A method for calculating oil and gas reserves based on reservoir geological modeling

Abstract

The present invention belongs to the field of oil and gas geological exploration, and provides an interpretation technology for calculating oil and gas reserves by using a reservoir geological modeling method. The method of the present invention first establishes a structural model based on the strata and structures of well logging and seismic interpretation, then establishes a sedimentary phase model guided by the sedimentary model and using the seismic reservoir prediction results as constraints, and finally uses drilling data and seismic wave impedance inversion parameters to obtain the variation function, performs random simulations according to the distribution laws of different sedimentary phases, and establishes a reservoir parameter model. On the basis of geological modeling, the volumetric method is finally used to complete the calculation of oil and gas reserves in the study area, and the obtained estimation results have good accuracy and reliability.

Description

Technical Field

[0001] The invention belongs to the field of oil and gas geological exploration and is an interpretation technology for calculating oil and gas geological reserves based on reservoir geological modeling. Background Art

[0002] The Sichuan Basin has well-developed beach-facies carbonate reservoirs, which have diverse types of reservoir space, large reservoir thickness, strong heterogeneity, and multiple sets of gas-water relationships in the corresponding gas reservoirs. These geological characteristics have brought challenges to the accurate calculation of oil and gas reserves. The traditional reserve calculation based on structural models can no longer meet the needs of detailed research. The volumetric method is very practical in the reserve calculation of clastic rocks, but for carbonate rocks, the key parameters are difficult to determine, so the calculation error is large. Liu Xueli et al. (2005) combined the characteristics of the fracture-cave reservoir in the Tahe Oilfield, introduced the concepts of continuity characteristic scale and cave pore volume ratio, and improved the static calculation method of reserves, but did not effectively characterize the heterogeneity inside the reservoir, and there was a certain difference from the actual value.

[0003] Due to the strong heterogeneity of carbonate reservoirs, it is challenging to accurately calculate the reserves of carbonate oil and gas reservoirs. The previous reserve estimation method for clastic oil reservoirs, the volumetric method, is used to calculate the reserves of carbonate oil and gas reservoirs, and the calculated results are quite different from the actual values. Therefore, the calculation method for carbonate oil and gas reserves needs to be further developed. To this end, the technology of the present invention provides a method for calculating oil and gas reserves based on reservoir geological modeling. Summary of the invention

[0004] The present invention provides a method for calculating oil and gas reserves based on reservoir geological modeling, which realizes the calculation of oil and gas geological reserves by establishing a structural model, a phase-controlled model and a reservoir attribute model based on reservoir geological modeling and adopting a volumetric method.

[0005] The object of the present invention is to provide a method for calculating oil and gas reserves based on reservoir geological modeling, the method mainly comprising the following steps:

[0006] The geological stratification data is used to control the layers on the well points, and the structural planes interpreted by seismic interpretation are used to control the large layers to establish the structural model Model (G) of the study area;

[0007] Based on the interpreted sedimentary facies, the sedimentary facies model Model(S) is established by using sequential index simulation and coordinated two-dimensional trend surface simultaneous constraints;

[0008] The sequential Gaussian simulation algorithm under phase-controlled conditions is used to establish a three-dimensional attribute model of porosity, permeability and gas saturation Model (A) through phase-controlled model constraints;

[0009] Based on reservoir characteristics and comprehensive reservoir evaluation, combined with the latest logging interpretation data, in the above steps to Based on geological modeling, the volumetric method can be used to calculate the geological reserves of the target layer in the study area. The specific formula is:

[0010]

[0011] In the formula, ST Indicates the oil volume under ground conditions, in m 3 ; BV Represents the total volume of the constructed model grid, in m 3 ; NTG It means net-to-gross ratio; ϕ represents porosity; S g Indicates gas saturation; B g It represents the volume coefficient. Before the reserve calculation, the net-to-gross ratio is first screened, and the reservoir is screened with 2m as the lower limit of the reservoir thickness. At the same time, it is considered that all layers outside the oil and gas boundary of the reservoir are water layers, and finally the reserves are calculated.

[0012] The specific implementation principle of the present invention is as follows:

[0013] 1. Data preparation and grid design

[0014] (1) Data preparation

[0015] Data preparation is the basis of reservoir modeling. Generally speaking, three-dimensional reservoir modeling requires the preparation of four types of data, namely well basic data, fault data, stratification data, and reservoir physical property data.

