SUBSIDENCE PREDICTION CAUSED BY THE OIL AND GAS DEVELOPMENT Anton Sroka Institute of Mining Surveying and Geodesy Technische Universität Bergakademie Freiberg/ Germany Email: anton.sroka@tu-freiberg.de Ryszard Hejmanowski Dept. of Mining Damage and Geoinformatics Faculty of Mining Surveying and Environmental Engineering AGH University of Science and Technology/Cracow/ Poland Email: hejman@agh.edu.pl Abstract: Oil and gas development from underground reservoirs disturbs original rock mass balance. The tending of the rock mass to achieve a new, even only temporary balance is manifested in the movements of the ground surface. Movements can affect ground infrastructure like offshore platforms, pipelines and buildings. For increasing the efficiency of the preventive actions a’priori precisely prediction of the subsidence is necessary. By the prediction of surface subsidence changes of pore pressure in time due to exploitation and geometry of the reservoir have to be taken into account. The prediction method based on the influence function of Knothe will be presented in the paper. Some applications according to the oil and natural gas developments will be discussed 1. Introduction Surface subsidence of areas where oil, gas and water are exploited are a serious problem in various parts of the World. In the coastal regions, vertical movements of the surface may result in flooding or generate extra costs for securing the banks. Such problems were encountered, e.g. in the area of Maracaibo Lake in Venezuela (ca. 3.5 m – maximum subsidence), Mexican Gulf, in California (ca. 10 m – maximum subsidence) and in Japan. The subsidence troughs may be huge in size and the damage to the objects standing on them is comparable to those in the mining areas. Considerable deformations of surface usually can be found in the places where thick fluid reservoirs occur and the host rocks have compaction qualities. Surface deformations in the areas of oil and gas exploitation can be efficiently predicted on the basis of methods employing the influence functions. These methods make use of relatively uncomplicated mathematical models and are simple in use. Regarding their high efficiency, these methods are not frequently met in the World’s literature, therefore the Authors decided to discuss the prediction model based on an influence function applicable to fluid mineral reservoirs. 3rd IAG / 12th FIG Symposium, Baden, May 22-24, 2006