ANOMALOUS VARIATIONS IN PRODUCTION OIL WELLS BEFORE AND AFTER THE GREAT HAICHENG AND TANGSHAN EARTHQUAKES

The process of development of an earthquake may influence the oil wells neighbouring the epicentral region. It is reflected by anomalous variation of oil production. However, quantity of oil production and well pressure are greatly controlled by man-made factors. By eliminating those factors, one may be able to reveal the relation of anomalous variations in oil wells and the occurrence of earthquaks.Anomalous phenomena in production wells are chiefly expressed as change from pumping to flowing wells and the sudden increase of quantity of oil production. This may signify the accumulation of stress in the earthquake generating regions causing change of pore pressure in the wells. If deep oil wells are located properly and the change of pore pressure is constantly observed and recorded, the phenomena might be observed as earthquake precursors.