Impact of In situ Stress on a Sandstone Reservoir Development In the Niger Delta

Abstract

This project evaluates insitu stresses 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,
geopressures and borehole stability. The rock strength and elastic
properties were evaluated using 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 (σh) 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 calculated from the interpreted
pore pressure, collapse pressure and minimum horizontal stress ( ) 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.