The Gas Reservoir Of Western Sichuan, River Damage Mechanism Research

As one of the most important base, it is huge on potential in oil and gas exploration and exploitation in western Sichuan, there are1.8to2.5×1012m3gas in western Sichuan. The reservoir of Xujiahe group in western Sichuan is a tight sandstone gas reservoir with Low-porosity, low-permeability, strong homogeneity and well-developed fractures. A series of key techniques were researched and applied, many improvements were got to protect the formation, but some of them were difficult to apply in field or inefficient to protect the reservoir. Therefore, it is of essence to study the damage mechanism of fracture and develop an effective technique to protect the reservoir.X-ray diffraction indicates that the rock of Xujiahe group in western Sichuan is rich in clay mineral. Chlorite and illite are at high levels overall. It will lead to lakage. aqueous trapping damage, stress sensitivity damage and damages of fluid sensitivity due to the types and contents of the clay minerals, their influences on the reservoir physical property and the feature of fractures.Fluid sensitivity and stress sensitivity are analyzed and evaluated in this paper, so do aqueous trapping damage and solid invasion. The damage mechanism of fluid sensitivity, solid invasion and water trapping are deep researched. Lab experiments show that the velocity sensitivity of the gas reservoirs in Xuer is middle to strong and that of Xusi is weak to middle minus; the stress sensitivity of matrix is middle to strong, thus the fractured gas reservoirs is with strong stress-sensitivity.According to the property of reservoirs, the damage mechanism and the well design of horizontal wells drilling, a drilling system is designed to protect the reservoir of Xujiahe group in western Sichuan. Lab experiments indicate that it can not also meet the well design but protect formation better.