. This method accurately extracts the anisotropic resistivity information of shale oil reservoirs, effectively eliminates the influence of well deviation, surrounding rock and anisotropy on the logging response, and ensures the accuracy of reservoir oil saturation calculation.

Description

A Method for Extracting Anisotropic Resistivity of Horizontal Well Shale Oil Reservoir

technical field

The invention relates to the technical field of petroleum exploration and development, belongs to the category of electrical logging methods, and in particular relates to a method for extracting the anisotropic resistivity of a horizontal well shale oil reservoir.

Background technique

Array induction logging is widely used in the exploration of oil and gas resources, and has remarkable characteristics for shale oil reservoirs. Its invasion is abnormally small and it is widely used in oil-based mud. However, the separation of curves in deviated wells and horizontal wells leads to inaccurate saturation parameters, and the synthetic curves cannot reflect the real information of formations under the influence of layer thickness. However, the simulation of array induction logging response in horizontal wells usually adopts three-dimensional processing method, which has low calculation accuracy and slow speed. At the same time, in horizontal wells, it is seriously affected by various factors such as instrument tilt and mud filtrate invasion, and cannot accurately reflect the real formation conditions. At present, there are few accurate extraction methods for the resistivity of horizontal wells, and it is urgent to develop a new method for extracting the anisotropic resistivity of horizontal wells to effectively measure the anisotropic resistivity information of shale oil reservoirs in horizontal wells.

Contents of the invention

In order to solve the above technical problems, the present invention discloses a method for extracting the anisotropic resistivity of horizontal well shale oil reservoirs. The method is based on the original signal of array induction logging, in order to provide accurate formation information for shale oil reservoir evaluation.

To achieve the above object, the present invention adopts the following technical solutions:

A method for extracting the anisotropic resistivity of a horizontal well shale oil reservoir, comprising the steps of:

s1. Obtain the formation thickness, formation horizontal resistivity, and natural GR curve information of adjacent wells, as well as the measured horizontal well array induction logging N subarrays and the synthesized apparent resistivity curves, wherein the horizontal well array induction logging subarray includes short source-spacing subarrays and long-source-spacing subarrays;

s2. Based on the short source distance sub-array curve and the measured horizontal well GR curve, divide the formation boundary of the horizontal well;

s3. Establish an interpretation model, construct a layered isotropic processing model M ₁ and a homogeneous anisotropic processing model M ₂ ;

s4. Invert the i-th subarray curve to obtain the formation resistivity profile Rts ⁱ , and use this result as the initial value of the next long source distance subarray;

s5. Inverting the apparent resistivity curves of each sub-array in turn to obtain the corresponding formation resistivity profiles Rts ⁱ , i=1,...,N;

s6. For the jth formation in the layered isotropic processing model M ₁ , combined with the inversion results in step s5, use the homogeneous anisotropic processing model M ₂ to invert the anisotropic resistivity R _hj and R _vj ;

s7. Step s6 is repeated sequentially to process each layer in the layered isotropic processing model _M1 , and then obtain the anisotropic resistivity of each formation.

Optionally, step s3 includes the following steps:

s3.1. Based on the electrical characteristics of shale oil reservoirs and the drilling environment, consider the effects of wellbore, formation folds, layer thickness and well deviation, and establish an actual formation model;

s3.2. Neglecting the influence of formation folds, after performing borehole correction on the N subarray signals in step s1, a corresponding interpretation model is established;

s3.3. Considering the influence of layer thickness and anisotropy respectively, the stratum is equivalent to the stratum with thickness influence and no anisotropy influence and the stratum with anisotropy and no thickness influence, and then sequentially builds the layered isotropic processing model M ₁ and homogeneous anisotropic processing model M ₂ ;

s3.4. Layered isotropic processing model M ₁ includes parameters Rts ⁱ , θ and H _j , where Rts ⁱ is equivalent isotropic resistivity, H _j is formation thickness, θ is well deviation, and i represents the first i sub-arrays, j represents the jth formation, and the layered isotropic processing model M1 is used to eliminate the influence of layer thickness;

s3.5. The homogeneous anisotropy processing model M ₂ includes parameters R _hj , θ and R _vj , where R _hj is the horizontal resistivity, R _vj is the vertical resistivity, θ is the well deviation, and j represents the jth Stratigraphic, homogeneous anisotropy processing model _M2 is used to obtain anisotropy information.

