The Anastomosing River Delta Sedimentary System And Configuration Analysis Of Youshashan Oil Field

Youshashan Oilfield is characterized with multiple layers, thin thickness, scattered distribution, developed faults and complex structure. Because of the poor geological research, the reservoir producing extent was low, and the development effect was not ideal. Therefore, to identify the sedimentary system and sedimentary microfaces using lithology, logging and ground outcrop data, establish sedimentary faces model and analyse sand body configurations will lay a good foundation for the next step of stable production.According to the regional background information of Youshashan Oilfield, based on the observation, measurement, mapping and analysis of outcrop, through the deep research of core, chemical examination analysis data and well logging data, the objective interval of the study area was defined as a typical anastomosed river delta-shore shallow lake sedimentary system. According to the lithology, sedimentary structure, electrofacies, the shape of the sand body, Longitudinal sequence and anatomy of small scale outcrop, that the objective interval of the study area was divided into 4 subfacies, named anastomosed river delta plain, delta front, prodelta, shore shallow lake,and further subdivided into 12 microfacies. Sediment characteristics, evolvement rule and the control effect on oil and gas in each sedimentary microfacies were detailediy analysed. The sedimentary model of anastomosed river delta-shore shallow lake sedimentary system were established. The reservoir property of underwater distributary channel, mouth bar and sheet sand was better in sedimentary microfacies. The abundance of oil and gas reserves was high. the three kinds of sedimentary microfacies control the oil and gas reserves combined accounted for 76.67% of total reserves. Beach sand, far sand dam, subsea natural barrier,beach and bar sand bodies were of poor reservoir property, the sand body thickness was thin, and oil and gas reserves abundance was relatively low, accounting for 7.01%,5.88%, 5.10% and 2.36% of the total reserves respectively. Delta plain anastomosed channel microfacies had coarse granularity, thick sand body, and good reservoir property, however, fault was developed in Youshashan oilfield, so the sealing ability was poor, oil and gas reserves abundance was relatively low, only accounting for 2.98% of total reserves.Using the configuration analytic hierarchy and cyclicity contrast method, the reservoir configuration of Youshashan oil field was divided into eight levels, 11 kinds of configuration units: anastomosed channel, burst sedimentary unit, underwater distributary channel(main channel), the lateral margin of underwater distributary channel, subsea natural barrier, dam nuclear, lateral margin of dam, sheet sand, beach and bar, beach sand, far sand dam. Each configuration unit had 2 kinds of split relationship in the plane. named the continuous transition type and mutation type contact respectively; There had three kinds of superimposed relationship in section, named the type of scour filling, the contact type of superposed, the type of isolated distribution. The geological knowledge database of anastomosed river delta-shore shallow lake sedimentary system was improved, the subsequent reservoir stochastic modeling was founded.