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Summary Carbonate reservoirs tend to be oil-wet/mixed-wet and heterogeneous because of mineralogy and diagenesis. The objective of this study is to improve oil recovery in low-temperature dolomite reservoirs using low-salinity and surfactant-aided spontaneous imbibition. The low-salinity brine composition was optimized using ζ-potential measurements, contact-angle (CA) experiments, and a novel wettability-alteration measure. Significant wettability alteration was observed on dolomite rocks at a salinity of 2,500 ppm. We evaluated 37 surfactants by performing CA, interfacial-tension (IFT), and spontaneous-imbibition experiments. Three (quaternary ammonium) cationic and one (sulfonate) anionic surfactants showed significant wettability alteration and produced 43–63% of original oil in place (OOIP) by spontaneous imbibition. At a low temperature (35°C), oil recovery by low-salinity effect is small compared with that by wettability-altering surfactants. Coreflood tests were performed with a selected low-salinity cationic surfactant solution. A novel coreflood was proposed that modeled heterogeneity and dynamic imbibition into low-permeability regions. The results of the “heterogeneous” coreflood were consistent with that of spontaneous-imbibition tests. These experiments demonstrated that a combination of low-salinity brine and surfactants can make originally oil-wet dolomite rocks more water-wet and improve oil recovery from regions bypassed by waterflood at a low temperature of 35°C.
- Geology > Mineral > Silicate (1.00)
- Geology > Rock Type > Sedimentary Rock > Carbonate Rock > Dolomite (0.65)
- Energy > Oil & Gas > Upstream (1.00)
- Materials > Chemicals > Commodity Chemicals > Petrochemicals (0.47)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Carbonate reservoirs (1.00)
- Reservoir Description and Dynamics > Improved and Enhanced Recovery > Waterflooding (1.00)
- Reservoir Description and Dynamics > Improved and Enhanced Recovery > Chemical flooding methods (1.00)
- Reservoir Description and Dynamics > Formation Evaluation & Management (1.00)
A Comparative Enhanced Oil Recovery Study Between Low-Salinity Water and Hybrid Surfactant Process for a Carbonate Reservoir
Belhaj, Ahmed Fatih (University of Calgary) | Fakir, Shasanowar Hussain (University of Calgary) | Singh, Navpreet (University of Calgary) | Sarma, Hemanta Kumar (University of Calgary)
Abstract Over the years, water-based enhanced oil recovery (EOR) techniques have continuously been of interest for their superior technical and economic feasibility. Low-salinity water (LSW) flooding is an attractive EOR method that can operate at a lower cost while significantly improving the performance of the conventional waterflooding process. Despite its widely acclaimed efficiency, one of the limitations of LSW flooding is its inability to significantly alter the fluid–fluid properties in the reservoir. The hybrid application of low-salinity water with surfactant (LSS) is a novel hybrid EOR approach with great efficiency in lowering oil-water interfacial tension (IFT) and altering the rock surface wettability. In this study, an extensive comparative analysis is held between LSW and LSS on a carbonate rock to evaluate the extent of the improvement achieved via the addition of the surfactant to the low-salinity water system. The experimental analysis between LSW and LSS is compiled based on the evaluation of fluid-fluid and rock-fluid interactions. The fluid-fluid interactions were assessed using interfacial tension (IFT) tests. The IFT between LSW and LSS solutions and crude oil was measured using the spinning drop tensiometer. The rock-fluid interactions were examined using zeta potential experiments, reservoir-condition HPHT coreflooding experiments in composite cores, and contact angle measurements in a unique and specifically-designed HPHT imbibition cell. The results of IFT tests showed more effective oil-water interactions of the LSW when the surfactant was added to 1%diluted-seawater (1%dSW). IFT measurements of LSS solutions displayed significantly lower values which were substantially lower than LSW solution. The zeta potential experiments using the streaming potential method showed a clear trend of yielding more negative values for LSS solutions versus LSW at 1%dSW. The contact angle measurements confirmed a 17° difference for LSS when compared to LSW. These outcomes demonstrated a favorable wettability alteration of the carbonate rock from oil-wet to intermediate-wet with the addition of a low concentration of the surfactant. Coreflooding data proved conclusively that the addition of 0.2wt% of the surfactant to the LSW flooding yielded an additional 9.11% of oil recovery. The comprehensive experimental work followed in this study including contact angle and coreflooding data under HPHT conditions and zeta potentiometric studies on surface charges using whole brine-saturated cores make the findings more representative of field conditions. This paper is aimed to improve the understanding of the ability of a surfactant to improve the fluid-fluid interactions and alter the rock-fluid properties when added to LSW flooding.
