A quantitative evaluation method for the development effect of natural water drive oil reservoirs

Abstract

The present invention provides a method for quantitatively evaluating the development effect of natural water-driven oil reservoirs. The method firstly introduces two evaluation indicators, namely, the interlayer difference production coefficient and the energy utilization coefficient, for the factors affecting the development of natural water-driven oil reservoirs; then, a natural water-driven oil reservoir development effect evaluation index system is established based on the two evaluation indicators; finally, a multi-factor comprehensive evaluation of the development effect of the oil reservoir to be evaluated is performed according to the established system. The method provided by the present invention establishes a natural water-driven oil reservoir development effect evaluation index system for the first time, and realizes a multi-factor quantitative evaluation of the development effect of natural water-driven oil reservoirs. In addition, the method is easy to operate, has strong adaptability, and can reflect the development characteristics of natural water-driven oil reservoirs and their water-driven effects; at the same time, its evaluation results can point out the main factors that restrict the development effect of the oil reservoir, and provide a basis for targeted development adjustments in the next step.

Description

Technical Field

[0001] The invention relates to the technical field of oil reservoir development, and mainly relates to a method for quantitatively evaluating the development effect of a natural water-driven oil reservoir. Background Art

[0002] Natural water-driven oil reservoirs refer to oil reservoirs that are developed mainly by relying on the natural energy of the water body connected to the oil body without water or gas injection to supplement the formation energy. Its geological characteristics are small oil-bearing area, large fluidity, complex oil-water relationship, and sufficient natural energy; its development characteristics are based on natural energy development, high oil recovery rate, high water-free recovery rate and ultimate recovery rate, but the water content rises quickly and unevenly.

[0003] At present, the evaluation methods of water flooding development effect are mainly focused on water injection development of oil reservoirs, while the evaluation methods for the development effect of natural water flooding oil reservoirs are relatively less studied, and mainly adopt the "Oil Field Development Level Classification" (SY / T 6219-1996). However, the evaluation results of the development effect of natural water flooding oil reservoirs based on the "Oil Field Development Level Classification" (SY / T6219-1996) cannot be quantified. Moreover, in the existing technology, Wang Yiling (2014) used traditional reservoir engineering methods to evaluate the development effect of natural water-driven oil reservoirs from the aspects of formation energy retention, water content increase rate, production decline law, recovery rate, etc., but the evaluation conclusion was only based on single-factor indicator evaluation, and did not consider multi-indicator comparative comprehensive evaluation; Li Kewen and Wang Yilong (2015) used an improved fuzzy comprehensive evaluation method to conduct a comprehensive evaluation and analysis of the development effect of water-driven oil reservoirs, but this evaluation method was only based on the relevant indicators of water injection development reservoirs. The evaluation indicators cannot reflect the three major contradictions of natural water-driven oil reservoirs in plane, within layer, and between layers, and cannot fully and accurately reflect the development effect of natural water-driven oil reservoirs.

[0004] From the above, it can be seen that there is no unified technical method system at home and abroad for the evaluation of the development effect of natural water drive oil reservoirs, which can realize the quantitative evaluation of the development effect of natural water drive oil reservoirs and provide targeted guidance on improving the development effect of such oil reservoirs through the evaluation results.

[0005] Therefore, in order to solve the technical problems existing in the above-mentioned prior art, the technical field is in urgent need of a quantitative evaluation method for the development effect of natural water drive oil reservoirs. Summary of the invention

[0006] In order to solve the technical problems existing in the above-mentioned prior art, the present invention proposes a method for quantitatively evaluating the development effect of natural water-driven oil reservoirs. Based on the two newly introduced evaluation indicators of interlayer difference production coefficient and energy utilization coefficient, this method establishes a natural water-driven oil reservoir development effect evaluation index system, realizes a scientific evaluation of the development effect of natural water-driven oil reservoirs, meets the development effect evaluation needs of natural water-driven oil reservoirs, clarifies the contradictions between the reservoir plane, interlayer and intralayer, and provides guidance for improving the development effect of oil fields. The specific contents are as follows:

[0007] The present invention provides a method for quantitatively evaluating the development effect of a natural water drive oil reservoir, which mainly comprises the following steps:

[0008] Step 1, according to the factors affecting the development of natural water drive oil reservoirs, set the interlayer difference production coefficient and energy utilization coefficient;

[0009] Step 2, establishing a natural water drive reservoir development effect evaluation index system consisting of multiple evaluation indicators; the multiple evaluation indicators include interlayer difference production coefficient and energy utilization coefficient;

[0010] Step 3, according to the natural water drive oil reservoir development effect evaluation index system, determine the actual value of each evaluation index of the oil reservoir to be evaluated, the threshold range of each evaluation index in the three evaluation levels of "excellent, good, and poor", and the weight of each evaluation index;

[0011] Step 4, scoring each of the evaluation indicators using a single factor grading calculation method according to the actual value, the threshold range and the weight;

[0012] Step 5, summing up the score values ​​of each evaluation index, and taking the summed value as the total evaluation score of the oil reservoir to be evaluated;

[0013] Step 6: According to a preset scoring level, determine the level of the sum value, and use the level as a quantitative evaluation result of the natural water drive reservoir development effect of the oil reservoir to be evaluated.

[0014] Preferably, the inter-layer differential production coefficient is the ratio of the standard deviation of the geological reserve production degree of each sub-layer to the average production degree.

[0015] Preferably, the water content of the sublayer reaches more than 90%, and the geological reserves of the sublayer are controlled by produced wells and producing wells.

[0016] Preferably, the interlayer differential producing coefficient is used to reflect the impact of reservoir heterogeneity on reservoir development results.

[0017] Preferably, the energy utilization coefficient is the ratio of the underground cumulative oil production to the edge and bottom water intrusion.

[0018] Preferably, the energy utilization coefficient is used to reflect the utilization rate of water-driven oil in natural water-driven oil reservoirs.

[0019] Preferably, the multiple evaluation indicators also include: 4 development technology indicators, 2 production management indicators, 1 economic benefit indicator, the degree of control of the well pattern on reserves, the plane sweep coefficient, and the intra-layer sweep coefficient;

[0020] Among them, the well pattern's control degree on reserves, plane sweep coefficient, intra-layer sweep coefficient, inter-layer differential production coefficient, and energy utilization coefficient constitute five contradiction-reflecting indicators;

[0021] The four development technical indicators are composed of water cut increase rate, remaining recoverable reserves oil production rate, natural decline rate and recovery factor;

[0022] The two production management indicators are composed of comprehensive production time rate and old well measures efficiency;

[0023] One of the economic benefit indicators is the operating cost per ton of oil.

