Innovative Methods for Drilling Extended Reach Wells in Challenging Reservoirs

Abstract

ERD (Extended Reach Drilling) and MRC (Maximum Reservoir Contact) wells are classified by the ratio of measured depth (MD) to true vertical depth (TVD). Wells with a ratio above 2 are defined as ERD wells, and those with a horizontal hole length exceeding about 8,000 to 9,000 feet are considered MRC wells. Various factors drive the need for such well designs, including surface locations, geopolitical situations, environmental impact, and government-defined sensitive areas. The subject well qualifies as both ERD and MRC, with a measured depth of 37,600 feet (MD) and a true vertical depth of 8,979 feet (TVD), resulting in an ERD ratio of 4.188. Horizontal wells offer a better productivity index than vertical or deviated wells but designing and planning these wells present significant challenges. It is crucial to balance reservoir exposure and well profile to maximize productivity. The primary advantage of drilling an EMRC (Extended Maximum Reservoir Contact) well is placing it in the most productive part of the reservoir, especially in thin oil reservoirs with gas caps. However, real-time geo-steering requires numerous reactive adjustments to manage drilling and subsurface requirements, which can sometimes limit accessibility for post-drilling activities and reduce rigless options. The subject well was planned with a limited entry liner, necessitating careful planning to ensure well accessibility for lower completion. Mitigation was best achieved by visualizing and simulating subsurface geometry and making proactive, smooth alterations rather than aggressively geo-steering the well in search of the oil-water contact (OWC). Planning this extensive ERD well involved directional planning, bit and BHA design, hole cleaning calculations, directional control points/formation markers, and mud design.