ABSTRACT

Polar compounds in oil, especially asphaltene and resin, have important implications on the oil recovery from carbonate reservoirs; yet their isolated effects, independent of other oil properties, are not well understood. Thus, two different crude oils with similar densities and resin contents, but with dissimilar asphaltene contents, were selected to better understand asphaltene’s effect on: wettability alternations upon water injection, IFT changes, and areal sweep efficiency. It was found that crude oil with greater amount of asphaltene hinders the wettability alteration by undiluted and diluted seawaters, due to sustained hydrophobicity caused by polar compounds adsorbing onto the rock surface. Conversely, crude oil with lower amount of asphaltene, combined with low salinity waters, resulted in pronounced wettability alteration. Based on image analysis of the surface of carbonate rocks, higher areal sweep efficiencies were obtained for non-asphaltenic crude oil (around 35%, versus 6% to 30% for asphaltenic crude oil), using seawaters diluted ten-and fifty-fold, corresponding to the lowest contact angle values measured (36° and 22°, respectively). Asphaltene is thus deemed to play a key role in the wettability alteration of carbonate rocks, consequently affecting the performance of enhanced oil recovery during low salinity water injection.

摘要

石油中的极性化合物，尤其是沥青质和树脂，对从碳酸盐岩储层中采油具有重要意义。然而，它们与其他油特性无关的隔离效果尚未得到很好的理解。因此，选择了两种密度和树脂含量相似但沥青质含量不同的不同原油，以更好地理解沥青质对以下方面的影响：注水时的润湿性变化，IFT变化和面扫效率。已经发现，由于极性化合物吸附在岩石表面上而产生了持续的疏水性，因此含有大量沥青质的原油会阻碍未稀释和稀释的海水对润湿性的改变。相反，具有较低沥青质含量的原油，再加上低盐度水，会导致明显的润湿性变化。根据碳酸盐岩石表面的图像分析，使用稀释了十倍至五十倍的海水，非沥青质原油的面扫描效率更高（约为35％，沥青质原油为6％至30％），对应于测得的最低接触角值（分别为36°和22°）。因此，沥青质被认为在碳酸盐岩的润湿性改变中起关键作用，因此影响了低盐度注水过程中提高采收率的性能。