Research On The Formation And Expansion Characteristics Of Induced Fractures In MH Glutenite Reservoirs

Sand-conglomerate reservoirs are wide distributed in our country.On account of gravel inside and limited by different sizes of gravel,density of gravel development,strength of gravel and etc.All of these factors lead to lower porosity and permeability,and serious heterogeneity of sand-conglomerate reservoirs.Thus the naturaldeliverability's level is low.In order to meet the industrial production requirements,we raise the production by.Fracturing effects decide by the control of fracture shapeduring hydraulic fracturing.For exploit sand-conglomeratate servoirs efficiently,we must grasp the regularity of formation and extensions ofinducing joint which is in the sand-conglomeratestrata.Thispaper use MH sand-conglomerate reservoir as the carrier,based on the anisotropism of sand-conglomerate strata and mechanical properties of rock.With the help of simulation software(RFPA),we study the characteristicsof formation and extensions of inducing joint during the pressurizing process of well from three aspects that differential of crustal stress,characteristics of gravel and well track.We grasp the morphological characteristics of inducing joint,extension regularity and main controlling factorthrough this study.The main results achie-ved and understanding are as follows:(1)On the condition thatgravel concentration is 40%,gravel diameter is 5mm,gravel is 1.5 times the intensity of matrix.When the differential of crustal stresses increasing,the expansion rate of majorfracture increasing rapidly,meanwhile,micro-fracture does not change.With the differential of crustal stress decrease,bifurcatefissure appeared in the terminal ofholeand produce the micro-crack.(2)On the condition that the differential of crustal stress is 6 MPa,gravel concentration is 40%,gravel is 1.5 times the intensity of matrix.The fracture always extends between gravels when it encounters the junction of gravel during the process of extension.This illustrates the shielding effect between gravels is not so evident.Cementation degree is a key factor of extension.Fracture will extend around the gravelwhen gravel diameter is small.Fracture will thread gravel when the gravel diameter increasing.This illustrates gravel diameter have a smaller control and shielding effect on fissure extension.With the increase of gravel diameter the control and shielding effect will be more obvious.(3)On the condition that the differential of crustal stress is 6 MPa,gravel diameter is 5mm,gravel is 1.5 times the intensity of matrix.With gravel concentration decrease,the extension of fissure is control by horizontal maximum principal compressive stress,and lower effect on shielding and induction.With gravel concentration increase,the induction effect of gravel will be more obvious.At the same the dispersed effect of fissure is obviously and a mass of fissure appeared.This illustrates gravel provide a better condition for fracture network develops.(4)On the condition that the differential of crustal stress is 6 MPa,gravel concentration is 40%,gravel diameter is 15mm.With the increase of strength of gravel,the shielding effect will be more obvious,when strength of the gravel is less 2 times than the intensity of matrix,the strength of the gravel are not enough to prevent fracture from threading gravel,when more than 2 times,the strength of the gravel can completely prevent fracture from threading gravel.(5)It was more complicated to discovery pattern in the extension of induced joint with the gravel existed.Gravel and the distance of the well are the key factors to in duced joint extending.Even in the case of gravel have high strength,the induced join t will extend through gravel when it is nearby well.