A Non-Damaging Friction Reducing Agent for Slick-Water Fracturing

Abstract

Abstract Friction reducers (FRs) are crucial components in any slickwater fracturing fluid. Revising the previous literature showed that the majority of research focused on evaluating the friction-reduction performance of these chemicals. Another important aspect, which a few studies addressed, is the potential damage friction reducers can cause, especially to low-permeability formations. Friction reducers are polymeric in nature (typically polyacrylamide); therefore, they can either filter out onto the surface of the formation or penetrate deeply to plug the pores. Breaking these polymers at temperatures lower than 200°F remains a challenge. This work evaluates a non-damaging and breakable friction reducer that can be a replacement for liner gel with enhanced proppant-carrying capacity. Friction-reduction performance, proppant settling, breakability, and coreflood experiments were conducted to investigate the new friction reducer (FR1) in terms of friction-reduction, breakability, and the potential damage it might cause to tight sandstone cores at 150°F. The results of the new friction reducers were compared against two conventional friction reducers; one polyacrylamide-based (FR2), and one guar-based (FR3). Different breakers were used to examine the breakability performance; ammonium persulfate (APS), sodium persulfate (SPS), hydrogen peroxide (H2O2), and sodium bromate (SB). The friction reduction of the new chemical was always higher than 65% in both fresh water and 2 wt% KCl. The presence of calcium chloride did not affect the friction-reduction performance, compared to performance reduction in the cases of FR2 and FR3. The presence of 1 gpt of different types of breakers did not affect the friction-reduction performance, even for stronger breaker (friction-reduction performance was 67% with APS breaker comparing to 68.5 % with no breaker). The new friction reducer is easily breakable in the three tested breakers: ammonium persulfate, sodium persulfate, and hydrogen peroxide. Among the three, ammonium persulfate was the most efficient breaker. Static and dynamic proppant settling tests indicated a superior performance of FR1 compared to the other conventional friction reducer (FR2). Coreflood experiments showed that the new friction reducer FR1 did not result in any formation damage with APS breaker at low KCl concentration (5 wt%) and high KCl concentration (20 wt%). A 9% formation damage was observed at weaker breaker (SB), comparing to 47 and 41.5% damage when the other two conventional friction reducers FR2 and FR3 were tested, respectively. The proposed friction reducer has higher friction-reduction performance and better proppant-carrying capacity with no formation damage compared to the conventional friction reducers.