- Asia > Middle East (0.46)
- North America > Canada (0.28)
- North America > United States (0.28)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock (0.69)
- Geology > Rock Type > Sedimentary Rock > Carbonate Rock (0.56)
Abstract Over the years, laboratory studies and a limited number of field trials have demonstrated the potential of enhancing oil recovery using controlled-salinity water flooding. The injected brine composition is one of the promising techniques that could alter the wettability of carbonate rocks by changing the concentration of the potential determining ions (PDIs), specifically Ca, Mg, and SO4 ions. In this study, a comprehensive experimental study was conducted to investigate the rock-fluid and fluid-fluid interactions at rock-water and oil-water interfaces. The first step of the study was to measure the interfacial tension (IFT) using the spinning-drop tensiometer and study the dynamic behavior of the oil-water interactions. The zeta potential of carbonate rock samples was then measured using a specially-designed zeta potentiometer capable of utilizing the whole core plug, rather than the pulverized samples. The streaming potential technique was used for the zeta potential measurements and the experiments were conducted under different modified brine composition and rock saturation conditions. Subsequently, wettability alteration experiments were conducted using a specially designed high-pressure high-temperature (HP/HT) cell. The IFT measurements showed an increasing trend as salinity decreases, clarifying that rock-water interactions are more dominant over oil-water interactions. Results of the zeta potential experiments showed a clear trend of yielding more negative values as the seawater gradually diluted down to 1%dSW, due to the expansion of the electrical double layer. On the other hand, when the brine composition was modified, the increase of the PDIs (Ca and Mg) did not have as much impact on zeta potential as the SO4 ions. In the wettability alteration experiments, both diluted and composition-modified brine generated a higher imbibition rate, resulting in a higher total oil production when compared with the experiments using the seawater. Furthermore, the wettability alteration of the rock surface trended more towards water-wetness conditions, as inferred from the contact angle measurements. The measurement of zeta potential before and after wettability alteration tests showed that the zeta potential value became less negative after the experiment, which suggested the expulsion of oil from the rock. This was further verified by the measurements of zeta potential for the unsaturated rock and saturated rock with brine and oil. The findings from this study would provide a better understanding of the rock-fluid and fluid-fluid interactions during controlled-salinity water flooding, which will benefit future studies in this area.
- Asia > Middle East (0.69)
- North America > United States (0.68)
- Geology > Rock Type > Sedimentary Rock > Carbonate Rock (0.69)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock (0.68)
Abstract In recent years, interest in water-based EOR methods and the combination of modified seawater with chemicals has grown due to their economic improvement of oil production. The hybrid application of low salinity water with surfactants (LSS) flooding has a promising potential to significantly increase the oil recovery. LSS flooding, a novel hybrid EOR approach, has recently proven its capability of altering rock surface wettability and reducing oil-water IFT. In this study, we present a comprehensive assessment of the fundamentals and recent developments of LSS flooding, as well as lessons learned from previous studies and the key uncertainties associated with successful implementation. The study begins with an overview of surfactant flooding, low salinity water (LSW) flooding and the hybrid application of LSW flooding processes. The LSS flooding process in different reservoir types and the recovery mechanisms associated is then discussed. The recent laboratory studies for LSS flooding and the surfactant losses associated in porous media are also reviewed. Recent studies of LSS flooding have concluded the advantages of higher oil recovery, higher surfactant stability, lower surfactant retention, and lower chemical consumption compared to conventional surfactant flooding. Most of the LSS flooding application has been performed on sandstones with remarkable outcomes, meanwhile, it’s application in carbonates has garnered attention in recent years and some promising findings were reported. The efforts of this work can provide further understanding of the LSS flooding process and its underlying mechanisms, especially in carbonates which are not fully covered in the literature. Finally, this paper gives more insight into the potential success of LSS flooding over surfactant and LSW flooding processes.
