Guar Replacement with Synthetic Polymers - Utica Shale Case Histories

Abstract

Abstract This study was conducted to determine the advantages of replacing guar-based polymers with polyacrylamide (PAM) engineered polymers in unconventional shale gas plays. Hydraulic fracturing of unconventional shale gas reservoirs usually consists of low-viscosity slickwater treatments where the water/sand mixture is pumped into the reservoir at high treatment rates (80+ bpm). At such high fluid velocities, the proppant/water slurry is abrasive to fracturing equipment resulting in decreased service life plus higher repair and maintenance costs. Additionally the low-viscosity slurry will allow proppant to fall out of suspension. This causes poor proppant placement in the fracture, leading to decreased well production response. In these situations it is advantageous to use a hybrid design where guar polymers are added to the slurry to increase viscosity and aid in maintaining suspension of the sand. The disadvantage of using guar-based polymers for this application is a polymer residue is left in place following the fracturing treatment, which can decrease the production of the well. A guar-alternative, PAM, has been developed for use as a friction reducer in slickwater treatments and to increase the viscosity of the water/sand mixture when added in increased concentrations. This PAM has been specifically engineered so that the polymer chain can be broken into discrete units using traditional oxidative breakers and then flowed back out of the well when production begins. This breaking mechanism leaves behind less polymer residue than old-style guar treatments. This system has been used numerous times in the Utica shale and has resulted in superior production performance versus the wells that have been completed in the same area using guar polymers. This paper will focus on multiple Utica shale wells that have been successfully completed using the PAM engineered polymer scheme. Production data on a statistically significant number of offset wells will be presented, drawing from publically available production data. Production periods of up to 2 years will be included to illustrate the advantages this system has over the traditional hybrid fracturing using guar-based fluid systems. Data will be provided which demonstrates that wells completed using this PAM system produce, on average, 66% more hydrocarbons than offset wells completed using conventional systems. This paper will demonstrate that there is an effective alternative to guar gel available for use in hydraulic fracturing operations. This alternative solution leaves behind significantly less polymer damage, enhances fracture conductivity, and improves hydrocarbon production.