Overcoming the Challenges for the First Longest Extended Reach Horizontal Slim Well

Abstract

Extended-reach drilling (ERD) has become a key strategy for maximizing reservoir contact, unlocking bypassed reserves, and reducing surface footprint, emissions, and overall development costs. Slim-hole ERD wells, in particular, offer a cost-effective and environmentally sustainable means of enhancing reservoir access—especially when drilled with water-based mud (WBM), which presents economic and ecological advantages over oil-based mud (OBM).

This paper presents a landmark case study from an onshore UAE field, where two planned maximum reservoir contact (MRC) wells were consolidated into a single extended-reach horizontal (ERH) well. The well was drilled to a total measured depth (MD) of 27,513 ft with a 6″ lateral section extending 16,040 ft setting global records for the longest slim-hole lateral, and longest 4-1/2″ limited-entry liner completion. The operation was executed in a geologically complex carbonate reservoir with high bottomhole temperatures exceeding 300°F, severe circulation losses, variable pore pressures, and the presence of four interpreted faults along the well path.

In addition to subsurface challenges, a significant operational constraint was the use of a high-spec rig that had a known history of equipment reliability issues and no prior experience executing ERD wells. This increased the risk of non-productive time (NPT) and equipment-related failures, requiring meticulous planning and continuous real-time monitoring to mitigate potential disruptions.