Naturally fractured carbonate reservoirs have very low oil recovery efficiency owing to their wettability and tightness of matrix. However, smart water can enhance oil recovery by changing the wettability of the carbonate rock surface from oil-wet to water-wet, and the addition of surfactants can also change surface wettability. In the present study, the effects of a solution of modified seawater with some surfactants, namely C₁₂TAB, SDS, and TritonX-100 (TX-100), on the wettability of carbonate rock were investigated through contact angle measurements. Oil recovery was studied using spontaneous imbibition tests at 25, 70, and 90 °C, followed by thermal gravity analysis to measure the amount of adsorbed material on the carbonate surface. The results indicated that Ca²⁺, Mg²⁺, and SO₄²⁻ ions may alter the carbonate rock wettability from oil-wet to water-wet, with further water wettability obtained at higher concentrations of the ions in modified seawater. Removal of NaCl from the imbibing fluid resulted in a reduced contact angle and significantly enhanced oil recovery. Low oil recoveries were obtained with modified seawater at 25 and 70 °C, but once the temperature was increased to 90 °C, the oil recovery in the spontaneous imbibition experiment increased dramatically. Application of smart water with C₁₂TAB surfactant at 0.1 wt% changed the contact angle from 161° to 52° and enhanced oil recovery to 72%, while the presence of the anionic surfactant SDS at 0.1 wt% in the smart water increased oil recovery to 64.5%. The TGA analysis results indicated that the adsorbed materials on the carbonate surface were minimal for the solution containing seawater with C₁₂TAB at 0.1 wt% (SW + CTAB (0.1 wt%)). Based on the experimental results, a mechanism was proposed for wettability alteration of carbonate rocks using smart water with SDS and C₁₂TAB surfactants.

中文翻译：

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通过将自来水和表面活性剂自吸成碳酸盐来改变润湿性和采油

天然裂缝性碳酸盐岩储层由于其润湿性和基体致密性而具有非常低的采油效率。但是，智能水可以通过将碳酸盐岩表面的润湿性从油润湿性变为水润湿性来提高采油率，并且添加表面活性剂也可以改变表面润湿性。在本研究中，通过接触角测量研究了改性海水与一些表面活性剂（即C ₁₂ TAB，SDS和TritonX-100（TX-100））的溶液对碳酸盐岩润湿性的影响。使用自吸实验在25、70和90°C下研究油的采收率，然后进行热重力分析以测量碳酸盐表面上吸附物质的量。结果表明，Ca 2 ⁺，Mg²⁺和SO ₄ ^2-离子可能会将碳酸盐岩的润湿性从油润湿变为水润湿，并且在改性海水中离子浓度更高时，还会获得进一步的水润湿性。从吸收液中除去NaCl可以减小接触角并显着提高采油率。在25和70°C的条件下，用改良海水可获得较低的采油率，但是一旦温度升至90°C，自发吸水实验中的采油率就会急剧增加。C ₁₂智能水的应用0.1 wt％的TAB表面活性剂将接触角从161°更改为52°，并将采油率提高到72％，而智能水中存在0.1 wt％的阴离子表面活性剂SDS则将采油率提高到64.5％。TGA分析结果表明，对于含海水的溶液，其碳酸盐表面的吸附材料最少，其中C ₁₂ TAB含量为0.1 wt％（SW + CTAB（0.1 wt％））。根据实验结果，提出了使用智能水，SDS和C ₁₂ TAB表面活性剂改变碳酸盐岩润湿性的机理。