Study Of Rock Mechanics And Stress Of Tight Sandstone Reservoir In The Chang-8 Formation In The Southern Margin Of Ordos

Yanchang formation is rich in oil and gas resources in the southern margin of Ordos Basin.According to the existing exploration and development results,the exploration and development potential in the southern part of the Ordos Basin is huge and has good prospects for exploration and development.Under the tectonic setting,the abnormal formation pressure of Chang 8 strata leads to complicated rock mechanics and stress in formation.Under this complex geological condition,it has brought great difficulties to the reconstruction and construction of the reservoir,which is characterized by the poor effect of fracturing,low production of single well and difficult economic development.In this paper,based on the theories and methods of petroleum geology,geophysical logging,reservoir geology,rock mechanics and oil and gas reservoir reconstruction,the rock mechanics and in-situ stress parameters are tested under the simulated stratigraphic conditions,and the rock mechanics and ground stress are explained in combination with the data of well logging data and fracturing construction curves.The static rock mechanics parameters are calculated by the three axis rock mechanics experiment.The experimental results show that the deformation of the rock is mainly elastic plastic deformation under the condition of formation.With the increase of the confining pressure,the yield failure strength of the rock specimen is greatly increased,and the significant change from elastic brittle to elastic-plastic to strain hardening is produced.Using the logging data and considering the influence of gamma value,we constructed a shear wave time difference interpretation model which accords with the research area.The rock mechanics strength parameter,the elastic parameter interpretation model and the dynamic and static transformation relation are established directly.The rock mechanics parameters are analyzed by the rock mechanics interpretation results,and the rock mechanics strength parameter modeling under the simulated stratum condition is carried out.The magnitude of Chang 8 stress is calculated by means of laboratory rock acoustic emission and differential strain test,fracturing method HPF inversion and logging data calculation.Through the calibration of the experimental and calculated values The results show that the Chang-8 reservoirs is the normal stress state.The direction of the maximum main stress of the Chang-8 segments is determined by the method of viscous remanence and the hole wall caving.Based on the analysis results of rock mechanics and geostress characteristics,the difference of regional ground stress is counted and the characteristic parameters of brittleness are calculated.In combination with the conditions of multiple cracks in the fracturing design and the properties of common proppant,the feasibility of fracture network formation in the study area is demonstrated and the optimization of proppant is carried out at the same time.In this paper,the characteristics of rock mechanics and ground stress in Chang-8 reservoirs Formation in the southern Ordos and its application in the reservoir reconstruction are studied,and the corresponding research results are obtained,which can provide a theoretical basis and data base for the fracturing design in the study area.