Methods of estimating and predicting abnormal formation pressures

The authors describe in this paper quantitative techniques for the prediction and estimation of formation pressures that have been used for more than 20 years in the former USSR. The described methods are divided into two groups: (1) methods used before drilling, and (2) methods used during drilling. rst group includes: (a) methods for the prediction of abnormally-high pressure using geological and geophysical data in regions with non-equilibrium compaction; (b) methods for the prediction of abnormally-high pressures in regions with uplift and erosion, or subsidence, of compacted sedimentary rocks; (c) methods for the prediction of low pressure in regions with permafrost; and (d) methods of seismic exploration. thods belonging to the second group basically involve the use of well-logging and drilling data: (a) the method of equivalent depth33Foster and Whalen, 1966; Alexandrov, 1987. the method of normal compaction trend44Dobrynin and Serebryakov, 1978. the method of compressional curves55Dobrynin et al., 1982. (d) a method based on the analysis of the concentration of the radioactive isotope 40K in shales.