[0024] Preferably, the step 3 comprises:

[0025] Determine the actual value of each evaluation index of the reservoir to be evaluated by using reservoir engineering methods;

[0026] Combined with the development characteristics of natural water drive oil reservoirs, the threshold ranges of the three evaluation levels of "excellent, good and poor" for each evaluation index are determined;

[0027] The weight of each evaluation indicator is determined according to the degree of influence of each evaluation indicator on the natural water flooding development effect.

[0028] Preferably, in step 4, the single factor classification calculation method is:

[0029] When the evaluation level of an evaluation indicator is "excellent", the score of this item is 100% of the weight score of this item;

[0030] When the evaluation level of a certain evaluation indicator is in the "good" range, the score of the item = the weight score of the item × [0.4 + 0.6 × (the actual value of the item - the lower limit of the definition) / (the upper limit of the definition - the lower limit of the definition)]; wherein the lower limit of the definition is the minimum value of the threshold range of the item, and the upper limit of the definition is the maximum value of the threshold range of the item;

[0031] When the evaluation level of an evaluation indicator is in the "poor" range, the score of the item is 40% of the weight of the item.

[0032] The present invention provides a method for quantitatively evaluating the development effect of a natural water-driven oil reservoir. The evaluation method mainly includes: step 1, setting an interlayer difference production coefficient and an energy utilization coefficient according to factors affecting the development of a natural water-driven oil reservoir; step 2, establishing a natural water-driven oil reservoir development effect evaluation index system composed of multiple evaluation indicators; the multiple evaluation indicators include an interlayer difference production coefficient and an energy utilization coefficient; step 3, according to the natural water-driven oil reservoir development effect evaluation index system, determining the actual value of each evaluation indicator of the oil reservoir to be evaluated, the threshold range of each evaluation indicator in the three evaluation levels of "excellent, good, and poor", and the weight of each evaluation indicator; step 4, scoring each evaluation indicator using a single factor classification calculation method according to the actual value, the threshold range and the weight; step 5, summing the score values ​​of each evaluation indicator, and taking the summed value obtained by the summation as the total evaluation score of the oil reservoir to be evaluated; step 6, judging the level of the summed value according to the preset scoring level, and taking the level as the quantitative evaluation result of the development effect of the natural water-driven oil reservoir of the oil reservoir to be evaluated.

[0033] Compared with the prior art, the method for quantitatively evaluating the development effect of natural water drive oil reservoirs provided by the present invention has at least the following advantages:

[0034] 1. In order to reflect the influence of reservoir heterogeneity on reservoir development effect, the present invention proposes an interlayer differential production coefficient on the one hand, and proposes an energy utilization coefficient on the other hand to characterize the size of natural water and water utilization. Then, based on the interlayer differential production coefficient and energy utilization coefficient proposed for the first time, the development characteristics of natural water-driven reservoirs are accurately characterized, which makes up for the shortcomings of development effect evaluation indicators.

[0035] 2. In the evaluation method provided in this application, in order to accurately and comprehensively reflect the development characteristics of natural water-driven oil reservoirs and their water-driven effects and to make the evaluation results more comprehensive and integrated, a natural water-driven oil reservoir development effect evaluation index system covering four major categories and 12 development effect evaluation indicators is established for the first time for natural water-driven oil reservoirs.

[0036] 3. The evaluation method provided in this application realizes the quantitative evaluation of the development effect of natural water drive oil reservoirs through four categories and 12 development effect evaluation indicators; at the same time, the four categories and 12 development effect evaluation indicators also reflect the three major contradictions of natural water drive oil reservoirs in the plane, within the layer, and between the layers, and comprehensively and accurately reflect the development effect of natural water drive oil reservoirs.

[0037] 4. In the evaluation method provided by this application, the evaluation parameters required for calculating the development effect evaluation index are all conventional basic parameters of the reservoir, which can be obtained through conventional technical means, so the evaluation parameters are easy to obtain; and when calculating the development effect evaluation index, it is only necessary to bring the evaluation parameters into the calculation formula, so the evaluation process is simple and easy to operate. Therefore, the evaluation method provided by this application has strong field applicability and a wide range of application scenarios.

[0038] 5. In the evaluation method provided in this application, the evaluation results of 12 development effect evaluation indicators in four categories can clearly point out the main factors restricting the development effect of the reservoir, providing a basis for targeted development adjustments in the next step.

[0039] In summary, the present invention provides a unified technical method system for evaluating the development effect of natural water drive oil reservoirs - a natural water drive oil reservoir development effect evaluation index system, so as to realize multi-factor quantitative evaluation of the development effect of natural water drive oil reservoirs, and to provide targeted guidance on improving the development effect of such oil reservoirs through the evaluation results. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 A method flow chart showing a method for quantitatively evaluating the development effect of a natural water drive oil reservoir in an embodiment of the present invention is shown;

[0041] Figure 2 A hierarchical structure diagram of a natural water drive reservoir development effect evaluation index system in an embodiment of the present invention is shown;

[0042] Figure 3 A comparison chart of recovery rates of different blocks of the X oil field in an embodiment of the present invention is shown;

[0043] FIG. 4(a) shows a scatter diagram of the relationship between the plane sweep coefficient and the recovery rate of each block unit of the X oil field in the embodiment of the present invention; FIG. 4(b) shows a scatter diagram of the relationship between the interlayer differential production coefficient and the recovery rate of each block unit of the X oil field in the embodiment of the present invention; FIG. 4(c) shows a scatter diagram of the relationship between the intralayer sweep coefficient and the recovery rate of each block unit of the X oil field in the embodiment of the present invention; FIG. 4(d) shows a scatter diagram of the relationship between the old well measures efficiency and the recovery rate of each block unit of the X oil field in the embodiment of the present invention; FIG. 4(e) shows a scatter diagram of the relationship between the ton oil operating cost and the recovery rate of each block unit of the X oil field in the embodiment of the present invention; FIG. 4(f) shows a scatter diagram of the relationship between the energy utilization coefficient and the recovery rate of each block unit of the X oil field in the embodiment of the present invention; FIG. 4(g) shows a scatter diagram of the relationship between the natural decline rate and the recovery rate of each block unit of the X oil field in the embodiment of the present invention;

