oa Geologic Controls from Pore Pressure Variation in Najmah,Sargelu Formations — A Case Study from Raudhatain Field, North Kuwait

Najmah, Sargelu Formations have a complex petroleum system due to high pressure 17 to 15 ppg.,<br>low formation porosity and variable fracture porosity. Pore pressure is extremely variable and difficult<br>to predict.A geological study is done in Raudhatain field to understand pore pressure variation.<br>Real time pore pressure, well logs, cores and image log fractures are used for the study. Fracture<br>intensity logs from image log fracture data are generated. Correlations are prepared by integrating<br>these data and well test result.Structure contour, Isochore and Pressure maps are prepared.<br>Structure maps at all stratigraphic levels show uniform trend. Open fracture intensity are high at<br>structural high areas in Lower Najmah Limestone and Sargelu and strike parallel to the regional trend.<br>Away from structural high area open fracture intensity is moderate with strike parallel to regional<br>trend. Pore pressure maps at the top of these two intervals show maximum pressure atstructural high<br>areas and uniform pressure gradient for rest of the area. Isochore maps at the top of these two<br>intervals show uni directional depositional trend and maximum formation thickness at structural high.<br>Well tested in Lower Najmah Limestone and Sargelu has surfaced oil.<br>Open fracture intensity in Upper Najmah Limestone and Najmah Shale are low and limited to structural<br>high and its strike direction is inconsistent.Sharp contrast in pore pressure are observed between<br>structural high and areas away from it. Isochore maps at the top of these two intervals show shift in<br>depositional axis and maximum formation thickness are not always at structural highs.<br>In Upper Najmah Limestone and Najmah Shale limited fracture connectivity has resulted in more<br>abrupt pressure variation.Maximum pore pressure are localised at structural highs due to high<br>concentration of open fractures. In Sargelu and Lower Najmah Limestone high fracture intensity and<br>consistent fracture strike have resulted in more uniform pressure variation away from structural high.<br>Open fractures parallel to the regional trend act as conduit for reservoir fluid migration and helped in<br>transmitting formation pressure. Maximum formation thickness at structural high also resulted in<br>increase in effective reservoir thickness in Sargelu. The present study is a base work for building<br>fracture network modeling.