Carbonate Mineral Effect on Surface Charge Change During Low-Salinity Imbibition

F. Feldmann, E. Al-Shalabi, W. Alameri
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引用次数: 1

Abstract

Low-salinity waterflooding is a relatively simple and cheap improved oil recovery technique in which the reservoir salinity is optimized to increase oil recovery. Multivalent ion enriched as well as diluted brines have shown promising potential to increase oil production over conventional waterflooding. While the literature generally acknowledges that low-salinity improves oil recovery, the physical mechanisms behind low-salinity effects are still controversial. Surface charge change refers to a low-salinity mechanism in which modified brine is believed to cause a re-equilibrium of the carbonate surface potential. As a result of surface charge change, the rock wettability alters towards a more water-wetting state. This experimental study combines zeta potential, spontaneous imbibition, and contact angle measurements to highlight the effect of carbonate minerals on surface charge change. Initially, zeta potential measurements were conducted to compare the impact of five carbonate minerals (Indiana Limestone, Edward Limestone, Reservoir Limestone, Austin Chalk, and Silurian Dolomite) and brine compositions (Formation-water, Sea-water, and Diluted-sea-water) on carbonate surface charge. Moreover, the impact of potential determining ions (calcium, magnesium, and sulfate) on the mineral surface charge was investigated. The effect of carbonate minerals on spontaneous oil recovery was investigated by comparing the spontaneous imbibition of Formation-water, Sea-water, and Diluted-sea-water into the five carbonate minerals. Moreover, the wettability alteration during the spontaneous imbibition tests was quantified by conducting contact angle measurements. The brine-mineral zeta potential measurements were positive for Formation-water, slightly negative for Sea-water, and strongly negative for Diluted-sea-water. While calcium and magnesium ions promoted stronger positive electrical potentials, sulfate ions caused a zeta potential reduction. The magnitude of surface charge change was significantly different for the five tested carbonate minerals. Under the presence of Diluted-sea-water, the zeta potential measurements of Indiana Limestone and Austin Chalk resulted in strong negative electrical potentials. Reservoir Limestone and Edward Limestone showed less negative zeta potentials, while Silurian Dolomite and Diluted-sea-water resulted in slightly negative zeta potential results. Compared to Formation-water, Sea-water, and particularly Diluted-sea-water caused significant spontaneous oil recovery. The high spontaneous oil recovery of Diluted-sea-water and Indiana Limestone and Austin Chalk correlated with strong negative brine-mineral zeta potentials. Moderate spontaneous oil recovery was observed for the slightly negative zeta potential Sea-water and limestone/chalks systems. The contact angle measurements showed oil-wet contact angles under the presence of Formation-water, while the introduction of Sea-water and Diluted-sea-water promoted stronger water-wet contact angles. This work is one of the very few studies that investigates the effect of carbonate rock mineralogy on surface charge change and spontaneous oil recovery.
碳酸盐矿物对低盐渗吸过程中表面电荷变化的影响
低矿化度水驱是一种相对简单、廉价的提高采收率技术,通过优化油藏矿化度来提高采收率。与常规水驱相比,多价离子富集盐水和稀释盐水在提高石油产量方面表现出了良好的潜力。虽然文献普遍承认低矿化度可以提高采收率,但低矿化度效应背后的物理机制仍存在争议。表面电荷变化是指一种低盐度机制,在这种机制中,改性卤水被认为引起碳酸盐表面电位的再平衡。由于表面电荷的变化,岩石的润湿性向更亲水的状态转变。本实验研究结合zeta电位、自发渗吸和接触角测量来强调碳酸盐矿物对表面电荷变化的影响。首先,通过zeta电位测量来比较5种碳酸盐矿物(印第安纳石灰石、爱德华石灰石、储层石灰石、奥斯汀白垩石和志留系白云石)和盐水成分(地层水、海水和稀释海水)对碳酸盐表面电荷的影响。此外,还研究了电位决定离子(钙、镁和硫酸盐)对矿物表面电荷的影响。通过对比地层水、海水和稀释海水对5种碳酸盐矿物的自吸作用,探讨了碳酸盐矿物对自然采收率的影响。此外,通过测量接触角,量化了自吸过程中润湿性的变化。盐矿物zeta电位测定结果对地层水呈阳性,对海水呈轻微阴性,对稀释海水呈强烈阴性。钙和镁离子促进了更强的正电位,而硫酸盐离子则导致了zeta电位的降低。5种被测碳酸盐矿物的表面电荷变化幅度有显著差异。在稀释海水的存在下,印地安那石灰石和奥斯汀白垩的zeta电位测量结果显示出很强的负电位。储层灰岩和爱德华灰岩的zeta电位为负,志留系白云岩和稀释海水的zeta电位为负。与地层水相比,海水,特别是稀释后的海水具有显著的自发采收率。稀释海水、印第安纳石灰岩和奥斯汀白垩的高自发采收率与强的负盐矿物电位相关。在zeta电位略负的海水和灰岩/白垩体系中,观察到适度的自发采收率。接触角测量结果显示,地层水存在时,油湿接触角增大,而海水和稀释海水的引入使水湿接触角增大。本研究是目前为数不多的研究碳酸盐岩矿物学对地表电荷变化和自发采收率影响的研究之一。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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