A method for correcting in-situ stress of shale formation

Abstract

A method for calibrating in-situ stress of shale formation, comprising: 1. collecting experimental core data, geological data, logging data, drilling fluid, and drilling and completion reports in a research work area; 2. drilling standard rock samples at different depths; 5. ~6 groups, respectively vertical, parallel to the bedding direction, and 45° to the central axis; drying and measuring the density longitudinal wave and shear wave time difference; 3. After soaking the rock samples for different times, measure the density longitudinal wave and shear wave time difference; 4. According to the steps 2. Calculate the elastic stiffness coefficients and anisotropy parameters from the measured values; 5. Measure the elastic stiffness coefficient of the core after soaking, and obtain the relationship between the variation range of the elastic stiffness coefficient and soaking time; 6. Connect the experimental results with the field logging data , calculate the elastic stiffness coefficient, elastic modulus and Poisson's ratio, and finally calculate the in-situ stress of the formation. The invention corrects the influence of drilling fluid on shale hydration through the correction of logging value and stiffness coefficient, and proposes a more accurate calculation method.

Description

technical field [0001] The invention belongs to the technical field of oil drilling, and in particular relates to a method for correcting in-situ stress of mud shale formations. Background technique [0002] Reservoir geomechanics refers to various geomechanical problems encountered in reservoir development, generally involving parameters such as rock mechanics, pore pressure, and in-situ stress. have an important impact. This requires the acquisition of the in-situ stress profile of the studied formation, and the in-situ stress calculation based on logging data is a research hotspot. With the increase in energy demand, unconventional shale oil and gas reservoirs have received more and more attention. During the drilling of shale oil and gas reservoirs, the drilling fluid invading the formation will cause obvious hydration, and the hydration will also cause the rock acoustic time difference to change. Therefore, the formation pressure calculated by using the logging acous...

AI Technical Summary

Problems solved by technology

During the drilling process of shale oil and gas reservoirs, when the drilling fluid invades the formation, there will be obvious hydration, and the hydration will also cause the change of rock acoustic time difference, while the acoustic data of the formation obtained by open-hole logging are all after hydration. Therefore, the formation pressure calculated by using logging acoustic data has a large deviation from the actual one, and often cannot provide reliable in-situ stress information for drilling and completion

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