Abstract
The amount of polymer damage created by a fracturing system has been a problem for many years. Polymer damage results in the reduction of fracture conductivity and effective propped fracture length. One method to reduce polymer damage is to reduce gel loadings. Historically systems that were developed to reduce polymer loadings have encountered numerous problems. The limiting factor for reducing the amount of polymer in a fracturing system is the point where the viscosity of the fluid is not adequate to transport proppant. In areas of low permeability gas wells, poor proppant transport results in less than desired production due to decreased fracture length in the reservoir.
Many of these low-polymer fracturing systems are not operationally feasible due to the lack of a suitable water source for the system to yield its peak viscosity. In addition to the operational issues of locating a suitable water source, another constraint on some of these systems is the requirement to use a liquid KCl substitute in place of granular KCl. These issues have limited the use of the low-polymer systems in many areas. The shear sensitivity associated with the use of organometallic crosslinkers is a problem encountered by many low-polymer systems. High tubular velocities will shear degrade the fluid reducing it's proppant transport capability compared to that of a borate crosslinked system.
This paper will discuss a modification to a well-established borate crosslinked fluid and system that eliminates these problems. Case histories will be given for the applications and results of this reduced polymer system that yields comparable viscosities to higher polymer loading systems.
