Petrophysical Property Study And Its Applied Research On Xinchang Structure Of Western Sichuan Depression

Xujiahe formation in western Sichuan is rich in gas and beers a good exploration and exploration prospect. However, the Xujiahe formation is deeply buried and has characteristics of poor petrophysical property, high formation pressure and complex trap, which make the geology character of studying quite complex. This paper has taken the gas reservoir of T3X2 and T3X4 of Xinchang gas filed which is in the middle of western Sichuan depression as research object, on the basis of laboratory rock mechanical experiments, thoroughly analyzed and studied the characteristics of western Sichuan area deep stratum rock petrophysical properties and its application.The petrophysical properties of T3X2 and T3X4 have been analyzed on the basis of basic physical parameters and laboratory rock mechanical parameters tests, including porosity and permeability distribution characters and their interrelationship at normal temperatures and pressures, P and S wave velocities at normal temperatures and pressures, dynamic and elastic parameters and its changing regularity with pressure and temperature, rock deformation characteristics of statics at triaxial compression condition and statics parameters and its relation with porosity and density, relation between cohesion, internal frictional angle and particle size, the relation between tensile strength and fluid staturation, anisotropy of rock petrophysical parameters.Based on the above experiments researches, the paper has analyzed the previous studies, including rock mechanics strength parameters, elastic parameters interpretation model and dynamic and static conversion relationship. Rock petrophysical parameters logging interpretation and evaluation methods were made and rock mechanical parameters profiles of T3X2 and T3X4 were established.Using ADS logging calculation methods to determine geopressure, on the basis of comparing logging geopressure calculation model, Huang model swastika chosen to calculate the geopressure profile of sing well, and by using cracking materials, the model was confirmed to be reliable. By using the model, the geopressure profiles of T₃X² and T₃X⁴ were established, lateral comparison and lateral distribution regularity of single well geopressure was analyzed. Methods to determine geopressure direction such as wave velocity anisotropy were collected and classified, and the geopressure of sing well were determined. Finally, it was confirmed that the direction of the maximum horizontal principal stress was east-west.Through analyzing previous cracking pressure and collapse pressure calculation formula and comparing with the cracking data and accidental interval, it has been proved that the calculation model is reliable and it could satisfy the engineering requirement for predicting the cracking pressure and collapse pressure. Using the calculation model, three pressure profiles of single well for T₃X² and T₃X⁴ had been established.