Research On Reservoir Characteristics Of Qianfoya Formation Of Middle Jurassic In The Bazhong Area,Sichuan Basin

Bazhong area is located in the northeast of Sichuan Province.The layer of the Qianfoya formation develops continuously,and is one of the most important oil-bearing series.Based on the fact that there is little research on the reservoir micro-characteristics?reasons for Low permeability reservoir and formation mechanism of micro-residual oil,this thesis is focus on theQianfoya formation.In this thesis,I analysis the mineral types and contents of the rock systematically,conclude the types and intensity of diagenesis,illustrate the types and structure features of pore,summarize the features of reservoir micro-characteristics.The following main results and understanding are achieved:(1)Thesis defined the rock types?structure features?diagenesis types of the reservoir of the Qianfoya formation.The main rock types are lithic feldspathic sandstone and feldspathic lithic sandstone.The compositional maturity and texture maturity of sandstone are low.The main destructive diagenesises are compaction?cementation?corrosion,while the constructive diagenesis is dissolution,etc.(2)Thesis confirmed the pore type and make the classification of it.Primary pores and secondary pores are two pore types in the eighth member of Qianfoya formation,and the primary pore is the main type of this area.Select four parameters,including the displacement pressure?mercury-injecting efficiency?the mean value of throat radius?coefficient of variation,which have a good correlation with permeability to sort the pore structure,also,that classification is a combination with the shape of mercury injection iii curves?casting thin sections?the data of grain-size.Base on the above data,I divide the pore structure of this area into three classes.(3)Thesis analysis of the effect of diagenesis in Qianfoya reservoir in Bazhong area.Strong compaction is the main factor leading to low porosity and low permeability of reservoir,which destroys the primary pore of the reservoir,and the cementation further strengthens the density of the reservoir.The development reservoirs of dissolution,dissolution and microcracks effectively improve the physical property of the reservoir.(4)Thesis revealed the origins of low permeability formation within the eighth member of Qianfoya formation,thinking that the sedimentation is the internal cause to make the “reservoir's congenital condition” bad.The strong intensity of destructive diagenesis and the low intensity of constructive diagenesis are the outer causes,which make the“reservoir's postnatal environment” poor.Also,I present an idea that soft particle filling effect may be a reason for the low permeability reservoir.(5)Thesis summarizes the Bazhong Qianfoya reservoir composition,sedimentary facies,reservoir and favorable areas of dissolution and dark mudstone contact relationship.Among these factors,the high energy coarse facies belt is the basis,the rock composition and the clay film are the conditions,and the dissolution transformation is the key.It is suggested that the distribution range of high quality reservoirs is mainly located in the main channel sedimentary microfacies,dark mudstone development zones,thick sand body development zones and other main control factors.