Potential Evaluation of Ion Tuning Waterflooding for a Tight Oil Reservoir in Jiyuan OilField: Experiments and Reservoir Simulation Results

Abstract

Low salinity waterflood (LSF) is a promising improved oil recovery (IOR) technology. Although, it has been demonstrated that LSF is an efficient IOR method for many sandstone reservoirs, the potential of LSF in tight oil reservoir is not well-established. This paper presents a systematic evaluation of the potential of low salinity waterfloding for the tight reservoirs in Jiyuan Oilfield, China. This investigation pushes the application envelope of low salinity waterflooding towards the reservoir with low permeability (lower than 0.5mD), formation salinity of up to 45,180ppm, reservoir temperature of 70°C and in-situ oil viscosity of 0.6 cp.Our laboratory evaluation included zeta potential tests for interface of oil/brine and brine/rock, thermodynamic analysis through disjoining pressure calculation, corefloods using representative core samples.Thermodynamic analysis showed that decreasing divalent cations and salinity makes the electrical charges at both oil/brine and brine/rock interfaces become strongly negative, which enhanced the repulsive forces between oil and rock due to the double electric layer expansion. As a result, the rock turns more water-wet. Secondary corefloods were conducted with two different brines, which include shallow aquifer water and ion tuning water with consideration of field application. Coreflooding Experimental results were history matched to obtain the relative permeability curves. Results showed that compared to shallow aquifer water, low-salinity water exhibited a higher oil relative permeability and lower water relative permeability at the same water saturation and a lower residual oil saturation to water.Laboratory results were input into a reservoir simulator to investigate the potential of low-salinity water flood in Jiyuan oilfield. It showed that suitably formulated ion tuning water (ITW) has the potential to accelerate oil production and improve displacement efficiency, thus resulting in a higher recovery factor with only a fraction of pore volume of low-salinity water injected.To conclude, this paper demonstrates that ITWF has a good potential as an IOR/EOR technology in tight reservoirs, the key points are described as follows. Firstly, the mechanism of ITWF was interpreted by thermodynamics of wettability. Secondly, laboratory experiments have shown that ITWF could improve oil recovery by accelerating the oil production rate and decrease the residual oil production.Thirdly, the potential of ITWF in a tight oil reservoir in Jiyuan oilfield is investigated using a mechanistic model based on input data of laboratory experiments.

Extended DLVO-based estimates of surface force in low salinity water flooding

“…(5)), which in return impacts the double layer expansion, we examined the effect of concentration of monovalent cation (NaCl) and divalent cation (Mg 2+ , Ca 2+ ) on the disjoining pressure (Figs. [3][4][5]. Divalent cations however plays a more significant role in disjoining pressure than monovalent does at a certain concentration.…”

“…One such technique that has gained interest within industry is low salinity water flooding (LSW), involving injection of low salinity brine into the reservoir under secondary and tertiary conditions [2]. It has been shown that salinity level and water chemistry, through its effect on Crude Oil/Brine/Rock (COBR), can exhibit significant incremental oil recovery from lab-scale to reservoir scale, in both sandstone and carbonated reservoirs [3][4][5][6][7][8][9][10][11][12][13][14][15].…”

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].…”

“…Changing water flood salinity/chemistry can increase oil recovery from sandstone and carbonate reservoirs by 5-25%, though why this happens is unclear [13,17,[19][20][21][22][23][24][25][26][27][28][29]. Several mechanisms have been proposed to describe how the low salinity effect (LSE) increases oil recovery, including: (1) fines mobilisation [30], (2) limited release of mixed-wet particles [30], (3) increased pH and reduced interfacial tension (IFT) similar to alkaline flooding [31], (4) multi-component ion exchange (MIE), (5) expansion of the double layer, (6) salt-in effect [12], and (7) osmotic pressure [32].…”

“…Several oil companies, such as BP [34], Shell [35], Saudi Aramco [36], and PetroChina [17,18,21,37] have conducted numerous lab experiments, i.e., Log-Inject-Log, Single Well Chemical Tracer Test (SWCTT), and field scale trials. Their results have shown that, while in some cases LSWF has achieved an additional 5-25% oil recovery, in other cases, only minor incremental oil recovery was observed [38].…”