An important discovery in Well Luntan-1 of the Tarim Basin, China, and its significance for ultra-deep oil and gas exploration

doi:10.3969/j.issn.1672-7703.2020.02.007

Abstract

Abstract: In January 2020, light crude oil was obtained from Lower Cambrian dolomite with burial depth deeper than 8200 m in Well Luntan-1, which is located in the Lunnan low bulge in the Tabei uplift. The result indicated a major breakthrough in ultradeep oil and gas exploration in the old craton of Tarim. This paper describes the process of discovering Well Luntan-1 and analyzes the discovery history of the ultra-deep Cambrian subsalt oil reservoirs, with the intention of providing reference for the exploration of new zones, new strata and new types in other similar areas. According to drilling results from Well Luntan-1, a set of high-quality source rocks is developed in the Cambrian Yuertusi Formation, and there are 2 sets of reservoir-cap assemblage. One is evaporite gypsum cap rocks in the Awatage Formation and dolomite reservoir in the Shayilike – Wusonggeer Formations. The other is mudstone cap rocks in the Yuertusi Formation and dolomite weathering crust reservoir in the Sinian Qigebulake Formation. The production layer in Well Luntan-1 is the Wusonggeer Formation, which is a volatile-oil reservoir with normal temperature and pressure gradients. In addition, trace natural gas was obtained from the weathering crust of the Sinian Qigebulake Formation. Exploration of the platform-basin transitional area in the Tarim Basin has experienced 2 strategic shifts: from clastic rocks to carbonate rocks, and from carbonate rocks to pre-salt dolomite. Well Luntan-1 is an important symbol of the second strategic shift, which is of milestone significance. The favorable accumulation conditions of Well Luntan-1 are the successive development of stable paleo- uplift and the high-quality source-reservoir-cap assemblages. Through analogy, this paper analyzes the exploration prospects for the Cambrian pre-salt dolomite in the Tarim Basin, and points out that favorable areas, such as the Tazhong-Gucheng area, the south slope of the Tabei area, and the northern Maigaiti slope-Keping area, are the key areas for the next steps in exploration.

CLC Number:

Yang Haijun, Chen Yongquan, Tian Jun, Du Jinhu, Zhu Yongfeng, Li Honghui, Pan Wenqing, Yang Pengfei, Li Yong, An Haiting. An important discovery in Well Luntan-1 of the Tarim Basin, China, and its significance for ultra-deep oil and gas exploration[J]. China Petroleum Exploration, 2020, 25(2): 62-72.

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