Ground stress evaluation method based on mechanical instability collapse of well wall

Abstract

The invention discloses a geostress evaluation method based on mechanical instability collapse of a well wall. The method comprises the following steps: screening mechanical instability collapsed well sections and classifying data; representing deep ground stress and borehole wall stress based on a tectonic strain coefficient; establishing a tectonic strain coefficient equation based on a stress limit equilibrium condition; solving the tectonic strain coefficient based on a least square method and calculating horizontal principal stress; In the present invention, the well wall stress instability collapsed well section data and collapsed data classification are screened, the stress limit equilibrium equation is created based on the strain factor and solve the overdetermined equation based on the information constraints of the critically collapsed formation, the maximum principal stress and minimum principal stress of the in-situ level of the evaluation deep part are calculated. an in-situ stress result rationality evaluation method is given, quantitative calculation and evaluation of the horizontal principal stress of the deep stratum are realized, and necessary deep stratum mechanics basic parameters are provided for underground deep engineering, especially oil and gas well engineering, oil and gas exploitation engineering and the like.

Description

technical field [0001] The invention relates to the technical fields of geomechanics, oil and gas well engineering, and oil and natural gas exploitation, in particular to an evaluation method for the magnitude of ground stress based on the instability and collapse of well wall mechanics. Background technique [0002] In-situ stress is an important basic parameter required for the design and implementation of underground deep engineering. Especially in the field of oil and gas drilling and production, the evaluation of deep in-situ stress is of great importance for well trajectory design, well wall stability evaluation, well completion optimization, stimulation fracturing, and production. Sand prediction and the establishment of a safe mining operation system are extremely important. At present, deep in-situ stress evaluation is mainly through drilling core stress testing, stress analysis of mine data such as fracturing and drilling, and in-situ stress profile logging calculat...

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Problems solved by technology

[0003] The traditional method needs to calibrate and constrain the stress size obtained from the stress test or mine data analysis to ensure the reliability of the stress calculation results of the well logging; There are many factors affecting the obtained data, which is difficult to meet the needs of scientific evaluation of in-situ stress; wellbore collapse and drilling-induced fractures are another important information that can be used to evaluate deep in-situ stress, but they are mainly limited to the evaluation of deep in-situ stress direction Analysis, although Mark D. Zoback proposed a theoretical model based on borehole collapse to calculate in-situ stress, but due to the heterogeneity of deep formation rocks, the irregularity of actual borehole collapse, and the parameters related to borehole collapse required by the model cannot Restricted by factors such as acquisition, at present, this theoretical model is still difficult to be effectively applied to the calculation and evaluation of the deep in-situ stress. Therefore, the present invention proposes a method for evaluating the in-situ stress based on the mechanical instability and collapse of the wellbore wall to solve the existing problems. problems in

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