[0016] (2) Grid design

[0017] In the modeling process, reasonable grid design is very important. If the grid size of the three-dimensional model is smaller, it means that the model is finer and its accuracy is higher. However, in practical applications, the grid size division is restricted by computer hardware and the accuracy requirements of the built model. On the one hand, in order to save computer resources, the number of grids should be as small as possible; on the other hand, in order to control the morphology of the geological body and ensure the modeling accuracy, the number of grids cannot be too small. The grid design needs to be based on the actual situation of the research area.

[0018] , structural modeling

[0019] The structural model is the basis of 3D geological modeling. The reliability and detail of the structural model directly determine the accuracy of the description of the reservoir unit by the 3D geological model. In the modeling work, efforts are made to improve the accuracy of the structural model through fine 3D seismic interpretation, 3D visual interactive editing of seismic data and structural model, so that the structural model can more realistically reflect the overall structural morphology and characteristics of the underground geological body.

[0020] According to the time-depth relationship provided by the synthetic seismic record, the average velocity plane map of the ground-each target layer is calculated, and then the average velocity plane map of each set of strata is superimposed to obtain a three-dimensional velocity model. In the superposition process, the drilling layer data is used for correction. The three-dimensional velocity field can also be used to convert the three-dimensional seismic data volume and the seismic wave impedance inversion data volume into the depth domain, laying the foundation for the next step of attribute modeling. The main structural models are: fault model and layer model. The fault and layer models are combined to establish the spatial grid of the strata and grid them. Finally, according to the actual geological conditions of the study area, a suitable number of layers and multiple regional stratigraphic structural models are established.

[0021] The structural model is used to produce plan views of stratigraphic structures at all levels. The maps are relatively accurate and can reflect the structural morphology and microstructural changes of the study area in detail.

[0022] , Establishment of sedimentary facies model

[0023] The distribution of sedimentary facies has its own inherent laws. The spatial distribution of facies has certain connections with sequence strata, between facies, and between sedimentary layers within facies. Therefore, when modeling facies, we should not only use the mathematical statistical relationship of well data, but also make full use of these connections to establish a reservoir facies model that conforms to geological reality as much as possible. For homogeneous reservoirs, the depositional differences of reservoir parameters in three-dimensional space are small, and the continuous random model can be used to directly establish the reservoir parameter distribution model. For the study area with large differences in marine carbonate sedimentary environment and complex reservoir structure, the discrete random model should be used to establish the sedimentary facies model first, and then the continuous random model should be used to establish the reservoir parameter distribution model through "facies-controlled modeling".

[0024] The first step of the phase-controlled modeling method is to draw the planar distribution of sedimentary microfacies based on sequence comparison and according to the existing geological data and logging data, so as to characterize the heterogeneity of the reservoir on a large scale.

[0025] , Phase-controlled attribute parameter model

[0026] The establishment of reservoir parameter model is the second step of the "phase-controlled modeling" method, which is mainly used to simulate continuous reservoir variables. The three-dimensional reservoir parameter model generally includes the reservoir porosity, permeability and gas saturation parameter models. The purpose of three-dimensional reservoir geological modeling is to obtain the three-dimensional spatial distribution of reservoir physical properties.

[0027] (1) Statistical analysis of reservoir physical parameters

[0028] When establishing the attribute model, the physical property parameters of a single well should be gridded first, so that the well model and the three-dimensional grid match each other, and the reservoir parameters in the well model should be averaged on the scale of the simulation grid. The purpose is to use the information of as input when modeling the attribute, that is, to control the attribute distribution between wells. Then, the discretized porosity logging data is analyzed.

[0029] (2) Porosity model

[0030] The most commonly used sequential Gaussian simulation method in random simulation is used in the simulation calculation of the porosity model. During the simulation calculation, the seismic wave impedance body is used for constraint, that is, the seismic wave impedance body is converted to the depth domain through the velocity model, and resampled according to the grid of the three-dimensional geological model. Then, under the control of the phase model, the wave impedance body is used as the second variable through the cokriging method to perform body-to-body conditional constraints on the calculation of the porosity model, so that the wave impedance inversion body plays an effective trend control role in the simulation calculation. The spatial variation of the porosity of different strata and microfacies reservoirs is quantitatively and intuitively expressed.

[0031] (3) Permeability model

[0032] The relationship between porosity and permeability is controlled by many factors, and the correlation is not good. Therefore, the permeability model is established in two steps. First, due to the different pore types of the reservoir, the relationship between porosity and permeability is diversified. When calculating the permeability model, the pore structure type is first determined by the relative amplitude difference between the acoustic wave and density of the logging curve, and the porosity model is calculated according to the porosity-permeability relationship of different pore structure types. When fractures develop, due to the existence of fractures, the porosity does not change much, but the permeability increases exponentially. Therefore, when calculating the permeability model, the fracture research conclusion data body should also be used to correct the permeability for fractures.

