SmartWater Flooding: Industry's First Field Test in Carbonate Reservoirs

Abstract

In recent years, improved/enhanced oil recovery by tuning the ionic composition of injection water has attracted the attention of the petroleum industry, and currently deemed as new emerging research trend. In view of research results for the last four years, we demonstrated in previous reports (SPE 137634; SPEREE Journal, vol. 14(5), pp. 578-593; SPE 143550, SPE 141082, SPE 154076; SPE 154077) that substantial oil recovery beyond conventional waterflooding from carbonates can be achieved by optimizing the salinity and ionic composition of field injection brine. Similar potential has been confirmed also in the secondary recovery mode. For recovery mechanisms, research confirmed that the driving mechanism is wettability alteration of carbonate rock surface and can be attributed to surface charges alteration, and microscopic dissolution of anhydrite. In this paper, we present the results of two field trials conducted in a carbonate reservoir to demonstrate the SmartWater Flood potential. Both field trials confirmed that in-house research results can be replicated at field scale. Injection of SmartWater revealed a reduction of ~7 saturation units in the residual oil beyond conventional seawater. Considering these field trials are the first-ever applications in carbonate reservoirs, they further provided another confirmation that SmartWater Flood has significant potential to be a new recovery method targeting carbonate reservoirs. A special type of single-well chemical tracer was used in these trials to measure the residual oil in the vicinity of the well following the injection of each water type. During all stages of field trials, careful QA/QC program was put in place to monitor variation in ionic composition in all injected or produced fluids and further insure optimum ionic composition of SmartWater slugs. Several field trials are planned to optimize the current process leading to a multi-well Demonstration Pilot to determine the impact on ultimate recovery and reserves.

A Novel, Field-Representative Enhanced-Oil-Recovery Coreflood Method

“…The new method can be applied to most EOR corefloods, including surfactant, alkali, polymer, or their combinations, and advanced ion management, where selective ions in the injection water are added or removed, or the injection water is diluted (also called low-salinity injection) to obtain EOR (Zhang et al 2007;Seccombe et al 2008;Yousef et al 2010;Gupta et al 2011;Vo et al 2012).…”

A Novel, Field-representative Enhanced Oil Recovery Coreflood Method

“…The reduction in brine viscosity offsets the enhancement from favorable wettability alteration (i.e., a favorable relative permeability shift), and ~0% shift in saturation is observed at F w =90% (Figure 14b). The benefit from low salinity injection EOR could be in the single digits (Yousef et al 2012), and oil recovery loss due to salinity reduction could be significant. Since the new method captures shifts both in fractional flow at practical water-cut and relative permeability curves, it can estimate recovery loss due to salinity reduction.…”

Enhanced Wettability Modification and CO2 Solubility Effect by Carbonated Low Salinity Water Injection in Carbonate Reservoirs

“…Many experimental techniques (interfacial tension measurement, contact angle measurement, NMR, -potential measurement, imbibition testing, and coreflooding testing) have suggested mechanisms 2 Journal of Chemistry responsible for wettability modifications, such as calcite dissolution [7,8], anhydrite dissolution [9], and surface charge change [10][11][12]. Although the underlying mechanism is still unclear, Yousef et al [13] confirmed the reduction of residual oil saturation through the single well tracer test in field trials.…”