Study on the Compressive and Tensile Properties of Gneiss Outcrop of Bozhong 196 Gas Field in China

In this paper, based on the gneiss outcrop of Bozhong 196 gas field in China, uniaxial compression and Brazil splitting tests were conducted by using cores of different orientations. The following compression properties were studied: the elastic compression modulus, Poisson's ratio and compressive strength of the gneiss outcrop. The following tensile properties were studied: the tensile modulus, the tensile strength and peak energy rate of gneiss outcrop. The results demonstrate the following: (1) The elastic compression modulus, compressive strength, tensile strength and peak energy rate of gneiss specimens with horizontal core-taking are greater than those with vertical core-taking. (2) The elastic compression modulus, Poisson's ratio and compressive strength of horizontally cored gneiss specimens are 29.688-45.760 GPa, 0.186-0.386, and 174.94-147.80 MPa, respectively; the elastic compression modulus, Poisson's ratio and compressive strength of the vertical gneiss specimens are 26.541-32.602 GPa, 0.429-0.476 and 169.37-134.46 MPa. (3) The tensile modulus of the horizontal gneiss specimens is 4.93-5.98 GPa. The tensile modulus of the vertical gneiss specimens is 0.96-2.11 GPa. The tensile modulus of the horizontal gneiss specimens is five times that of the vertical gneiss specimens. The elastic compression modulus of gneiss is 5-20 times that of the tensile modulus. (4) The tensile strength and peak energy rate of horizontally cored gneiss specimens are 14.33-17.55 MPa and 2598.67-4049.53 J/m(2), respectively. The tensile strength of the vertical gneiss specimens is 6.12-9.65 MPa, and the peak energy rate is 715.74-1515.30 J/m(2). (5) There is a good linear relationship between the peak energy rate and tensile strength of gneiss. The research results can provide a scientific and reasonable reference for in situ fracturing of Bozhong 196 gas field.

Automated summary

In this study, uniaxial compression and Brazil splitting tests were conducted on gneiss cores of different orientations from the Bozhong 196 gas field in China. The compression and tensile properties of the gneiss were studied. The results showed that gneiss specimens with horizontal core-taking had higher elastic compression modulus, compressive strength, tensile strength, and peak energy rate compared to those with vertical core-taking.