[0033] (4) Gas saturation model

[0034] The direct assignment method can be used. Since the distribution of gas saturation is mainly determined by factors such as capillary pressure and gas-water relationship, it cannot be obtained by inter-well interpolation calculation. Before establishing the gas saturation model, the reservoir distribution range and gas-water distribution relationship must be determined, so the gas saturation model is established in three steps. ① Establish a net-to-gross ratio model; Establish gas-water distribution model; Complete the gas-water saturation model.

[0035] , Reserves Calculation

[0036] Based on reservoir characteristics and comprehensive reservoir evaluation, combined with the latest logging interpretation results and other data, on the basis of the above geological modeling, the volumetric method can be used to calculate the geological reserves of the target layer in the study block. Before the reserve calculation, the net-to-gross ratio is first screened, and the reservoir is screened out with 2m as the lower limit of the reservoir thickness. At the same time, it is considered that all layers outside the oil and gas boundary of the reservoir are water layers. Finally, the reserve calculation is performed. The specific calculation formula is:

[0037]

[0038] In the formula, ST Indicates the oil volume under ground conditions, in m 3 ; BV Represents the total volume of the constructed model grid, in m 3 ; NTG It means net-to-gross ratio; ϕ represents porosity; S g Indicates gas saturation; B g It represents the volume coefficient. Before the reserve calculation, the net-to-gross ratio is first screened, and the reservoir is screened with 2m as the lower limit of the reservoir thickness. At the same time, it is considered that all layers outside the oil and gas boundary of the reservoir are water layers, and finally the reserves are calculated.

[0039] The oil and gas reserve calculation method based on reservoir geological modeling of the present invention has the following advantages:

[0040] (1) In the process of establishing sedimentary facies model and reservoir parameter model, the seismic wave impedance prediction results are used as constraints to achieve the combination of deterministic modeling and stochastic modeling, and the advantages of seismic reservoir lateral prediction are fully utilized to make the constructed model more consistent with geological reality;

[0041] (2) In the process of establishing the reservoir permeability model, the permeability is calculated according to different reservoir space types. In addition, the influence of fractures on reservoir permeability is taken into account. The fracture index representing the fracture development characteristics is established by using the fracture statistics of the core wells. The fracture index model is established to participate in the calculation of the permeability model. The established permeability model is more in line with the actual geological conditions.

[0042] (3) By establishing a model that is more in line with actual geological conditions, the calculated oil and gas reserves are more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a structural model established in the work area of ​​the embodiment of the present invention;

[0044] Figure 2 is a porosity model established in the work area of ​​the embodiment of the present invention;

[0045] Figure 3 is the permeability model established in the work area of ​​the embodiment of the present invention;

[0046] Figure 4 It is a water saturation model established in the work area of ​​the embodiment of the present invention. DETAILED DESCRIPTION

[0047] The specific implementation of the present invention is as follows:

[0048] The geological stratification data is used to control the layers on the well points, and the structural planes interpreted by seismic interpretation are used to control the large layers to establish the structural model Model (G) of the study area;

[0049] Based on the interpreted sedimentary facies, the sedimentary facies model Model(S) is established by using sequential index simulation and coordinated two-dimensional trend surface simultaneous constraints;

[0050] The sequential Gaussian simulation algorithm under phase-controlled conditions is used to establish a three-dimensional attribute model of porosity, permeability and gas saturation Model (A) through phase-controlled model constraints;

[0051] Based on reservoir characteristics and comprehensive reservoir evaluation, combined with the latest logging interpretation data, in the above steps to Based on geological modeling, the volumetric method can be used to calculate the geological reserves of the target layer in the study area. The specific formula is:

[0052]

[0053] In the formula, ST Indicates the oil volume under ground conditions, in m 3 ; BV Represents the total volume of the constructed model grid, in m 3 ; NTG It means net-to-gross ratio; ϕ represents porosity; S g Indicates gas saturation; B g It represents the volume coefficient. Before the reserve calculation, the net-to-gross ratio is first screened, and the reservoir is screened with 2m as the lower limit of the reservoir thickness. At the same time, it is considered that all layers outside the oil and gas boundary of the reservoir are water layers, and finally the reserves are calculated.

