The Effect Of Stresses And Natural Fractures In Tight-Sandstone Of Hydraulic Fracturing

With the long-term exploitation of conventional gas, reserves are depleted day by day, which lead to the exploitation of unconventional gas calls for higher and higher. But the unconventional gas reservoirs have the characteristics of low permeability, wide distribution and so on, which is the biggest bottleneck restricting the exploitation of unconventional gas, therefore, to improve the permeability of the reservoir and the recovery rate of single well are the most important problem to realize the commercial exploitation of unconventional gas. Practice has proved that the application of hydraulic fracturing can effectively improve the permeability of reservoir, but the effect is influenced by many factors, including reservoir lithology, reservoir stress state, natural fracture and fracturing fluid performance. In this paper, the main research on the stress state and the effect of natural fractures on the hydraulic fracturing effect is the main research of the dense sandstone, the main contents are as follows:Based on the uniaxial compression test, ultrasonic test and Brazilian disc and other laboratory test out of tight sandstone uniaxial compressive strength, elastic modulus, Poisson’s ratio and indirect tensile strength macro mechanics parameters. In order to ensure the reliability of the parameters of the above laboratory tests are carried out to take the average as the final results.The corresponding relationship between the micro parameter and the macroscopic parameters of the model are debugged by the Uniaxial compression test code. With the help of this curve, the micro mechanical parameters of the corresponding basic particle units can be quickly adjusted according to the laboratory test results, These micro parameters are the basis for establishing the model of hydraulic fracturing in tight sandstone.The numerical model of hydraulic fracturing was established by using the meso parameters, the influence of stress difference on the hydraulic fracturing parameters such as the crack initiation pressure and the crack growth relative length under different stress states is studied. The simulation results show that the stress difference is lower in the initiation of the crack initiation propagation and the crack length are relatively long in the same step. At the same time, the influence of natural fractures on the hydraulic fracturing is studied.