| Junggar Basin is an important large-scale superimposed petroliferous basins in western China, where the shallow oil and gas exploration can be traced back to the Qing Dynasty, has an important position in the history of China’s oil and gas exploration; their exploration focus has undergone a complex and tortuous process, but Junggar ago foreland basin has been the focus of attention. According to the latest tectonic units Xinjiang Oilfield Company, division scheme, this paper study area four trees sag basin is one of44full secondary structure elements belonging to the southern edge of North Tianshan piedmont thrust belt level structural units, recessed west Jinghe areas Ebinur, east to the southern tip of the red car line fault bounded anticline with Houma spit phase; Tianshan mountains in the southwest of Erin from black Burgenstock, southeast and Qigu phase fault-fold belt, north through Aika fault gradual transition to Chepaizi raised, sunken body is a big strike NWW monoclinic, location, mainly in the territory of Xinjiang Wusu and Kuitun, oil and gas exploration area of approximately6400km2. The depression is developed up on Carboniferous and Cambrian crystalline basement extruded depression, experienced a pressure twist-Depression-foreland three evolutionary stages of construction were the main Himalayan stereotypes, mainly sedimentary strata development Jurassic-Quaternary.The depression experienced since1937Dushanzi oil discovery since the course of nearly80years of exploration, discovered the Dushanzi, West Lake, Kayindike High Springs four oil and gas structures. But the process of multi-stage tectonic evolution of the area makes reservoir conditions become more complex, so that in recent years has not been a major breakthrough, with the oil companies on the southern edge of the shallow increasing emphasis on four trees dEPRESSION conditions, especially high-quality comprehensive and integrated reservoir study is imminent.Oil and gas exploration and practice for many years believed that more than four trees sag under the control of the tectonic evolution of the longitudinal development of the next, in the three sets of large reservoir combination Neogene Shawan is a combination of the most important oil and gas producing layer. But this group of reservoir development and distribution characteristics, especially the distribution of effective reservoir is not yet clear.This study systematically and comprehensively collected Sikeshu major depression dimensional seismic data, logging data, logging data, testing data and core analysis data to sedimentology, logging geology, reservoir geology and principles of petroleum geology, the method is based on four trees identified sedimentary facies and sedimentary depression mode Neogene Shawan establish its interpretation models, combined with production data to accurately identify the effective reservoir, established Shawan reservoir evaluation criteria for effective reservoir Shawan a comprehensive evaluation, recognize the Shawan distribution characteristics of the reservoir and its controlling factors.The four trees sag Neogene Shawan comprehensive reservoir study achieved the following:(1) the study area by Shawan south and north of different provenance control North Slope with major braided river delta-lacustrine depositional system and southern piedmont mainly developed fan-delta-lacustrine depositional system. Some sand from the sand to the three sections, the number of delta development, the area is on the increase.(2) study area Shawan lithic sandstone reservoir rock types based. Petrological characteristics can be summarized as "two low and one high", that is, low compositional maturity, low cement content, high textural maturity. Its lithology is mainly in fine sandstone.(3) The main types of interval intergranular porosity dissolved pore, intragranular dissolved pore, primary intergranular pore followed. Data analysis showed that mercury:Shawan expulsion reservoir pressure is high, with an average of1.6MPa, capillary pressure values ranged between4.4-10MPa, the maximum intake of mercury saturation of50%to70%, on the whole throat is small fine pore throat structure, reservoir connectivity is poor, a low porosity and low permeability reservoir of small throats. Class Ⅰ,Ⅱ class roared mainly concentrated in the eastern sag Sha Dushanzi region; class Ⅲ roared are visible in the region; IV class, V class roared mainly developed in Kayindike, West Lake area.(4) the region is characterized by the physical properties of low porosity and permeability, Dushanzi District sandstone average porosity of12%and average permeability of1x10-3μm2; Kayindike, average porosity sandstone Lake region of8%, the average permeability of0.4x10-3μm2.(5) reservoir is mainly affected by the combined effects of sedimentation and diagenesis. Delta plain, with the leading edge of Asia with better properties. Study area diagenesis main types of compaction, cementation, dissolution. Division of diagenetic stage showed Shawan Formation reservoir in the study area in diagenesis A period. Compaction is strong, is to reduce the reservoir properties of the main reasons; reservoir properties of the zones cements have a greater impact kaolinite, siliceous cement and carbonate minerals; while dissolution is mainly cuttings and feldspar dissolution, the impact on smaller properties, improve porosity and permeability of constructive diagenesis-dissolution is secondary; still exist abnormally high formation fluid pressure on the porosity preservation impact.(6) in the study area mainly developed in Kayindike conventional reservoirs, Lake region, where mainly low porosity and low permeability, porosity and permeability in the reservoir also occupy a certain proportion. Average of less than 12%porosity and permeability of less than0.1×10-3μm2typical low porosity and low permeability reservoir sand mainly developed in Sec. |
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