Enzymes Breakers for Guar and Derivatized Guar Fluid Systems in High Pressure High Temperature Formations

Abstract

Abstract Latest biotechnological developments have provided for enzymes technologies specifically for neutral to high pH crosslinked fluid systems designed for HPHT (High Temperature High Pressure) formations. The following paper content describes a temperature activated High Temperature (HT) enzyme breaker system successfully tested for guar and guar derivative stimulation fluids at 130° to 315° F temperature and 5-12 pH ranges. The enzyme HT breaker demonstrated significant improvements in proppant pack retained conductivity in multiple laboratory tests and confirmed by the results of case studies in HPHT wells. Industry standard tests were conducted in 3 different independent laboratories in North America and the Middle East. The overall goal was to evaluate and compare the effectiveness of standard oxidizers vs the newly developed HT Enzyme systems in reducing polymeric damage in the proppant pack. Conductivity damage is created by unbroken gel residue in the proppant pack and the dynamically formed filtercake on formation faces. The Retained Conductivity test temperatures ranged from 180-315°F. This study covers the impact on stimulation fluid viscosity and time for degradation at different temperatures. The laboratories tests demonstrated significant improvement, in the range of 83-98%, for retained conductivity in natural sand and ISP (Intermediate Strength Proppant) proppant packs when using the newly developed HT enzyme breakers. The optimum level of pH and breaker concentration were identified for rapid viscosity degradation – polymer fluid breaking. An engineering guideline was developed for HT enzyme breaker system utilization for HPHT formations. Virtually for all tests "broken" fluid viscosity was consistently less than viscosity for linear polymer system, and normally was in the range of the smallest measurable value for industry standard HPHT rheometers. The HT enzyme breaker system confirmed efficiency for high pH borate-crosslinked polymer systems designed for HPHT wells. Enzymes have been used for over 50 years as breakers. However, due to fact that these proteins are considered to be pH and temperature sensitive, utilization of enzymes breakers was limited. This new HT enzyme breaker system increases the application range for proppant fracturing in HPHT formations.