Optionally, step s4 includes the following steps:

s4.1. Use the reference resistivity of adjacent wells, the measured sub-array curves and synthetic curves of horizontal wells to provide initial values for inversion;

s4.2. For the first sub-array curve, combine the inversion initial value provided in step s4.1 with the layered isotropic processing model M ₁ constructed in step s3, invert to obtain the formation resistivity profile Rts ⁱ , and Use the result as the initial value of the next long source distance subarray;

s4.3. For the ith sub-array curve, use the formation resistivity profile Rts ^i-1 obtained from the inversion of the previous sub-array as the inversion initial value, invert to obtain the formation resistivity profile Rts ⁱ , and use this result as the following The initial value of a long-distance subarray.

Optionally, step s6 includes the following steps:

s6.1. The homogeneous anisotropy processing model M ₂ established in step s3 includes parameters R _h and R _v , wherein R _h is the horizontal resistivity, R _v is the vertical resistivity, and this model ignores the influence of layer thickness;

s6.2. For the jth formation in the layered isotropic processing model _M1 , use the N resistivity profiles of the current layer obtained in step s5 as inversion input information, combined with the homogeneous anisotropy constructed in step s3 Process the model M ₂ , invert the interpretation result of step s5, and obtain the anisotropic resistivity R _hj and R _vj of the current layer;

s6.3. Perform layer-by-layer inversion of all layers in the layered isotropic processing model _M1 , and repeat the above process to obtain the anisotropic resistivity of each formation.

The beneficial effect of the present invention is that the present invention provides a method for extracting the anisotropic resistivity of horizontal well shale oil reservoirs based on the original signal of array induction well logging, fully utilizes the information of adjacent wells, determines the position of the layer interface, and provides Subsequent processing provides initial values; two equivalent processing strategies are used for complex 3D formations, and multiple sets of initial values are provided for each equivalent model, which greatly improves the speed and accuracy of the inversion process; in the later interpretation and evaluation, Through the inversion results of the resistivity anisotropy of each layer, the reservoir oil saturation, movable oil saturation, etc. can be accurately calculated to provide reliable parameters for reservoir evaluation.

The method proposed by the invention can effectively eliminate the influence of well deviation, surrounding rock and anisotropy on the logging response, and effectively extract the anisotropic resistivity information of the shale oil reservoir of the horizontal well.

Description of drawings

Fig. 1 is a kind of flow chart of the method for extracting the anisotropic resistivity of the horizontal well shale oil reservoir based on the original signal of the array induction logging in the present invention;

Fig. 2 is a schematic diagram of an equivalent interpretation model of the present invention;

Fig. 3 is a schematic diagram of the layered isotropic processing model of the present invention;

Fig. 4 is a schematic diagram of the homogeneous anisotropy processing model of the present invention;

Fig. 5 is 65 ° and 80 ° three-layer stratum model of the present invention, wherein, (a) is 65 ° three-layer stratum model, (b) is 80 ° and is three-layer stratum model;

Fig. 6 is the original response of each sub-array of the model array induction logging in Fig. 5, where (a) is the original response of each sub-array of the 65° formation model array induction logging, (b) is the original response of each sub-array of the 80° formation model array induction logging array raw response;

Fig. 7 is the inversion result of the layered isotropic processing model corresponding to each sub-array of the present invention, wherein, (a) is the inversion result of the 65° layered isotropic processing model, (b) is the inversion result of the 80° layered isotropic processing model Isotropic processing model inversion results;

Fig. 8 is the inversion result of the homogeneous anisotropy processing model of the present invention, wherein, (a) is the inversion result of the 65° homogeneous anisotropy processing model, and (b) is the inversion result of the 80° homogeneous anisotropy processing model result.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

A method for extracting the anisotropic resistivity of a horizontal well shale oil reservoir, as shown in Figure 1, comprises the following steps:

s1. Obtain the formation thickness, formation horizontal resistivity, and natural GR curve information of adjacent wells, as well as the measured horizontal well array induction logging N sub-arrays (SGM ₀ , SGM ₁ ... SGM _N-1 ) and the synthesized apparent resistivity curves , wherein, the horizontal well array induction logging sub-array includes a short source distance sub-array and a long source distance sub-array;

s2. Based on the short source distance sub-array curve and the measured horizontal well GR curve, divide the formation boundary of the horizontal well;

s3. Establish an interpretation model, construct a layered isotropic processing model M ₁ and a homogeneous anisotropic processing model M ₂ ;

