Upper Ordovician paleo tectonic stress field simulating and fracture distribution forecasting in Tazhong area of Tarim Basin, Xinjiang, China

The structural fractures in the Upper Ordovician Lianglitage Formation in Tazhong area, which has active hydrocarbon show, is effective reservoir space for hydrocarbon accumulation. Fracture reservoir is controlled by paleo structural stress field. Based on the faults systems interpreted from seismic data, fractures characteristics from drilling and logging data, carbonate reservoirs are studied from acoustic emission, stress measurement, rock mechanics parameters and uniaxial tensile test. Considering the influence of faults on the fracture forming, 3-D finite element method is applied to simulate the period II Middle Caledonian paleo structural stress field in the Tazhong area and predict the distribution of fractures. The simulation result shows that during fracturing the maximum major stress effective value range from 47.9 to 58.3MPa, with average 51.97 MPa, tensile strength ranging from 5.13～6.91MPa, with average 5.81MPa. High value area of effective tensile stress is the favorable area for structural fractured reservoirs development, most distributed in the interchange area of fracturing belts and part section of fractured zone in the east of Tazhong area, coinciding with the Ordovician fracture-developed zone defined by fracture linear density statistic date from actual drilling, which provides new geological evidences for the Lower-Middle Ordovician carbonate rock prospecting and exploitation.