Hydrocarbon Accumulation Law Research In Chunguang Area Of Chepaizi Arch

Junggar basin is the significant oil-gas producing area of Northwest in our country. Chunguang area of Chepaizi arch is located in the west of the basin, which is the large monoclinic. It has gotten good oil-gas shows, and the main crude oil type is heavy oil and light oil. The two generated hydrocarbon sunkens--Changji sunken and Sikeshu sunken, possess multi-period structural characteristics, and complex reservoir forming patterns, so we study the Chunguang area and analyze the oil-gas migration ways, realize the oil-gas migration and accumulation rule, which is strategic significance for the next exploration deploy.This article aims at Chepaizi area, Junggar basin. With the study of deposition characteristic, structural evolution, petroleum geological condition, combining with seism, logging and drilling data, by detailed analysis of the sedimentary facies belt, structural evolution stages and forming petroleum entrapment pattern, we raise the favorable exploring direction.The main achievements and acquaintances:(1) The characteristics of hydrocarbon distribution of Chunguang area is widly distribution and varied series of strata. There exists heavy oil and light oil. Sha2section of Chun2, Sha2section of Chun8and Chun5well block is light oil deposit, and the others are heavy oil deposits.(2) The main pathway system of Chunguang area is consisted of breakage, unconformity and thick-layer, in which the crosswise pathway bed belongs to Cretacic unconformity, Paleogenic unconformity and sandy bay bottom thick-sand, and the lengthwise pathway bed mainly belongs to interlamination breakage, it presents Z pattern to distant pathway in the mass.(3) The research area is mainly formed by three stages. Stage I is from cretaceous terminal period to paleogene early period, which is the unconformity pathway through Hongche breakage and cretaceous bottom system of Permian oil sources deposit in Changji sunken. It is formed in the bottom of cretaceous and Jurassic reservoir, which is lightly influenced by the upper covering layer, and the crude oil is biodegradated to form heavy oil. Stage II is early Neogene, which is the beginning generation of light oil of Jurassic, and pathway through the unconformity of Hongche breakage and cretaceous bottom system, and mixing with the paleo-heavy oil, forming the mixing sources heavy oil deposit, and with new tectonisum, along the breakage to the unconformity of the sandy bay bottom, and forming reservoir at the sand wedging out. Stage III is from Neogene period so far, which mainly generates the light oil by the hydrocarbon source rock in Sikeshu sunken and Changji sunken, along to Aika breakage, thick-sand of sandy bay formation bottom and the unconformity of cretaceous bottom, to gather and form the reservoir in the northwest of Chunguang area.(4) By calculating and clearing the4-/1-DMDBT data, combing with the oil-gas pathway conditions, we confirm the migration direction of Chunguang block, of which the petroleum in the Chun50well block generating from Sikeshu sunken Jurassic hydrocarbon source rock is charging from northwest to center. The crude oil of northeast of Chun17well is generated by Changji sunken of Permian system, for bad preservation conditions, it was biological degradated to heavy oil, and then influenced by tectonic movement to secondary migration, charging from east to west. The other reservoirs of the research area belong to the petroleum mixed by the Changji sunken of Jurassic and the former generated heavy oil, to form the mixed reservoir, and once destroyed and migrating to Chunguang area, the direction is from southeast to northwest.(5) Chunguang area is located in between two hydrocarbon generation stove, the accumulation mode of different blocks is large different, Permian hydrocarbon source rocks of changji sag due to the thickness of the overlying strata is thinner, sealing ability is limited, and suffered from severe biodegradation of crude oil, formed a heavy oil reservoir. Late Jurassic light oil began to a large number of generated, mixed with the original of heavy oil reservoir, and under the new tectonic movement again adjust, into the paleogene and neogene strata in the accumulation. The Jurassic source rocks formed a new heavy oil reservoir, shipped together in the Paleocene and Neocene reservoir. Rely on interlayer fracture control, in the state of the light oil in Shawan groups of different sand into hiding.(6) The controlling factors of hydrocarbon accumulation of Chunguang are①Conducting scope of unconformity distribution control of hydrocarbon, the greater the distribution area of unconformity, the better conducting, the longer distance of hydrocarbon migration.②Faults control the distribution of hydrocarbon layer, the distribution of fracture is relatively wide, the Hongche faults as the main oil source faults, and for the vertical migration of hydrocarbon long-distance provided a channel.③The sedimentary facies control the hydrocarbon reservoir physical properties, different sedimentary facies, reservoir physical properties are also different. Reservoir quality of Shawan group is the sedimentary facies of delta front deposition.(7) By the research of petroleum entrapment regularity, we confirm the favorable target zone for the next exploring job.①The north wedging out belt of sandy bay formation in the work zone, especially the Sha2wedging out belt, is the light oil widely forming zone.②The northwest wedging out belt near Shal breakage is the favorable target zone of Sikeshu sunken of Jurassic.