INDOOR EVALUATION METHOD FOR SHALE BRITTLENESS AND IMPROVEMENT
LI Qinghui1，2，CHEN Mian1，JIN Yan1，WANG F P2，HOU Bing1，ZHANG Baowei1
(1. School of Petroleum Engineering，China University of Petroleum，Beijing 102249，China；
2. Bureau of Economic Geology，University of Texas，Austin 78758，USA)
Abstract：Brittleness of gas shale reservoir is of vital significance to testing and evaluating the brittleness of shale. In view of this，through literature investigation and lab tests，20 kinds of basic methods for testing brittleness，including methods based on strength，hardness and ruggedness are summarized，focusing on discussing testing theory and lab method for shale brittleness based on complete stress-strain characteristics. Considering brittleness fracture mechanism and fracture feature，brittleness of shale is defined as a synthetic characteristic of material，affected by its heterogeneity and external testing environment. To identify brittleness of shale，complete stress-strain curve consisted of pre-peak and post-peak parts should both be considered. To improve the accuracy of brittleness evaluation，complete stress-strain testing in underground environment should be simulated. Capacity for resisting inelastic deformation before rupture and losing rate of bearing capacity after rupture are the main mechanical performance of brittleness. To improve the evaluation accuracy，existing mechanical testing schemes are also modified. Meanwhile，brittleness characteristics of black shale from South China is tested through true triaxial rock mechanics tests and then evaluated using improved methods.
2012, Vol. 31 
