A method for updating porosity and permeability of a lithofacies-based reservoir based on displacement experiments
By conducting core displacement experiments, the relationship between displacement ratio and core porosity and permeability was calculated, and the reservoir porosity and permeability fields were corrected. This solved the problem of inaccurate geological models and improved the efficiency of reservoir development plan preparation and effectiveness evaluation.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHINA PETROLEUM & CHEMICAL CORP
- Filing Date
- 2024-12-03
- Publication Date
- 2026-06-05
AI Technical Summary
Existing technologies have failed to effectively update reservoir porosity and permeability fields affected by long-term development factors during reservoir development, resulting in inaccurate geological models and affecting the efficiency of mine development plan preparation and effectiveness evaluation.
Based on core displacement experiments, the quantitative relationship between the displacement ratio of different lithofacies and the change in core porosity was calculated. Combined with the correlation between core porosity and permeability, the correction values of porosity and permeability fields were calculated and corrected to update the geological model.
It provides a more accurate geological model, improves the accuracy of reservoir numerical simulation calculations, and enhances the efficiency of mine development plan preparation and the accuracy of effect evaluation.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of reservoir development technology, specifically a method for updating the porosity and permeability of lithologic reservoirs based on displacement experiments. Background Technology
[0002] Oil reservoir numerical simulation technology uses computers to simulate underground oil and water flows using numerical methods, predicting reservoir development dynamics. It is now widely used in the preparation of mining development plans and the prediction of results. In reality, an oil and gas reservoir can only be developed once, but by applying oil reservoir numerical simulation, the development process of different development methods can be easily repeated, allowing people to select the best development method.
[0003] Geological models are the foundation of reservoir numerical simulation calculations and are mostly built based on field interpretation data such as well logging data. Due to long-term development factors, the subsurface porosity and permeability fields change, and geological models need to be revised and updated over time. Currently, an effective method for updating model field data based on core wells has not yet been established.
[0004] Chinese patent application CN201911117148.2 discloses a method for correcting the static permeability of carbonate reservoirs based on dynamic monitoring data. The method comprises the following steps: Step 1, selecting multiple representative wells from the carbonate reservoir for dynamic monitoring to obtain dynamic monitoring data for each representative well; Step 2, obtaining the corresponding static permeability and dynamic permeability of each representative well based on the dynamic monitoring data; Step 3, determining a static permeability correction formula based on the static and dynamic permeability of the representative wells; Step 4, selecting a target well from the carbonate reservoir for dynamic monitoring to obtain dynamic monitoring data for the target well; Step 5, obtaining the corresponding static permeability of the target well based on the dynamic monitoring data, or obtaining both the static and dynamic permeability of the target well; Step 6, correcting the static permeability of the target well according to the dynamic or static permeability correction formula to obtain the corrected static permeability of the target well. This method involves updating well permeability through dynamic monitoring data, but does not involve updating porosity, nor does it consider changes in porosity and permeability calculated by petrographic analysis.
[0005] Chinese patent application CN202010926535.7 discloses a method for evaluating water-flooded formations based on lithofacies. The method includes: performing single correlation analysis on lithofacies to optimize lithofacies characterization parameters; constructing a quantitative lithofacies identification model, establishing a lithofacies discrimination function, and quantitatively identifying and classifying lithofacies; establishing differentiated physical property parameter models for different lithofacies; calculating the resistivity of formation water mixtures; establishing residual oil saturation models for different lithofacies; establishing permeability and water cut models for different lithofacies; establishing water-flooding subdivision criteria based on different lithofacies; and performing quantitative evaluation of water-flooded formations. While this method proposes establishing water-flooded formation evaluation criteria based on lithofacies, it does not utilize core displacement experimental data to update reservoir porosity and permeability, nor does it consider the influence of displacement ratio on reservoir properties.
[0006] Therefore, there is an urgent need for a method to update the porosity and permeability fields of lithological reservoirs based on core displacement experiments, which can provide a more accurate geological model for reservoir numerical simulation calculations and significantly improve the efficiency of mine development plan preparation and the accuracy of effect evaluation. Summary of the Invention
[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for updating the porosity and permeability of lithologic reservoirs based on displacement experiments.
