Reservoir Characteristics Of The Lower Gangchaigou Formation In The Chuangcheng Area, Qinshan Oilfield, Qaidam Basin

In this thesis, The lower member of Low-Ganchaigou Formation reservoir in Qie12wellblock of KunBei oilfield are taken as the object of the study. On the basis of theory and method of disciplines such as Sedimentary petrography, reservoir geology, field geology, logging geology, petroleum geology and reservoir sedimentology, The work of establishing the stratigraphic framework are firstly finished, followed the analysis of the sedimentary facies. Then a series of studies of the reservoir characterization are carried out in respect of its petrography, diagensis, pore types, pore structure, physical property and heterogeneity. At last,We synthesized the former research results to evaluate the quality of the reservoir.It is found that the depositional system of the braid river delta are broadly spreaded in the research area, which consist of micorfacies like aquatic distributary channel, floodplain, distributary channel and interdistributary area. The rock type of clastic reservoir are mainly conglomerate, granulated conglomerate and psephitic sandstone with low compositional maturity and low textural maturity. Reservoir experienced diagensis including compaction,cementation and disruption,which occurred between stage B of early diagensis and stage A of middle diagensis. Five kinds of diagenetic facies are identified in this study. The major constructive kind is mid-poroperm dissolution facies and the major destructive kind is compact matrix filling-cementation facies. Pores are generally primary pore and secondary pore. Throats are commonly lamellar throat. The type of pore structure is type III and type IV.The reservoir belong to low porosity and extra-low permeability kind,which is of moderate-high macro-heterogeneity and moderate micro-heterogeneity. Vertically,the reservoir of type I and type II are mainly distributed at the top of the section. Horizontally, the reservoir of type I can be observed chiefly in wellblocks like Qie125,Qie123,Qie121,Qie12and Qie10. the reservoir of type II is lesser and mostly appear in the rim of the sandbody where clay content is high.