Abstract of the proposal

A geological formation is abnormally pressured when the pore fluid pressure is significantly below or above the normal hydrostatic pressure for the depth considered. Phenomena of abnormal pressures in sedimentary basins are of considerable interest and importance to modem petroleum geology and environmental geology because of their theoretical and practical implications for issues ranging from waste disposal to oil generation. The proposed study is aimed at exploring the fundamental nature of the phenomena through a case study in the Shiwu area in northeastern China.

The Shiwu area is unique in that it is so far the only reported abnormally low pressured area in East Asia and that both abnormally high and abnormally low fluid pressures coexist in the same area. The abnormal fluid pressures are believed to be caused by a multitude of factors, including regional hydrodynamics, erosion and subsidence of formations, tectonic compression, heat transfer, and hydrocarbon generation. This project proposes to investigate the origin and evolution of the observed abnormal pressures through the development of compressive numerical models incorporating all of these factors and then to identify the mechanism or mechanisms most responsible for the generation and maintenance of abnormal fluid pressures in the area. The research will be based on database on the abnormal fluid pressures in this area compiled by one of the investigators and more data from laboratory testing on core samples to be collected.

The transition from abnormally low pressures to abnormally high pressures in the Shiwu area provides a challenging and unique case study to test all current hypotheses of abnormal fluid pressures. The proposed research will be the first of its kind designed specifically to investigate not only abnormal pressures but also the coexistence of underpressure and overpressure in a single sedimentary area using a multidisciplinary approach, combining geology, hydrology, geochemistry, laboratory testing, and advanced computer simulation techniques. It will make a significant contribution to the current knowledge base concerning the fundamental nature of basin-scale abnormal pressure phenomena. In addition, the proposed study will provide a foundation for further studies on the concept of using underpressured geological formations for safe disposal of hazardous liquid wastes, a major environmental problem in Hong Kong, Mainland China and elsewhere.

Related Publications:

Jiao, J. J. and C. Zheng, Abnormal fluid pressures caused by subsidence and erosion of sedimentary basins, Journal of Hydrology , 204, 1998, p124-137. [Full paper in pdf]

Jiao, J. J., C. Zheng, and R. J-C., Hennet, Analyses of underpressured reservoirs for waste disposal, Hydrogeology Journal, 5(3), 1997, p19-31.

Tang, Z., J. J. Jiao, S. He, and C. Zheng, Analyses of Abnormal Pressures in Shiwu Area in Northeast China (submitted)