[0008] To achieve the above objectives, the present invention adopts the following technical solution:
[0009] A method for updating the porosity and permeability of lithologic reservoirs based on displacement experiments includes the following steps:
[0010] Step 101: Calculate the quantitative relationship between the displacement ratio of different lithofacies and the change in core porosity;
[0011] Step 102: Calculate the correlation between core porosity and permeability;
[0012] Step 103: Obtain the correction values for the corresponding porosity field and permeability field at different displacement ratios;
[0013] Step 104: Correction yields a more accurate geological model for the porosity field and permeability field.
[0014] Preferably, in step 101, calculating the quantitative relationship between the displacement ratio of different lithofacies and the change in core porosity specifically includes: based on core displacement experiments of different lithofacies and different displacement ratios, calculating the quantitative relationship between the displacement ratio and the change in core porosity.
[0015] Preferably, in step 101, the quantitative relationship between the displacement ratio and the core porosity change is calculated using the following formula:
[0016] φ=f(PV)φ pre(I);
[0017] in:
[0018] PV is the core displacement multiple, which is dimensionless;
[0019] φ pre The original porosity of the core sample is a decimal.
[0020] φ is the core porosity after displacement, a decimal.
[0021] Preferably, in step 102, calculating the correlation between core porosity and permeability specifically includes:
[0022] Using core analysis data from cored wells and conventional well logging data for reservoir physical property interpretation, a scatter plot of reservoir porosity and permeability was first drawn, and then the relevant formulas for the two were obtained through regression.
[0023] Preferably, in step 102, the relevant formula between the two is:
[0024] log(k) = aφ + b(II);
[0025] in:
[0026] φ is porosity, a decimal;
[0027] k is the permeability, 10 -3 μm 2 ;
[0028] a and b are coefficients in the formula, and are decimals.
[0029] Preferably, in step 103, obtaining the correction values for the corresponding porosity field and permeability field at different displacement ratios specifically includes:
[0030] In geological models of different lithofacies, the correction amounts of the porosity field and permeability field are calculated as the displacement ratio changes, based on the correlations obtained in steps 101 and 102.
[0031] Preferably, in step 103, the correction amount of the porosity field as the displacement ratio changes is calculated using the following formula:
[0032]
[0033] in:
[0034] Δφ j This is the correction amount for porosity at the j-th well point, in decimal form;
[0035] Porosity, expressed as a decimal, is the porosity at well point j.
[0036] This represents the porosity at the location of the j-th well in the existing geological model, as a decimal.
[0037] Preferably, in step 103, the correction amount of the permeability field as the displacement ratio changes is calculated using the following formula:
[0038]
[0039] in:
[0040] Δk j This is the correction amount for the permeability at well point j, 10 -3 μm 2 ;
[0041] The permeability explained at well point j is 10. -3 μm 2 ;
[0042] Let be the permeability at the location of the j-th well in the existing geological model, 10 -3 μm 2 .
[0043] Preferably, in step 104, the geological model obtained by calibration to achieve a more accurate porosity field and permeability field specifically includes:
[0044] Based on the porosity and permeability fields in the original geological model, and combined with the calculated correction values of porosity and permeability at each grid, a more accurate geological model with porosity and permeability fields is obtained by summing them.
[0045] Preferably, in step 104, a more accurate geological model for the porosity field is calculated using the following formula:
[0046]
[0047] in:
[0048] and φ i These are the porosity at grid i in the geological model before and after correction, respectively, in decimal form.
[0049] Preferably, in step 104, a more accurate geological model for the permeability field is used, and the calculation formula is as follows:
[0050]
[0051] in:
[0052] and k i , respectively, represent the permeability at grid i in the geological model before and after calibration, in decimal form.
[0053] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:
[0054] This invention proposes a method for updating the porosity and permeability fields of lithological reservoirs based on core displacement experiments. This method can provide a more accurate geological model for reservoir numerical simulation calculations, and significantly improve the efficiency of mine development plan preparation and the accuracy of effect evaluation. Attached Figure Description
[0055] Figure 1 This is a flowchart of the present invention;
[0056] Figure 2 This is a comparison diagram of the permeability field before and after the update in an embodiment of the present invention;
[0057] Figure 3 This is a comparison diagram of the porosity field before and after the update in an embodiment of the present invention. Detailed Implementation
[0058] The following embodiments further illustrate specific implementations of the present invention's method for updating the porosity and permeability of lithologic reservoirs based on displacement experiments. The present invention's method for updating the porosity and permeability of lithologic reservoirs based on displacement experiments is not limited to the descriptions in the following embodiments.
