Cretaceous Facies Research And Reservior Evaluation In Chunfeng Oilfield

Chunfeng oilfield is located in the easten of Chepaizi bulge,westen uplift ofJunggar Basin. Following the Neogene Shawan formation,Cretaceous is the mostimportant series of strata to be explored in Chepaizi area and has a good explorationprospects. However, few research has been systematically carried out on Cretaceousand there are still a lot of problems to be solved such as the spreading features ofsedi-mentary facies, re-servoir cha-racteristic and high-quality re-servoirsdistribution,etc.With the instruction of reservoir sedimentation,petroleum geologyand other theories and on the basis of digestion and absorption of previous researchresults, this thesis studies sedimentary facies cloth characteristics and sedimentarysystem evolution rules, establishes depositional models of different sedimentaryperiod and evaluates Cretaceous reservoir properties and plane heterogeneity bymeans of comprehensive using of core,logging,seismic data and analytical data.Based on regional geological background research, combining with mudstonecolor value distribution, clastical rock compositional maturity and structure maturityanalysis, this thesis determines sediments in the Cretaceous period come from boththe northwest and northeast of the study area and mainly from the northwest.The over-all de-po-sitional en-viron-ment of the Cre-ta-ceous is weak oxi–dation-weak reduction shallow lake environment.By observing and describing the Cretaceous core of the study area, and at thesame time, by analyzing logging and seismic data, transgressive fan delta and beachbar have been recognized. Furthermore, middle fan braided channel, middle fan front,bar host, bar side, near-shore beach, far-shore beach, beach between the bar and othermicrofacies types have been respectively made out. On this basis, combined with thecharacter of sand body exhibition, the fan delta-beach bar depositional model ofQingshuihe group and beach bar depositional model of Hutubi-Lianmuqin group hasbeen established. And moreover, the evolution rule of Cretaceous sedimentary system in the research area has been cleared about.Based on laboratory analysis data, this thesis studies on the Cretaceous reservoirphysical properties and different kinds of diagenesis which affects the the reservoirproperties and comprehensively evaluates the reservoir of different sedimentary facies.This study suggests that the pore of Cretaceous in the research area consists of twotypes including primary pores and secondary pores, and the primary pores are inmajority. There are4diagenesis such as mechanical compaction, cementation,dissolition and metasomatism. The plane distribution of reservoir property isobviously controlled by sedimentary facies. Hutubi group has the best reservoirproperty, Shengjinkou group and the Qingshuihe group has the second best reservoirproperty, and the reservoir property of Lianmuqin group is the poorest because of itssmall sandbody distribution.