Horizontal completions continue to increase in popularity throughout the industry. In North America the majority of horizontal wells are drilled in shale gas formations. These formations require fracture stimulation for economic production. The majority of these stimulations are completed by fracturing four to six clusters of perforations simultaneously at high rates followed by a mechanical isolation with a composite bridge plug. As the horizontal wells increase in length the number of plugs required increases, with up to twenty plugs not being uncommon. These plugs are removed with a positive displacement motor (PDM) and mill run on either coiled tubing (CT) or jointed pipe. In longer-reach horizontal completions, plug removal using CT becomes more challenging as the efficiency of surface end loads transmitted to the mill are reduced. Quite often the deepest plugs can not be reached with standard coiled tubing, instead requiring larger-diameter, more costly, coiled tubing or jointed pipe. The need to extend the operating depth to effectively operate PDMs and reach the deepest plugs has led to development of several tool systems.
This paper will discuss the engineering, design, testing and initial field trial results of a variable fluid hammer extended-reach tool; how it was used to improve plug milling performance, to give superior control of weight on bit, to extend coiled tubing reach in the horizontal section and to reduce operational time. These field results will be compared with results using other methods of friction reduction, such as pipe-on-pipe friction reducers.