Method for determining heterogeneous carbonate reservoir saturation index

Abstract

The invention discloses a method for determining a heterogeneous carbonate reservoir saturation index. The method comprises the steps that a target rock reservoir is divided into at least two reservoir types according to a preset rule, a corresponding relation between the saturation index and irreducible water saturation of each reservoir type is acquired, the reservoir type of a core to be detected is determined according to the preset rule, the irreducible water saturation of the core to be detected is acquired, and the saturation index of the core to be detected is calculated based on the corresponding relation of the reservoir type according to the irreducible water saturation of the core to be detected.

Description

technical field [0001] The invention relates to the technical field of well logging evaluation of oil and gas reservoirs, in particular to a method for determining the saturation index of heterogeneous carbonate rock reservoirs. Background technique [0002] The conductivity of reservoir rock mainly depends on the fluid properties, saturation state and its spatial distribution in the pore space. For heterogeneous carbonate reservoirs, the pore structure has a significant impact on the resistivity, and sometimes fractures and caves have a great influence on the electrical conductivity. The influence of resistivity far exceeds the influence of oil and gas. Many researchers have tried to get rid of the traditional method of calculating saturation by relying solely on resistivity curves for more than 70 years, and tried to use various non-electric logging methods to calculate saturation of carbonate rocks. The effect is not ideal. Therefore, so far, the calculation of saturatio...

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Problems solved by technology

The general relational formula solves the problem of accurate quantitative calculation of the saturation of heterogeneous complex reservoirs theoretically, but under the current technical conditions, two key technical The relational expression is a general solution equation, which is inconvenient to be directly used in programming calculations. That is, under the existing logging technology conditions, it is quite difficult to determine all the parameters in the general relational relation. Therefore, in practical applications, it is necessary to select according to the actual reservoir characteristics to meet the accuracy requirements. The shortest form (also known as the best form); secondly, it is necessary to choose a reliable method to accurately determine each undetermined parameter in the best form, so that the final calculation model can reflect the relationship between reservoir resistivity and water saturation to the greatest extent. real law between

The first type of method belongs to the direct method, which is a conventional method for determining the saturation index n at present, but there are two shortcomings in practical application: First, in order to determine the saturation index n, it is necessary to carry out variable saturation lithoelectric experiments on each core ( Such as gas drive method), and the experiment usually takes a long time; secondly, it is difficult to dynamically determine the value of the saturation index n based on the logging data and reservoir characteristics by using this method

Most of these studies focus on sandstone reservoirs, and there are relatively few studies on the dynamic determination method of carbonate saturation index n

In addition, existing studies are more based on the analysis of the relationship between saturation index n and reservoir porosity and permeability. For heterogeneous complex carbonate rocks, the research shows that the variation range of saturation index n under the same porosity and permeability is Therefore, how to accurately determine the value of the carbonate saturation index n is a major challenge in the current logging evaluation

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