Rashid S. Al-Maamari

Laboratory investigation of low salinity waterflooding for carbonate reservoirs

Low salinity water flooding (LSW) research has been gaining more momentum in recent years for both sandstone and carbonate reservoirs. Published laboratory data and field tests have shown an increase in oil recovery by changing injected brine salinity, especially for sandstone reservoirs. It is widely accepted that low salinity water alters the wet ability of the reservoir rock from less to more water-wet conditions, oil is then released from rock surfaces and recovery is increased. The main objectives of the current study are to: test the potential of increasing oil recovery by LSW of a carbonate reservoir and to investigate the factors that control it. The impact of LSW on oil recovery was investigated by conducting core flood and spontaneous imbibitions experiments at 70 oC using Lekhwair limestone core samples, crude oil and synthetic brine (194,450 ppm) which was mixed with distilled water in four proportions twice, 5 times, 10 times and 100 times dilution brines. Moreover, both crude oil/brine interfacial tension measurements (IFT) and ionic exchange experiments were carried out at room temperature (25 oC). The results of the study show higher oil recovery as a result of reducing injected water salinity in both core flood and spontaneous imbibitions experiments. Core flood experiments showed an increase in oil recovery by 3 to 5 % of OOIP, while spontaneous imbibitions experiments showed an increased by 16 to 21 %. Additionally, spontaneous imbibitions experiments provide direct evidence of wet ability change by the LSW. The study also shows that the increase in oil recovery was obtained at much higher water salinity than the one observed in the case of sandstone rock. However, no relation was found between oil/brine IFT and ionic exchange analysis and the observed response of LSW in core flood experiments.

The application of air-sparging, soil vapor extraction and pump and treat for remediation of a diesel-contaminated fractured formation

Abstract The present study addresses the efficiency of an integrated air sparging, soil vapor extraction, and pump and treat system in the remediation of a diesel contaminated site in Oman. Cleanup efforts have targeted groundwater and soil in fractured formations. Site hydrogeological characterization was conducted including sampling and analysis of water and soil. Within seven months of the start of the treatment system, benzene gas in the unsaturated zone fell from an initial range of 15–60 ppm to below detection level, while total petroleum hydrocarbon in the groundwater dropped from 25–50 ppm to less than 0.5 ppm. Treatment processes have ceased while groundwater and soil are being monitored. Thus far, benzene gas has been undetected for the past 18 months, but total petroleum hydrocarbon in groundwater has rebounded to 1.2 ppm during the last four months.

Polymer flood produced water treatment trials

Summary Polymer-enhanced-oil-recovery (EOR) operation has been implemented for the production of oil from difficult mature oil fields in Oman. The polymer used to sweep oil toward production wells in this EOR technique is resulting in the generation of polymer-flood produced water (PFPW) of increasing viscosity. Current methods of treating oilfield produced water must be reconsidered for the effective treatment of PFPW of such changing quality. In a previous study, the use of polyaluminum chloride (PAC) was proposed for the coagulation of oil in produced water to be separated by flotation and filtration. As such, laboratory tests were conducted to evaluate the applicability of PAC and other chemicals for treatment of PFPW with higher viscosity than ordinary oilfield-produced water. These tests indicated clearly that aluminum sulfate (AS) was more effective for treatment of such higherviscosity water. A pilot plant developed during the earlier study was used to conduct coagulation/flocculation-, flotation-, filtration-, and adsorption-treatment trials for PFPW from an oil field at which polymer EOR was under way. For the final trial, the inlet PFPW viscosity was 1.4 cp at 40°C and oil concentration was greater than 200 mg/L. AS was applied for the coagulation/flocculation and flotation stages, and was found to be effective in reducing oil concentration to 1 mg/L. Filtration and adsorption stages resulted in further improvement of water quality. Most of the polymer used for EOR was believed to have been removed along with oil and suspended solids.

Flotation, Filtration, and Adsorption Pilot Trials for Oilfield Produced Water Treatment

Summary As an oil field matures, it produces larger quantities of produced water. Appropriate treatment levels and technologies depend on a number of factors, such as disposal methods or usage aims, environmental impacts, and economics. In this study, a pilot plant with a capacity of 50 m3/d was used to conduct flotation, filtration, and adsorption trials for producedwater treatment at a crude-oil gathering facility. The flexible design of the plant allows for the testing of different combinations of these processes on the basis of the requirements of the water to be treated. The subject water during this study was a complex and changing mixture of brine and oil from different oil fields. Induced-gas-flotation (IGF) trials were conducted, with different coagulant [polyaluminum chloride (PAC)] -addition rates from 0 to 820 mg⋅L–1. Inlet-dispersed oil-in-water (OIW) concentrations were quite varied during the trials, ranging from 39 to 279 mg⋅L–1 (fluorescence-analysis method). Turbidity also varied, ranging from 85 to 279 FTU. Through coagulation/flocculation and flotation, dispersed oils were removed from the water. PAC addition ranging from 60 to 185 mg⋅L–1 resulted in the reduction of the dispersed-oil concentration to less than 50 mg⋅L–1 in treated water; and PAC addition ranging from 101 to 200 mg⋅L–1 resulted in the reduction of the dispersed-oil concentration to less than 15 mg⋅L–1 in treated water. Turbidity was also reduced through flotation, with trial average reductions ranging from 57 to 78%. Filtration further reduced turbidity at rates greater than 80% through the removal of any suspended solids remaining from flotation. Activated-carbon adsorption reduced OIW concentrations of flotation-/filtrationtreated water to 5 mg⋅L–1 (infrared-analysis method) through the removal of dissolved oil remaining in the water. Results confirmed that such adsorption treatment would be more practical for water with lower chemical-oxygen-demand (COD) concentration because high-COD concentrations in water reduce the lifetime of activated carbon dramatically.