[0054] In order to more clearly express the technical advantages of the present invention, the embodiments of the present invention are further described in detail in conjunction with the accompanying drawings.

[0055] Figure 1This is the structural model established for the example work area. According to the actual geological conditions of the study area, there are 3 faults in the area, mainly containing four stratigraphic interfaces. The fault and stratigraphic models are combined to establish the spatial framework of the stratigraphy, and then gridding is performed, and finally a stratigraphic structural model with 4 layers is established.

[0056] Figure 2 This is the porosity model established for the example work area. As can be seen from the figure, the pores in this area are well developed, with a porosity range of 0-22.5%. The figure can quantitatively and intuitively express the spatial variation of the porosity of different strata and microfacies reservoirs.

[0057] Figure 3 This is the permeability model established for the work area in the embodiment. When calculating the permeability model, the fracture research conclusion data body should be used to correct the permeability for fractures. The final model is as follows Figure 3 ,As can be seen from the figure, the permeability ranges from 0 to 700 mD, and the permeability near wells DU5, QB1, DU3 and DU4 is larger, indicating that the reservoir seepage characteristics in this range are better.

[0058] Figure 3 The water saturation model established for the work area of ​​the embodiment. From the established water saturation model, it can be seen that the gas saturation in the vicinity of wells DU4, QB102 and DU5 is relatively high, indicating that the reservoir is mainly concentrated in this range.

[0059] Combined with the modeling results, the volumetric method was used to calculate the reserves of the example block. The initial volumetric reserves of Block A in the study area were 223.7*10 8 m 3 The reserves calculated using the technology of the present invention are also 223.7*10 8 m 3 The calculation results of the two are completely consistent, which shows the accuracy and reliability of the calculation. The previous volumetric reserves of the research block B are 173.65*10 8 m 3 The reserves calculated using the technology of the present invention are 124.64*10 8 m 3 The calculated reserves are relatively reduced, mainly because the vertical distribution boundary of the oolite beach in this area has been increased. Under the condition that the volume has not changed much, the porosity has changed significantly due to the vertical oolite beach boundary restriction.

[0060] The above embodiments are only used to illustrate the present invention, wherein the various implementation steps of the method can be changed, and any equivalent transformations and improvements based on the technical solution of the present invention should not be excluded from the protection scope of the present invention.

Claims

1. A method for calculating oil and gas reserves based on reservoir geological modeling, characterized in that Use the following specific steps: The geological stratification data is used to control the layers on the well points, and the structural planes interpreted by seismic interpretation are used to control the large layers to establish the structural model Model (G) of the study area; Based on the interpreted sedimentary facies, the sedimentary facies model Model(S) is established by using sequential index simulation and coordinated two-dimensional trend surface simultaneous constraints; The sequential Gaussian simulation algorithm under phase-controlled conditions is used to establish a three-dimensional attribute model of porosity, permeability and gas saturation Model (A) through phase-controlled model constraints; Based on reservoir characteristics and comprehensive reservoir evaluation, combined with the latest logging interpretation data, in the above steps to On the basis of geological modeling, the volumetric method can be used to calculate the geological reserves of the target layer in the study area. The specific formula is: In the formula, ST Indicates the oil volume under ground conditions, in m 3 ; BV Represents the total volume of the constructed model grid, in m 3 ; NTG It means net-to-gross ratio; ϕ represents porosity; S g Indicates gas saturation; B g It represents the volume coefficient. Before the reserve calculation, the net-to-gross ratio is first screened, and the reservoir is screened with 2m as the lower limit of the reservoir thickness. At the same time, it is considered that all layers outside the oil and gas boundary of the reservoir are water layers, and finally the reserves are calculated.

2. The method for calculating oil and gas reserves based on reservoir modeling according to claim 1, characterized in that: In the process of establishing sedimentary phase models and reservoir parameter models, the seismic wave impedance prediction results are used as constraints to achieve a combination of deterministic modeling and stochastic modeling, and the advantages of seismic reservoir lateral prediction are fully utilized to make the constructed model more consistent with geological reality.

3. The method for calculating oil and gas reserves based on reservoir modeling according to claim 1, characterized in that: In the process of establishing the reservoir permeability model, the permeability is calculated according to different reservoir space types. In addition, considering the influence of fractures on reservoir permeability, the fracture index representing the fracture development characteristics is established using the core well fracture statistics. A fracture index model is established to participate in the permeability model calculation. The established permeability model is more in line with the actual geological conditions.

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