Step s3 specifically includes the following steps:

s3.1. Based on the electrical characteristics of shale oil reservoirs and the drilling environment, consider the effects of wellbore, formation folds, layer thickness and well deviation, and establish an actual formation model;

s3.2. As shown in Figure 2, due to the limited detection range, the influence of formation folds is ignored, and after borehole correction is performed on the N subarray signals in step s1, a corresponding interpretation model is established;

s3.3. Considering the influence of layer thickness and anisotropy respectively, the stratum is equivalent to the stratum with thickness influence and no anisotropy influence and the stratum with anisotropy and no thickness influence, and then sequentially builds the layered isotropic processing model M ₁ and homogeneous anisotropic processing model M ₂ ;

s3.4. As shown in Figure 3, the layered isotropic processing model M ₁ includes parameters Rts ⁱ , θ and H _j , where Rts ⁱ is the equivalent isotropic resistivity, H _j is the formation thickness, and θ is Well deviation, i represents the i-th sub-array, j represents the j-th formation, and the layered isotropic processing model M1 is used to eliminate the influence of layer thickness;

s3.5. As shown in Figure 4, the homogeneous anisotropic processing model M ₂ includes parameters R _hj , θ and R _vj , where R _hj is the horizontal resistivity, R _vj is the vertical resistivity, and θ is the well deviation , j represents the jth formation, and the homogeneous anisotropy processing model _M2 is used to obtain anisotropy information.

s4. Invert the i-th subarray curve to obtain the formation resistivity profile Rts ⁱ , and use this result as the initial value of the next long source distance subarray;

Step s4 specifically includes the following steps:

s4.1. Taking the formation model shown in Figure 5 as an example, use the reference resistivity of adjacent wells, the measured sub-array curves and synthetic curves of horizontal wells to provide initial inversion values for data processing;

s4.2. For the first sub-array curve, as shown in Fig. 6, combined with the inversion initial value provided in step s4.1 and the layered isotropic processing model M ₁ constructed in step s3, the formation resistance is obtained by inversion rate profile Rts ⁱ , and use this result as the initial value of the next long source distance subarray;

s4.3. For the ith sub-array curve, use the formation resistivity profile Rts ^i-1 obtained from the inversion of the previous sub-array as the inversion initial value, invert to obtain the formation resistivity profile Rts ⁱ , and use this result as the following The initial value of a long-distance subarray.

s5. As shown in Figure 7, the apparent resistivity curves of each sub-array are inverted sequentially to obtain the corresponding formation resistivity profiles Rts ⁱ , i=1,...,N;

s6. For the jth formation in the layered isotropic processing model M ₁ , combined with the inversion results in step s5, use the homogeneous anisotropic processing model M ₂ to invert the anisotropic resistivity R _hj and R _vj ;

Step s6 specifically includes the following steps:

s6.1. The homogeneous anisotropy processing model M ₂ established in step s3 includes parameters R _h and R _v , wherein R _h is the horizontal resistivity, R _v is the vertical resistivity, and this model ignores the influence of layer thickness;

s6.2. As shown in Figure 8, for the jth formation in the layered isotropic processing model _M1 , the N resistivity profiles of the current layer obtained in step s5 are used as the inversion input information, combined with the construction in step s3 The homogeneous anisotropic processing model M ₂ of the step s5 is inverted to obtain the anisotropic resistivity R _hj and R _vj of the current layer;

s6.3. Perform layer-by-layer inversion of all layers in the layered isotropic processing model _M1 , and repeat the above process to obtain the anisotropic resistivity of each formation.

s7. Step s6 is repeated sequentially to process each layer in the layered isotropic processing model _M1 , and then obtain the anisotropic resistivity of each formation.

Of course, the above descriptions are not intended to limit the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or replacements made by those skilled in the art within the scope of the present invention shall also belong to the present invention. protection scope of the invention.

