Prediction of Surge and Swab from Field Data Compared with Existing Theory - Analysis of Two Wells in the North Sea

Existing theory of surge and swab are compared with field data. The purpose of this master thesis is to examine whether or not existing methods can be used for calculations of surge and swab pressure. Field data from two wells in the North Sea are analyzed through logs given in a matlab program developed by Verdande. A correlation between rapid change in block position and a corresponding alteration in standpipe pressure indicates intervals of surge and swab as long as the other relevant parameters are kept constant. Field data is then taken from these intervals and the pressure is calculated using existing methods. Events of surge and swab were only observed in one section. The intervals where surge and swab are observed are described by operations in the well. Different formations cause different problems and reasons for surge and swab to occur. Calculations of the pressure indicate that simplifying assumptions and other contribution affects might explain why the calculated pressure deviate from the field data