Study on hydraulic fracture extension of volcanic formation in J230 area, Xinjiang

Abstract

It is key of “network fracturing” stimulation to correctly recognize the rock failure pattern during hydraulic fracturing treatment. In this paper, basic characteristics of the Carboniferous volcanic reservoirs in J230 area of Xinjiang oilfield are overviewed. Triaxial in-situ stresses of the formation are interpreted by conventional well-logging data, and the natural fissure characteristics are interpreted by imaging well logging information, and intersection of geometry relationship between hydraulic fracture and cross natural cracks is described on approaching angle. Current experimental achievements of hydraulic fracture penetration cross or extension along natural fissure are summarized, mechanics criterion under the different action manner are established for opening and shear failure of natural fractures. Taking Carboniferous volcanic reservoir of J230 area as an example, a hydraulic fracture propagation model is obtained by calculation results under the action of hydraulic-natural cracks synergy. It is shown that the approaching angle in the formation is mainly 50°–60°, shear sliding failure will be firstly induced along natural-hydraulic fracture interface and then natural fissure will open because of going net pressure. With further increase of the net fluid pressure, hydraulic fracture propagated along the natural fissure because of tangential failure and gradually turns to the direction of maximum horizontal principal stress, which is conducive to the formation of network fractures in stimulated reservoir treatment.