[0059] Example 1:
[0060] A method for updating the porosity and permeability of lithologic reservoirs based on displacement experiments, such as... Figure 1 As shown, the steps are as follows:
[0061] Step 101: Calculate the quantitative relationship between the displacement ratio of different lithofacies and the change in core porosity;
[0062] Step 102: Calculate the correlation between core porosity and permeability;
[0063] Step 103: Obtain the correction values for the corresponding porosity field and permeability field at different displacement ratios.
[0064] Step 104: Correction yields a more accurate geological model for the porosity field and permeability field.
[0065] In step 101, calculating the quantitative relationship between the displacement ratio of different lithofacies and the change in core porosity refers to:
[0066] Based on core displacement experiments with different lithofacies and displacement ratios, the quantitative relationship between core porosity changes and displacement ratios was calculated. The specific formula is as follows:
[0067] φ=f(PV)φ pre (I);
[0068] in:
[0069] PV is the core displacement multiple, which is dimensionless;
[0070] φ pre The original porosity of the core sample is a decimal.
[0071] φ is the core porosity after displacement, a decimal.
[0072] In step 102, calculating the correlation between core porosity and permeability refers to:
[0073] Using core analysis data from cored wells and conventional well logging data for reservoir properties, a scatter plot of reservoir porosity and permeability was first plotted. Then, regression analysis was used to derive the correlation formula between the two. The specific formula is as follows:
[0074] log(k) = aφ + b(II);
[0075] in:
[0076] φ is porosity, a decimal;
[0077] k is the permeability, 10 -3 μm 2 ;
[0078] a and b are coefficients in the formula, and are decimals.
[0079] In step 103, the correction values for the corresponding porosity and permeability fields at different displacement ratios are obtained, which refer to:
[0080] In geological models of different lithofacies, the correction amounts for the porosity and permeability fields as the displacement ratio changes are calculated using the correlations obtained in steps 101 and 102. The specific formulas are as follows:
[0081]
[0082] In the formula, Δφ j This is the correction amount for porosity at the j-th well point, in decimal form; Porosity, expressed as a decimal, is the porosity at well point j. Δk is the porosity at the location of the j-th well in the existing geological model, a decimal; j This is the correction amount for the permeability at well point j, 10 -3 μm 2 ; The permeability explained at well point j is 10. -3 μm 2 ; Let be the permeability at the location of the j-th well in the existing geological model, 10 -3 μm2 .
[0083] Based on equations (III) and (IV), the correction values for porosity and permeability corresponding to each depth are calculated. Taking a depth of 1324.3m as an example, the permeability is 1680×10⁻⁶ when the flow rate is 25 times. -3 μm 2 The porosity is 0.364, and the original permeability of the model is 2074 × 10⁻⁶. -3 μm 2 The original porosity is 0.385, therefore the permeability correction can be calculated as -394 × 10⁻⁶. -3 μm 2 The porosity correction is -0.021.
[0084] In step 104, the correction yields a more accurate geological model for the porosity and permeability fields, which means:
[0085] Based on the porosity and permeability fields in the original geological model, and combined with the correction values for porosity and permeability at each grid obtained through interpolation, a more accurate geological model of the porosity and permeability fields is obtained. The calculation formula is as follows:
[0086]
[0087] In the formula, and φ i These are the porosity at grid i in the geological model before and after correction, respectively, in decimal form. and k i These are the porosity at grid i in the geological model before and after correction, respectively, in decimal form.
[0088] Based on equations (V) and (VI), the corrected porosity field and permeability field are calculated, and the results are compared with those of some strata before correction, as shown below. Figure 2 and Figure 3 As shown.
[0089] Example 2:
[0090] Using the method described in Example 1, the porosity and permeability fields of the geological model were updated in the Ng5-6 post-polymerization binary injection zone of Block 8 in the Gudong Oilfield based on the interpretation results of core wells and drilling.
