Implementing the Optimum Well Placement Strategy for Horizontal Injectors Drilled in Highly Heterogeneous Reservoirs of Central Saudi Arabia

Abstract

Targeting thin sand bodies while drilling across heterogeneous sandstone reservoir is a major challenge that requires integrated reservoir engineering, formation evaluation, geological and geophysical contributions. The objective of this paper is to exemplify geosteering challenges when drilling horizontal power water injector across Permian eolian sandstone reservoirs with high degree of structural and reservoir uncertainty. The integrated reservoir management team has utilized the geological and seismic impedance to locate a power water injector in the southwestern flank of the field to support pressures during production from offset wells. Seismic impedance indicated that the target area comprises of beds with high degree of lateral and vertical heterogeneity. The team decided first to drill the well utilizing a conventional logging while drilling (LWD) tool to geosteer the well in the horizontal section. The LWD was unable to trace the sand while drilling across the heterogeneous sandstone reservoir. The team decided to abandon the hole and sidetrack the well with a new lateral, utilizing directional and deep resistivity (DDR) while drilling to improve geosteering and optimizing of well placement. The DDR measurements provide remote detection of bed boundaries around the wellbore. This technique has been used successfully in other analogous sandstone reservoirs of Saudi Arabia to ensure maximum reservoir contact. The results of using this approach were very encouraging and a net to gross of 62% was achieved. It can be concluded from the results that the DDR technology is an effective way to efficiently drill and place water injector wells. It has the potential to reduce the number of injector wells drilled, thus cutting cost and meeting the production goals. Introduction Eolian and fluvial channel sand deposits are significant petroleum exploration targets in many basins around the world. The quality of sand and stratigraphic hydrocarbon trapping mechanism plays an important role to the type of wells drilled to produce the hydrocarbons. Power water injector wells are drilled to maintain pressure and improve oil recovery. The success of the water injector depends on how effectively the wells are placed relative to reservoir quality, flow direction and structure. Therefore it is essential to characterize the eolian and fluvial channel sand depositional system.