Ali A. Yousef

New Insights on the Role of Multivalent Ions in Water-Carbonate Rock Interactions

in the oil industry today. Almost all the conventional reservoirs go through a waterflood cycle to recover a portion of the remaining oil after pressure depletion. A considerable amount of oil still remains trapped underground, however, even after secondary waterfloods. This is attributed to inefficient macroscopic sweep and the microscopic capillary trapping caused by interfacial and surface forces that retain the oil within the pores. Currently, the oil industry is showing great interest in improved enhanced oil recovery (EOR) technologies to either maximize the ultimate oil recovery by waterflooding or recover additional oil from the residual oil left behind after waterflooding. The chemical properties of the injected water initially were not considered in the design of a waterflooding project except for the purpose of preventing formation damage triggered by an incompatibility between injected and formation waters. In recent years, extensive research into both sandstone and carbonate reservoirs has shown that tuning the salinity and ionic composition of the injected water can favorably affect oil/brine/rock interactions, alter rock wettability, enhance microscopic displacement efficiency and eventually improve waterflood oil recovery. As reported in other work, we refer to brine with a designed composition as “SmartWater” and to the waterflooding process governed by increased oil recovery as “SmartWater Flooding.” Unlike conventional EOR, SmartWater Flooding can be implemented at any time during the life cycle of a reservoir, and with minimal investment in current operations it can potentially provide higher

A Comprehensive Experimental Study of Pore-Scale and Core-Scale Processes During Carbonated Water Injection Under Reservoir Conditions

Enriching the injection water with CO2 has demonstrated promising results as a method for improving oil recoveries and securely storing CO2 in oil reservoirs. However, the mutual interactions taking place between carbonated water and reservoir oil at elevated reservoir conditions are not fully understood. Here we present the results of a thorough investigation of the processes leading to additional oil recovery through integrating pore-scale visualisations and coreflood experiments. Four pore-scale visualization (micromodel) experiments were performed at reservoir conditions using the recombined live oil under different injection scenarios (tertiary and secondary). Having identified the underlying dynamic interactions at pore-scales, the performance of different injection scenarios for carbonated water injection (CWI) was investigated using carbonate reservoir rocks. Five coreflood experiments were carried out using both fully and half-saturated carbonated water to sensitise the impact of CO2 content of injection water on the performance of CWI. In-situ liberation of gaseous phase was identified (from direct visualisations) as the predominant mechanism controlling the performance of carbonated water injection. The gas phase formation would bring about higher degrees of oil swelling, and it would also create a three phase flow regime which leads to further reduction of residual oil saturation. The observations confirm that the performance of CWI should be investigated under reservoir conditions using multi-components live oil and reservoir cores. Any simplification, e.g. one components make-up gas or reduced pressure/temperature, of the reservoir conditions would misleadingly change the pore-scale event and hence, the performance of CWI. From the core displacement tests, it was observed that secondary CWI could recover a significant amount of additional oil, which was 26% compared to plain seawater injection. The tertiary carbonated water would effectively mobilise 15.3% of the residual oil (after seawater injection). When CO2 content of injected CW (carbonated water) was halved, the oil recovery dropped by 1/3. The results revealed that the oil recovery would be lower if CO2 concentration is reduced but the extent of oil recovery reduction would be much less than the level of reduction in CO2 concentration. The unique and integrated research approach employed here enables us to produce a more complete and reliable set of findings and understandings at realistic reservoir conditions. During CWI under reservoir conditions, an “in-situ WAG-type” three-phase flow would be generated with more effective sweep efficiency and pore-scale advantages.

A Critical Review of Alternative Desalination Technologies for Smart Waterflooding

The results of this review study show that there is no commercial technology yet available to selectively remove specific ions from seawater in one step and optimally meet the desired water-chemistry requirements of smart waterflooding. As a result, different conceptual process configurations involving selected combinations of chemical precipitation, conventional/emerging desalination, and produced-water-treatment technologies are proposed. These configurations represent both approximate and improved solutions to incorporate specific key ions into the smart water selectively, besides presenting the key opportunities to treat produced-water/ membrane reject water and provide ZLD capabilities in smartwaterflooding applications. The developed configurations can provide an attractive solution to capitalize on existing huge producedwater resources available in carbonate reservoirs to generate smart water and minimize wastewater disposal during fieldwide implementation of smart waterflood.

Interfacial Rheology at the Crude Oil/brine Interface - A Microscopic Insight of SmartWater Flood

Summary SmartWater flooding (SWF) has been proven as an effective and successful recovery method for carbonates, in which the injected water alters the carbonate rock wettability to produce incremental oil. Core-scale displacement experiments have demonstrated significant incremental recoveries of SmartWater in both secondary and tertiary modes and single-well chemical tracer tests have demonstrated this potential in the field at a larger scale. Still, the underlying mechanisms responsible for SmartWater wettability alteration of carbonates are not well understood. In this study, we are investigating the effect of salinity and ionic composition on a crude oil monolayer using Langmuir trough technique. Solely ions brines were used (CaCl2, MgCl2, Na2SO4, NaCl) in addition to seawater dilutions. Results confirmed the sensitivity of the interfacial monolayer to brine composition: a salinity decrease increases interfacial compressibility while sulfate and magnesium ions have shown interfaces with higher compressibility compared to sodium and calcium ions. The ultimate goal of this study is to enhance our understanding of carbonate wettability alteration by integrating interfacial rheological properties and its dependency on various parameters. These efforts will ultimately lead to additional oil recovery trough optimization of the fluid/fluid interactions involved in oil/brine/rock systems during SmartWater flooding.