Abstract: Hydrocarbon Potential of Lower Paleozoic Sequences in Alashan Platform and Adjacent Area of Northwest China

Chuanmao Liang, Gerald M. Friedman

In recent years, China has stepped up its exploration of oil and gas in northwestern China, particularly in Tarim and Eldos platforms, where highly productive oil and gas fields have been discovered in lower Paleozoic sequences. In early 1993, China Oil and Gas General Company called internationally for bids on exploration in northwestern China. This paper discusses hydrocarbon potential of Cambrian and Ordovician strata of the Alashan region in northwestern China. The Alahan massif, between the Tarim and Eldos platforms, was part of the huge North China Platform. Regional lithofacies, paleogeographic and tectonic analyses suggest that the Alashan massif was in part or entirely epicontinental during early Paleozoic times. The southern margin was passive, and deep-water sediments were aid down off the shelf edge on the slope, rise and bottom of the adjacent sea. As a result of Caledonian and later tectonic activities, the lower Paleozoic deep-water sediments overthrust northward onto the Alahan platform along its southern margin, which can be compared with the Oklahoma region in the Quachita overthrust belt in tectonic and paleogeographic development. The lower Paleozoic shallow marine sequences, especially carbonate strata, underlying the overthrust allochthonous strata may become highly productive reservoirs. Four lithofacies can be regarded as most potential hydrocarbon reservoirs in these Cambrian-Ordovician strata: 1) tidal stromatolite lithofacies; 2) barrier oolitic and intraclastic grainstone lithofacies; 3) slope and submarine canyon and fan-conglomerate lith facies; and 4) tidal-shelf paleokarstified lithofacies.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994