Robert M. Tjon-Joe-Pin

Characterization of Breaker Efficiency Based Upon Size Distribution of Polymeric Fragments Resulting from Degradation of Crosslinked Fracturing Fluids

Fluid viscosity reduction is commonly used to gauge polymer degradation. Although viscosity reduction indicates polymer degradation, it is misleading to conclude that this reduced viscosity equates to improved fracture conductivity. Polymer fragments which are desolubilized from the gelled fluid no longer contribute to fluid viscosity but do, unfortunately, contribute significantly to proppant pack damage. A recent study disclosed laboratory procedures to characterize the efficiency of get breakers based upon the Size distribution of the generated polymeric fragments. The study focused on 8-week evaluations of the effects of various breakers on linear, guar-based fracturing fluids from room temperature to 210°F. The studies indicated that enzyme breakers continued to degrade the polymeric molecular weight for at least eight weeks. The molecular weight reduction attributed to the enzyme breakers outperformed oxidative breakers at all conditions evaluated. This study discloses the results of similar efforts conducted to characterize the efficiency of breakers applied in crosslinked fracturing fluids. The data yield a quantitative profile of the polymeric fragments as well as a measure of the relative degrading efficiencies of the various oxidative and enzymatic breakers. The studies were conducted with borate-crosslinked guar, zirconium- crosslinked guar, and zirconate-crosslinked CMHPG. Detailed analyses of the data are provided.

Application of Polymeric Damage Removal Treatment Results in Multi-Fold Well Productivity Improvement: A Case Study

Damage to proppant pack and formation permeability can drastically decrease well production. In many cases the damage is due to inconsistent degradation of gelled stimulation fluids and residual filter cake on the formation face. Several methods have been employed with limited success to remove polymeric damage in an effort to increase well productivity. A new technique utilizing polymer specific enzymes has been developed to facilitate removal of polymeric damage. The new, environmentally safe, remedial treatment can be applied over a wide pH range and at temperatures as high as 300 F. Laboratory analysis has shown that multi-fold permeability improvements can be achieved through polymeric damage removal with the new system. A case study of several low productivity wells suffering from polymeric damage was conducted. Production histories and return flow analysis were evaluated to characterize the damage and guide the remedial treatment design. The case histories of several wells treated with the remedial polymeric damage removal treatment demonstrate multi-fold improvements in well productivity.