This paper was prepared for the SPE-European Spring Meeting 1974 of the Society of Petroleum Engineers of AIME, held in Amsterdam, the Netherlands, May 29–30, 1974. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal provided agreement to give proper credit is made. Discussion of this paper is invited. Three copies of any discussion should be sent to the Netherland Section of the Society of Petroleum Engineers, P. O. Box 228, The Hague, the Netherlands. Such discussion may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines. Summary Overpressures are encountered on the North Sea in rocks of Tertiary to Permian age. The distribution of overpressures varies from basin to basin and examples are discussed. The mud logging techniques such as d-exponent, temperature records and wireline logging techniques such as the sonic transit time - depth plot and the shale resistivity - depth plot may indicate overpressures in specific cases. However the adjustment of mud weights and casing setting depths in exploration and appraisal wells in the North Sea, based on the overpressure prediction techniques, is not justified generally at present due to the unreliability of the methods. Introduction The term overpressure is used for formation fluid pressure exceeding the normal hydrostatic fluid pressure. The formation pressure gradients vary from 0.433 psi/ft for pressure gradients vary from 0.433 psi/ft for fresh and brackish water to approx. 0.465 psi/ft for salt water with a salinity of 80000 ppm NaCl eq. Appendix 1 shows the nomenclature used. Overburden pressure gradients calculated from bulk density logs vary from 0.80 psi/ft at shallow depths to 0.95 - 1.0 psi/ft at greater depths. These values are in agreement with the formation strength data obtained from tests carried out below a cemented casing of which results are presented in Appendix 2. Knowledge of the distribution of overpressures will make drilling safer and will attribute to more economical casing schemes. OVERPRESSURE PREDICTION METHODS A summary of the overpressure detection methods is shown in Appendix 3. One group of methods has to be applied during the actual drilling phase, while the methods in the evaluation phase can be applied after the hole is drilled.