[0044] FIG. 5( a ) shows a scatter diagram of the relationship between the energy utilization coefficient and the recovery factor of each block unit of the X oil field in the embodiment of the present invention at the low water content stage (0 < water content < 20%); FIG. 5( b ) shows a scatter diagram of the relationship between the energy utilization coefficient and the recovery factor of each block unit of the X oil field in the embodiment of the present invention at the medium water content stage (20% ≤ water content < 60%); FIG. 5( c ) shows a scatter diagram of the relationship between the energy utilization coefficient and the recovery factor of each block unit of the X oil field in the embodiment of the present invention at the high water content stage (60% ≤ water content < 90%); FIG. 5( d ) shows a scatter diagram of the relationship between the energy utilization coefficient and the recovery factor of each block unit of the X oil field in the embodiment of the present invention at the ultra-high water content stage (water content ≥ 90%);

[0045] FIG. 6( a ) shows a scatter diagram of the relationship between the natural decline rate and the recovery factor of each block unit of the X oil field in an embodiment of the present invention at a development stage where the recoverable reserves extraction degree is less than 50%; FIG. 6( b ) shows a scatter diagram of the relationship between the natural decline rate and the recovery factor of each block unit of the X oil field in an embodiment of the present invention at a development stage where the recoverable reserves extraction degree is greater than or equal to 50%. DETAILED DESCRIPTION

[0046] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0047] For natural water drive oil reservoirs, there is currently no standard or method to achieve quantitative evaluation of the development effect of natural water drive oil reservoirs. The present invention takes into account the important characteristics of natural water drive oil reservoirs that are different from conventional water injection development reservoirs, such as sufficient natural energy and difficulty in controlling water content, and concludes that the water drive development effect mainly depends on the edge and bottom water characteristics and development technology policies. Based on this and the results of the analysis of key factors affecting the development effect of natural water drive oil reservoirs, an embodiment of the present invention proposes a method for quantitative evaluation of the development effect of natural water drive oil reservoirs to meet the needs of quantitative evaluation of the development effect of natural water drive oil reservoirs, clarify the contradictions between the plane, interlayer, and intralayer of the reservoir, and provide guidance for improving the development effect of the oil field. The specific contents of the embodiment of the present invention are as follows:

[0048] Figure 1 A method flow chart of a method for quantitatively evaluating the development effect of a natural water drive oil reservoir in an embodiment of the present invention is shown. Figure 1 As shown, the embodiment of the present invention provides a method for quantitatively evaluating the development effect of a natural water drive oil reservoir, comprising the following steps:

[0049] Step 1 (S1), according to the factors affecting the development of natural water drive oil reservoirs, the interlayer difference production coefficient and energy utilization coefficient are set.

[0050] In specific implementation, since the factors affecting the development of natural water-driven oil reservoirs include the heterogeneity of the oil reservoir, the size and utilization of the natural water body, the embodiment of the present invention proposes two concepts, namely, the interlayer difference production coefficient and the energy utilization coefficient, and uses them as evaluation indicators for evaluating the development effect of natural water-driven oil reservoirs. Among them, the interlayer difference production coefficient is to reflect the influence of the heterogeneity of the oil reservoir on the development effect of the oil reservoir, and the energy utilization coefficient is to characterize the size and utilization of the natural water body.

[0051] In this implementation step, the interlayer differential production coefficient is the ratio of the standard deviation of the geological reserve recovery degree of each sub-layer to the average recovery degree, which is used to reflect the impact of the heterogeneity of the reservoir on the reservoir development effect. Among them, the water content of the sub-layer reaches more than 90%, and the geological reserves of the sub-layer are controlled by the produced wells and the producing wells.

[0052] In this implementation step, the energy utilization coefficient is the ratio of the underground cumulative oil production to the edge and bottom water intrusion, which is used to reflect the utilization rate of water-driven oil in natural water-driven oil reservoirs.

[0053] In the development of natural water-driven oil reservoirs, the amount of edge and bottom water (i.e., natural water) intrusion refers to the underground amount, while the cumulative oil production data of the oil field represents the surface amount. If the cumulative oil production of the oil field is directly used to calculate the energy utilization coefficient, it is impossible to accurately represent the size of the natural water body and the water utilization. Therefore, there is a volume coefficient conversion between the surface and underground cumulative oil production. Therefore, in this implementation step, when calculating the energy utilization coefficient, the cumulative oil production data needs to be converted into underground volume. Among them, the specific conversion formula is: underground cumulative oil production = N p B o / ρ o Among them, N p Indicates the cumulative oil production, in 10,000 tons; B o Represents the crude oil volume coefficient, expressed as a decimal; ρ o Indicates the density of ground crude oil in g / cm 3 .

[0054] Step 2 (S2) is to establish a natural water drive reservoir development effect evaluation index system consisting of multiple evaluation indicators, including interlayer differential production coefficient and energy utilization coefficient.

[0055] During the specific implementation, evaluation indicators that affect the development effect of natural water drive oil reservoirs are selected, and an evaluation indicator system for the development effect of natural water drive oil reservoirs consisting of multiple evaluation indicators is established. Figure 2 FIG. 2 shows a hierarchical structure diagram of a natural water drive reservoir development effect evaluation index system in an embodiment of the present invention. Figure 2As shown, among them, multiple evaluation indicators include: 5 contradiction manifestation indicators, 4 development technology indicators, 2 production management indicators, and 1 economic benefit indicator.

[0056] In this implementation step, there are 5 contradiction-reflecting indicators, which are composed of the degree of control of reserves by the well network, plane sweep coefficient, intra-layer sweep coefficient, inter-layer differential utilization coefficient, and energy utilization coefficient; 4 development technology indicators are composed of water cut increase rate, remaining recoverable reserves oil production rate, natural decline rate and recovery factor; 2 production management indicators are composed of comprehensive production time rate and effectiveness of measures for old wells; 1 economic benefit indicator refers to the operating cost per ton of oil.

[0057] Step 3 (S3), according to the natural water drive reservoir development effect evaluation index system, determine the actual value of each evaluation index of the reservoir to be evaluated, the threshold range of each evaluation index in the three evaluation levels of "excellent, good, poor" and the weight of each evaluation index.

[0058] In specific implementation, the implementation steps include:

[0059] S3-1, based on the evaluation index system for the development effect of natural water drive oil reservoirs, use reservoir engineering methods to determine the actual values ​​of various evaluation indicators of the reservoir to be evaluated.

