Polysaccharide Derivatives Provide High Viscosity and Low Friction at Reduced Temperatures
Authors: White J.L. , Means J.O. , Jehlik K.D. , Barrett N.D. 
Published: December 2007

American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc.

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Continuous mixing of gelled aqueous frac fluids is desirable since it reduces treating time, equipment and storage requirements, and eliminates batch mixing of large volumes of fluid that might not be used. In the past, the time required for conventional thickeners to achieve friction reduction and viscosity, particularly with cold fluids, has limited particularly with cold fluids, has limited continuous mixing as a treating technique during cold weather, and in shallow wells with low bottom hole temperatures. New, low residue polysaccharide derivatives have now been developed, however, which achieve high viscosity and low friction much more rapidly than conventional thickeners. For example, the new thickener in 40 degrees F can reduce friction up to three times more effectively than the conventional thickeners and also provide viscosities up to four times greater. provide viscosities up to four times greater. The advantages of low residue fluids to minimize damage and hence potential losses in production are discussed. The proper use production are discussed. The proper use and design criteria for low residue systems are examined.

Continuous mixing with the thickener permits use of higher breaker concentrations permits use of higher breaker concentrations to reduce shut-in times and thus provide faster, more effective well clean-up. In conjunction with the new gelling agent, additives such as clay control agents and new surfactants are utilized to shorten clean-up times by as much as one-half and to increase frac fluid recovery from 2–3 times over conventional water based treatments. It appears to be a growing opinion in the industry that short shut-in times to minimize fluid retention may be a key to improved production by fracturing. production by fracturing

Introduction

In the past several years many new frac fluids have been developed. In many cases, these fluids met specific requirements such as high temperature stability, low formation damage, more rapid clean-up of ultra high viscosity.

Guar gum has been an effective gelling agent in frac fluids for many years. In the majority of aqueous base conventional frac treatments, guar gum is still the thickener most commonly used. Guar gum generally meets the basic requirements of an efficient and economical frac fluid. Guar gives low friction pressures, good viscosity in a variety of brines, low fluid loss and effective breakdown control following the treatment. The fluid loss control of guar gum is particularly effective as compared to other aqueous thickeners.