Abstract: The shelly limestone reservoir of commercial oil and gas wells are found in the Sichuan Basin, but the production capacity is relatively low. The full size rock cores from the pilot well Jiaoye 32HF and from the storage layer rock outcrops were used for the studies. The studies include microscopic structures, mechanical properties and hydraulic fracturing physical modeling. The test results indicate that, 1) both the primary and the secondary fissures of the shelly limestone are well developed with the porosity ranging from 0.04% to 1.4% with an average of 1.4%. 2) A weak heterogeneous is observed in the vertical and horizontal joints of the shelly limestone; an obvious brittle property exists in the uniaxial compressive test of the intact rock cores. The heterogeneous property in the rock layers will be beneficial to the development and the expansion of the compressive cracks. 3) In the triaxial tests, the strength and the stiffness of the intact rock samples increase with the confining pressures. The brittle failure mode is gradually changed to the ductile failure mode. 4) After the compressive failure, cracks are developed in the direction that perpendicular to the minor principal stress. These compressive cracks can be connected with the nature fissures and these connected fissures can improve the oil/gas productivities.

Key words: Shell Limestone, Storage Layer, Rock Parameters, Hydraulic Fracture, Fissure Patterns