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

Abstract

A new thickening system extends the temperature range of traditional viscoelastic surfactant-based fluids and provides additional downhole benefits. Based on a low-molecular-weight associative polymer, the thickener forms an associative gel with surfactants at elevated temperature. This results in a gel structure that can carry proppant. Recent laboratory work has shown that viscosity alone may not accurately assess proppant transport. Thus, the aim of this paper is to evaluate rotational and oscillatory measurements to determine the viscous and elastic properties of the fluid. In addition, dynamic and static proppant settling tests were conducted using a high pressure/ high-temperature visualization cell to confirm the effect of elastic properties on proppant settling. This combination of measurements can better predict whether the fluid can be applied successfully in the field.Thirty-three different formulae across a wide polymer and surfactant concentration range were examined at temperatures up to 250°F. Also, the effect of other fracturing fluid additives, such as friction reducers and nonemulsifying agents, were examined. Finally, proppant-settling tests were conducted with three proppant types of the same size, but different density and shape at a range of concentrations.Experimental results show that each formula had a certain operating temperature range where the elastic modulus dominates. A polymer-to-surfactant concentration ratio of 1.4 was found to give the widest working temperature range with the highest elastic characteristics; the same range also gives better proppant suspension. At temperatures less than 100°F, the viscous regime was dominant for all tested formulas. However at the same temperature, the elastic modulus increased with shear rate. This gives a good proppant-carrying capacity during dynamic conditions (mixing and injection) with a small pressure drop. The friction-reducing agent was found to have a tendency to reduce the operating temperature range. However, the non-emulsifying agent reduced the effect of the friction reducer and enhanced the performance.

Supramolecular dynamic binary complexes with pH and salt-responsive properties for use in unconventional reservoirs

“…A large relaxation time implies that the supramolecular structure that is viscosifying the solution remains intact and does not disintegrate. This points towards a highly structured complex fluid, similar to the viscoelastic behavior that has previously been observed in crosslinked polymer based fracturing fluids [ 61 ]. The predominately elastic behavior exhibited over the entire range of applied frequencies indicates the type of fluid characteristics that would increase the resistance of proppant settling [ 62 ].…”

Supramolecular Viscosity Modifiers With Salt-responsive and Ph-switchable Characteristics for Hydraulic Fracturing Applications

“…A large relaxation time implies that the supramolecular structure that is viscosifying the solution remains intact and does not disintegrate. This points towards a highly structured complex uid, similar to the viscoelastic behavior that has previously been observed in crosslinked polymer based fracturing uids 53 .…”

Improving Fracture Conductivity by Developing and Optimizing Channels within the Fracture Geometry: CFD Study

“…Enhancing crosslinker chemistry Ainley et al 1993, Putzig and St. Clair 2007, Sun and Qu 2011, and Legemah et al 2013 Enhancing breaker chemistry Brannon 1994, Sarwar et al 2011, Gunawan et al 2012, and Patil et al 2013 Fracture fluid additives Bang et al 2008, andKim et al 2015 Foamed fluids Hutchins and Miller 2005, Gupta et al 2005, Chen et al 2005, Friehauf and Sharma 2009, and Gupta and Carman 2011 Viscoelastic surfactant systems Samuel et al 1999, Gomaa et al 2011, and Gomaa et al 2015 Polymer chemistry Cramer et al 2004, and Gomaa et al 2014Proppant Technology Brannon et al 2004 These improvements contributed incrementally toward the goal of attaining the maximum theoretical conductivity that can be achieved in a homogeneous proppant pack.…”