[0060] In this implementation step, the calculation formula for the actual value of each evaluation indicator is as follows:

[0061] The degree of control of reserves by well pattern

[0062] In this formula, R f Indicates the degree of control of well pattern on reserves, in %; N o1 Indicates the geological reserves that cannot be affected due to boundary effects, in 10,000 tons; N o2 It indicates the geological reserves that cannot be used beyond the oil leakage radius, in 10,000 tons; N o Indicates the geological reserves being utilized, in 10,000 tons.

[0063] Inter-layer difference utilization coefficient

[0064] In this formula, R v It represents the inter-layer difference utilization coefficient, expressed as a decimal; R oi Indicates the recovery degree of geological reserves in the i-th layer, in %; It represents the average value of the geological reserve recovery rate of each sub-layer, in %; n represents the number of sub-layers. The sub-layers involved in the calculation need to meet two conditions: one is that the water content reaches more than 90%; the other is that the produced wells and the producing wells can control the reserves of the sub-layer.

[0065]

[0066]

[0067] Energy utilization coefficient

[0068] In this formula, B e Indicates the energy utilization coefficient, expressed as a decimal; N p Indicates the cumulative oil production, in 10,000 tons; W p Indicates the cumulative water production, in ten thousand cubic meters; B o Indicates the crude oil volume coefficient, expressed as a decimal; B oi Represents the original crude oil volume coefficient, expressed as a decimal; ρ o Indicates the density of ground crude oil in g / cm 3 ; W e Indicates the cumulative water intrusion, that is, the water intrusion at the edge and bottom, in ten thousand cubic meters; C t Indicates the effective compression coefficient of the formation rock, in MPa -1 ; Δp represents the formation pressure drop, in MPa.

[0069] Water content rise rate

[0070] In this formula, f w ' represents the water content increase rate, in %; f w2 Indicates the moisture content at the end of the year, in %; f w1 Indicates the moisture content at the end of the previous year, in %; R 2 Indicates the degree of extraction at the end of the year, in %; R 1 Indicates the extraction level at the end of the previous year, in %.

[0071] Remaining recoverable reserves oil production rate

[0072] In this formula, v represents the remaining recoverable reserves oil production rate, the unit is %; Q o2 Indicates the verified annual oil production in that year, in 10,000 tons; N R Represents recoverable reserves in 10,000 tons; N p1 It indicates the cumulative oil production in the previous year, in ten thousand tons.

[0073] Natural decline rate

[0074] In this formula, a represents the natural decline rate, in %; Q o1 It indicates the verified annual oil production in the previous year, in 10,000 tons; Q o2 It indicates the verified annual oil production in that year, in 10,000 tons; Q o3 It indicates the annual oil production of new wells verified in that year, in 10,000 tons; Q o4It indicates the oil production verified by the production increase measures in the current year, in ten thousand tons.

[0075] Recovery rate

[0076] In this formula, E R Represents the recovery rate, in %; N R Represents recoverable reserves in 10,000 tons; N o Indicates the geological reserves being utilized, in 10,000 tons.

[0077] Comprehensive production time rate = oil and water well utilization rate × production time rate / 100.

[0078] Effectiveness of measures for old wells

[0079] In this formula, η represents the effectiveness of measures for old wells, in %; ω e It indicates the number of wells with production increase effect in the annual production increase measures for old wells, in units; ω indicates the total number of wells with annual production increase measures for old wells, in units.

[0080]

[0081] S3-2, based on the development characteristics of natural water drive reservoirs, determine the threshold range of each evaluation indicator in the three evaluation levels of "excellent, good, and poor".

[0082] In the specific implementation, in order to obtain the threshold range of various evaluation indicators that can be generally accepted, the threshold range of various evaluation indicators in the three evaluation levels of "excellent, good, and poor" is determined based on the petroleum and natural gas industry standard "Oilfield Development Level Classification" (SY / T 6219-1996), combined with the specific situation of the change law of natural water drive reservoir indicators. Among them, for the evaluation indicators specified in the industry standard, the threshold range follows the original industry standard; for the evaluation indicators without industry standards, the threshold range of various evaluation indicators in the three evaluation levels of "excellent, good, and poor" is determined through mine data analysis (i.e.: analysis of the development characteristics of natural water drive reservoirs), numerical simulation, expert opinions and other methods.

[0083] In this implementation step, the threshold of each evaluation index is the limit of the evaluation index value that characterizes the degree of development effect.

[0084] S3-3. Determine the weight of each evaluation indicator based on its impact on the development effect of natural water drive oil reservoirs.

[0085] In the specific implementation, according to the influence of various evaluation indicators on the development effect of natural water drive oil reservoirs, the weight of each evaluation indicator is established by using the hierarchical analysis method. Specifically, the "1-9 scale method" is introduced, and the judgment scale value between each element at each level is given by the pairwise comparison judgment method, forming a 12-row 12-column judgment matrix P = (u ij ) 12×12 , i represents the i-th row, j represents the j-th column. Use linear algebra methods to solve the eigenvector of the judgment matrix W = (W 1 , W 2 , …, W 12 ), and then get the weight W of each evaluation index i (i=1, 2,…, 12).

[0086] Here, the inventors need to point out that: in the above-mentioned AHP calculation process, there are many mathematical methods for solving weights, and there is no sole limitation. In this implementation step, linear algebra methods are used to collectively refer to them.

[0087] Step 4 (S4), scoring each evaluation index using a single factor grading calculation method according to the actual value, threshold range and weight.

[0088] In order to describe the impact of different values ​​of each single factor on the reservoir development effect, it is necessary to define the level of each single factor and the calculation method. The level of single factor classification adopts the commonly used three-level classification method, namely excellent, good and poor. Referring to the golden ratio of 0.618 and the percentage passing standard of 60 points commonly used in my country, 0.4, 0.6 and 1 are taken as the coefficients of "poor", "good" and "excellent" levels respectively. Different formulas are used to calculate the corresponding scores of different levels of impact on development effect.

[0089] In this implementation step, the single factor classification calculation method is:

[0090] When the evaluation level of an evaluation indicator is in the "poor" range, the score of this item is 40% of the weight of this item;

[0091] When the evaluation level of a certain evaluation indicator is in the "good" interval, based on the "poor" score, according to the linear law, the slope is determined to consider the proportion of the "good" interval, and finally multiplied by the weight score to get the evaluation value of the indicator. Specifically: the score of this item = the weight score of this item × [0.4 + 0.6 × (the actual value of the item - the lower limit of definition) / (the upper limit of definition - the lower limit of definition)]; Among them, (the actual value of the item - the lower limit of definition) / (the upper limit of definition - the lower limit of definition) is the increase of the actual value of the evaluation indicator compared with the lower limit of definition with the lower limit of definition and the upper limit of definition as the endpoint values ​​on both sides; the lower limit of definition refers to the minimum value of the threshold range of this item; the upper limit of definition refers to the maximum value of the threshold range of this item;

[0092] When the evaluation grade of an evaluation indicator is "excellent", the score of this item = 100% of the weight score of this item.

