IMPACT OF INSITU STRESS ON A SANDSTONE RESERVOIR DEVELOPMENT IN THE NIGER DELTA

ABSTRACT

This project evaluates insitu stress and her impact on sandstone reservoir development using a field in the Niger Delta and presents a well-scale geo mechanical model to address the pore pressure, geopressure and borehole stability. The rock strength and elastic properties were evaluated using well logs and relevant models, an average vertical stress gradient of 0.9PSI/feet is interpreted from the extrapolated density logs. The hydrostatic pressure gradient of 0.43 PSI/feet. Pore pressure against the shales are estimated by Eaton’s disequilibrium compaction method, which are found to be mildly overpressure (0.45 psi/feet). The minimum horizontal stress (Shmin) gradient ranges between 0.59 and 0.81 psi/feet. Wellbore stability is shown to be a function of the insitu stress as addressed by the Mogi failure model and the assessed failures are corroborated with the caliper log observations. Safe and effective downhole pressure window is inferred from the interpreted pore pressure, collapse pressure and Shmin to avoid any kick, loss or compressive wellbore failures by optimum mud weight designing. Inferences on drilling are discussed which will be helpful for better reservoir development and be a foundation for the mode of EOR processes to be carried out in future.