Quantitative evaluation method of fault vertical opening-closing performance during oil-gas reservoir-forming period

Abstract

The invention provides a quantitative evaluation method of fault vertical opening-closing performance during an oil-gas reservoir-forming period and belongs to the technical field of oilfield exploration. The method is independent from experiments, is low in cost, can accurately judge fault vertical opening-closing performance during the oil-gas reservoir-forming period and is applicable to quantitative evaluation of various lithologic cover strata. The method includes following steps: selecting multiple faults of a known area in a studied region as sample points, making longitudinal geological sections perpendicular to leading directions of the faults, and judging vertical opening-closing performance of the faults at the sample points according to distribution features of oil and gas above and below the faults; calculating fault opening-closing coefficient S of each sample point, recording correlation between the fault vertical opening-closing performance of the sample points and the corresponding fault opening-closing coefficient S, and establishing a judgment threshold; calculating fault opening-closing coefficient S corresponding to faults of unknown areas in the studied region, vertically closing the faults when the fault opening-closing coefficient S corresponding to the faults is greater than the judgment threshold, and vertically opening the faults otherwise.

Description

Technical field [0001] The invention belongs to the technical field of oil field exploration, and in particular relates to a quantitative evaluation method for the vertical opening and closing of a fault during the hydrocarbon accumulation period. Background technique [0002] A fault is a structure in which the rock in the surface layer of the earth's crust is significantly displaced along the fracture surface. Under the action of the fracture, the surrounding rock particles on the fracture surface and the lower two plates break and slide into the fracture surface to form fillings inside the fault. The filling particles develop between them. Associated fissures can provide advantageous channels for oil and gas migration. Therefore, faults are important channels for oil and gas migration and important blocking conditions for oil and gas accumulation. Accurate understanding of the opening and sealing of faults during the hydrocarbon accumulation period will help to correctly under...

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Problems solved by technology

However, these three methods all have certain limitations in use: both the "cross-section positive pressure method" and the "break-reservoir displacement pressure difference method" need the support of laboratory simulation equipment, the cost is high, and the on-site There is a high dependence on the center of the fault, which seriously restricts the application of these two methods in oilfield exploration; while the "fault opening coefficient method" can only be applied to the study of the vertical opening and closing of faults after the cessation of activity, but the oil and gas accumulation period Usually coincides with the fault activity period, so this method cannot be applied to the evaluation of the vertical opening and closing of faults during the oil and gas accumulation period, and has limited value for guiding exploration

In addition, the above three methods only consider the shale content parameters of the caprock, so they can only be applied to the evaluation of the vertical opening and closing of faults under the condition of argillaceous rock type caprocks, and cannot be applied to gypsum rocks and carbonate rocks. , coal seams and other rock caprocks

[0004] Therefore, the existing quantitative evaluation methods for the vertical opening and closing of faults have several shortcomings, such as high cost, not suitable for evaluating the vertical opening and closing characteristics of faults during the oil and gas accumulation period, and only suitable for argillaceous rock-type cap rocks.

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