[0093] In specific implementation, each evaluation index is calculated and scored according to the above-mentioned single-factor grading calculation method.

[0094] Step 5 (S5), summing up the score values ​​of various evaluation indicators, and taking the summed value as the total evaluation score of the oil reservoir to be evaluated.

[0095] Step 6 (S6), according to the preset scoring level, determine the level of the sum value, and use the level as the quantitative evaluation result of the natural water drive reservoir development effect of the oil reservoir to be evaluated.

[0096] The embodiment of the present invention provides a method for quantitatively evaluating the development effect of a natural water-drive oil reservoir. It proposes two indicators, namely, an energy utilization coefficient and an interlayer difference utilization coefficient, for the first time, and establishes a natural water-drive oil reservoir development effect evaluation index system for the first time, covering four categories and 12 development effect evaluation indicators, including contradiction manifestation indicators, development technology indicators, production management indicators, and economic benefit indicators. It can accurately characterize the development characteristics of natural water-drive oil reservoirs and their water-drive effects, make up for the shortcomings of development effect evaluation indicators, and solve the problems existing in the prior art that the three major contradictions of the reservoir plane, within the layer, and between the layers cannot be reflected, and the development effect of natural water-drive oil reservoirs cannot be fully reflected and evaluated.

[0097] Moreover, the quantitative evaluation method for the development effect of natural water drive oil reservoirs provided by the embodiment of the present invention realizes the multi-factor quantitative evaluation of the development effect of natural water drive oil reservoirs, the evaluation parameters are simple to obtain, the evaluation process is simple and easy to operate, and the field applicability is strong. The only quantitative evaluation result of the target oil reservoir obtained can scientifically and accurately evaluate the development effect of natural water drive oil reservoirs, point out the main factors that restrict the development effect of oil reservoirs, and provide a basis for targeted development adjustments in the next step. In addition, the quantitative evaluation method for the development effect of natural water drive oil reservoirs provided by the embodiment of the present invention is applied to carry out development effect evaluation of 10 natural water drive development units of X oil field, and the conformity rate of the evaluation results with the actual production situation reaches more than 90%. It can be seen from this that the quantitative evaluation method for the development effect of natural water drive oil reservoirs provided by the embodiment of the present invention can be applied to the quantitative evaluation of the development effect of natural water drive oil reservoirs, and based on the characteristics of simple acquisition of evaluation parameters, simple evaluation process and easy operation, it is conducive to large-scale promotion and application on site, and can provide guidance for the quantitative evaluation of the development effect of similar oil reservoirs in Jidong, Shengli, Dagang, Liaohe and other domestic areas, and has broad application prospects.

[0098] In order to enable those skilled in the art to better understand the present invention, the method for quantitatively evaluating the development effect of natural water drive oil reservoirs provided by the present invention is described below through specific examples.

[0099] Embodiment 1:

[0100] The research object of this embodiment is the B block unit of the X oil field, which belongs to a shallow high-porosity and high-permeability natural water drive development oil reservoir. A quantitative evaluation method for the development effect of a natural water drive oil reservoir in an embodiment of the present invention includes the following steps:

[0101] 1) Select the evaluation indicators that affect the development effect of natural water drive oil reservoirs and establish the evaluation index system of natural water drive oil reservoir development effect. The evaluation index system of natural water drive oil reservoir development effect includes: 5 contradiction manifestation indicators (the control degree of well network on reserves, plane sweep coefficient, interlayer differential utilization coefficient, intralayer sweep coefficient, energy utilization coefficient), 4 development technology indicators (water cut increase rate, remaining recoverable reserves oil production rate, natural decline rate and recovery rate), 2 production management indicators (comprehensive production time rate, old well measures efficiency), and 1 economic benefit indicator (operating cost per ton of oil).

[0102] 2) According to the production data of block B, the actual value of each evaluation index of block B is determined by using reservoir engineering methods. Specifically, the production data of block B is brought into the calculation formula of the actual value of each evaluation index, and the specific actual value is obtained by calculation. The calculation process is as follows:

[0103] In the B block unit, the geological reserves N that cannot be affected due to boundary effects o1 The geological reserves that cannot be used are 370,000 tons, exceeding the oil spill radius. o2 556,000 tons, using geological reserves of N o 10.173 million tons. f The calculation formula is used to calculate the control degree of well pattern on reserves R f 90.9%;

[0104] In the B block unit, the first layer of geological reserves recovery degree R o1 The second layer geological reserve extraction rate is 27.7%. o2 The third layer geological reserve recovery rate is 35.3%. o3 The fourth layer geological reserve extraction rate is 23.7%. o4 The average value of the geological reserve recovery rate of each sub-layer is 31.4%. is 27.8%, and n is 4. Based on R v The calculation formula is used to calculate the inter-layer difference utilization coefficient R v is 0.17.

[0105] In Block B, the oil-bearing area affected by the edge and bottom water is 4.4 km 2 The oil-bearing area controlled by the well pattern is 6.2km 2Based on the calculation formula of the plane wave coefficient, the plane wave coefficient is calculated to be 0.71.

[0106] In the B block unit, the volume of the oil layer affected by the edge and bottom water in the layer is 9.272 million cubic meters, and the oil-bearing volume of the entire small layer is 11.171 million cubic meters. Based on the calculation formula of the intra-layer sweep coefficient, the intra-layer sweep coefficient is calculated to be 0.83.

[0107] In block B, the cumulative oil production is N p The cumulative water output is 2.833 million tons. p The crude oil volume coefficient is 26.147 million cubic meters. o The original crude oil volume coefficient B is 1.067. oi is 1.134, the density of crude oil on the ground is ρ o 0.9562g / cm 3 ; Cumulative water intrusion W e The effective compression coefficient of the formation rock is 29.3 million cubic meters. t 0.0011MPa -1 , the formation pressure drop Δp is 2.1MPa. Based on the energy utilization coefficient B e According to the calculation formula, the energy utilization coefficient is calculated to be 0.11.

[0108] In the B block unit, the water content at the end of the year is f w2 The moisture content at the end of last year was 90.5%. w1 The extraction rate at the end of the year was R 2 At the end of last year, the extraction rate was R 1 is 27.1%. Based on the water content increase rate f w ', the water content rise rate f is calculated w ' is -4.0%.

