New Viscoelastic Surfactant Fracturing Fluids Now Compatible With CO2 Drastically Improve Gas Production in Rockies

Abstract

Historically, carbon dioxide (CO2)-foamed fracturing fluids were used to stimulate wells in the Waltman field in Wyoming—due to the low formation permeability and rock properties—and have been proven effective, but still not perfect. Limitations on the amount of proppant placed near water zones and formation damage from polymer residuals were the main drawbacks. A never ending quest for efficiency and higher production rates called for different options. One of those options was the recently developed CO2 viscoelastic surfactant (VES) fluid system. It has recently been employed to eliminate the disadvantages of the traditional polymer-based fluid. This VES-CO2 fluid system combines the benefits of viscoelastic surfactant-based fluid—such as low formation damage, superior proppant transport, and low friction pressures—with carbon dioxide advantages of enhanced cleanup and better hydrostatic pressure. This fluid was recently selected for the fracturing treatments on three wells. Initial production from these wells was observed in the range of 5 to 7 MMcf/D, significantly greater than neighboring wells' gas rates of 2 MMcf/D stimulated with polymer-based fluid. Introduction The Waltman-Cave Gulch field complex is located on the northeast flank of the Wind River Basin, 50 miles west-northeast of Casper, Wyoming (Kuuskraa et al. 1996), Figure 1. Production from this complex was established in 1959 from Lance formation. The full extent of the Lance sands in the Cave Gulch (shallow) structural accumulation was rediscovered in 1994. The production boundaries of Waltman-Cave Gulch are not yet established. Current development priorities are defining the deep Frontier, Muddy, and Cloverly reservoirs and extending the Cave Gulch (shallow) accumulation to the southeast and northwest. The Waltman-Cave Gulch complex is located on the Waltman Anticline, a north-south trending asymmetric fold of Laramide age. The fold is bound on the west by a high angle reverse fault. The complex produces from three geologically distinct accumulations, the Waltman (stratigraphic), Cave Gulch (shallow), and Cave Gulch (deep), Figure 2. All the wells discussed in this paper are located in Waltman (stratigraphic) accumulation, and completed in Lance formation.

Viscoelastic Behavior and Proppant Transport Properties of a New Associative Polymer-Based Fracturing Fluid

“…More than 7,500 nitrogen-and carbon-dioxide-foamed treatments have been used successfully to place proppant and stimulate formations. In Canada alone, around 15,000 viscoelastic-surfactant-fluid treatments have been performed, including 3,500 with nitrogen (N2) or carbon dioxide (CO2) for energized flowback assistance (Gupta et al 2005;Chen et al 2005;and Hughes et al 2008).…”

Recent Advances in Viscoelastic Surfactants for Improved Production From Hydrocarbon Reservoirs

“…For example, barium titanate pyroelectric nanoparticles increase the viscosity of solutions composed of sodium fatty acid methyl ester sulfonate (Luo et al 2012). Bandyopadhyay and Sood (2005) studied the rheology of semidilute solutions of the cationic surfactant cetyl trimethylammonium tosylate (CTAT) in the presence of silica colloids with diameters of 0.1 mm. Upon addition of 1.3-wt% silica particles to 1.4-wt% CTAT solutions, the relaxation time increases by 600%, the high-frequency-plateau modulus G 0 increases by 37%, and the zero shear-rate viscosity g 0 increases by 1,600% compared with solutions of pure CTAT.…”

Recent Advances in Viscoelastic Surfactants for Improved Production from Hydrocarbon Reservoirs

“…As shown by Chen et al, foaming the VES with 70% CO 2 roughly doubles the viscosity over that of 4% VES straight fluid. The use of this system for field applications has been reported (Chen et al 2005;Arias et al 2008;Al-Muntasheri 2014). Zwitterionic surfactants such as the betaines shown in Figure 7(b) and 7(c) and carbon dioxide in a separate phase along with a cosurfactant such as C 12 alkyl dimethyl benzyl ammonium chloride have been described .…”

“…P3D (Pseudo threedimensional) fracture simulation demonstrated a fracture half-length of about 338 ft with an average conductivity of 587 md-ft for the first well and a fracture half-length of about 511 ft with an average conductivity of 553 md-ft for the second well. Furthermore, wells in Waltman field in Wyoming provide another example of VES-CO 2 fluid systems (Arias et al 2008). Four of the wells that were treated with VES-CO 2 fluid (70% quality) were compared with nearby wells treated with linear hydroxypropyl guar (LHG) polymer system with gel loading of 40 lbm/mgal.…”