Hydraulic Fracturing: Internal Breakers for Viscoelastic-Surfactant Fracturing Fluids

Abstract

This article, written by Technology Editor Dennis Denney, contains highlights of paper SPE 106216, "Internal Breakers for Viscoelastic-Surfactant Fracturing Fluids," by James B. Crews, SPE, and Tianping Huang, SPE, Baker Oil Tools, prepared for the 2007 SPE International Symposium on Oilfield Chemistry, Houston, 28 February-2 March. The paper has not been peer reviewed. Over the past 2 decades, viscoelastic-surfactant (VES) fluids used for gravel packing, frac packing, and conventional hydraulic fracturing have relied primarily on external or reservoir conditions to break the fluid's viscosity. Internal-breaker technology has been developed that allows breaking VES fluids into easily producible fluids without the need for contacting reservoir hydrocarbons. Very little pressure or time is required to break the fluid when an internal breaker is present. Introduction During the 1980s, a VES fluid was developed for gravel packs. Also introduced was the concept that no internal breaker was required. This concept was also applied to VES fluids developed for frac packing and conventional hydraulic fracturing during the 1990s. The stated reason for not requiring an internal breaker was that the VES micelles, which impart fluid viscosity, are sensitive to and will break upon contacting reservoir hydrocarbons, including gas hydrocarbons such as methane, ethane, and propane. During production, reservoir hydrocarbons are said to come into contact with the VES fluid in the pores of the reservoir and, thereby, will readily break the VES-fluid viscosity and allow the once-viscous fluid to be removed easily. It should be noted that a viable internal-type breaker technology has not existed for VES fluids until recently. With the introduction of internal VES-breaker technology has come the ability to evaluate the need for such technology. The full-length paper details laboratory data for evaluating the cleanup of VES fluids with and without internal breaker. The data show internal breakers may improve VES-fluid cleanup without the need for relying on an external breaking mechanism and show how VES fluids without internal breaker may be difficult to move and clean up under certain conditions. Internal Breakers In a broad sense, internal breakers are compounds placed within the VES fluid during surface mixing that will go wherever the fluid goes, ensure the VES fluid breaks, and break the VES fluid into an easily producible fluid. The use of internal breakers also should improve the rate and ease of VES-fluid cleanup and prevent viscous emulsions from forming when problematic reservoir hydrocarbons contact, mix with, and break VES-laden fluid in the reservoir.