Single-Size-Ball Interventionless Multi-Stage Stimulation System Improves Stimulated Reservoir Volume and Eliminates Milling Requirements: Case Studies

Abstract

In the last decade, there has been a tremendous growth in multi-stage fracturing for unconventional plays employing stimulation sleeves with open hole (OH) packers or cementing. Standard ball-activated frac sleeve systems with graduated ball seats have primarily been used because they can significantly save completion time and cost by facilitating the performance of multiple stimulations in a single continuous process compared with the conventional Plug and Perforate (P-n-P). However, traditional ball-activated frac sleeves have limitations in the number of stages that can be handled, the pressure drop and friction loss each one creates and the need to mill through the ball seats after stimulation. As the number of frac stages increases, the ball seat sizes become dramatically smaller leading to large increases in the surface treating pressure and hydraulic horse power (HHP) needed to generate a given net downhole pressure or injection rate. To solve these limitations a revolutionary ball-activated fracturing system has been designed. This system behaves in similar fashion of activation to the traditional graduated ball seat frac sleeve in that the ball locks into place on the seat, but all the ball seats are the same size and retract, allowing the first ball to pass through all sleeves until it reaches the lowermost one. Similarly the next ball, which is the same size, lands on the next seat up and so on, allowing a virtually unlimited number of zones to be treated for either OH or cemented application. With this new system, there is no milling operation involved and the completion string maintains full drift inside diameter (ID) ready for production after stimulation operations have been completed. In this paper the authors will describe in detail the operational mechanism of this new frac sleeve and present case studies of its use which illustrates the effect of this new technology in optimizing fracturing operations both in horsepower requirements and overall completion time and cost.