Exceptional Proppant FlowbackControl for the Most Extreme Well Environments: The Shape of Things to Come

Abstract

Abstract Proppant flowback in deep hot, highly productive wells is a major problem in the oil and gas industry. Under these extreme conditions, many of the current products and processes to control flowback often fail. As such, improved or alternative technology and procedures are constantly being sought. One such technology is the development of deformable proppants. Material and structural improvement to a deformable proppant has allowed laboratory test conditions to be extended to higher temperature, closure stress and flowrate. As a result of this fine tuning, exceptional proppant flowback control has been obtained. Testing of this new deformable proppant, blended with typical fracturing proppant, has shown 50 fold increases in flowrate and 100 fold increases in pressure drop are attainable without pack failure, while still maintaining fracture conductivity. This deformable proppant has been applied in wells where current technology would either fail or have serious drawbacks. In two primarily gas producing reservoirs, the addition of this deformable proppant to proppant packs placed during fracturing treatments, has been observed to very effectively control proppant flowback under conditions of high bottom hole temperature, high fracture closure stress and high production regimes. The developmental testing, successful application and well performance all indicates significant improvement in proppant pack integrity. Introduction Initial reservior pressures in deep hot wells can cause the closure stress on the proppant to be a fraction of what the producing well will be when put on line1. This can be devastating to the proppant in place as it can be produced almost as rapidly as it was placed in the formation and more can be produced at each production cycle. Elongated deformable particles have been laboratory tested and applied in high production, high temperature gas wells for controlling proppant flowback under these high stress conditions. These gas wells stimulated in South Texas have proven laboratory data correct in not only preventing proppant flowback, but also stabilizing the pack and preventing subsequent flowback during production stress cycles. Statement of Theory The deformable particles set between proppant grains, indent when stress is applied. This locks the proppant grains and deformable particles into a pack that increases the resistance to proppant flowback2. Increasing the concentration of the deformable particles in the pack mixture further increases the resistance to flowback, however, past laboratory tests demonstrate that a ratio of 3:1 proppant to a substantially spherical deformable particles yield the greatest resistance to proppant flowback2,4 with the least interference in permeability. A new high stress (HS) deformable particle, having a needle like shape, works in a similar manner but even more efficiently. These elongated particles are sized about 1mm in diameter by 7 mm in length. This increases the number of individual proppants stabilized by each deformable particle while decreasing the number of high stress deformable particles needed to control proppant flowback. These new high stress deformable particles have an optimum ratio of 9:1 proppant to deformable particle when uniformly mixed into the pack. A graph of the initial flowback from the first field test and laboratory results are included to demonstrate that a net effective stress of 2,500-psi is required for the new particles to deform sufficiently at the 9:1 ratio to stabilize the proppant pack. Below this net effective stress increased concentrations of the new particles are required for pack stabilization. Also with this shape the HS particles require a minimum perforation diameter of 0.25 inches.