Journal of Petroleum Geology,
vo1. 20(3), July 1997, pp. 287-306
©Copyright 1997. Scientific Press, U.K. All rights reserved.
NORTH
JIANGSU BASIN, EASTERN CHINA: ACCUMULATION OF IMMATURE OILS AND DIAGENESIS OF PALAEOGENE
RESERVOIR ROCKS
Jin Qiang*, Wang Weifeng*, Xu Huaimin*, Yang Shaochun* and Qian
Ji**
Large
quantities of immature and low-maturity oil have been discovered in the North Jiangsu
Basin, East China. Intense tectonic activity and the differential accumulation of immature
oils during the Palaeogene have resulted in reservoir rocks which have variable
sedimentary and diagenetic characteristics. Studies of oil geochemistry and reservoir
diagenesis suggest that oil generation and accumulation took place early in the basin's
history (i.e. during early diagenesis), significantly inhibiting later modification of the
reservoir rocks. There has been no large-scale tectonic activity since the oil pools
formed, and the reservoirs' petrophysical properties and pore construction therefore
reflect early diagenesis. Diagenetic modification of the reservoir rocks was more intense
below the oil-water interface where oil did not accumulate. Alteration in these rocks
included calcite cementation, the formation of quartz overgrowths, and the development of
pressure solution.
