Flowback of proppant and formation sand often poses serious challenges to operating companies when these solids cause equipment damage, costly and frequent cleanup treatments, and production decreases. These flowback problems are often compounded in severity in wells with production of heavy oil and high water cuts. Once the proppant is produced out, there is no mechanical means to keep the unconsolidated sand in the perforations or behind the casing in place. Similarly, formation sand from the perforations not aligned with the propped fractures produces out freely during well production once the proppant filling the perforation tunnels produces out.
To combat the proppant and sand-production problems and revive the production of wells that have been shut in because of solids production, field trials of an on-the-fly coating, curable resin system were performed to determine whether this resin system is a viable solid flowback control that can provide an effective means to establish screenless completions in this field. This paper presents the results of these field trials involving the screenless completions using the on-the-fly, curable resin-coating system in treating the proppant. Detailed descriptions of the completion procedures, challenges and difficulties, and lessons learned during the course of these hydraulic-fracturing treatments are presented.
Field results indicate this on-the-fly, resin-coating treatment effectively stops the proppant and formation sand from producing back while allowing the production rates to be maintained as designed. The process has drastically decreased the number of solids-cleanout workovers in the treated wells compared to the offset wells in the same field in which the resin treatments were not performed. The resin treatment provides a reliable and cost-effective alternative in marginal reservoirs, eliminating the need for sand-control screens and providing access to other intervals, when needed, without wellbore restrictions.
The case studies discussed in this paper regard oil wells operated by CAPSA, Argentina. The producing formations in these wells generally have high permeability, unconsolidated sand, and high water cut or water-oil ratio (WOR). Throughout the past several years, the operator has applied gravel-pack completions in a limited number of wells to control production of formation sand and fines with low success. The objective of this completion technique was to create a tight gravel pack in the annulus between perforated casing and the sand screen, with the attempt to squeeze as much gravel out into the formation as possible to control migration of formation sand and fines. Hydraulic-fracturing treatments using curable-coated proppant were also performed to bypass near-wellbore damage and lower the drawdown as an attempt in minimizing flowback of formation sand with production fluid. The production results, however, indicated that these completion methods were not as successful as planned.
Wells completed with gravel pack using premium screens successfully stopped sand production from the formation, but this type of completion significantly reduced fluid production because of high skin damage. For wells in which hydraulic fracture treatments were performed, both frac sand and formation sand were observed to produce back, filling the wellbore. Formation sand plagued the operator with decreased production and plugging of progressive cavity pumps (PCP), requiring frequent workovers and downtime. Sand production prevented the operator from boosting the well production to desired levels. In addition to the disappointing performance of these completions, the frequency of workovers required to clean out proppant and formation sand in these wells averaged once every three to four months. As a result, the operator considered field trials of a newly developed curable resin for controlling flowback of proppant and formation sand.