The Study Of The Reservoir And In-situ Stress Characteristics About The Shaximiao Formation In Area GM

On the basis of collecting the predecessors’ geological research in area GM, we have deeply analyzed the characteristics of the basic geological condition,the region tectonics, the reservoir and the engineering geology about the Shaximiao formation in area GM, Which have let us know the characteristics of the sedimentary facies, the sandstones distribution and the dynamic characteristics of the gas reservoir. Based on the rock mechanics experiment, we have built a prediction model and profile of the mechanical parameter and have analyzed the characteristics of the rock mechanical parameter. According to the logging and fracturing data, combining with the optimized method of the calculation model, using the existing measurement and analysis method about in-situ stress, and optimizing the in-situ stress calculation model, we have built the prediction model and profile of the in-situ stress in the gas reservoir of the Shaximiao formation, in area GM. Have known the stress state, the characteristics and the category feature of the reservoir in-situ stress profile, and have analyzed the causes of the abnormal high fracture pressure, which can put forward to some valuable suggestions for the live using of the in-situ stress. Through the research analysis, we have drawn the following conclusion:(1)The rock mechanics strength is higher and the reservoir heterogeneity is stronger in the gas reservoir of the Shaximiao formation, in area GM. Vertically, the lowest compressive strength reservoir is Js33-2, the highest is Js33-1, and the middle is Js23; the elastic modulus has the similar characteristics with the compressive strength; the Poisson ratio shows an increasing tendency from the top to the bottom; The Js23 has the highest tensile strength, and its’ average is about 7MPa, the tensile strength of the both layer in the lower Shaximiao formation is almost the same, and the difference is small. On the plane, the rule of the mechanical parameter is inferior, but, for a general veiw, it has a decreasing tendency from the center structure belt to the two wings.(2)According to the structural feature of the region in-situ stress field and the region tectonics in the research area presently, combining with the characteristics of the rock mechanics strength and the existing using constraints of the calculation model about the in-situ stress, the combined springs model is the best calculation model for the gas reservoir of the Shaximiao formation, in area GM.(3)Through analyzing the in-situ stress state of the Shaximiao gas reservoirs in area GM, we have known the stress state of the Shaximiao formation reservoir is σH>σV>σh, in area GM, so it belongs to the strike-slip in-situ stress model. Through analyzed the well logging data and the structure of the area Dongpo, it is speculated that the maximum horizontal stress orientation is close to EW and the minimum is close to SN in the Shaximiao formation reservoir, in area GM.(4)Having known the characteristics of the in-situ stress size and profile which belongs to the main sand of the Shaximiao formation reservoir, in area GM. The difference between the reservoir and the surrounding rock is generally small; which is no good to control hydraulically fracture height. There are three kinds of the in-situ stress profile: the high-low-high, low-low-high and straight type. The straight type is mainly distributed in southwest structure.(5)The reservoir has the high fracture pressure in the Shaximiao formation, in area GM. The fracture pressure in the center structure belt and the north is higher, the fracture pressure is lower in southwest area, and the reduce may be caused by the lower of the facture development and the reservoir’s mechanics parameters in the southwest area.