A Novel Solution to Control Payzone Losses

Abstract Downhole losses is one of the most challenging and costly events in drilling and workover operations. When it comes to controlling losses in the reservoir section, it becomes more critical due to the special design needed for loss circulation material (LCM). These LCM should be reservoir friendly such that they are easily removable or do not create a source of permanent damage. This work investigates a novel solution of utilizing pre-crosslinked polymer gel systems to control downhole losses in brines without jeopardizing the reservoir quality. Two different pre-crosslinked polymer gel systems were evaluated as fluid loss control for use with completion or workover brines in a 50:50 ratio. The systems underwent fluid loss control, dissolution efficiency and regain flow tests. Fluid loss control test was conducted on 10 micron ceramic disk by placing the mixed fluid in HPHT cell at different pressures up to 1,500 psi and recording the fluid loss volume at multiple time durations. The generated filtercake was immersed in acid treatments for 24 hours to assess the external filtercake solubility. Furthermore, regain flow on the ceramic disk prior to forming the filtercake and after the treatment was measured to evaluate both the remaining external and internal filtercake damage. Based on the findings of this study, it was concluded that the pre-crosslinked polymer gel systems were very efficient in controlling the brine fluid loss by creating both external and internal filtercakes. Initial spurt loss of brines from the evaluated systems was about 15-25%, with differential pressures between 500 – 1,500 psi and temperatures of 150-250°F. In addition, external filtercake dissolution showed efficient solubility in acid treatment ranging from 85 to 91 wt.%. However, the internal filtercake of the used ceramic disk after remediation was not adequately removed. Thus, regain flow of 11-13% was observed using two test methods i.e. constant time with an applied pressure of 5 psi and constant volume with an applied pressure of 100 psi. Although the internal filtercake dissolution showed low solubility, the system can efficiently work in carbonate formations due to its reactivity with acid. This work evaluates pre-crosslinked polymer gel systems to control downhole losses in completion and workover applications. It focuses on how friendly the system in minimizing losses efficiently and addressing the best methods to be applied in the field without affecting reservoir quality.