Laboratory Investigation of Novel Oil Recovery Method for Carbonate Reservoirs

Yousef, Ali; Al-Saleh, Salah; Al-Kaabi, Abdulaziz; Al-Jawfi, Mohammed Saleh

doi:10.2118/137634-ms

Cited by 218 publications

(187 citation statements)

References 33 publications

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“…5. It must be emphasized that the mechanism for improved oil recovery by removing NaCl from SW is different from the low salinity (LS) EOR effect observed by Yousef et al (2010) by diluting SW. For observing LS EOR effects in limestone, the formation must contain dissolvable anhydrite, CaSO 4 (s) . In that case, the catalyst, SO 4 2− , for the wettability alteration process is stored as a mineral in the formation, and when the LS fluid with low content of NaCl is flooded into the formation, the LS brine will be enriched in Ca 2 þ and SO 4 2− due to dissolution of anhydrite.…”

Section: Oilmentioning

confidence: 95%

Modified seawater as a smart EOR fluid in chalk

Puntervold

Strand

Ellouz

et al. 2015

Journal of Petroleum Science and Engineering

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Section: Oilmentioning

confidence: 95%

Modified seawater as a smart EOR fluid in chalk

Puntervold

Strand

Ellouz

et al. 2015

Journal of Petroleum Science and Engineering

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“…Flooding with d 10 GSW improved the oil recovery by 3% of OOIP after flooding first with GSW. Yousef et al 10 observed the greatest kick in oil recovery when using 20 times diluted seawater.…”

Section: Energy and Fuelsmentioning

confidence: 99%

“…Recently, Yousef et al 10 showed that improved oil recovery was achieved when successively flooding composite reservoir carbonate cores with 2, 10, and 20 times diluted seawater. The oil recovery in each step increased by an additional 7, 9, and 1.5% of OOIP, respectively, after first flooding the core with ordinary seawater.…”

Section: ■ Introductionmentioning

confidence: 99%

“…The objective of this work is to discuss/confirm a chemical mechanism for low salinity EOR effects in carbonates, by using preserved core material containing dissolvable anhydrite from a similar reservoir formation as used in the study by Yousef et al, 10 with a special focus on the relationship between the concentration of SO 4 2− and NaCl present in the low saline brine.…”

Section: ■ Introductionmentioning

confidence: 99%

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Low Salinity EOR Effects in Limestone Reservoir Cores Containing Anhydrite: A Discussion of the Chemical Mechanism

et al. 2015

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It is well accepted that seawater injection is able to improve the water wetness of carbonate reservoirs at high temperatures, and in that way, it can act as an enhanced oil recovery (EOR) fluid. A recent laboratory investigation showed that increased oil recovery also was obtained from carbonate reservoir cores by successively flooding composite limestone cores by 2, 10, and 20 times diluted seawater. The study confirmed that it is possible to obtain low salinity EOR effects also in carbonates, and not only in sandstones. In the present study, preserved reservoir core material from a similar limestone formation was used with the objective to obtain a chemical understanding of the mechanism for the improved oil recovery. It was verified, that the core material contained significant amounts of anhydrite (CaSO 4 ), which appeared to be the key factor for observing the low salinity EOR effect. The concentration of sulfate in the injection brine increased due to increased dissolution of anhydrite as the salinity and concentration of inactive salt, NaCl, decreased. Both an increase in the sulfate concentration and a decrease in NaCl content in the injected brine will have a positive effect on the wettability alteration process. An oil displacement test was conducted on a restored reservoir core at 100°C using 100 times diluted formation water in a tertiary flooding process, after first injecting formation water. This showed a low salinity EOR effect of 22% of original oil in place (OOIP), corresponding to an 88% increase in oil recovery. Also 30 times diluted seawater increased the oil recovery by 18% of OOIP in a tertiary flood after first flooding the core with formation water. After flooding a core successively at 100°C with formation water, seawater, and 10 times diluted seawater, the oil recovery increased gradually by 25, 30, and 33% of OOIP. The chemical low salinity EOR mechanism was discussed in terms of dissolution of anhydrite and a decrease in the NaCl concentration. This wettability alteration mechanism is, in principle, the same as that reported previously for injection of seawater and modified seawater into chalk cores, involving a symbiotic interaction between Ca 2+ , Mg 2+ , and SO 4 2− at the rock surface. In this case, supply of extra Ca 2+ and SO 4 2− was obtained by dissolution of anhydrite. The low salinity EOR technique can have a great economic potential regarding oil recovery from high temperature carbonate reservoirs containing significant amounts of dissolvable anhydrite distributed in the pore space.

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“…These new waterflooding strategies are economical and environment-friendly, and thus have attracted increasing interests from oil industry. The change of flooding efficiency by modifiedbrine is usually attributed to the dependence of wettability on brine ionic composition, 2,3,[12][13][14][15] which is denoted as ion-tuned wettability in this paper.…”

Section: Introductionmentioning

confidence: 99%

Molecular dynamics for ion-tuned wettability in oil/brine/rock systems

Tian

Wang

2017

AIP Advances

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The dependence of wettability on brine ionic composition in oil/brine/rock systems, which is denoted as ion-tuned wettability, has important applications in geoscience. Due to the involvement of non-continuum effects, molecular dynamics (MD) simulation is necessary to improve understanding of its mechanism. This work establishes a reliable molecular dynamics (MD) framework to study ion-tuned wettability. We prove that our model system can well represent the wettability of the real oil/brine/rock system, and that the wettability alteration from the MD results is qualitatively consistent with the EDL repulsion theory when ion-binding does not exist. In the process to establish the MD framework, our work suggests that adding counter ions to balance interface charges is good for studying concentration effect on wettability, and the contact angle defined from mass center coordinates is effective to measure the wettability of the nano-scale MD system. This work provides the basis for on-going studies using MD simulation to reveal the mechanism of ion-tuned wettability.

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Laboratory Investigation of Novel Oil Recovery Method for Carbonate Reservoirs

Cited by 218 publications

References 33 publications

Modified seawater as a smart EOR fluid in chalk

Modified seawater as a smart EOR fluid in chalk

Low Salinity EOR Effects in Limestone Reservoir Cores Containing Anhydrite: A Discussion of the Chemical Mechanism

Molecular dynamics for ion-tuned wettability in oil/brine/rock systems

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