Study On The Adaptability Of Stratigraphy And Well Pattern In Qidan Oilfield, Qaidam Basin

Qigequan oilfield is a typical long interval thin oil reservoir in qaidam basin, main blocks is lithologic - structural reservoir influenced by lithology on constructing background, with reservoir depth from 366 to 1407.9m. There are lots of thick structure reservoirs in high constructing position and low thin oil layers without unified oil-water interface, locally for oil-water transition zone of reservoir, and then very complex oil-water interface. It is deposited at three kinds of sedimentary environment of intersection, the north-west of north-east side of alluvial fan, southwest of braided river delta and lake shore on the east side. The sedimentary background leads to the the sedimentary facies change quickly, sediment points to the opposite sex difference, high shale content, low compositional maturity, multiple reservoir interaction with, the change of reservoir physical properties, and very uneven distribution with characteristics of strong heterogeneity. The granularity of the reservoir sand body in two major components, due to near provenance, content source, obviously rapid deposition controlled by the ancient climate and development of marina (shallow) lake environment at the same time. That is to say, the main oil and gas reservoirs are constituted of the overall poor sorting coarse conglomeratic sandstone-glutenite and orting well grained sandstone.Oilfield is now in the middle and later of development stages, but some problems were also exposed in the development process of the segmentation formation, mainly displayed in the following two aspects:① Reservoir including small layers, thin layers, seriously heterogeneity, contradiction between of plane and interlayer,, and the development series of strata are not divided refinedly enough;② There are low exploitation degree and water drive reserves producing degree in Oil field. Main parts and the main small layers havn’t get effective development for low recovery degree.Through the adaptability analysis of developing series of strata and well pattern, We selected formation, pattern classification methods of the boundary technology close to the actual need in oil fields development, to reduce the influence of reservoir heterogeneity and increase oil reserves producing degree, achieving the goal of improving ultimate recovery.The in-depth research was studied on the fine reservoir description work, and the oil wells productions were splited on the basis of reservoir geological characteristics. Then the study the dynamic characteristics of waterflood development was completed in the stage of comprehensive water injection development and layered system development, including analysis of water injection and oil production, water cut, injection-production ratio index From the formation to the oil group. By adaptability analysis of developing series of strata and well pattern, the classification methods oil fields of formation and pattern close to the actual need were selected development technology, to reduce the influence of reservoir heterogeneity, and increase oil reserves producing degree, then achieve the goal of improving ultimate recovery.