A method for splitting production of a tight oil and gas reservoir

Abstract

A kind of compact oil and gas reservoir productivity splitting method, step one, calculate oil and gas splitting coefficient KH;Step two, to oil and gas splitting coefficient KH heterogeneity correction;Step three, based on the heterogeneity of the corrected reservoir KH, introduce gas saturation, gas measuring total hydrocarbon and formation depth, using the data model of different single layer of well composition, each gas testing result data of this data model is regarded as the liquid production of pseudo liquid profile, carry out production splitting, establish new production splitting model;The calculation result shows that, on the basis of the heterogeneity correction of KH coefficient, by simultaneously introducing gas layer depth, sand body gas saturation and gas measuring total hydrocarbon parameters, the advantages of accurately evaluating the productivity of compact oil and gas reservoir can be obtained, easy to popularize, with important application prospect and economic value.

Description

Technical Field

[0001] This invention relates to the field of oil and gas field exploration technology, specifically to a method for dividing the production capacity of tight oil and gas reservoirs. Background Technology

[0002] In oilfield development, drill pipe formation testing includes both single-layer and multi-layer combined tests. When conducting multi-layer combined tests, the reservoirs are not interconnected and are spaced at certain distances, resulting in differences in reservoir characteristics. Using the same reservoir parameters to analyze the combined test layer's productivity would introduce errors. Therefore, productivity is typically divided among the combined test layers, allocating productivity to multiple reservoirs (Zhang Chong, 2017). Reservoir productivity division is a crucial technical aspect of reservoir productivity evaluation, especially for most multi-layer sandstone oilfields. The accuracy of reservoir productivity division directly impacts the implementation of enhancement measures, ultimately affecting the recovery rate. For gas reservoir productivity division, current methods primarily utilize the KH method (permeability-reservoir thickness) (Tong Xiaohua et al., 1996; Yang Dongyu, 2012), clustering fuzzy methods, numerical simulation methods (Jiang Bici, 2015), and production dynamic data. Among these methods, the formation coefficient method and the clustering fuzzy method mainly utilize geological parameters such as effective formation thickness and effective permeability obtained from a detailed reservoir description to allocate production. However, these methods suffer from significant errors due to their overly singular consideration of factors. While many scholars have researched numerical simulation-based production allocation methods (Li Shuang et al., 2006), these methods require model building and fitting, a complex process. Furthermore, the models often exhibit multiple solutions and slow computation speeds, making them unsuitable for production allocation in multi-layer combined oilfields (Zhang Weijie, 2018). Existing technologies for dividing oil and gas reservoir production capacity using gas production profile testing mainly include: a method and device for dividing gas production capacity of multi-layer syngas wells in tight low-permeability sandstone gas reservoirs (application number 201811386497.X), a method for dividing oil well production capacity based on dynamic-static coupling (application number 201811526908.0), and a method and system for dividing production capacity of multi-layer syngas wells (application number 201910972695.2). These methods can accurately test the production capacity of each production layer, but they also have the following two problems: ① Gas production profile testing is time-consuming and expensive, and not every block has this testing data, which greatly limits its widespread use; ② Even if these valuable gas production profile data are available, the calculated gas production capacity of each layer is constant within the study area. This problem is fatal because it does not consider the individual differences caused by differences in reservoir or sedimentary facies within the same layer, and these individual differences will cause different gas production capacities. Regarding the use of dynamic production data for calculation, existing technologies mainly include a method for dividing oil well production considering time variation and inter-layer interference (201810169147.1), a dynamic production dividing method for multi-layer syndicated vertical wells (application number 201910068855.0), a new method for dividing the production of syndicated oil wells (application number 202010189294.2), and a production dividing method combining dynamic and static parameters (application number 202010322869.3).These methods are costly, time-consuming, and affect production output. In addition, a method for splitting the dynamic production output of multi-layer commingled vertical wells uses special sample analysis data (relative permeability curves) for calculation. Since the relative permeability curves depend on core samples and the analysis costs are very high, it has significant limitations for use in wells without core samples.

[0003] The traditional KH method for dividing oil and gas production capacity only involves two parameters: effective permeability K and effective thickness H. It fails to consider the differences in gas saturation at different effective thicknesses, nor does it account for the varying degrees of oil and gas filling caused by different formation depths. Therefore, existing methods for dividing production capacity in tight oil and gas reservoirs suffer from drawbacks such as multiple solutions, high costs, or failure to consider individual differences, resulting in low accuracy in capacity division calculations and limited applicability. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, the present invention aims to provide a method for splitting the production capacity of tight oil and gas reservoirs. The method calculates the traditional oil and gas splitting coefficient KH, and based on the heterogeneity correction of the KH coefficient, it constructs a new model for splitting the production capacity of tight oil and gas reservoirs by simultaneously introducing gas layer depth, sand body gas saturation and total hydrocarbon parameters. This model can more accurately calculate the gas production capacity of different strata and has important application prospects and economic value.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] A method for partitioning the productivity of tight oil and gas reservoirs includes the following steps:

[0007] Step 1: Calculate the oil and gas splitting coefficient KH

[0008] The KH equation for the oil and gas splitting coefficient is:

[0009]

[0010] In the formula, H i Let m be the effective thickness of the i-th smallest layer; K i Let mD be the effective permeability of the i-th smallest layer.

