Experimental Study of Residual Gas Saturation using both Spontaneous and Forced Imbibition Method, where IsoparL is the Wetting Phase
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Today most of the oil is produced. This has triggered a wider interest for gas reservoirs. To determine how much gas that can be recovered in a reservoir it is important with good knowledge of the trapped gas saturation. This includes getting more information about trapped gas which demands more research in this area. Trapped gas saturation is recognized as an important factor in the process of recovering gas. In this project, literature has been studied and a lot of experimental work was done. Several papers have been read, and a basic knowledge of trapped gas, both what it is and how it can be determined, has been obtained. A main objective when reading was to gain knowledge about factors that affect the amount of trapped gas in a reservoir. In addition to reading about the theory, it has bee tested in the lab. The main purpose of the lab work was to see how rate change would affect the residual gas saturation, by using USS method. Spontaneous co-current imbibition experiments were also obtained. Six cores; three Berea plugs and three cores from the northern sea were chosen for execution of the experiments. In total 3-4 USS experiments were executed for every core, where an important area of study should have been to figure out how different pressure differences would affect the results. In addition one spontaneous imbibition experiment where done for each core. Normally water is used as the wetting phase. In this study IsoparL was chosen as the wetting fluid due to simplification factors in the lab. Previous studies of spontaneous imbibition experiments had shown good results when using IsoparL, so it was assumed that it could be used in USS experiments as well. It was discovered that IsoparL did not work well as the wetting fluid. By using this fluid, all the results obtained would be in the region of ΔP>0. So the most important conclusion obtained from this study is that water should be used as the wetting fluid when studying Sgr by using USS method. It was found that Sgr will decrease as rate increase when studying rates equal or larger than 4 ml/h with IsoparL as the wetting fluid.