Islam, M. S. (Dhofar University Salalah) | Kleppe, J. (Norwegian University of Science and Technology) | Rahman, M. M. (Bangladesh University of Engineering and Technology) | Abbasi, F. (Dhofar University Salalah)
Low salinity water-flooding (LSW) is a promising Improved Oil Recovery (IOR) process in which the salinity of the injected water is controlled to progress oil recovery over conventional seawater-flooding and other EOR methods. Published laboratory studies and field test cases in the last two decades have suggested several mechanisms of oil recovery by LSW, which is still an immature area of research. However, the commercial reservoir simulators have limited capability to model LSW accurately. The principal objective of this paper is to evaluate the potential of IOR using LSW for the Norne Field's E-segment.
There is about 60% oil is still trapped as residual oil especially in the Ile and Tofte formations of the Norne Field's E-Segment even after the completion of primary recovery and seawater-flooding as a secondary recovery technique. LSW simulation is, therefore, run for a period of 18 years from 2005 to 2022 to extract this residual oil adhered to rock wall. LSW simulation studies using original wells indicated that water injection with optimal salt concentration of 1,000 ppm TDS (total dissolved salts) or 1.0 kg/m3 yields substantially higher oil production (34.13 MSCM) compared to seawater-flooding (32.95 MSCM).
With the encouraging finding of LSW, the next stage of the study is involving simulation of different scenarios. Six different cases have been investigated. Case 1 is the base case with seawaterflooding using the existing wells. The other five cases are all LSW, with the following well configurations: (2) using the original wells, (3) using the original wells in addition to a new producing well, (4) using the original wells in addition to a re-completed producing well, (5) using the original wells in addition to a new injection well, and (6) using the original wells in addition to a re-completed injection well. Case 3 indicated the highest oil recovery (50.10 MSCM) compare to other five cases. Thus, it could be concluded that the Norne Field's E-Segment is a good candidate for LSW to extract the residual or trapped oil.
In this study, LSW simulation results have shown the alteration of wettability from neutral-wet to strongly water-wet, which in turn is resulting in a favorable mobility ratio, is the most important IOR mechanism for the Norne Field's E-Segment. LSW in this case is found to give near to piston-like displacement.