[0011] Step 2: Correct the oil and gas splitting coefficient KH for heterogeneity using the conversion formula for KH heterogeneity correction:

[0012] Jkh i =KH max / KH i (2)

[0013] In the formula, Jkh i Let Jkh be the value of the i-th smallest layer, and KH be the value of the smallest layer. max The maximum value in KH, KH i Let Jkh be the KH value of the i-th smallest layer.i The value serves as a weighting coefficient reflecting the differences in oil and gas production capacity;

[0014] Step 3: Establish a tight oil and gas reservoir productivity partitioning model

[0015] Based on the corrected reservoir KH heterogeneity, the introduction of gas saturation, total hydrocarbon measurements, and formation depth, a data model of wells producing a single layer from different locations is adopted. Each gas test result from this data model is treated as the production volume of a pseudo-production profile, and production is segmented to establish a new production segmentation model Q. oi :

[0016]

[0017]

[0018] Where: K i - represents the effective permeability of the i-th smallest layer, mD; H i Let m be the effective thickness of the i-th smallest layer; S gi -Gas saturation of the i-th sublayer, %; Jkh i =KH max / KH i This reflects the heterogeneity of KH; Gla i - Total hydrocarbons measured in the i-th sublayer; Di - Depth of the middle layer of the i-th sublayer, m; η i - is the production splitting factor.

[0019] The beneficial effects of this invention are:

[0020] (1) Gas logging total hydrocarbon (Gl) is a commonly used method in well logging. It can well reflect oil and gas show problems. The higher the oil and gas saturation, the larger the gas logging total hydrocarbon value, so it can well judge the gas production capacity of the formation. Oil and gas migrate from bottom to top, so the chance of oil and gas injection varies at different formation depths. The deeper the formation, the higher the degree of oil and gas injection, and the greater its oil and gas saturation and oil and gas production capacity. Therefore, this invention uses Jkh to perform heterogeneous correction on KH, and introduces parameters such as gas layer depth (equivalent to pressure), sand body gas saturation, and gas logging total hydrocarbon (Gl) to further correct the traditional KH. It effectively avoids the problem of low accuracy of its production capacity splitting method due to model construction problems in the existing technology, and can accurately evaluate the production capacity of tight gas layers. It has important application prospects and economic value.

[0021] (2) The model established by this invention is mainly based on common logging data and well logging gas data of various oil fields or single wells to directly establish the interpretation model. It does not need to rely on special sample analysis, so it is easy to promote. Attached Figure Description

[0022] Figure 1This is a flowchart of a method for dividing the production capacity of tight oil and gas reservoirs.

[0023] Figure 2 This example illustrates the traditional KH capacity splitting method.

[0024] Figure 3 This embodiment illustrates a method for dividing the production capacity of a tight oil and gas reservoir according to the present invention. Detailed Implementation

[0025] The specific applications of the present invention will be described in detail below with reference to the embodiments.

[0026] Reference Figure 1 A method for partitioning the productivity of tight oil and gas reservoirs includes the following steps:

[0027] Step 1: Calculate the traditional oil and gas splitting coefficient KH

[0028] The study of reservoir production segmentation is a very important technical link that is directly related to the evaluation results of reservoir utilization. Especially for the development of most multi-layer sandstone oilfields, the accuracy of reservoir production segmentation directly affects the implementation of production enhancement measures and, in turn, the improvement of the final recovery rate.

[0029] The commonly used traditional splitting KH equation in China is:

[0030]

[0031] In the formula, H i Let m be the effective thickness of the i-th smallest layer; K i Let mD be the effective permeability of the i-th layer. This equation uses a single parameter and does not consider the influence of interlayer interference, resulting in a split where layers of all effective thicknesses contribute. However, data on water absorption and production clearly show that some layers contribute little or nothing. This conventional production splitting method is more suitable for sandstone reservoirs with small production intervals, few perforated layers, and weak reservoir heterogeneity; however, it is less suitable for sandstone reservoirs with strong reservoir heterogeneity, long production intervals, and many perforated layers.

[0032] Step 2: Correction of heterogeneity of traditional oil and gas splitting coefficient KH

[0033] The KH values ​​differ for reservoirs with different gas production capacities, but the difference is not significant for tight oil and gas reservoirs. To improve prediction accuracy, the traditional oil and gas splitting coefficient KH is corrected for heterogeneity using a conversion formula for KH heterogeneity correction.

