Study On Crack Propagation Mechanism Of Glutenite Reservoir In MH Block Of Xinjiang

Mahu depression is located in central Junggar Basin and is a reservoir mainly consisted of glutenite.Compared with conventional sandstone reservoirs the glutenite reservoirs in Mahu depression overall presents low porosity and low permeability.Earlier exploration wells showed that fracturing fluid loss was great and production efficiency changed obviously by fracturing.Analysis revealed that one of the most important factor is the unclear extension mechanism.So it is necessary to explore glutenite reservoirs fracture propagation mechanism and study fracture proppants migration in detail.The rock mechanics of the target reservoir is significant different from the conventional sandstone due to the presence of a large number of gravel.This paper summarizes and analyzes the geological characteristics of the target reservoir,and analyzes the mechanics feature of several exploration wells by using core scanning system and high pressure and high temperature core biaxial mechanical testing device.The study of this paper has focused on the rock pores structure,rock strength analysis and rock stress orientation.Based on the data analysis,it shows that fluid loss is large during fracturing treatment,and the geometry of fractures is complex and significant differences of stimulation effect are found between neighboring wells..The characteristics of fracture breakdown and propagation in the glutenite reservoirs are not identical with the conventional sandstone reservoirs.This paper has built a flow-stress-damage coupling model,studying the basic theory of fracture propagation of the glutenite reservoir and combining poroelasitc theory and damage mechanics theory.This paper has analyzed the anisotropy,principal stress contrast,gravel concentration,gravel size and other factors in the conventional sandstone reservoir,using RFPA real rupture analysis of fracture propagation.The results show that at a greater anisotropy,the rough and discontinuity of fracture can be significantly larger.The geometry of fractures is more irregular and the angle between the fracture and the minimum principal stress is smaller by an increase of the principal stress contrast.Due to a higher gravel concentration,the resistance of fracture propagation is larger.It could be easier to occur flow around phenomenon as the gravel size is greater.