The Sedimentary Facies Research Of Member 3 Of Hetaoyuan Formation In The Eastern Of Wangji Oilfield

Located at the middle part of the northern slope in Biyang Sag, Wangji oil field is a southeast-pitching, wide and gently-inclined nose-like structure. There are 9 eastnorth-trending and east-north-north-treading normal faults. The whole region is a terrace increasingly uprising from the southwest to the northeast.In 1977 Wangji oil field was first put into exploration and development as a complex block reservoir. In 1990 it was developed by water flooding method. At present irregular water injection pattern is being adopted with water cut up to 94.7%. The vertical and plane heterogeneity is serious and there exist interbedded conflicts. To-be-produced remaining oil is sparsely distributed with the ratio of water to oil increasing quickly and low water displacement efficiency. Therefore, the research on reservoir sedimentary characteristics, sand body distribution, and sedimentary micro-facies distribution and so on is fundamental to injection-production fluid-production adjustment, injection-production pattern flexibility analysis and adjustment plan optimizing of small block reservoirs with high water cut in Wangji oil field.Integrated with drilling, logging, and coring data, rock composition, architecture and conformation in the area have been determined through core observation, and derived from the petrologic characteristics of the third member of Hetaoyuan Formation in Biyang Sag the lithofacies has been determined; single well facies analysis has been done applying lithofacies analysis results and logging facies, with reference to logging data; on the basis of fine correlation and classification in the research area, new achievements have been gained on the structure, especially small faults which affect petroleum and water distribution pattern; according to rock types determined by core observation and oil testing data and so on, the geologic factors causing abnormal lithology-electricity response characteristic have been studied, and the recognition method of this kind of rocks has been developed, laying foundation for the accurate recognition of sandstone and mudstone. As the study region is characterized by small area, near source, shallow-water fast deposition and so on, in this paper, based on petrologic data derived from coring, with the application of logging facies analysis, integrated with various information, the target intervals in the research area is regarded as delta front. Understandings and achievements are as following:The east part of Wangji oil field is composed of relatively near-source coarse-grained Houzhuang braided river delta sediments, dominated by coarse glutinite and fine sandstone, including shale, mudstone, sandy mudstone, argillaceous siltstone, fine sandstone, siltstone, medium sandstone, coarse sandstone, conglomerate and glutinite and so on. Arkosic arenite and ithic arkose predominate, with some rock fragment sandstone and arkosic rock fragment sandstone. Feather faults associated with the main controlling faults have been found, which made up local small traps with the main controlling faults. Reservoir sand body grains were typically transported by drag flows. The grain size accumulation probability curves can be summed into three types. Parallel, wave, crossing beddings and other drag-flow-oriented sedimentary structures are dominant in the study area. To conclude, with logging facies research results, it has been regarded that the third member of Hetaoyuan Formation in the research area is a delta sedimentary system, dominated by delta front with under water distributary channel, mouth bar, sand sheet, interchannel and lacustrine as the main micro-facies.