[0091] The Ng5-6 post-polymer binary injection test area in Block 8 of the Gudong Oilfield is a meandering river deposit, belonging to a high-porosity, high-permeability reservoir with an oil-bearing area of 0.8 km². 2 Geological reserves 338×10 4The oilfield has a recovery rate of 46.3% and a comprehensive water cut exceeding 998.4%. Maintaining high and stable production in this old oilfield is crucial at this stage. However, the formation mechanism and distribution patterns of residual oil underground are extremely complex. The geological bodies controlling the distribution of residual oil are becoming increasingly smaller, and in-depth development during the ultra-high water cut period requires increasingly detailed research on the distribution of residual oil. To further guide the tapping of residual oil potential in old oilfields, more accurate three-dimensional geological models are needed to guide research on the impact of reservoir heterogeneity on residual oil, providing a basis for adjusting subsequent development plans.
[0092] The method includes the following steps:
[0093] 1. Calculate the quantitative relationship between displacement ratio of different lithofacies and core porosity changes.
[0094] Taking core wells W1, W2, and W3 in different lithofacies of the binary injection zone of the Ng5-6 isolated island in the eighth area of Gudong as examples, the quantitative relationship between the displacement ratio of different lithofacies and the change of core porosity was obtained by regression analysis based on the core displacement test data of multiple different displacement ratios.
[0095] 2. Calculate the correlation between porosity and permeability.
[0096] Based on data from numerous core wells and well logging interpretations within the block, a functional relationship between porosity and permeability was obtained through regression analysis.
[0097] 3. Calculate the correction values for the corresponding porosity and permeability fields at different displacement ratios.
[0098] In geological models of different lithofacies, the correction amounts for the porosity and permeability fields as the displacement ratio changes are calculated using the correlations obtained in steps 101 and 102. The specific formulas are as follows:
[0099]
[0100] In the formula, Δφ j This is the correction amount for porosity at the j-th well point, in decimal form; Porosity, expressed as a decimal, is the porosity at well point j. Δk is the porosity at the location of the j-th well in the existing geological model, a decimal; j This is the correction amount for the permeability at well point j, 10 -3 μm 2 ; The permeability explained at well point j is 10. -3 μm 2 ; Let be the permeability at the location of the j-th well in the existing geological model, 10 -3 μm 2 .
[0101] Based on equations (I) and (II), the correction values for porosity and permeability at each depth are calculated. Taking well W3 at a depth of 1320.5m as an example, the permeability at 25 times the flow rate is 1042×10⁻⁶. -3 μm 2 The porosity is 0.332, and the original permeability of the model is 1327 × 10⁻⁶. -3 μm 2 The original porosity is 0.351, therefore the permeability correction can be calculated as -285 × 10⁻⁶. -3 μm 2 The porosity correction is -0.019, and the permeability correction range for the entire model is 123-527×10⁻⁶. -3 μm 2 The porosity correction range is -0.014 to 0.037.
[0102] 4. Correction yields a more accurate geological model with well-defined porosity and permeability fields.
[0103] Based on the porosity and permeability fields in the original geological model, and combined with the correction values for porosity and permeability at each grid obtained through interpolation, a more accurate geological model of the porosity and permeability fields is obtained. The calculation formula is as follows:
[0104]
[0105] In the formula, and Φ i These are the porosity at grid i in the geological model before and after correction, respectively, in decimal form. and k i These are the porosity at grid i in the geological model before and after correction, respectively, in decimal form.
[0106] Based on equations (III) and (IV), the corrected porosity field and permeability field are calculated, and the results are compared with those of some strata before correction, as shown below. Figure 2 and Figure 3 As shown.
[0107] By adopting the above technical solution:
[0108] Based on core displacement tests, a quantitative relationship between the displacement ratio and core porosity changes in reservoirs of different lithofacies was obtained, thus yielding core porosity correction values for different displacement ratios in different lithofacies. Then, using data from sealed core wells, the correlation between core porosity and permeability was obtained. Furthermore, combining this with a dynamic model, during numerical simulation, correlation function formulas were introduced for the displacement ratio and porosity / permeability correction values for reservoirs of different lithofacies. Finally, the porosity and permeability field data in the geological model were updated as the displacement ratio changed, which can more accurately reflect the dynamic heterogeneity changes of the reservoir and improve the accuracy of numerical simulation calculations.
