A Logging Evaluation Method for Rock Brittleness in Tight Sandstone Reservoir

Abstract

The invention relates to a rock brittleness logging evaluation method of tight sandstone reservoirs, which is characterized in that it comprises the following steps: 1) obtaining the core brittleness index of the tight sandstone in the target interval; 2) obtaining the rock mineral composition of the tight sandstone in the target interval 3) Determine the brittle minerals of the tight sandstone in the target interval; 4) Obtain the rock brittleness index at each depth point of the tight sandstone in the target interval; 5) According to the rock brittleness index at each depth point of the tight sandstone in the target interval, comprehensive formation fracturing Results The fracability evaluation of tight sandstone reservoirs was carried out. The invention can effectively avoid the error caused by the judgment difference of brittle minerals and the equal weight, is efficient and fast, has small calculation error and strong versatility.

Description

technical field [0001] The invention relates to a logging evaluation method for rock brittleness in tight sandstone reservoirs, belonging to the field of logging technology. Background technique [0002] The brittleness index of rock is one of the important contents in the study of the "seven-property relationship" of well logging, and it is also an important reference index that should be considered in the design of oil and gas volume fracturing in tight sandstone reservoirs. The methods used for rock brittleness evaluation at home and abroad can be summarized into three categories: the first is the brittleness evaluation method based on elastic strain, which defines brittleness as: "the fracture of a rock with little or no plastic deformation. This method can measure the stress-strain relationship of rocks in the laboratory and calculate the brittleness of rocks. Although it can reflect the brittleness of rocks more truly, it is difficult to apply to well logging predictio...

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Problems solved by technology

The methods used for rock brittleness evaluation at home and abroad can be summarized into three categories: the first is the brittleness evaluation method based on elastic strain, which defines brittleness as: "the fracture of a rock with little or no plastic deformation. properties”; this method can calculate the rock brittleness by measuring the stress-strain relationship of the rock in the laboratory, although it can reflect the rock brittleness more truly, but because this method can only be obtained from laboratory analysis, it is difficult to apply to well logging prediction

The second is the brittleness evaluation method based on rock elastic parameters. This method is to characterize its brittleness by Young's modulus and Poisson's ratio; if high-precision density logging and shear wave logging data are obtained, this method can be used to directly calculate the rock brittleness index , and can use the laboratory scale to calculate the conversion of rock dynamic and static elastic parameters. However, in actual logging, most wells only measure conventional logging data but have no shear wave logging data, so it is difficult to apply this method to calculate brittleness. index

The third is the brittleness evaluation method based on rock mineralogy. This method mainly evaluates rock brittleness by calculating the proportion of brittle minerals such as quartz and carbonate rocks or the elements that make up brittle minerals. Although this method is simple and easy to use, it has relatively limited conditions. However, there are still two major problems in using mineral components to carry out brittleness evaluation. First, if the determination of brittle minerals is different, the evaluation methods will be quite different. The contribution to the brittleness of rocks is equal. In fact, due to the different chemical composition of each mineral, the physical brittleness of the rocks is not the same. However, it is precisely because of the existence of these two reasons that the brittleness based on rock mineralogy The error of the evaluation method is relatively large, and the application of this method is limited due to the different types of rock mineral composition in each region

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