Brian Beall, Robert Tjon-Joe-Pin, & Harold Brannon, BJ Services
This paper presents the results of a new treatment designed to improve the cleanup of horizontal/openhole completions. The wells evaluated in this study were drilled using either starch or cellulose polymers, xanthan polymer, and sized calcium carbonate or salt particulates. These clean "drill-in fluids" were introduced to minimize the damage to the wellbore when compared to that observed with conventional drilling fluids. Although used to minimize formation damage, testing and experience have shown that insufficient polymer degradation can significantly reduce flow capacity at the wellbore leading to reduced well productivity or injectivity. Acid treatments are typically applied in attempts to remove or "by-pass" the damage created by the filter cake. These acid treatments are often marginally successful, particularly when applied in extended length intervals. Previous studies were conducted to develop laboratory procedures to better simulate and characterize the damage attributable to these "clean" drill-in fluids. Various chemical breaker systems were subsequently applied to evaluate the effectiveness of their relative filter-cake degradation capabilities. Laboratory studies have demonstrated that drill-in fluid filter cake can be effectively removed through the application of a newly developed technique incorporating an enzyme-based polymer degradation system. The data show that through utilization of this new technology, smaller, less costly treatments can be used to treat entire openhole intervals to zero-skin potential with dramatically improved treatment efficiency. Much smaller, lower concentration acid treatments can then be effectively applied to stimulate the interval. Surveys following the field application of the new system have shown not only increased flow, but also flow throughout entire length openhole intervals.