This paper describes the principles of cyclic production implemented in a matured water flood field to manage the occurrences of short circuit in a pattern. Systematic surveillance and reservoir management tools are used to analyze the fracture initiation, impact on production and reserves performance and predict the future behavior of the field. These include analytical tools, diagnostic methods, tracer surveys and downhole temperature monitoring which lead to the implementation of cyclic production methodology.
The tight reservoir is situated in a gently dipping, fault bounded matrix carbonate in North Oman. The reservoir is thick with relatively thin oil column heights of typically 5 to 30m and low permeability. The under-saturated reservoir contains light oil, with low viscosity (API gravity of 35°)
Due to inadequate aquifer support a full water injection scheme at matrix condition was implemented 10 years after natural depletion with multilateral horizontal water injectors drilled about 30m below the producers. During peak production, the water was unintentionally injected above fracture pressure which caused fracturing in several patterns in this field.
Cyclic production is implemented in these patterns as other different methods failed to recover the oil production due to short circuit. Since May 2008, the injectors and producers are operated on scheduled cycles in three patterns where these short circuits were observed. After several years of cyclic program implementation, encouraging results were obtained where up to 20% of reserves lost due to short circuits were recovered.
The paper also describes the challenges faced during the implementation of cyclic program mainly due to flexibility of compression capacity, manpower rotation and water injection limitations; frequency and accuracy of testing and number of wells supported by the injector.