Study on characteristics of waterflooding in fractured reservoirs based on discrete fracture model

Water can rapidly breakthrough in natural fractured reservoirs and can result in waterflooding, usually shown as high water cut and low oil production in oil field. It is of great significance to study the characteristics of waterflooding in fractured reservoirs to recognize the fracture in order to enhance oil recovery. A discrete fracture model was established; water cut and water cut derivative curves were used to study the characteristics of waterflooding with a single fracture in different fracture widths and locations. It is found that the water cut curve of fractured reservoirs behaves in a step-type characteristic for proper fracture width but will disappear if the fracture width is very small or too great. According to the characteristics of water cut derivative curve, the fracture width increases to a specified value, the peaks shown on the curve will change from single to double but will revert back to one peak if the fracture width is very high. In addition, the time interval of the two peaks is positively related to fracture width, and the differences of the two peaks will behave more obvious if smaller distance between the fracture and injection well is chosen. From this study, an initial diagnosis of the reservoir fracture development can be carried out according to the characteristics of water cut curve and water cut derivative curve.