Increased interest in minimizing environmental risk from chemicals has sparked the innovation of new universal breakers for use in high-temperature fracturing fluids. Enzymes have been used for many years in fracturing applications with great success, but their use could be limited due to polymer specificity and thermal stability.A novel type of breaker system, derived from biological sources and displaying catalytic, polymer degrading activity similar to that of enzymes, was obtained and tested for its ability to reduce the viscosity and molecular weight of polymers used in hydraulic fracturing applications. The universal breakers (UB) are miscible, catalytic, renewable, biodegradable and are not polymer-specific. Additionally, these breakers do not display the thermal denaturation limitations of enzyme breakers, and can thus be used over a much wider temperature range.Three novel universal breakers were tested for their ability to break the viscosity of various oilfield polymers (guar, carboxymethyl guar, and xanthan) at temperatures of 175, 200, and 225 °F. UB-1 and UB-3 showed rapid catalytic activity at 175, 200, and 225 °F, and reduction in viscosity. UB-2 was more effective at temperatures equal to and greater than 200 °F. Additionally, all UB breakers showed activity against xanthan, with UB-1 and UB-3 being the most effective. This paper will describe the testing program for the viscosity-reducing ability of three novel universal breakers against both linear and crosslinked high-yield guar, guar, carboxymethyl guar, and xanthan in alkaline and high-temperature conditions. Comparisons of the UB breakers to conventional polymer-specific enzymes and oxidative breaker systems will be discussed. Finally, this paper will include recommendations for field applications, including economic impacts on fracturing fluid systems.
The development of new environmentally responsible breakers for use in high-temperature fracturing fluids (≥ 250 °F) was sparked by efforts to minimize environmental risks from oilfield chemical systems. A novel type of breaker system, derived from biological sources and displaying catalytic activity, was discovered and tested for its ability to reduce the viscosity of polymers commonly used in hydraulic fracturing applications. The breakers are miscible, catalytic, biodegradable, and come from sustainable resources. Additionally, these breakers do not display the thermal denaturation limitations of enzyme breakers. Two novel, environmentally-responsible breakers, UB-1 and UB-3, were tested for their ability to break the viscosity of crosslinked guar and derivatized guar polymers at temperatures of 250, 275, and 300 °F. UB-1 was more effective in breaking crosslinked guar polymers. UB-3 was more effective in breaking crosslinked derivatized guar polymers (i.e. carboxymethyl guar). As hydraulic fracturing technology is used in more challenging reservoirs, the need increases for effective breakers that function at elevated temperatures. At high temperatures, oxidative and enzyme breakers have drawbacks: Oxidative breakers become too reactive and enzymes denature. Our previous paper (SPE-159396) detailed the efficacy of the new breaker technology at mid-range temperatures (175 to 225 °F). This paper will explore the use of these breakers at higher temperatures. This paper will include the testing program for the viscosity-reducing ability of these novel breakers in guar and carboxymethyl guar in alkaline and high-temperature conditions (> 250 °F). They will also be compared with oxidative breakers. Finally, the paper will include recommendations for field applications, including economic impacts on fracturing fluid systems.
A successful wellbore displacement and clean-up is a critical step during well completion operations. A poor cleaning performance can lead to increased cost of completion operations, potential formation damage, and thus reduced oil and gas productions. Failure to achieve a balanced displacement system can lead to negative pressures on cement jobs and tie-backs, wellbore control issues, and wellbore instability. Deepwater wells require a crucial and complete evaluation of a displacement system which will provide a balanced, effective, and efficient cleaning spacer system. Traditional displacement spacer systems typically consist of a solvent spacer and a surfactant spacer. A solvent spacer consisting of d-limonene is effective for removing oil-based drilling fluids from the wellbore; however, this is incompatible in water-based spacer systems and results in an underbalanced displacement system. On the other hand, a surfactant spacer is ineffective in displacing ester/isomerized olefin (IO) based drilling fluids. As the chemistry of drilling fluid additives become more diversified to accommodate various base oils, such as the blend of ester/IO used here, so too must the chemistry of cleaner/displacement additives to ensure appropriate compatibility. On many occasions, barite residue from the weighted spacer was found to adhere strongly to pipe surfaces and be nearly impossible to remove chemically upon contact with the surfactant spacer. This issue can cause incomplete zonal isolation. A new, balanced, and high-performance displacement system (ADS-RD) was developed and optimized for its ability to effectively remove oil-based drilling fluids, barite residue, and water wet pipe surfaces. Lab test results showed that ADS-RD was fully compatible, consistently achieved an average of 98% cleaning efficiency, and yielded water wet pipe surfaces against the ester/IO based invert emulsion drilling fluids. ADS-RD also proved to be an effective and efficient solution to other oil-based invert emulsion drilling fluids. This paper presents the testing program and lab test results for ADS-RD against a traditional displacement system with various oil-based invert emulsion drilling fluid systems with densities up to 14.8 lb/gal. This paper will also include cost savings and recommendations for field applications.
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