Monitoring Fracturing Fluid Flowback and Optimizing Fracturing Fluid Cleanup in the Bossier Sand Using Chemical Frac Tracers

Abstract

Proper fluid and proppant placement are crucial to a successful propped fracture stimulation. Numerous completion diagnostic technologies are available to characterize the placement of the treatment. Until recently, characterization of fracturing fluid cleanup could only be simulated in the laboratory and anecdotally monitored in the field. A technique utilizing a family of unique, environmentally friendly, fracturing fluid compatible, chemical tracers has now been developed for quantifying segment-by-segment recovery for individual fracturing treatments and stage-by-stage recovery for multi-stage fracturing treatments. East Texas Bossier Sand case histories demonstrate that individual, chemically-differentiated and/or proppant-differentiated, fracturing treatment segments are often not being effectively recovered. It has also been demonstrated that the chemical make-up and/or the proppant scheduling of these individual fracturing fluid segments may not only be detrimentally effecting their incremental cleanup but ultimately the production contribution from the corresponding portions of the fractured reservoir. The validation of improvements in fracturing fluid cleanup and production enhancement resulting at least in part from changes in the chemistry of the fracturing fluids and/or changes in proppant scheduling are demonstrated using the tracer technology. Introduction Chemical Frac Tracers In an effort to bolster the level of understanding regarding the dynamics of hydraulic fracture placement and subsequent fluid flowback and cleanup, the technology of chemical frac tracers (CFT's) was born. Borrowing from many years of experience with interwell tracing, several families of non-radioactive chemical compounds were identified that could potentially be placed in segmented portions of the frac fluid so as to more directly measure the flowback efficiency of each fluid segment. Armed with this flowback profile data together with the treatment pressure history of the frac treatment, it was believed that much could potentially be learned both about the dynamics of segmented fluid placement as well as segmented fluid flowback and cleanup. Given the established formation/fracture damage potential for conventional proppant transport fluids, those fluid segments not adequately recovered following the treatment could, in principle, detrimentally affect the effective flow capacity of the fractured interval. Chemical frac tracers were designed to be placed in chemically-differentiated and/or proppant-differentiated fluid segments of the fracturing fluid so as to assess the cleanup of the fracture as a function of segment fluid chemistry and/or fracture geometry. In so doing, it was believed that the sufficiency or insufficiency of addition rates for key frac fluid additives such as polymers, breakers and gel stabilizers could be assessed. It was also believed that the relative cleanup of individual frac treatment stages in a multiple stage completion procedure could be monitored. It was further hoped that inferences could be made from these data regarding lateral placement effectiveness of proppants and vertical communication between zones.

Experimental study on the effect of tight gas fracturing flowback fluid composition on the performance of modified polyacrylamide viscosity reducing and slippery water system

“…The number of fracturing operations in tight gas blocks is high, with a single well injection volume of about 20,000 m 3 , and the fracturing flowback rate is about 30% to 80%. The large amount of fracturing flowback fluid produced must be effectively treated in accordance with the national “Environmental Protection Law” and local environmental protection regulations, and the high‐viscosity and high‐COD heavy‐polluting wastewater must be resourcefully utilized (reused) or zero‐emission harmless treatment 8,9 …”

“…The large amount of fracturing flowback fluid produced must be effectively treated in accordance with the national "Environmental Protection Law" and local environmental protection regulations, and the high-viscosity and high-COD heavy-polluting wastewater must be resourcefully utilized (reused) or zero-emission harmless treatment. 8,9 Many studies have been conducted by major oilfields, universities, and laboratories both domestically and internationally on the treatment and reuse of flowback fluids. Currently, the most mainstream treatment methods are divided into three categories: transporting the flowback fluid to a wastewater treatment plant for processing and discharge, reinjection, and reuse as a reconstituted fracturing fluid.…”

Chloride concentration gradients in tank-stored hydraulic fracturing fluids following flowback

“…Once fracing is completed, a portion of the fracing fl uid is recovered through a process called fl owback (Sullivan et al 2004, URS 2009, Woodroof et al 2003a. Th e recovered fl uid (also called fl owback) typically is stored temporarily in open pits near the well called reserve pits (Deuel et al 1999, Leuterman et al 1988 or sumps (French 1980).…”

Stimulation Flowback Management--Keeping a Good Completion Good

“…A great deal of emphasis has been placed on utilizing techniques such as forced closure (15), or not (20) or reverse screenout(3) to attempt to mitigate such behavior and to maximize proppant concentration at the fracture heel. Methods have been presented to maximize post-stimulation cleanup by evaluation of the maximum gas production (1,24), examining chemical signatures (14,18,26) and especially modeling the fluid behavior in the fracture (2,4,16,17,19). Elegant as these approaches are, none provide an explanation for the persistent observation of very short effective fracture lengths.…”