New Exploration Plays Predicted from Novel Petroleum System Models of the Paleozoic Strata in Tarim Basin, NW China

Wenzhi Zhao¹ and Suyun Hu²
¹PetroChina Exploration and Production Company, Beijing, China
²PetroChina Research Institute of Petroleum Exploration and Development, Beijing, China

Tarim Basin in NW China is a multicyclic petroliferous basin, characterized by Paleozoic carbonates and Mesozoic-Cenozoic clastic sediments, with an area of 350,000 km2. Because of its complex tectonic history, the petroleum potential of the Tarim Basin remains a contentious issue. Of particular notice are the diverse opinions on the petroleum potential of the Paleozoic marine sequence. The prevailing view up to a few years ago was that oil generation from the Cambrian-Ordovician strata had occurred from the end of Ordovician-Silurian age and subsequently from the end of Carboniferous-Permian age, while these rocks are currently at highly mature to overmature stages with respect to oil generation. An logical extension of this argument is that hydrocarbons generated from the early phase of thermal maturation had been lost as the result of several orogenic events, where only a small proportion of the early generated hydrocarbons being preserved following the destruction of paleo oil accumulations. Results from our recent work as part of the China National Oil and Gas Research Program (Project 04) have revealed several different perspectives of the petroleum systems in the Tarim Basin, including (1) a significantly delayed hydrocarbon generation from the Cambrian-Ordovician source rocks, (2) a much boarder oil window (over 400 million years) from parts of the basin due to the coupling of the low geothermal regimes and slow burial, leading to oil generation during the Cretaceous-Paleogene period; and (3) much greater potential of gas generation from thermal cracking of the dispersed liquid hydrocarbons in the deep buried source rocks. The revised hydrocarbon resource assessment put the total remaining oil and gas resources in the Tarim Basin at 8.5 billion tons and 10 BCM respectively. The revised oil resource is more than doubled the early estimate (Chinese Ministry of Land and Resources, 2005), distributed in an area of 50,000-80,000 km² in the Tabei – Manxi - Tazhong region. The revised gas resource is three times as much as the early estimate, adding 1000-1500 m of potential gas pays in the deeper parts of the basin. The results are encouraging in term of the exploration in renewed exploration efforts for giant gas accumulations in the deep carbonate sequence.

AAPG Search and Discovery Article #90175©2013 AAPG Hedberg Conference, Beijing, China, April 21-24, 2013