Secondary and Tertiary Recovery of Crude Oil from Outcrop and Reservoir Rocks by Low Salinity Waterflooding

Abstract

A wide range of outcrop sandstones and carbonates have been tested for waterflood response to one twentieth dilution of synthetic seawater, using a single crude oil that gave high response to low salinity flooding for a reservoir rock. The tested outcrop rocks included 17 sandstones and 6 carbonates. Gas permeabilities ranged from 1.49 to 7,187 mD and porosities from 10 to 39%. The average reduction in residual oil for tertiary response was only 1.5% OOIP with the highest being 5.8% OOIP; some rocks showed no response. After testing, three of the outcrop rocks that responded to injection of low salinity brine were restored by cleaning and re-aging with crude oil using procedures comparable to those commonly used in restoration of reservoir cores. When re-tested, the response to low salinity flooding was eliminated for two of the cores and significantly reduced for the third core. Companion plugs for 6 of the sandstones and 3 carbonates were tested for increased oil recovery using low salinity connate and injected brine; this data provided comparison with the measurements for high salinity connate and injection brine. Six of the plugs showed increase in recovery for the low salinity waterfloods, and three showed decrease. Results are also summarized for the effects of reduction in salinity for 11 sandstone cores taken from five reservoirs and 8 carbonate cores all taken from the same reservoir. Comparison between results for outcrop and reservoir cores, including literature data, indicates that overall response to low salinity flooding is significantly higher for the reservoir cores.

Effect of multi-component ions exchange on low salinity EOR: Coupled geochemical simulation study

“…However, there is a pressing need to develop cost-effective techniques to enhance oil recovery in the period of low oil prices. Engineering the injected water chemistry and using water wisely to enhance oil recovery is a novel and emerging research area, which is called low salinity water flooding [4][5][6][7], smart water flooding [8][9][10][11][12], designer water flooding [13][14][15][16], or ion tuning water flooding [17,18]. Many researchers found that low salinity water injection could achieve an incredible additional oil recovery in sandstone and carbonate reservoirs from both experiments and field tests [19,20].…”

Brine-Dependent Recovery Processes in Carbonate and Sandstone Petroleum Reservoirs: Review of Laboratory-Field Studies, Interfacial Mechanisms and Modeling Attempts

“…In addition, cores particles solely containing different clay types, such as kaolinite, illite, chlorite and montmorillonite, have been reported to show similar electrostatic behavior with quartz-dominated Berea sandstones [56,180]. In several other studies (like [33,38,116]), it was reported that sandstone reservoir rocks responded better to low saline brine than outcrop rocks, which demonstrated that different sources of sandstone show varying responses to brine-dependent recovery due to different pore geometries and grain structures [168].…”

“…The earliest comprehensive study undertaken by Morrow and colleagues [11][12][13][14]86,87] demonstrated the effect of oil-brine-rock interactions on improving oil recovery in a clay-rich rock formation and presented additional oil recovery from the brine-dependent process due to salinity gradient and wettability shift. Since then, numerous studies have been conducted with most tests showing positive results [13,21,[23][24][25][26][27][28][29][30][31][32][33][34], while no response was observed in other tests [28,[36][37][38][39][40].…”

“…Since these early studies, a significant volume of research studies at laboratory-scale and a few limited field-scale trials [20][21][22] have been conducted in both sandstone and carbonate rocks. Many of the published studies showed a positive response [11,13,21,[23][24][25][26][27][28][29][30][31][32][33][34], which translates into additional oil production, but a few others showed no benefit [28,[35][36][37][38][39][40]. Generally, an increase in oil recovery as high as 30% in laboratory experiments and a decrease in residual oil saturation ranging from 2-50% in field trials have been reported as compared to conventional water injection.…”

 Brine-Dependent Recovery Processes (Smart-Water/Low-Salinity-Water) in Carbonate and Sandstone Petroleum Reservoirs: Review of Laboratory-Field Studies, Interfacial Mechanisms and Modeling Attempts

“…Therefore, it is possible to observe improved water-wetness due to low saline brine injection on quartz grain, but presence of clays can either increase pore surface charge or provide a higher surface area and an anchor point for the oil compounds to further increase the effect of wettability changes. In addition, cores partcles solely containing different clay types, such as kaolinite, illite, chlorite and montmorillonite, has been reported to show similar electrostatic behavior with quartz-dominated Berea sandstones [124,125] In several other studies, it was reported that sandstone reservoir cores responded better to low saline brine than outcrop cores [43,60,126], which demonstrated that different sources of sandstone shows varying responses to brine-dependent recovery due to different pore geometry and grain structure [107]. Carbonate rocks On the other hand, carbonate rocks are primarily composed of calcite (CaCO3) and dolomite (CaMg(CO3)2), with variety of other minerals like anhydrite/gypsum (CaSO4), magnesite (MgCO3), Aragonite (CaCO3), apatite (phosphate source), quartz, siderite (FeCO3), evaporite, pyrite, etc.…”