阴离子表面活性剂在含油和去油地层砂表面吸附的差异

Differences in Adsorption of Anionic Surfactant on Oily and Deoiled Reservoir sand

为了了解阴离子表面活性剂在砂岩油藏岩石表面吸附的真实情况 ,对比研究了十二烷基苯磺酸钠 (ABS)在含油和去油地层砂表面吸附的差异。地层砂取自胜利东辛油区辛 11 5 31断块油藏 ,水洗风干 ,含油 4.93% (称为油砂 ) ;此油砂经苯 /乙醇 (1∶ 1)抽提脱油后烘干 ,为去油地层砂 (净砂 )。吸附实验温度 6 0℃。ABS在净砂上吸附较快 ,约 10h吸附达到饱和 ,饱和吸附量为 45 .1μmol/g砂 ;在油砂上吸附较慢 ,吸附达到饱和至少需 2 8h ,饱和吸附量为 35 .6 μmol/L ,较净砂饱和吸附量约低 2 1%。ABS在油砂和净砂上的吸附等温线均呈S形 ,二者的差别是在高ABS浓度区油砂上的吸附量明显下降 ,而净砂上的吸附量大体不变。油砂和净砂上ABS的吸附量在加入电解质量 (NaCl,≤ 2 0 g/L)时大幅度增加 ,加入碱 (Na2 CO3 ,≤ 5 g/L)时略有减少。讨论了产生以上实验结果的原因。认为使用含油地层砂测定表面活性的吸附损耗更接近油藏地层实际情况 ;与不含油的净砂相比 ,表面活性剂在油砂上吸附较慢 ,吸附量较小 ,这有利于表面活性剂驱油作用的发挥 ;采用浓度适当高的表面活性剂段塞 。

To acquire realistic knowledge of surfactant adsorption on rock in sandstone reservoirs, the adsorption of sodium dodecyl benzyl sulfonate (ABS) on oily and oil-free reservoir sand is studied comparatively. The sand samples taken from Xing 11-531 fault block reservoir of Dongxing, Shengli, are water flushed and dried in open air to give oily sand of oil content 4.93%; the latter is extracted by benzene/ethanol mixture in ratio 1∶1 and oven dried to give clean, or deoiled, sand. The adsorption is conducted at 60℃. The adsorption of ABS proceeds faster and reaches its saturation value of 45.1 μmol/g of sand in ca. 10 hrs on clean sand samples and proceeds slower on oily sand samples and reaches its saturation value of 35.6 μmol/g of sand, a value by 21% lower than that on clean sand, in more than 28 hrs. The ABS adsorption isoterms on the sand samples are S-shaped with differences in that the adsorption amount at high equilibrium concentration section notably decreases on oily sand but maintains practically unchanged on clean sand. The electrolyte added (NaCl, ≤20 g/L) significantly enhances and the alkaline added (Na 2CO 3, ≤5 g/L) slightly reduces the adsorption of ABS on the sands. The experimental results are discussed and reasoned. It is ascertained that measurements of surfactant adsorption/consumption on oily reservoir sand samples are closer to the phenomena in reservoirs; surfactant adsorption on oily sand proceeds slower and in less extent than that on clean sand, a fact favorable to surfactant functioning in EOR operations; applying surfactant slug of higher and proper concentration appears to be more effective.