Development Characteristics and Guiding Significance to Oil and Gas Exploration of the Sinian Rift in Tarim Basin of China

Abstract

Tarim basin, especially the deep area, is becoming one of the most attractive areas for hydrocarbon exploration in China. The extensional tectonic environment during the Sinian period and the movements of the multistage faults in the Tarim basin make a contribution to the development of the Sinian rift, the poor research on which bring great difficulties to the further exploration within the deep area in Tarim basin. Based on drilling data, new 3D seismic data and aeromagnetic data, the tectonic development characteristics of the Sinian in the whole Tarim basin have been firstly depicted meticulously. And analysis shows that the Sinian rift in Tarim basin is mainly controlled by the rifting of ancient Tianshan ocean and ancient Kunlun ocean and which results in the occurrence of three aulacogens such as Maigaiti aulacogen, Manjiaer aulacogen, and Awati aulacogen and three ancient uplifts such as Tabei uplift, Bachu-tazhong uplift and Hetian uplift. Moreover, the Sinian sedimentary system in Tarim basin can be subdivided into the former rift sedimentary system and the latter depression sedimentary system. The rift sedimentary system is dominated by clastic rock, tillite and volcanic rock and assumes the wedge reflections on the seismic section. In addition, the depression sedimentary system mainly develops carbonate deposits, especially dolomite, which is characterized by the parallel and continuous sheet reflection of weak amplitude on the seismic section. The further analysis discloses that the Sinian tectonic movement has great guiding significance in oil and gas exploration, which can be interpreted as the following four aspects. Firstly, the Sinian rift and its successive subsidence directly control the sedimentary distribution of the source rock within the Sinian and Yuertusi Formation in the Lower Cambrian. Secondly, the margins of the Sinian successive rift control the distribution of the platform margin facies belt and successive ancient uplifts control the distribution of platform facies within the Lower Cambrian which can act as favorable reservoirs. Thirdly, platform margin facies belt developed within both the Lower Cambrian and the Sinian ancient uplifts control the distribution of gypsum rock in the Middle Cambrian which can act as important cap-rock. Fourthly, the big structural traps successively develop under the gypsum rock in the Middle Cambrian, which can be the favorable hydrocarbon accumulation zones, especially in the Bachu and Madong.

AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015