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

YANG Haijun1 CHEN Yongquan1 TIAN Jun1 DU Jinhu2 ZHU Yongfeng1 LI Honghui3 PAN Wenqing1 YANG Pengfei1 LI Yong1 AN Haiting4

(1.PetroChina Tarim Oil Field Company)
(2.PetroChina Exploration & Production Company)
(3.PetroChina Research Institute of Petroleum Exploration & Development)
(4.CNPC Bureau of Geophysical Prospecting INC.)

【Abstract】In January 2020, light crude oil was obtained from Lower Cambrian dolomite with burial depth greater than 8,200 m in Well Luntan-1, which was located in the Lunnan low bulge in the Tabei uplift, indicating a major breakthrough in ultra-deep oil and gas exploration in old craton of Tarim Basin. This paper describes the background of well Luntan-1 discovery and analyzes the exploration history of the ultra-deep Cambrian pre-salt oil reserves, aiming to provide experience and reference for the exploration of new zones, new strata, and new types in other similar areas. According to the drilling results, Well Luntan-1 penetrated a set of high-quality source rocks in Cambrian Yuertusi Formation and 2 sets of reservoir-cap assemblages, which are evaporite gypsum cap rocks in the Awatage Formation and dolomite reservoir in the Shayilike-Wusonggeer Formations, and mudstone cap 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 with volatile oil at normal temperature and pressure systems. In addition, trace natural gas was obtained from the weathering crust of the Sinian Qigebulake Formation. The exploration of the platform-basin area in the Tarim Basin has experienced 2 strategic shifts from clastic rocks to carbonate rocks, and then to pre-salt dolomite. Well Luntan-1 is an important sign of the second strategic shift, which is of milestone significance. The favorable oil accumulation conditions of well Luntan-1 are the successive development of stable paleo-uplift and the high-quality source-reservoir-cap assemblages. By analogy, this paper analyzes the exploration prospect of the Cambrian pre-salt dolomite in Tarim Basin and points out that the Tazhong-Gucheng area, the south slope of the Tabei area and the northern Maigaiti slope-Keping area are the favorable and key zones for further exploration.

【Keywords】 Tarim Basin; Well Luntan-1; ultra-deep exploration; great breakthrough; pre-salt dolomite;

【DOI】

【Funds】 National Science and Technology Major Project of China (2016ZX05004-004) National Science and Technology Major Project of China (2017ZX05008-005-004)

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This Article

ISSN:1672-7703

CN: 11-5215/TE

Vol 25, No. 02, Pages 62-72

March 2020

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Article Outline

Abstract

  • 0 Introduction
  • 1 Geological setting and exploration overview
  • 2 Geological characteristics of Sinian-Cambrian oil and gas in Well Luntan-1
  • 3 Strategic significance of the discovery of Well Luntan-1
  • 4 Prospects for Cambrian pre-salt exploration
  • 5 Conclusion
  • References