[0109] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.
Claims
1. A method for updating the porosity and permeability of lithological reservoirs based on displacement experiments, characterized in that, The steps include the following: Step 101: Calculate the quantitative relationship between the displacement ratio of different lithofacies and the change in core porosity; Step 102: Calculate the correlation between core porosity and permeability; Step 103: Obtain the correction values for the corresponding porosity field and permeability field at different displacement ratios; Step 104: Correction yields a more accurate geological model for the porosity field and permeability field.
2. The method for updating the porosity and permeability of lithologic reservoirs based on displacement experiments as described in claim 1, characterized in that, In step 101, the quantitative relationship between the displacement ratio of different lithofacies and the change in core porosity is calculated. Specifically, this includes: based on core displacement experiments of different lithofacies and different displacement ratios, calculating the quantitative relationship between the displacement ratio and the change in core porosity.
3. The method for updating the porosity and permeability of lithologic reservoirs based on displacement experiments as described in claim 2, characterized in that, In step 101, the quantitative relationship between the displacement ratio and the core porosity change is calculated using the following formula: φ=f(PV)φ pre (I); in: PV is the core displacement multiple, which is dimensionless; φ pre The original porosity of the core sample is a decimal. φ is the core porosity after displacement, a decimal.
4. The method for updating the porosity and permeability of lithological reservoirs based on displacement experiments as described in claim 1, characterized in that, In step 102, the correlation between core porosity and permeability is calculated, specifically including: Using core analysis data from cored wells and conventional well logging data for reservoir physical property interpretation, a scatter plot of reservoir porosity and permeability was first drawn, and then the relevant formulas for the two were obtained through regression.
5. The method for updating the porosity and permeability of lithologic reservoirs based on displacement experiments as described in claim 4, characterized in that, In step 102, the relevant formulas for the two are as follows: log(k) = aφ + b(II); in: φ is porosity, a decimal; k is the penetration rate, 10 -3 μm 2 ; a and b are the coefficients of the formula, and are decimals.
6. The method for updating the porosity and permeability of lithologic reservoirs based on displacement experiments as described in claim 1, characterized in that, In step 103, the correction values for the corresponding porosity field and permeability field at different displacement ratios are obtained, specifically including: In geological models of different lithofacies, the correction amounts of the porosity field and permeability field are calculated as the displacement ratio changes, based on the correlations obtained in steps 101 and 102.
7. The method for updating the porosity and permeability of lithologic reservoirs based on displacement experiments as described in claim 6, characterized in that, In step 103, the correction amount of the porosity field as the displacement ratio changes is calculated using the following formula: in: Δφ j This is the correction amount for porosity at the j-th well point, in decimal form; Porosity, expressed as a decimal, is the porosity at well point j. This represents the porosity at the location of the j-th well in the existing geological model, as a decimal.
8. The method for updating the porosity and permeability of lithologic reservoirs based on displacement experiments as described in claim 6, characterized in that, In step 103, the correction amount of the permeability field as the displacement ratio changes is calculated using the following formula: in: Δk j This is the correction amount for the permeability at well point j, 10 -3 μm 2 ; Let be the permeability obtained at well point j, 10 -3 μm 2 ; Let be the permeability at the location of the j-th well in the existing geological model, 10 -3 μm 2 .
9. The method for updating the porosity and permeability of lithologic reservoirs based on displacement experiments as described in claim 1, characterized in that, In step 104, a more accurate geological model for the porosity field and permeability field is obtained through calibration, specifically including: Based on the porosity and permeability fields in the original geological model, and combined with the calculated correction values of porosity and permeability at each grid, a more accurate geological model with porosity and permeability fields is obtained by summing them.
10. The method for updating the porosity and permeability of lithologic reservoirs based on displacement experiments as described in claim 9, characterized in that, In step 104, a more accurate geological model for the porosity field is calculated using the following formula: in: and φ i These are the porosity at grid i in the geological model before and after correction, respectively, in decimal form.
11. The method for updating the porosity and permeability of lithologic reservoirs based on displacement experiments as described in claim 9, characterized in that, In step 104, a more accurate geological model for the permeability field is calculated using the following formula: in: and k i , respectively, represent the permeability at grid i in the geological model before and after calibration, in decimal form.