An Integrated Transport Model for Ball-Sealer Diversion in Vertical and Horizontal Wells

Abstract

Abstract Ball sealer diversion has been proven to be both an effective and economic way to selectively stimulate low permeability oil and gas reservoirs in hydraulic fracturing and matrix acidizing treatments. However, the design and implementation of a successful ball sealer diversion treatment is still a challenge. Often the designer depends on experience, and lacks the knowledge of accurate ball transport and sealing behaviors. An integrated model for selecting operating factors such as fluid and ball properties, as well as predicting the ball sealers transport and hydraulic behavior prior to pumping is needed for optimizing the stimulation process. In this paper, an integrated transport model is presented to describe the relationships among the ball sealer transport sealing behavior, wellbore deviation, wall effect, perforation density and size, fluid properties, pumping rate and ball properties. In addition, the smoothness of ball, perforation phasing, and velocity profile inside the wellbore during ball seating are also taken into consideration. Recommendations are provided for determining the number of ball sealers per job for either single or multiple stage treatment, the designed pumping rate, and the physical properties of the fluid and ball sealer. A hydraulic analysis model is presented for the overall fluid dynamics starting from surface, through wellbore, to reservoir. This analysis describes the effects of reservoir condition, pressure drop on perforations, and actual sealing efficiency on the surface treatment pressure profile. This paper will investigate the effects of the diversion factors on the ball transport behaviors such as transport time, ball sealer efficiency and surface pressure.