ABSTRACT: CO2 fracturing has been pilot tested to improve the hydraulic fracture complexity of the near-well area in Jimsar thin interbedded shale reservoirs. However, the characteristics of hydraulic fractures created by CO2 in this reservoir has not been studied systematically from experiment. Aiming at this, we conducted true triaxial fracturing experiments on the tight shale with thin interbedded bedding (from Jimsar formations) by using liquid CO2. In the experiments, the effect of natural fracture, pump rate, and horizontal principle stress difference on fracture morphology was studied respectively. Also, the characteristics of fractures created by CO2 was compared with water. The results show that the bedding planes of thin interbedded rock is easy to be opened by low viscosity of CO2 and the vertical fractures intersecting with bedding planes build complex fracture network. When natural fractures exist in rock samples, the natural fractures are opened simultaneously with the bedding planes. Increase pump rate can enhance fracture complexity. Due to the ultra-low viscosity, strong penetration ability of liquid CO2, and the weak bonding strength of the horizontal bedding planes, the horizontal principal stress difference has less effect on fracture propagation in the CO2 fracturing experiment of bedding rich core samples.

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