[0109] In Block B, the verified annual oil production is Q o2 76,000 tons, recoverable reserves N R The cumulative oil production last year was 2.987 million tons. p1 Based on the calculation formula of the remaining recoverable reserves oil production rate v, the remaining recoverable reserves oil production rate v is calculated to be 32.9%.

[0110] In the B block unit, the annual oil production verified last year was Q o1 The annual oil production was 74,000 tons. o2 The annual oil production of the new well was 76,000 tons. o3 The oil production volume verified by the production increase measures in that year was Q o4Based on the calculation formula of the natural decline rate a, the natural decline rate a is calculated to be 11.4%.

[0111] In block B, recoverable reserves N R 2.987 million tons, and the geological reserves of N o Expressed as 10.173 million tons. Based on the recovery factor E R The calculation formula for calculating the recovery factor E R It is 29.4%.

[0112] In Block B, the utilization rate of oil and water wells is 78.0%, and the production time rate is 89.4%. Based on the calculation formula of the comprehensive production time rate, the comprehensive production time rate is calculated to be 69.8%.

[0113] In the B block unit, the number of wells with production increase effects in the annual production increase measures of old wells ω e The number of wells with annual production increase measures is 69, and the total number of wells with annual production increase measures is 75. Based on the calculation formula of the efficiency of measures for old wells η, the efficiency of measures for old wells η is calculated to be 92.0%.

[0114] In Block B, the actual annual production and operation cost of the oil field was RMB 140.06 million, and the annual oil production was 76,000 tons. Based on the calculation formula of the operating cost per ton of oil, the operating cost per ton of oil was calculated to be RMB 1,850 per ton.

[0115] In block B, the actual values ​​of the determined evaluation indicators are shown in Table 1.

[0116] Table 1. Actual values ​​of evaluation indicators for natural water flooding development effect in Block B

[0117]

[0118] 3) Combined with the development characteristics of natural water drive reservoirs, the threshold ranges of the three evaluation levels of "excellent, good, and poor" for each evaluation index are determined, as shown in Table 2. The specific determination process is as follows:

[0119] In order to obtain the generally accepted threshold ranges of various evaluation indicators, the threshold ranges were determined based on the petroleum and natural gas industry standard "Oilfield Development Level Classification" (SY / T 6219-1996) and combined with the specific conditions of the natural water drive reservoir indicator variation law.

[0120] The threshold ranges for the evaluation indicators specified in the industry standards follow the original industry standards, including the degree of control of reserves by the well network, the rate of increase in water cut, the rate of oil production based on remaining recoverable reserves, and the comprehensive production time rate.

[0121] For evaluation indicators that do not have industry standards, their threshold ranges are determined through mine data analysis, numerical simulation, expert opinions and other methods, including eight evaluation indicators: plane sweep coefficient, intra-layer sweep coefficient, inter-layer differential utilization coefficient, energy utilization coefficient, natural decline rate, recovery factor, effectiveness of old well measures, and operating cost per ton of oil.

[0122] There are 10 block units in the natural water drive development reservoir of X Oilfield, and their production technical indicators are shown in Table 3. Figure 3 FIG. 2 shows a comparison chart of recovery rates of different blocks in the X oil field in an embodiment of the present invention. Figure 3 As shown in the figure, the recovery rate distribution of each block unit is not balanced. When 25% is selected as the boundary value of the evaluation level "excellent", the block units that reach the "excellent" level account for 20%. When 15% is selected as the boundary value of the evaluation level "good", the block units at the "poor" level account for 30%. Therefore, the proportions of "excellent, good, and poor" levels are 20%, 50%, and 30% respectively, which basically conforms to the normal distribution level. Therefore, 25% and 15% are used as the boundary values ​​of recovery rate in the three evaluation levels of "excellent, good, and poor".

[0123] Cluster analysis is performed based on the correlation between the recovery factor and the other seven evaluation indicators, and the threshold range of each evaluation level is determined by the clustering results. Figure 4 includes: Figure 4(a) to Figure 4(g) , shows a scatter plot of the relationship between the evaluation index and the recovery rate of each block unit in the X oil field in the embodiment of the present invention. Figure 4(a) to Figure 4(g) As shown in Table 2, after being clustered into three categories, the boundaries of "excellent, good, and poor" for the five evaluation indicators, namely, plane sweep coefficient, intra-layer sweep coefficient, inter-layer differential utilization coefficient, effective rate of old well measures, and operating cost per ton of oil, are relatively clear, and their threshold ranges can be directly obtained, as shown in Table 2. However, the two evaluation indicators, namely, energy utilization coefficient and natural decline rate, are greatly affected by the development stage, and their boundaries of "excellent, good, and poor" are not uniform, and further evaluation is required after subdividing the development stage.

[0124] The energy utilization coefficient reflects the utilization rate of water-driven oil in natural water-driven oil reservoirs. Considering the universality of the indicators reflecting the characteristics of natural water-driven oil reservoirs and development technology policies, the threshold range is determined by dividing the reservoir into four stages according to the industry standard model with a water content of 20%, 60%, and 90%. The energy utilization coefficient of each block unit at different water content stages is calculated using reservoir engineering methods and numerical simulation methods. Figure 5 includes Figure 5(a) to Figure 5(d) , shows a scatter plot of the relationship between energy utilization coefficient and recovery rate at different development stages of each block unit of the X oil field in an embodiment of the present invention, such as Figure 5(a) to Figure 5(d) As shown in the figure, after being clustered into three categories, the boundaries of “excellent, good, and poor” energy utilization coefficients in different development stages are relatively clear, and the threshold ranges are determined in Table 2.

[0125] The natural decline rate is greatly affected by the development technology policy. Referring to the SY / T 6219-1996 industry standard, the threshold range is determined by dividing it into two stages with 50% of the recoverable reserves as the dividing line. FIG6 includes: FIG6(a) and FIG6(b), which show the scatter plot of the relationship between the natural decline rate and the recovery rate at different development stages of each block unit of the X oil field in the embodiment of the present invention. As shown in FIG6(a) and FIG6(b), the threshold range is determined by the above method as shown in Table 2.

