Microwash Treatment Case History

Abstract

Abstract This paper is a case history of two successful applications of mesophase technology for wellbore cleanouts and flow back enhancement. The first application was as a remedial treatment after the well's ESP pumped off and the second application was part of the completion process. Both wells were completed as open-hole horizontal wells, one with expandable sand screens (ESS) and the other with stand alone mesh type premium screens (SAS). Wells in this field are typically drilled with 65 pcf invert oil emulsion drill-in fluid (DIF) and can be as much as 800 psi over balance to formation pressure. The DIF is intuitively managed with respect to mud solids control, so there is no actual QA/QC on the solids management. The ESS completion was treated remedially with coiled tubing (CT) and rotating jet blasters months after the completion. The horizontal well was accessed through a Y-tool bypass that was part of the ESP completion. The SAS completion was treated with CT and rotating jet blasters after running the screen and setting the packer; prior to running the ESP completion, due to casing size limitations for running a Y-tool bypass. Introduction Despite increased emphasis on reduced drilling and production costs, attaining the maximum sustainable production of oil and gas wells is still critical to their economic development and optimized recovery. Productivity impairments associated with the fundamental mechanisms of near wellbore formation damage associated with drilling and completion fluids are well investigated and established.1 These near wellbore impairments are further exacerbated in open-hole completions, where a reduction in permeability can have a substantial impact on well productivity. In principle, minimizing the formation of an internal filtercake by appropriately selecting a sized weighting agent to bridge across the formation pores to prevent spurt loss should abate this reduction in permeability; however, in the field, the continual mechanical and fluid erosion of the external filter cake makes minimizing spurt loss and formation of an internal filtercake virtually impossible.2 Eliminating or reducing the effects of skin damage associated with drilling and completion fluids before a well is produced is advantageous. We report here two successful applications of a mesophase technology that is designed to clean up oil-based mud (OBM) filter cakes and the associated near wellbore filtrate damage. The treatment was applied post production, remedial, in WELL-1 and pre-production, as part of the new well completion in WELL-2. The observations demonstrate that the advantages and productivity enhancement of cleaning up OBM DIF and its associated damage as part of the completion prior to production. Background Invert emulsion DIFs are commonly used in drilling the heterogeneous duning Unayzah sandstones due their drilling performance and reduced risk of formation damage associated with in-situ clay swelling. These wells were drilled with a 65 pcf invert emulsion OBM DIF that utilized sized calcium carbonate (CaCO3) for bridging of the formation pores (Fig. 1). After the wells were drilled to total depth (TD), the holes were swept with diesel, followed by a high viscosity pill, and displaced to solids-free oil based mud in preparation to running the sand screen completions. WELL-1 and WELL-2 were both open-hole (OH) completed with ESS and SAS, respectively. WELL-1 is a twice-sidetracked 1600' horizontal producer that initially produced at 1.4 MBFD. Within the first month the rate of production had precipitously fallen to 0.5 MBFD, at which point the ESP was chronically failing due to under load and subsequently shut-in pending remediation. The clean up of the previous laterals with mud acid systems proved unsuccessful.