Study On Subcritical Crack Propagation Of Tight Sandstone Under Fluid

For the economic development of the countries in the world,energy resources has become an important strategic material,its survival and development,while facing the increasing depletion of conventional energy,mining and utilization of non conventional energy sources become more and more important.Following shale oil and gas,tight oil has become another hot spot of unconventional oil and gas exploration and development worldwide.The complex crack network formation of tight oil development is essential,previous research is mainly concentrated in the interaction between the expansion of the main crack and the main fracture and natural fracture,the formation mechanism of the relative lack of micro cracks in tight reservoir.Based on this,using tight sandstone from Ma An cun,Ga Ji Zhen,Hui dong County,Liangshan,Si chuan,Chinese to do rock mechanics test.This paper firstly measured the basic mechanical parameters of sandstone,understand the content and the mechanical properties of the clay minerals,followed by the double torsion constant displacement of dense sandstone relaxation method of subcritical crack growth,at the same time using the double torsion test of fracture toughness of tight sandstone is measured.By fitting calculation found that rock stress intensity factor at the tip of crack propagation rate and the exponential relationship,the conclusion analysis found that tight sandstone in different saturated solution conditions,the crack propagation rate of size:V _{distilled water}>V _{slickwater 1}>V _slickwater2>V _dry,in addition to the crack propagation of tight sandstone in different fluid conditions the threshold value.At the end of this paper,the time of crack propagation is deduced,which provides a theoretical basis for future research.