This paper discusses the successful application of a pillar fracturing technique in a water injection well wherein a major operator previously experienced poor injectivity within the target zone.
The aim of the pillar fracturing technique was to achieve the highest possible fracture conductivity to enhance water injectivity for reservoir pressure maintenance. This technique creates infinite conductivity channels with proppant distributed within the fracture as aggregates or groups separated by clean fluid. These proppant groups function as pillars to hold the fracture open and help enable fluid flow in the open channels between proppant pillars. The conductivity of a partially open fracture with proppant pillars can be several orders of magnitude greater than that of a conventional fracture filled with proppant after closure. After a pillar style hydraulic treatment, the propping agent remains in the fracture grouped to form pillars because of the sticky resin that was applied to the proppant just before being blended (intermittently) into the fluid system that was pumped during the treatment. This helps the grains in the resulting pillars to adhere together and help prevent the fracture from entirely closing, forming open conduits for fluid flow. The overall success of this fracturing stimulation treatment depends on the sequenced pumping technique, allowing the propping agent to form proppant aggregates during their placement into the formation.
This paper presents the enhanced pillar fracturing technique, pre-job well analysis and design, Minifrac data calibration, and actual pumping operation execution. The well intersects a reservoir with sandstone lithology that had not been fractured previously. The sandstone formation is subdivided into three intervals of 60, 40, and 60-ft thickness, with distinct shale layers separating them. Based on the log interpretations and formation geomechanical analysis, two pillar fracturing stages were determined necessary to treat the entire targeted formation and maintain balanced injectivity in all three intervals. An optimum hydraulic fracturing design was developed and executed to deliver optimal well performance. Actual operational execution involved use of specially designed surface equipment and adhesive enhancement proppant coating to install highly conductive flow paths while maintaining reservoir and proppant pack stability. This resulted in a successful treatment that sustained 16,000 barrels of water injection per day (BWIPD).
The successful application of the pillar fracturing technique in this well motivated the operator to extend the pillar fracturing technique to other injector and producer wells.