Fracturing Fluid for Extreme Temperature Conditions is Just as Easy as the Rest
Abstract
As exploration goes deeper, most conventional methods have to be modified or completely re-engineered to hold up to these extreme conditions. Fracturing fluids are no exception to these changes. Fluids have evolved rapidly to adjust to an ever changing market. The trick is to make them as easy as possible to deliver on location. There have been several attempts at developing new high temperature fluids that will give good stability and deliver the fracture properties desired. Most of these to date require special handling and have operational difficulties.
A new high temperature synthetic low-pH crosslinked fluid system has been developed to avoid these pitfalls. The system employs a synthetic co-polymer in an environmentally compliant oil-based emulsion that hydrates very rapidly with excellent fluid rheology properties. Proppant pack regain conductivity using encapsulated oxidizers has also shown very good cleanup at these temperatures. The system uses exceedingly low polymer concentrations (18 to 40 pptg) compared to others (60 to 100 pptg) at temperatures from 350 to over 450°F. The fluid can also be energized with nitrogen or carbon dioxide or foamed if needed. Operationally, fracturing with this fluid can be performed with conventional equipment without any modifications. The paper will present the chemistry and technology of this new fluid including rheology and cleanup data.
This new technology has the potential to change the manner in which ultrahigh-temperature wells are completed.
Introduction
Fracturing fluids have undergone radical changes in order to withstand ever deeper, hotter and higher pressures to place proppant. In the past 250°F was considered extreme given the types of fluids available. As zirconium and titanium crosslinked fluids gained popularity and became easier to use, more wells were completed to take advantage of their availability. There have been several historical completions with conventional guar derivatives in excess of 400°F but with excessive loadings, special additives and specialized equipment. The jobs were pumped to completion and could be claimed as successful. However, the conventional fluids in most cases could not be tested to show any stability at these elevated temperatures. Most natural polymers, including guar, have a temperature limitation around 360°F. At this temperature the backbone of the polymer tends to melt. There are no current additives in the industry that can hinder this process for more than about 30 minutes. Since more stimulation treatments are needed with fluid’s stability at the BHST for longer time periods, a new fluid would have to be developed to handle these criteria. More importantly the fluid would have to be chemically simple and pumpable with existing equipment. Several products have been introduced and patents granted for these types of fluids since the 1980s. Several service companies have developed and performed limited field testing with this type of fluid. They are all synthetic co-polymers usually slightly acidic to neutral pH and crosslinked with zirconium.