Minimizing Formation Damage Caused by Drilling Fluids in Horizontal Wells with Low Formation Pressure. A Case Study in Llanos Orientales Basin, Colombia

Abstract From the drilling stage of an oil or gas well, minimizing formation damage in the reservoir is a key objective. Among the most common drilling induced formation damage mechanisms are solids plugging, emulsion formation due to mud filtrate invasion, and fluid losses. These damage mechanisms are usually mitigated through sealing strategies using bridging agents such as sized calcium carbonate, in combination with loss circulation materials (LCM). However, in high permeability and high porosity zones, or in depleted reservoirs, this may not be enough, and formation damage due to fluid invasion and solids plugging can still occur3. This paper presents an alternative to minimize formation damage in horizontal wells with up to 4,000 ft of geo steering, located in the Llanos Orientales Basin of Colombia. In this area, low pressure zones prone to fluid losses are encountered while drilling the Ubaque Formation. A stabilized microbubble (Aphrones) based fluid system was proposed as an alternative to reduce formation damage, minimize fluid invasion, and low probability of fluid losses while maintaining borehole stability. The methodology consisted of a robust laboratory design, where specialized testing was conducted to determine the optimal range of critical fluid properties, such as LSRV, microbubble content, rheology, and fluid stability, to ensure proper field application. Subsequently, a field pilot test was carried out in a horizontal well drilled in a zone with low pore pressure around 7.9 ppg, where a conventional fluid system could induce losses because of differential pressure. While drilling first well, no fluid losses were observed, validating the use of the Aphrones system. The pilot was successfully applied in a total of seven wells. The use of Aphrones in drilling fluid enabled the drilling of the target zone with the following advantages: no fluid losses, no use of solids, and no requirement for remedial treatments. Additionally, borehole stability and effective cleanup of the production interval were ensured, leading to key operational benefits, such as: No hole cleaning pills needed during drilling. Reduction drilling time because a better hole gauge. Lower operational time and costs by avoiding the use of post drilling filter cake removal pills. The results from implementing the stabilized microbubble mud system directly contributed to reducing formation damage by minimizing fluid loss and maintaining low filtrate levels. This positively impacted well productivity, establishing the technology as an efficient, technically robust, and economically competitive alternative for drilling productive zones with similar characteristics.