Reservoir Distribution Rule Of Triassic Yanchang Formation In The Xiasiwan Oilfield In Zaolin Region

This paper, made Triassic Yanchang formation as the major study-target in the Xiasiwan oilfield in Zaolin region. Comprehensive with utilization of drilling, loggingand various analytic data, applying the modern Sedimentology,theories and techniques of reservoir evaluation, the structure, the sedimentary facies, the reservoirs, the reservoir forming conditionand and reservoir-forming rule of the Chang6reservoir, chang2reservoir and each reservoir groups were studied in-depth.The study showed that:generally, the study area agrees well with the tectonic background of west-dip big monocline, low amplitude inherited somenose-like structures were developed in local region. Whereas the Chang2reservoir and Chang3reservior were mainly composed of delta plain subphase sedimentary, and mainly developed distributary channels and inter-channel bays. Whereas the Chang6were composed of delta plain front sub-facies sedimentary, and mainly developed the distributary channels and subaqueous distributary channels. The basic features of the reservoir were as follows:(1)The Chang2and Chang3oil-bearing were mainly composed of the medium-fine granular arkose.(2) The Chang2, Chang3and chang6reservoir sandstone went through A period of early diagenesis-A period of late diagenesis. It was mainly on the stage-A of late diagenesis or stage-B.(3)The Chang2and Chang3oil-bearing were middle low porosity and middle low permeability reservoir.The Chang6was mainly low porosity and low permeability reservoir.(4)Dissolution pore-intergranular pore was the main porous composition in the Yanchang formation. The Chang2and Chang3reservoir had big pores and fine throat, and chang6had middle pores and fine throat. Connected pores, superimposed points of sand bodies and fractures were the main migration path of oil and Gas. Hydrocarbon reservoir mainly occurred primary migration, and the reservoir forming time happened at110-125Ma, belonged to late Early Cretaceous age. Sedimentary facies and reservoir characteristical were the main controlling factors to influence the distribution of oil and gas. What’s more, also controlled by nose-like structure setting. The Chang2of Yanchang Formation states the relationship between the hydrocarbon distribution and Jurassic system tight sandstone cap rocksocclusion.