Resin coated proppants (RCP's) have been used to prevent proppant flowback for several years in the hydraulic fracturing of oil and gas wells. Proppant flowback problems, however, still exist with the commercially available RCP's and several operators report failures around the world under a variety of well conditions. To date, a clear explanation of the RCP failure mechanisms and the conditions under which failure occurs has not been presented in the industry.
A correlation between the unconfined compressive strength (UCS) of RCP materials and the proppant flowback potential has been previously presented by Vreeburg, et al. This paper will present the results of a study on a variety of factors which effect the proppant flowback of a number of commercially available RCP materials. These factors include 1) the effect of fluid pH (7 to 12) and fluid type (KCL, seawater and a HPG/Borate fracturing fluid), 2) the effect of fluid/proppant slurry shear, 3) the effect of closure pressure during RCP curing, 4) the effect of stress cycling and 5) the effect of downhole flow conditions on proppant flowback.
Since the introduction of proppant fracturing in 1949, it has become a tool widely used by operating companies to increase both oil and gas well deliverability and ultimate hydrocarbon recovery in a number of reservoirs around the world. Technological advancements in hydraulic fracturing which have taken place over the years have allowed the practitioner to increase the utilization of this tool to a broader scope of application than was originally envisioned. A case in point is the recent utilization of hydraulic fracturing in high permeability reservoirs which had only ten years earlier been thought to be very poor candidates for hydraulic fracturing based on both treatment problems anticipated (i.e., well screenouts during treatment due to excess fluid loss) and low productivity improvement following the treatment. The development of modern hydraulic fracture design programs, mixing equipment with the capability of pumping high concentrations of sand and new high efficiency fracturing fluids have contributed greatly to these successful hydraulic fracture treatment results in high permeability reservoirs. There are still several remaining technical advancements which are being addressed in hydraulic fracturing to allow this tool further utilization in the industry.