Features of study complex carbonate reservoir rocks` wetting using laboratory methods

Surface properties of rocks are the important parameter and have a great influence on the process of oil displacement by water. In real systems the wettability can range from highly hydrophilic to strongly hydrophobic depending on interaction between mineralized water and oil with rock surfaces. If the preferential wettability of any of two liquids is not observed in the rock, then the system has a neutral wetting. Some components of oil can wet the selected areas of porous surface around the reservoir. Under election wettability a spotted heterogeneous wettability of rock surface is understood. Wetting characteristic is a necessary criterion for evaluating the reservoir. There are qualitative and quantitative methods for estimating the wettability, which are divided into direct and indirect. Paper presents results of the study the surface properties of carbonate deposits, characterized by a complex structure of the hollow space and the complex composition of the mineral skeleton. Determination of wettability was carried out by two methods: according to industrial standard and Amott method. Characteristics of the rocks surface properties of different lithological types were established. To study the influence of extraction on the surface properties the wettability index was measured twice: in samples with natural oil saturation and in extracted samples. The regularities of changes in the surface properties along the well section of carbonate deposits were determined, a comparison of the wettability index and reservoir rock properties, as well as the residual water was performed by capillary pressure method. The descriptiveness analysis of various methods for determining the wettability was conducted and difference causes in the results of research were determind by methods of industrial standard and Amott. The presence of deposits, characterized by selective wetting was found.