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Characteristics Of Natural Gas Accumulation In Xujiahe Formation In The Middle Of West Sichuan Depression

Posted on:2011-08-17Degree:MasterType:Thesis
Country:ChinaCandidate:L JinFull Text:PDF
GTID:2120360308459407Subject:Mineral & P production and exploration
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Sichuan Basin is an important natural gas exploration area, its the middle of the western depression is the main gas production area for Southwest subsidiary of Sinopec. Since Late Triassic,Western Sichuan depression has experienced Indosinian,Yanshanian and Himalayan movements,leading to the multi-stage changes of poroperm characteristics,structural features,fluid properties and geo-pressure fields,as well as reservoiring through repeated migration and accumulation of hydrocarbons.Gas inUpperTriassic Xujiahe Formation in Western Sichuan depression has been accumulated around the Pengguan hydrocarbon-generating sag,and distributed in the eastern,western and northern slopes of the sag.Through field research, field profile, sample tests, drilling data, and the status of research abroad, comprehensive the characteristic of source rock geochemistry: TOC, Microscopic examination of kerogen type, thermal decomposition parameters and characteristics of extracts were ethnic group, saturated hydrocarbon chromatographic characteristics of hydrocarbon source rocks on the comprehensive analysis and evaluation of obtained, the average organic carbon than 1.5%, chloroform bitumen "A" generally greater than 0.12%, Ro than 1%, the main type of organic matter typeâ…¢, lower source rocks west than the east, while the upper part of hydrocarbon source rocks in the eastern source rock is better than the west, that center of the hydrocarbon west to east transfer. In addition, use of PetroMod basin modeling software to simulate the Hydrocarbon generation history, pore evolution of reservoir, pore evolution of cap. Overall performance is to be the third of Xujiahe formation for the boundary line for the following paragraph to the three source rocks, that Ma'antang,Xiaotangzi, the second and the third of Xujiahe formation source rocks, north-east from the Southwest, into the same generation hydrocarbon stage gradually advance, while for the same geological period, is manifested in which the students the western region was less marked than oil and gas stage after east district, the fourth and the fifth source rocks, the performance of the grounds of southwest to northeast , then showed a contrary trend, that is, into the same hydrocarbon phase lag gradually over time, but for the same geological period, the performance of the South West Region are oil and gas phase advance than the northeast region;Xinchang field in the eastern the reservoir of the second of Xujiahe formation compaction during the Late Jurassic,end of Suining Formation deposition Xiaoquan field in western region after as late Middle Jurassic, what time the West to the East as early as late north-south difference in time, not to large, the fourth of Xujiahe formation later than the second of Xujiahe formation; The cap rock,the third of Xujiahe formation in the western region Yazihe to end of the third of Xujiahe formation deposition have ability of the sealing gland, the middle of the Xinchang feild to the end of the fourth of Xujiahe deposited with the sealing gland ability, the eastern part of Fenggu area later that about to be fifth of Xujiahe formation have the ability,the fifth of Xujiahe formation eastern and middle area earlier, have the ability to cover on the earlier period of Shaximiao formation, but the west area have the sealing ability of shale with relatively late, in the Suining formation early.Combined with previous chronology in the accumulation, tectonic evolution history, fracture history and other research results summarized that the original gas reservoirs in the UpperTriassic in West-ern Sichuan depression have been formed in middle-late Indosinian to middle-late Yanshanian. Since Late Creta-ceous,the whole reservoirs have been compacted,peak of hydrocarbon generation and expulsion has finished,and hy-drocarbons have been"sealed up"as a result of the compaction.This area has been strongly deformed by Himalayan movement and the hydrocarbons"sealed up"during the earlier compaction have been reactivated by the fractures.Therefore,the reservoiring of gas inUpperTriassic Xujiahe Formation of inWestern Sichuan depression are characterized by the early"palaeo-structures"to be the basis of gas accumulation,intermediate"compaction seal-up"to be the condition of gas preservation,and the late"fracture activation"to be the key to gas enrichment.
Keywords/Search Tags:The middle of the western Sichuan depression, Xujiahe formation, Source rock, Hydrocarbon generation history, reservoiring characterisitcs
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