Analysis on Accumulation Conditions and Target Optimization of Paleogene - Neogene Gas Reservoirs in Western Qaidam Basin

doi:10.3969/j.issn.1006-6535.2021.01.004

Abstract

Abstract: There are abundant Paleogene-Neogene oil and gas resources in the western Qaidam Basin, but the natural gas exploration level is relatively low. In order to promote future exploration of natural gas in the study area, the study area was selected and evaluated by ideas of source-cap rock controlling hydrocarbon accumulation and structure-deposit-trap controlling reservoir, secondly, experimental analysis, basin simulation and geological evaluation technologies are used to study the characteristics of gas source rock, reservoir stratum, trap, caprock and preservation conditions, and finally, favorable exploration targets were proposed. The findings show that there are 5 sets of gas source rocks (R_o ≥ 0.8%) taken from the western Qaidam Basin, the primary gas source rocks are E₃² and N₁, with significant late hydrocarbon generation characteristics, mainly distributed in the northwest Qaidam Basin and locally in the southwestern Qaidam Basin near the Mangya depression, with an area of about 4 743.40 km² and a total hydrocarbon amount generated of about 1.17×10¹² m³; the reservoirs in the western Qaidam Basin are classified by two types: clasolite and carbonatite, with tight lithology and petrophysical changes; there are 2 sets of regional caprocks in the western Qaidam Basin; the deep caprock is properly preserved while the shallow caprock is poorly preserved; the deep layers of the effective gas source rock area are dominated by structural traps such as late E₃¹ and E₃² (fault) anticlines and fault noses, and consistent in time and space in gas generation period, accumulation period and preservation period. Based on above findings, three favorable natural gas exploration zones, namely Shizigou-Ganchaigou, Xianshuiquan-Youquanzi-Cucumbermao and Nanyishan were selected, and 12 favorable traps and 3 more favorable traps were identified. There is much for reference of the results of the study to the further exploration of natural gas in western Qaidam Basin.

Key words: natural gas reservoirs, accumulation conditions, Paleogene, Neogene, western Qaidam Basin

CLC Number:

TE122

Tian Jianhua, Dong Qingyuan, Liu Jun. Analysis on Accumulation Conditions and Target Optimization of Paleogene - Neogene Gas Reservoirs in Western Qaidam Basin[J]. Special Oil & Gas Reservoirs, 2021, 28(1): 26-33.

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