Chapter 2 The Geology of Abnormal Pore Pressures

Abstract

This chapter explores the geology of abnormal pore pressures in several geographical locations of the world. The geology of Jhatla area of the Punjab—in northern Pakistan east of the Indus river and south of the foothills of the Himalayas—shows that it contains a thick, dominantly regressive Tertiary sequence with non-marine Oligocene to Upper Pliocene sandstones and silts lying on marine and paralic Eocene limestones and marls of the Nummulitic series. The prevailing opinion in India and Burma for overpressures is that these pressures are caused by the weight of the superincumbent strata. Abnormal pore pressure is a serious problem because it causes blow-outs in boreholes being drilled for petroleum. There is much to learn about the geology of abnormal pressures; its proper understanding is important for the exploration and development of those areas that have abnormal pressures and it is certain that these abnormal pressures play a significant role in the migration of crude oil and gas and the formation of the traps.