Study On Mechanical Properties Of Shale Under Uniaxial Confinement

The study of sealing capacity of argillaceous shale cap rocks has always been a hotspot in oil and gas geology research.For the time being,the seal evaluation of cap rock mostly stays in the stage of static qualitative assessment and quantitative analysis,and its dynamic evolution is still relatively weak.For highly evolved cap rocks,the OCR method can be used for quantitative recovery in the evaluation of the historical structural evolution closure.In the OCR method,determining the value of the apparent pre-consolidation stress is the key.In this paper,the argillaceous shale in the Bayu village of Liutang,Chongqing and Daozhen,Guizhou was studied.The thick wall steel drum to constrain the lateral deformation of the specimen in the uniaxial strain compression experiments.The influence of lithology,bedding angle and test temperature on the apparent pre-consolidation stress of argillaceous shale cap rocks were analyzed,and at the same time explored the mechanical properties of its “brittle to fragile”,providing a theoretical reference for the static-dynamic evaluation model of the sealing capacity of argillaceous shale cap rocks,the main contents are as follows:(1)The composition of the sample used was obtained by XRD diffraction test.The analysis results showed that the composition of quartz and clay in the samples of each group was relatively high,and each accounted for approximately 30%-40%;the appearance of different samples The color has a direct relationship with the colored minerals;(2)Through uniaxial strain compression experiments with rock samples of different material compositions,the content of hard minerals(such as quartz)is low,the apparent pre-consolidation stress and the critical boundary of the critical confining pressure of the “brittle-ductile” transition;There is a certain exponential relationship between the lateral pressure coefficient and clay matter content.The higher the clay content is,the larger the front lateral pressure coefficient is,and the middle and back lateral pressure coefficients have no obvious relationship with the clay matter content.(3)Uniaxial strain tests were carried out for tests with bedding angles of 0°,22.5°,45°,67.5°,and 90°,the bedding effect of the apparent pre-consolidation stress and lateral pressure coefficient of the shale of different bedding angles was analyzed,and the critical confining pressure of the “brittle-ductile” transition was analysis;(4)By performing the uniaxial strain compression experiments on the same shale at different test temperatures,the test shows that as the test temperature increases,the initial critical consolidation pressure and the critical confining pressure of the “brittle-ductile” transition of argillaceous shale appear to varying degrees.And it had analyzed the energy conversion during the test on the perspective of energy.