Abstract
One pilot study presently being conducted through CSS thermal recovery technology to explore a shallow poorly-consolidated viscous oil bearing sandstone reservoir in Kuwait with extensive integrated reservoir evaluation efforts to optimize the future development strategy.
The reservoir largely consists of two separate deltaic sand packages representing multi-stacked channel facies resulting to stratified reservoir intervals with variable degree of fluid saturations. Reservoir characterization uncovers high matrix contents along with calcite, dolomite, and clays as cements which essentially control uneven pore-geometry that fabricate the petrofacies types into multiple thin stratified-pay intervals, each being < 30’ thick with variable fluid saturations resulting from long transitional thief zones posing high risk for thermal recovery. Thus, a seemingly simple channel-based reservoir interval has been greatly altered by diagenetic episodes that need evaluation towards an arduous perforation, completion and production strategy to pursuit the well-defined individual thin pay-interval.
Single-well thermal recovery scheme under"injection-soak-production" sequence being conducted presently in three vertical wells, each subjected to first cycle injection of moderate quality steam (~75% at 4200 F) at rates 400 to 600 barrels EW/d at about 450 psig injection pressure for 26 to 71 days, followed by a soak period of 10 to 60 days. Subsequent total production estimates SOR between 0.2 and 0.9. In two wells, cumulative oil/water productions and 15% to 34% water cut indicate an excellent response to thermal stimulation. The encouraging injection parameters of steam slug size, high injection rates at low pressures, and subsequent productions provide valuable information towards upcoming second cycle injection and future steam flood strategy.
The ongoing CSS pilot is providing some critical information for the future commercial development phase. As such, all pertinent data are closely evaluated to ensuring the optimal strategy to meet the long-term development plan for this viscous oil asset.