Claims (4)

1. A horizontal well shale oil reservoir anisotropic resistivity extraction method is characterized by comprising the following steps:

s1. obtaining the stratum layer thickness, the stratum horizontal resistivity and the natural GR curve information of an adjacent well, and actually measuring N sub-arrays of the horizontal well array induction logging and a synthesized apparent resistivity curve, wherein the horizontal well array induction logging sub-array comprises a short source distance sub-array and a long source distance sub-array;

s2, dividing horizontal well stratum interfaces based on the short source distance subarray curve and an actually measured horizontal well GR curve;

s3. establishes an explanation model and a layered isotropic processing model M ₁ And a homogeneous anisotropy processing model M ₂ ；

s4. inverses the ith sub-array curve to obtain the formation resistivity profile Rts ⁱ And taking the result as an initial value of a next long source distance sub array;

s5. sequentially inverts apparent resistivity curves of the sub-arrays to respectively obtain corresponding formation resistivity profiles Rts ⁱ ，i＝1,…,N；

s6. model M for layered isotropic processing ₁ And (5) combining the inversion result of the step s5 with the jth stratum, and adopting a homogeneous anisotropy processing model M ₂ Inverting the anisotropic resistivity R of the current layer _hj And R _vj ；

s7. sequentially loops step s6 to process the layered isotropic spotPhysical model M ₁ And obtaining the anisotropic resistivity of each stratum.

2. The method for extracting the anisotropic resistivity of the horizontal well shale oil reservoir according to claim 1, wherein the step s3 comprises the following steps:

s3.1, aiming at the electrical characteristics of a shale oil reservoir and the drilling environment, considering the influences of a well hole, stratum folds, layer thickness and well deviation, and establishing an actual stratum model;

s3.2, neglecting stratum fold influence, and establishing a corresponding interpretation model after borehole correction is carried out on the N sub-array signals in the step s 1;

and S3.3, respectively considering the layer thickness and the anisotropic influence, and equating the stratum to a stratum with the layer thickness influence and without the anisotropic influence and a stratum with the anisotropic influence and without the layer thickness influence, and further sequentially constructing a layered isotropic processing model M ₁ And a homogeneous anisotropy processing model M ₂ ；

S3.4 layered Isotropic treatment model M ₁ Including the parameter Rts ⁱ Theta and H _j Wherein Rts is ⁱ For equivalent isotropic resistivity, H _j The stratum thickness is shown, theta is well deviation, i represents the ith sub-array, j represents the jth stratum, and the layered isotropic processing model M1 is used for eliminating the layer thickness influence;

s3.5. homogeneous Anisotropic Process model M ₂ Comprising a parameter R _hj Theta and R _vj Wherein R is _hj For horizontal resistivity, R _vj Homogeneous anisotropy processing model M for vertical resistivity, theta for well deviation, j for jth formation ₂ For obtaining anisotropy information.

3. The method for extracting the anisotropic resistivity of the horizontal well shale oil reservoir according to claim 1, wherein the step s4 comprises the following steps:

s4.1, providing an inversion initial value by utilizing the reference resistivity of the adjacent well, the actually measured subarray curve of the horizontal well and the synthetic curve;

s4.2. For the first subarray curve, combine the stepss4.1 and the layered isotropic processing model M constructed in step s3 ₁ And obtaining formation resistivity profile Rts by inversion ⁱ And taking the result as the initial value of the next long-source-distance sub-array;

s4.3, for the ith sub-array curve, performing inversion on the previous sub-array to obtain a formation resistivity profile Rts ^i-1 As an initial value of inversion, obtaining formation resistivity profile Rts by inversion ⁱ And the result is used as the initial value of the next long source range sub-array.

4. The method for extracting the anisotropic resistivity of the horizontal well shale oil reservoir according to claim 1, wherein the step s6 comprises the following steps:

s6.1. homogeneous anisotropy processing model M established in step s3 ₂ Including a parameter R _h And R _v Wherein R is _h For horizontal resistivity, R _v For vertical resistivity, the model ignores layer thickness effects;

s6.2. model M for layer isotropy ₁ Taking the N resistivity profiles of the current layer obtained in the step s5 as inversion input information of the jth stratum, and combining the homogeneous anisotropic processing model M constructed in the step s3 ₂ And (5) inverting the interpretation result of the step s5 to obtain the anisotropic resistivity R of the current layer _hj And R _vj ；

S6.3. Model M is treated isotropically in layers ₁ And (4) performing layer-by-layer inversion on all the layers, and repeating the process to obtain the anisotropic resistivity of each stratum.

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