Invasion of drilling fluids filtrate and solids into porous, permeable, fractured or vuggy zones can cause formation damage and presents a major source of drilling problems. Furthermore, downhole mud losses also increase environmental and financial risks associated with drilling operations, costing over $1B annually.
This thesis investigates the use of in situ prepared calcium carbonate nanoparticles (CNP) for fluid loss prevention in invert emulsion drilling fluids. CNP at 5 wt% concentration were synthesized within a custom ‘carrier’ emulsion using a modified microemulsion approach. Subsequently, the carrier emulsion was used to deliver target concentration of NPs to a host drilling fluid of interest via volumetric dilution. High pressure, high temperature (HPHT) fluid loss experiments on commercial invert emulsion drilling fluids showed that CNP at concentration of 0.5 wt% provided a 20–50% improvement over conventional lost circulation materials (LCM). In addition, basic properties of mud samples were not affected significantly in the presence of the carrier emulsion.
In order to evaluate performance of CNP under real-life conditions, six full-scale field tests were conducted in horizontal wells in Alberta, Canada. Industry-scale synthesis of CNP followed the lab-bench process and was implemented at a specialized mixing facility. The results suggested that the scale-up from 3×10-4 m3 (300 mL) to 20 m3 did not affect average particle size or final properties of the carrier emulsion. Furthermore, field HPHT data showed good agreement with the lab experiments, where the average fluid loss in the test wells was reduced by 20–30% compared to the control wells using conventional drilling fluids. Finally, analysis of mud losses revealed that the cumulative losses while drilling were on average 20–30% lower in the presence of 0.5 wt% CNP, which suggested that NPs help to reduce downhole losses.