A New Model for Matching Fracturing Fluid Flowback Composition

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractRecovery of fracturing fluid is considered a critical aspect for achieving production performance that meets the expectations of fracture treatment designs. Fluid recovery is often described simply as a percentage of load recovery on a volume basis, without consideration of the composition of the recovered water. Some of this water may in fact be formation water and not original load water at all. Analysis of the ionic composition of the water can determine whether the recovered water is formation water or treatment water. This paper describes a new model that embodies the physics of flow during back-production of a fracturing treatment and incorporates a chemistry "layer" that allows for matching fracturing fluid flowback compositions. The model accommodates formation water having a separate composition from the fracturing fluid. The movements of sodium, potassium, chloride, sulfate, carbohydrate, boron, etc. are modeled during shut-in and production. The compositions of the produced water calculated by the simulator were compared to field production samples.The process of matching the produced water analyses after the fracturing treatment first required a good match of the produced water rates as a function of both time and the produced gas rates. Reservoir and fracture properties were optimized to match the water production. The ionic composition of the flowback water was then matched by adjusting various parameters that might affect how the water was recovered from the reservoir. The information obtained by adjusting these parameters includes relative permeability curves, capillary pressure curves, and some fracture structure details. Deviations of the model from the observed return profiles indicated areas where the understanding of fluid chemistry and physics of flow might be improved.

Shales Leaching Modelling for Prediction of Flowback Fluid Composition

“…Methods focused on computer programs, supported by precipitation tests [33], statistics of reservoir data [34] or statistics of fracturing wells in chosen basin of gas bearing shales can be specified. However evaluation is not possible because the proposed tools are often unavailable and not described enough to test them due to the unnormalized character of the data [35]. Nevertheless very useful information can be found on the basis of Total Organic Carbon (TOC) regarding salt migration into flowback fluid streams [33].…”

“…Nevertheless very useful information can be found on the basis of Total Organic Carbon (TOC) regarding salt migration into flowback fluid streams [33]. Also ionic strength and the influence of ion interactions exhibit a crucial role [35]. Due to the unnormalized character of the data presented in the literature, the models are often non-comparable.…”

“…A promising model was presented by Gdanski et al [35]. The model allows one to predict the amount and composition of the flowback fluid.…”

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.…”