Research On The Reservoir And Pool Characteristics Of Chang4+5 And Chang6 Oil-Bearing In Pingqiao Of Ansai Area

Pingqiao area is a stressly research block of Xingzichuan oil production plant in Yanchang oilfield. At present, it has more than 1400 wells which are many and dense, and Chang 2, Chang 4+5,Chang 6 reservoir are the main producing formation. While the study of the geological evaluation is so insufficient seriously that effect the wholephase of oilfield development work. In addition, the previous work in geological evaluation isn’t adequate to meet the current stage of development of the task demand because well control is more and more dense during the development of oilfield. Therefore, research on the reservoir and oil accumulating regulations of Chang 4+5 and Chang 6 Oil-bearing have important practical significance for the reasonable oilfield development in the next.Based on field geological observation, core description and particle size analysis method, in accordance with many varieties of sedimentary facies symbols, plentiful symbols of sedimentary facies, determined that the Chang 4+5 and Chang 6 reservoirs in Pingqiao oil region mainly are delta front subfacies, and the sedimentary micro facies are mainly composed ofunderwater distributary channel, among them the Chang 61-1 periods channel effect is stronger, large sand body area and thickness, and the Chang 4+52 periods underwater distributary channel sand body is mainly develop in Pingbei area.The petrologic features of the Chang 4+5 and Chang 6 reservoirs were determinedusing thin sections, cast thin sections, mercury intrusion porosimetry, cathode luminescence, scanning electron microscopy, X-ray diffraction and other techniques. It can be idenfied that the two reservoirs were composed primarily of fine arkose, with laumontite and chlorite as the main types of cement. Pores mainly included laumontite dissolution pores and inter-grain pores, whose throats were mostly small and thin. A comprehensive reservoir assessment indicated that both the Chang 4+5 and Chang 6 reservoirshad an ultra-low porosity and permeability and can be classified as Ⅲa reservoir.In the research area Chang 4+5 and Chang 6 reservoir mainly is lithologic reservoir, distribution of reservoir is extremely imbalanced, from longitudinal and horizontal distribution characteristics, oil and gas enrichment degree of Chang 4+52 and Chang 61-1 thin layer is high, which also is the main strata in the study area; Reservoir distribution is mainly controlled by the lithologic distribution and shade of skeleton sand body; The comprehensive evaluation of reserves showed that the Chang 4+5 and Chang 6 reservoir pertains to small-medium, moderate shallow, low productivity and low abundance, and mainly are light conventional oil reservoir.Through the above research, put forward five recommendations progressive development: ① Macro planning layer series of development;② Improve the single well production by means of checking the layer fill hole;③ Increase waterflooding developmentefforts to base on the existing well pattern;④ To further improve the well pattern;⑤ Improve the injection production well pattern and adjust the injection production incomparability.