APPLICATION STUDY OF TEMPORARY PLUGGING ASSISTED FRACTURING IN TRANSITION ZONES OF SABEI OILFIELD

Abstract

The northern oil and water transition zone of the Sabei Oilfield is the largest development area of the whole Daqing Changyuan transition zone. At present, it is producing with ultra-high water cut, and both water flooding and polymer flooding are under operation. In order to clarify the distribution characteristics and existing state of the remaining oil in the transitional zone, liquid nitrogen freezing and ultraviolet fluorescence microscopy are used to quantitatively characterize the microscopic occurrence of residual oil in cores after different volumes of water flooding, the relationship between water flooding intensity and microscopic residual oil distribution in free state and immobile state is established. Analysis results of residual oil in SII layer of the Sabei Oilfield show more immobile residual oil. Conventional fracturing measures have been done to improve oil recovery, but its efficiency deteriorated year by year, which is only 51.1% of the measures done for the oil-rich zones. Therefore, temporary plugging assisted fracturing technology using fiber was carried out to improve the stimulation efficiency in the transition zone. Also, an improved permeability calculation model was established to analyze the influence of the fracture length, fracture height, and oil viscosity on productivity ratio and recovery factor. Based on these results, the optimal value ranges of operational parameters were obtained. Then, eight wells were stimulated using the temporary plugging assisted fracturing technology in the field. The results show that after fracturing the average daily oil production rate increased by 6.3 t and the cumulative oil production from eight wells increased by 17386 t in 720 days, demonstrating the efficacy of the temporary plugging assisted fracturing technology compared with conventional fracturing.