Abstract

The use of curable resin precoated proppants was often applied in the Permian Basin to control proppant flowback. However, these precoated proppant materials continued to allow proppant to produce back, especially during production surges because they did not provide sufficient consolidation strength to handle high drawdown. Since early 2005, a low-temperature curable liquid resin system has been selected to treat the proppant on-the-fly mainly during the tail-in stages in most of 1,500 hydraulic fracturing treatments. This paper highlights how the proppant back-production problems were successfully overcome through the application of this curable resin system. Detailed descriptions of the treatments, challenges, and lessons learned during the course of these fracturing treatments are presented.

Evaluation of these treatments has revealed that an optimum concentration of resin coating maximizes bonding between proppant grains and the consolidation strength of the coated proppant pack, locking the grains in place while minimizing any reduction of conductivity. Field results indicate that application of on-the-fly resin coating treatments effectively stops proppant flowback while allowing production rates to be maintained as designed. These treatments have drastically decreased the number of workovers for treated wells compared to those treated with resin precoated proppant or without resin treatments. This resin treatment process provides an economical means for controlling proppant flowback in wells with marginal reserves.

Introduction - Background
Permian Basin

The Permian Basin is a large oil and natural gas producing area that is part of the mid-continent oil producing area. It is so named because it has one of the world's thickest deposits of rock from the Permian geologic period. It reaches from south of Lubbock, Texas to south of Midland and Odessa, Texas and extends westward into the southeastern part of New Mexico. The Permian Basin comprises several component basins: of these, Midland Basin is the largest, Delaware Basin is the second largest, and Marfa Basin is the smallest (Fig. 1). The Permian Basin extends beneath an area approximately 250 miles wide and 300 miles long

The Permian Basin is now in a mature stage of exploration and development. Production per well ranges from 5 to 200 BOPD, water production from 100 to 2,000 BWPD, and gas production from 0.10 to 2 MMscf/D. Although most of the wells were completed in sandstone formations, other formations include carbonates, dolomites, chalks, shales, and formations laminated with one or more of these materials. The rock formations are considered mostly competent formations; however, in some rare cases, weakly consolidated or unconsolidated formation materials are produced back during well production.

Proppant Flowback

Proppant flowback in the Permian Basin has been a problem in hydraulic fracturing treatments for many years. As proppant produces out of the fractures along with the produced fluids, fracture conductivity diminishes with time as the fracture width decreases. This choking effect causes the potential production of the well to decline. If the produced proppant remains in the wellbore, it may cover the perforation interval, limiting the production flowpath into the wellbore. A well cleanup is often required to remove the unwanted proppant from the wellbore to re-establish production from the entire perforated interval.

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