[0126] Table 2. Threshold range of evaluation indicators for Block B

[0127]

[0128]

[0129] Table 3. Production technical indicators of different block units in X oilfield

[0130]

[0131]

[0132] 4) According to the influence of each evaluation index on the development effect of natural water drive oil reservoir, the weight of each evaluation index is established by using the hierarchical analysis method, and the "1-9 scale method" is introduced. The judgment scale value between each element at each level is given by the pairwise comparison judgment method, forming a 12-row 12-column judgment matrix P = (u ij ) 12×12 , i represents the i-th row, j represents the j-th column. The meaning of scales 1 to 9 is shown in Table 4, and the judgment matrix is ​​shown in Table 5. The eigenvector of the judgment matrix is ​​solved by linear algebra method W = (W 1 , W 2 , …, W 12 ), and then get the weight W of each evaluation index i (i=1, 2, ..., 12). In this embodiment, the sum-product method is used to solve the weights, and the specific calculation process is as follows:

[0133] First, normalize the judgment matrix by column, See Table 6. Sum the normalized judgment matrix row by row, and we have See Table 7. i Normalize, get Vector W=(W 1 , W 2 , …, W 12 ) is the eigenvector of the required judgment matrix, W i (i=1, 2, ..., 12) is the weight of each evaluation index, see Table 8.

[0134] Table 4. Analytical hierarchy process scale

[0135] Scale meaning 1 Indicates that the two indicators are equally important. 3 Indicates that one indicator is slightly more important than the other. 5 Indicates that one of the two indicators is significantly more important than the other. 7 Indicates that one of the two indicators is more important than the other. 9 Indicates that one of the two indicators is extremely more important than the other 2，4，6，8 They are the middle values ​​of the above adjacent judgments 1 and 3, 3 and 5, 5 and 7, and 7 and 9. reciprocal <![CDATA[If the judgment a is obtained by comparing index i and j ij , then the judgment for comparing index j and i is a ji = 1 / a ij >

[0136] Table 5. Evaluation index judgment matrix of block B

[0137]

[0138]

[0139] Table 6. Evaluation index judgment matrix after normalization of block B

[0140]

[0141] Table 7. Evaluation index w of block B i value

[0142]

[0143] Table 8. Weights of evaluation indicators for Block B

[0144]

[0145] 5) The evaluation score of each indicator is determined using the single factor grading calculation method. For the specific values ​​of the evaluation scores of each indicator, please see Table 9.

[0146] The single factor grading calculation method is: when the indicator evaluation level is "excellent", the score is 100% of the weight score of the item; when it is in the "good" interval, the score = the weight score of the item × (0.4 + 0.6 × (parameter value - lower limit) / (upper limit - lower limit)); when it is in the "poor" interval, the score is 40% of the weight score. The specific calculation process of each indicator evaluation score is as follows:

[0147] The actual value of the well network's control over reserves is 90.9%, the weight is 0.060, and the indicator evaluation level is "excellent". Therefore, the score of the well network's control over reserves is: 0.060×100%=0.060.

[0148] The actual value of the plane sweep coefficient is 0.71, the weight is 0.115, the indicator evaluation level is "good", and the score of the plane sweep coefficient is: 0.115×(0.4+0.6×(0.71-0.6) / (0.8-0.6))=0.084.

[0149] The actual value of the inter-layer difference utilization coefficient is 0.17, the weight is 0.115, the indicator evaluation level is "excellent", and the score of the inter-layer difference utilization coefficient is: 0.115×100%=0.115.

[0150] The actual value of the intra-layer contagion coefficient is 0.83, the weight is 0.115, the indicator evaluation level is "excellent", and the score of the intra-layer contagion coefficient is: 0.115×100%=0.115.

[0151] The actual value of the energy utilization coefficient is 0.11, the weight is 0.115, the indicator evaluation level is "good", and the score of the energy utilization coefficient is: 0.115×(0.4+0.6×(0.11-0.1) / (0.3-0.1))=0.049.

[0152] The actual value of the water content rise rate is -4.0%, the weight is 0.060, the indicator evaluation level is "excellent", and the score of the water content rise rate is: 0.060×100%=0.060.

[0153] The actual value of the remaining recoverable reserves oil production rate is 32.9%, the weight is 0.035, the indicator evaluation level is "excellent", and the score of the remaining recoverable reserves oil production rate is: 0.035×100%=0.035.

[0154] The actual value of the natural decline rate and recovery factor is 11.4%, the weight is 0.060, the indicator evaluation level is "excellent", and the score of the natural decline rate and recovery factor is: 0.060×100%=0.060.

[0155] The actual value of the recovery factor is 29.4%, the weight is 0.115, the indicator evaluation level is "excellent", and the score of the recovery factor is: 0.115×100%=0.115.

[0156] The actual value of the comprehensive production time rate is 69.8%, the weight is 0.060, the indicator evaluation level is "good", and the score of the comprehensive production time rate is: 0.060×(0.4+0.6×(69.8-60) / (70-60))=0.060.

[0157] The actual value of the effectiveness of the measures for old wells is 92.0%, the weight is 0.035, the indicator evaluation level is "excellent", and the score of the effectiveness of the measures for old wells is: 0.035×100%=0.035.

[0158] The actual value of the operating cost per ton of oil is 1850, the weight is 0.115, the indicator evaluation level is "poor", and the score of the operating cost per ton of oil is: 0.115×40%=0.046.

[0159] Table 9. Evaluation index scores of Block B

[0160] index Rating Evaluation score The degree of control of reserves by well pattern excellent 0.060 Plane wave coefficient good 0.084 Inter-layer difference utilization coefficient excellent 0.115 Intralayer Sweep Coefficient excellent 0.115 Energy utilization coefficient good 0.049 Water content rise rate excellent 0.060 Remaining recoverable reserves oil production rate excellent 0.035 Natural decline rate excellent 0.060 Recovery rate excellent 0.115 Comprehensive production time good 0.060 Effectiveness of measures for old wells excellent 0.035 Operating cost per ton of oil Difference 0.046

[0161] 6) Sum the scores of each indicator, and the total evaluation score of block B is 0.834. The specific calculation process is:

[0162] 0.060+0.084+0.115+0.115+0.049+0.060+0.035+0.060+0.115+0.060+0.035+0.046=0.834.

[0163] 7) The scoring levels are divided into excellent, good, medium and poor. 0.9-1.0 is excellent, 0.8-0.9 is good, 0.6-0.8 is medium, and below 0.6 is poor. The score of Block B is 0.834, and its evaluation level is good. Therefore, the evaluation result of the natural water flooding development effect of Block B can be determined as "good", indicating that the overall development effect of natural water flooding in Block B is good.