[0034] Jkh i =KH max / KH i (2)

[0035] In the formula, Jkh i Let Jkh be the value of the i-th smallest layer, and KH be the value of the smallest layer. max The maximum value in KH, KH i Let Jkh be the KH value of the i-th smallest layer. The Jkh calculated by Formula 2 amplifies the difference in the original KH values; that is, a larger original KH value will result in a larger calculated Jkh, and a smaller original KH value will result in a smaller calculated Jkh. i The value will be used as a weighting coefficient to reflect the differences in oil and gas production capacity.

[0036] Step 3: Establish a tight oil and gas reservoir productivity partitioning model

[0037] Oil wells typically use the contribution rate of each layer's fluid production in each production profile to divide the oil production of each layer. This method is relatively reliable, but improving the reliability of production division is a significant challenge in areas lacking production profile data. Effective permeability, effective thickness, gas layer depth, sand body gas saturation, and total hydrocarbons measured in gas logging have a significant impact on the flow rate of each layer. Among these, effective permeability, effective thickness, gas layer depth, and sand body gas saturation data are available on conventional well logging charts, while total hydrocarbons measured in gas logging data are found in the well logging data. Based on the traditional production division, reservoir KH heterogeneity correction is performed, and gas saturation, total hydrocarbons measured in gas logging, and formation depth are introduced. A data model of the composition of wells producing a single layer is used, and each gas test result of this data model is treated as the production volume of a pseudo-production profile for production division (Table 1). A new production division model Q is then established. oi .

[0038]

[0039]

[0040] Where: K i - represents the effective permeability of the i-th smallest layer, mD; H i Let m be the effective thickness of the i-th smallest layer; Sg i -Gas saturation of the i-th sublayer, %; Jkh i =KH max / KH i This reflects the heterogeneity of KH; Gla i - Total hydrocarbons measured in the i-th sublayer; D i - Depth of the middle layer of the i-th sublayer, m; η i - is the production splitting factor.

[0041] Gas logging (Gl) is a commonly used method in well logging. It effectively reflects oil and gas displays; the higher the oil and gas saturation, the larger the Gl value, making it an important indicator for assessing reservoir production capacity. Oil and gas migrate upwards, so the chance of oil and gas injection varies at different formation depths. Generally, deeper formations receive more oil and gas, resulting in higher oil and gas saturation and production capacity. This invention presents a method for partitioning the production capacity of tight oil and gas reservoirs. It uses Jkh to perform heterogeneous correction on KH, and further corrects the traditional KH by introducing parameters such as gas layer depth, sand body gas saturation, and Gl value. Figure 2 It can be seen that the traditional KH method results in relatively dispersed production data with a low correlation of 0.26, while the improved method produces more concentrated production data. Figure 3 The correlation coefficient was 0.99, significantly higher than that of the traditional KH method, indicating a substantial improvement in interpretation accuracy. This invention comprehensively considers gas saturation, total hydrocarbon content in gas measurements, and reservoir depth, overcoming the shortcomings of existing technologies such as the inaccurate KH productivity coefficient for oil splitting, and the inaccurate stratified production and water injection rates in water wells. Field verification showed that this invention achieved a high accuracy rate, improving interpretation accuracy by 71.5% (see Table 2). The method of this invention provides good guidance for analyzing the remaining oil potential of gas reservoirs and formulating stratified stimulation measures.

[0042] Table 1 Summary of Raw Data from Single-Layer Geological Collection

[0043]

[0044]

[0045] Table 2. Statistics on Yield Allocation by Different Methods

[0046]

Claims

1. A method for partitioning the productivity of tight oil and gas reservoirs, characterized in that, Includes the following steps: Step 1: Calculate the oil and gas splitting coefficient KH The KH equation for the oil and gas splitting coefficient is: In the formula, H i Let m be the effective thickness of the i-th smallest layer; K i Let mD be the effective permeability of the i-th smallest layer. Step 2: Correct the oil and gas splitting coefficient KH for heterogeneity using the conversion formula for KH heterogeneity correction: Jkh i =KH max / KH i (2) In the formula, Jkh i Let Jkh be the value of the i-th smallest layer, and KH be the value of the smallest layer. max The maximum value in KH, KH i Let Jkh be the KH value of the i-th smallest layer. i The value serves as a weighting coefficient reflecting the differences in oil and gas production capacity; Step 3: Establish a tight oil and gas reservoir productivity partitioning model Based on the corrected reservoir KH heterogeneity, the introduction of gas saturation, total hydrocarbon measurements, and formation depth, a data model of wells producing a single layer from different locations is adopted. Each gas test result from this data model is treated as the production volume of a pseudo-production profile, and production is segmented to establish a new production segmentation model Q. oi : Where: K i - represents the effective permeability of the i-th smallest layer, mD; H i Let m be the effective thickness of the i-th smallest layer; S gi -Gas saturation of the i-th sublayer, %; Jkh i =KH max / KH i This reflects the heterogeneity of KH; Gla i - Total hydrocarbons measured in the i-th sublayer; D i - Depth of the middle part of the i-th sublayer, in m; η i - is the production splitting factor.

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