Prediction of Pore pressures gradient profile using wire line-logging data

Abstract

Pore pressure prediction prior drilling a well is most essential for selection of casing, setting depth, and optimum mud weight . If the pore pressures are not accurately predicted prior to drilling, catastrophic incidents, such as well blowouts, may take place and endanger the life of personnel beside we might lose the well completely The well will be drilled in normal formation using mud weight gradient as higher slightly than normal pore pressure gradient (0.465psi/ft.). On the other hand, when we encounter abnormal formation (> 0.465psi/ft.) the mud weight should be increased higher than when we are in normal situation as stated before. It has been observed that sonic and resistivity reading can qualify or indicate the occurrence of the abnormal pressure (qualitative tools). To quantify pore pressure as a figure, EATON used empirical equation from his observation from the qualitative behavior of both resistivity and sonic (quantitative tools) In this research the pore pressure gradient, over pressure gradient and fracture pressure gradient are predicted and plotted vs. Depth by using Eaton empirical equations (resistivity &sonic well log data) using IP software program (Interactive Petro physics) in order to facilitate the calculation of pore pressure (formation pressure). The values of pore pressure at specified depth that obtained from curve are correlated to the values obtained from same depth through direct calculation using equations related to pore pressure prediction; the values of pore pressure show approximately the same results.