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Oil/water/rock wettability: Influencing factors and implications for low salinity water flooding in carbonate reservoirs

Journal Article · · Fuel
 [1];  [1];  [2];  [3];  [2]
  1. Curtin Univ., Kensington, WA (Australia). Dept. of Petroleum Engineering; Southwest Petroleum Univ., Chengdu (China). State Key Lab. of Oil and Gas Reservoir Geology and Exploitation
  2. Curtin Univ., Kensington, WA (Australia). Dept. of Petroleum Engineering
  3. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Wettability of the oil/brine/rock system is an essential petro-physical parameter which governs subsurface multiphase flow behaviour and the distribution of fluids, thus directly affecting oil recovery. Recent studies [1–3] show that manipulation of injected brine composition can enhance oil recovery by shifting wettability from oil-wet to water-wet. However, what factor(s) control system wettability has not been completely elucidated due to incomplete understanding of the geochemical system. To isolate and identify the key factors at play we used in this paper SO42—free solutions to examine the effect of salinity (formation brine/FB, 10 times diluted formation brine/10 dFB, and 100 times diluted formation brine/100 dFB) on the contact angle of oil droplets at the surface of calcite. We then compared contact angle results with predictions of surface complexation by low salinity water using PHREEQC software. We demonstrate that the conventional dilution approach likely triggers an oil-wet system at low pH, which may explain why the low salinity water EOR-effect is not always observed by injecting low salinity water in carbonated reservoirs. pH plays a fundamental role in the surface chemistry of oil/brine interfaces, and wettability. Our contact angle results show that formation brine triggered a strong water-wet system (35°) at pH 2.55, yet 100 times diluted formation brine led to a strongly oil-wet system (contact angle = 175°) at pH 5.68. Surface complexation modelling correctly predicted the wettability trend with salinity; the bond product sum ([>CaOH2+][–COO-] + [>CO3-][–NH+] + [>CO3-][–COOCa+]) increased with decreasing salinity. Finally, at pH < 6 dilution likely makes the calcite surface oil-wet, particularly for crude oils with high base number. Yet, dilution probably causes water wetness at pH > 7 for crude oils with high acid number.
Research Organization:
Curtin Univ., Kensington, WA (Australia); Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Southwest Petroleum Univ., Chengdu (China)
Sponsoring Organization:
Southwest Petroleum Univ. (China); USDOE National Nuclear Security Administration (NNSA)
Grant/Contract Number:
NA0003525
OSTI ID:
1421633
Report Number(s):
SAND2017--13621J; PII: S0016236117312747
Journal Information:
Fuel, Journal Name: Fuel Vol. 215; ISSN 0016-2361
Publisher:
ElsevierCopyright Statement
Country of Publication:
United States
Language:
English

References (25)

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Low-salinity flooding in a selected carbonate reservoir: experimental approach journal March 2013
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Dolomite surface speciation and reactivity in aquatic systems journal October 1999
Influence of brine composition and fines migration on crude oil/brine/rock interactions and oil recovery journal December 1999
Thin liquid films in improved oil recovery from low-salinity brine journal April 2015
The low salinity effect at high temperatures journal July 2017
Contamination of silica surfaces: Impact on water–CO2–quartz and glass contact angle measurements journal March 2014
Altering wettability to recover more oil from tight formations journal September 2016
Low salinity injection into asphaltenic-carbonate oil reservoir, mechanistical study journal April 2016
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Critical review of low-salinity waterflooding journal August 2014
Ions tuning water flooding experiments and interpretation by thermodynamics of wettability journal December 2014
A comprehensive review of low salinity/engineered water injections and their applications in sandstone and carbonate rocks journal March 2016
Functional Wettability in Carbonate Reservoirs journal October 2016
Insights into the Mechanism of Wettability Alteration by Low-Salinity Flooding (LSF) in Carbonates journal March 2015
Electrostatics and the Low Salinity Effect in Sandstone Reservoirs journal January 2015
Smart Water as Wettability Modifier in Carbonate and Sandstone: A Discussion of Similarities/Differences in the Chemical Mechanisms journal September 2009
Zeta potential in oil-water-carbonate systems and its impact on oil recovery during controlled salinity water-flooding journal November 2016
Modeling Low-Salinity Waterflooding journal December 2008
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Potential of Low-Salinity Waterflood To Improve Oil Recovery in Carbonates: Demonstrating the Effect by Qualitative Coreflood journal March 2016
Electrokinetics of Carbonate/Brine Interface in Low-Salinity Waterflooding: Effect of Brine Salinity, Composition, Rock Type, and pH on ? -Potential and a Surface-Complexation Model journal June 2016
Mechanisms of Wetting Alteration by Crude Oils journal March 1998
Osmosis During Low Salinity Water Flooding conference April 2013

Cited By (4)

An overview of the oil-brine interfacial behavior and a new surface complexation model journal April 2019
Smart water flooding performance in carbonate reservoirs: an experimental approach for tertiary oil recovery journal April 2019
Effect of SO 4 −2 ion exchanges and initial water saturation on low salinity water flooding (LSWF) in the dolomite reservoir rocks journal May 2019
Response of Non-Polar Oil Component on Low Salinity Effect in Carbonate Reservoirs: Adhesion Force Measurement Using Atomic Force Microscopy journal December 2019

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