[0164] The actual production situation of Block B is as follows: the contradictions between the layers and within the layers of Block B are relatively small, but the dominant seepage channels on the plane are developed, the edge and bottom water are easy to flow along the high permeability strips, and the operating cost per ton of oil is high and the economic benefits are poor. How to further expand the plane sweep and achieve energy efficiency is the key to further improve the development effect. From the above evaluation results, it can be seen that the evaluation score of the operating cost per ton of oil is 0.046, the evaluation level is poor, and thus the economic benefits are poor; although the evaluation level of the energy utilization coefficient is good, the evaluation score is low, only 0.049, so the natural energy utilization rate of the edge and bottom water is low. It can be seen that the evaluation results obtained by the evaluation method provided in this embodiment are consistent with the actual production situation of Block B, indicating that the evaluation method provided in this embodiment can meet the evaluation requirements of natural water drive oil reservoirs. In addition, from the above evaluation results, it can be seen that the main factors restricting the development effect of the unit reservoir of Block B of X Oilfield are high operating cost per ton of oil and low energy utilization coefficient. Therefore, the next step can be to adjust the development according to the operating cost per ton of oil and the energy utilization coefficient.

[0165] The applicant declares that the present invention illustrates the detailed process flow of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned detailed process flow, that is, it does not mean that the present invention must rely on the above-mentioned detailed process flow to be implemented. Those skilled in the art should understand that any simple changes to the present invention, equivalent replacement of various raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0166] For the method embodiments, for the sake of simplicity, they are all described as a series of action combinations, but those skilled in the art should know that the present invention is not limited by the order of the actions described, because according to the present invention, some steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also know that the embodiments described in the specification are all preferred embodiments, and the actions and components involved are not necessarily required by the present invention.

[0167] The above is a detailed introduction to a method for quantitatively evaluating the development effect of a natural water drive oil reservoir provided by the present invention. Specific examples are used in this article to illustrate the principle and implementation method of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. A method for quantitatively evaluating the development effect of natural water drive oil reservoirs, characterized in that: The main steps include: Step 1, according to the factors affecting the development of natural water drive oil reservoirs, set the interlayer difference production coefficient and energy utilization coefficient; Step 2, establishing a natural water drive reservoir development effect evaluation index system consisting of multiple evaluation indicators; the multiple evaluation indicators include interlayer difference production coefficient and energy utilization coefficient; The interlayer differential production coefficient is the ratio of the standard deviation of the geological reserve recovery degree of each sublayer to the average recovery degree; The expression of the inter-layer difference activation coefficient is: ， in, It represents the inter-layer difference utilization coefficient, expressed as a decimal; It indicates the extraction degree of geological reserves in the i-th layer, in units of %; It indicates the average value of the geological reserve recovery degree of each sub-layer, in units of %; n indicates the number of sub-layers. The sub-layers involved in the calculation need to meet two conditions: one is that the water content reaches more than 90%; the other is that the produced wells and the producing wells can control the reserves of the sub-layer; The energy utilization coefficient is the ratio of the underground cumulative oil production to the edge and bottom water intrusion; The expression of the energy utilization coefficient is: in, It represents the energy utilization coefficient, expressed as a decimal; Indicates the cumulative oil production in 10,000 tons; Indicates the cumulative water production, in ten thousand cubic meters; It represents the volume coefficient of crude oil, expressed as a decimal; It represents the original crude oil volume factor, expressed as a decimal; Indicates the density of crude oil on the ground, in g / cm3; It represents the cumulative water intrusion, that is, the water intrusion at the edge and bottom, in ten thousand cubic meters; It indicates the effective compression coefficient of formation rock, in MPa-1; Indicates formation pressure drop, in MPa; Step 3, according to the natural water drive oil reservoir development effect evaluation index system, determine the actual value of each evaluation index of the oil reservoir to be evaluated, the threshold range of each evaluation index in the three evaluation levels of "excellent, good, and poor", and the weight of each evaluation index; Wherein, the step 3 comprises: using reservoir engineering methods to determine the actual values ​​of the evaluation indicators of the reservoir to be evaluated; Combined with the development characteristics of natural water drive oil reservoirs, the threshold ranges of the three evaluation levels of "excellent, good and poor" for each evaluation index are determined; Determine the weight of each evaluation indicator according to its influence on the effect of natural water flooding development; Step 4, scoring each of the evaluation indicators using a single factor grading calculation method according to the actual value, the threshold range and the weight; The single factor grading calculation method includes: when the evaluation grade of a certain evaluation indicator is "excellent", the score of this item is 100% of the weight score of this item; When the evaluation level of a certain evaluation indicator is in the "good" range, the score of this item = the weight score of this item × [0.4 + 0.6 × (the actual value of this item - the lower limit of definition) / (the upper limit of definition - the lower limit of definition)]; wherein the lower limit of definition is the minimum value of the threshold range of this item, and the upper limit of definition is the maximum value of the threshold range of this item; When the evaluation level of an evaluation indicator is in the "poor" range, the score of this item is 40% of the weight of this item; Step 5, summing up the score values ​​of each evaluation index, and taking the summed value as the total evaluation score of the oil reservoir to be evaluated; Step 6: According to a preset scoring level, determine the level of the sum value, and use the level as a quantitative evaluation result of the natural water drive reservoir development effect of the oil reservoir to be evaluated.

2. The evaluation method according to claim 1, characterized in that: The water content of the sublayer reaches more than 90%, and the geological reserves of the sublayer are controlled by produced wells and producing wells.

3. The evaluation method according to any one of claims 1 to 2, characterized in that: The interlayer differential production coefficient is used to reflect the impact of reservoir heterogeneity on reservoir development results.

4. The evaluation method according to claim 1, characterized in that: The energy utilization coefficient is used to reflect the utilization rate of water-driven oil in natural water-driven oil reservoirs.

5. The evaluation method according to claim 1, characterized in that: The multiple evaluation indicators also include: 4 development technology indicators, 2 production management indicators, 1 economic benefit indicator, the degree of control of the well network on reserves, the plane sweep coefficient, and the intra-layer sweep coefficient; Among them, the well pattern's control degree on reserves, plane sweep coefficient, intra-layer sweep coefficient, inter-layer differential production coefficient, and energy utilization coefficient constitute five contradiction-reflecting indicators; The four development technical indicators are composed of water cut increase rate, remaining recoverable reserves oil production rate, natural decline rate and recovery factor; The two production management indicators are composed of comprehensive production time rate and old well measures efficiency; One of the economic benefit indicators is the operating cost per ton of oil.

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