Formation and Distribution of Coal Measure-Derived Hydrocarbon Accumulation in NW China

Wenxhi Zhao, Yan Zhang, Dafeng Xu, and Changyi Zhao

This study recognizes that the following conditions are necessary for the Jurassic coal measure-derived oil and gas fields in NW China: (1) The Jurassic original basins, which were dominated by lacustrine to low-positional swamp environments, should exist to accept coal-measure related sediments; (2) the original depositional settings were characterized by low and gentle depressions and humid climate where oil-prone organic materials accumulated; (3) the development of the subsequent basins and successive sedimentation should occur on the Jurassic original basins, which are necessary to keep the coal measure source rocks progressively maturing; and (4) a certain degree of tectonic compression took place soon after the maturation of source rocks, which provided the driving force for the effective expulsion of oil and gas from coal measures.

Most of the coal measure-derived oil & gas fields in NW China are horizontally distributed along the inner side of lake strandlines. They occur vertically above or below the threshold of maturation. Owing to the sharp variations of lithology and facies in coal measures, the lithologies and hydrocarbon compositions of oil and gas reservoirs play a significant role in the oil and gas accumulations of the coal measures sequences.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California