- Europe (1.00)
- South America (0.93)
- North America > United States > California (0.46)
- (2 more...)
- Geology > Geological Subdiscipline (0.93)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Sandstone (0.50)
Coreflood Tests to Evaluate Enhanced Oil Recovery Potential of Wettability-Altering Surfactants for Oil-Wet Heterogeneous Carbonate Reservoirs
Shi, Yue (The University of Texas at Austin) | Mohanty, Kishore (The University of Texas at Austin (Corresponding author)) | Panda, Manmath (Kinder Morgan Inc)
Summary Oil-wetness and heterogeneity are two main factors that result in low oil recovery (OR) by waterflood in carbonate reservoirs. The injected water is likely to flow through high-permeability regions and bypass the oil in the low-permeability matrix. In this study, systematic coreflood tests were carried out in both "homogeneous" cores and "heterogeneous" cores with a wettability-altering surfactant. The homogeneous coreflood tests were conducted to evaluate surfactant retention, as well as to compare tertiary surfactant flooding with secondary surfactant flooding. The heterogeneous coreflood test was proposed to model bypassing in low-permeability matrix during waterfloods, and dynamic imbibition of surfactant into the low-permeability matrix. Surfactant retention results suggest that retention increases as initial oil saturation decreases. The retention of selected surfactant in the target reservoir cores was measured to be within a range of 0.07-0.12 The results of homogeneous coreflood tests showed that both secondary waterflood and secondary surfactant flood can achieve high OR ( 50%) from relatively homogeneous oil-wet cores. A shut-in phase after the surfactant injection resulted in a surge in oil production, which suggests that enough time should be given for wettability alteration by surfactants. The results of heterogeneous coreflood tests showed that more oil is bypassed in the tighter matrix by waterflood if the permeability is higher in the flooded layer and this bypassed oil is the target for the wettability-altering surfactant floods. Slow wettability-altering surfactant injection leads to imbibition into bypassed regions. When the oil-wet carbonate reservoirs have large unswept regions after waterflood, wettability-altering surfactants can significantly improve OR if enough time is given for imbibition. Introduction Carbonate reservoirs tend to be oil-wet/mixed-wet due to positively charged rock surface and negatively charged acidic and/or asphaltic components from crude oil.
- North America > United States > Texas (1.00)
- Asia > Middle East (0.93)
- Geology > Rock Type > Sedimentary Rock > Carbonate Rock (0.47)
- Geology > Mineral > Silicate > Phyllosilicate (0.46)
- North America > United States > Texas > Permian Basin > Central Basin > Seminole Field > Word Group > San Andres Formation (0.99)
- North America > United States > Texas > Permian Basin > Central Basin > Seminole Field > Wolfcamp Reef Formation > San Andres Formation (0.99)
- North America > United States > Texas > Permian Basin > Central Basin > Seminole Field > Wolfcamp Lime Formation > San Andres Formation (0.99)
- (2 more...)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Carbonate reservoirs (1.00)
- Reservoir Description and Dynamics > Reservoir Fluid Dynamics > Flow in porous media (1.00)
- Reservoir Description and Dynamics > Improved and Enhanced Recovery > Waterflooding (1.00)
- Reservoir Description and Dynamics > Improved and Enhanced Recovery > Chemical flooding methods (1.00)