Abstract In North America shale gas projects, operators aim to extend the horizontal sections to boost single well production and reduce drilling and completion costs. However, as the horizontal section length increases, especially when the laterals exceed 3500 meters, numerous complex drilling challenges arise. These include issues with weight transfer during slide drilling, high downhole friction and torque, mud losses caused by high mud weight and friction loss in long horizontal section, short service lives and low efficiency of downhole tools, limited capability to track thin strata due to restricted logging equipment, and difficulties in deploying production casing, including risks such as differential sticking and prolonged running times. To address these challenges, this paper presents an optimized well design strategy for the drilling of unconventional extended-reach unconventional horizontal wells. Firstly, a slim hole design is adopted to cut costs related to casing, cement, and drilling fluids. Secondly, the upper drilling string is switched from 4″ to 4.5″ drill pipes to provide enough torque and hydraulic power, and the Bottom Hole Assembly (BHA) utilizes even-wall stator positive displacement motors (PDM) and motorized rotary steerable systems (RSS) to enhance drilling efficiency in the intermediate and horizontal sections. Third, the oil-based mud (OBM) system is optimized for stability, low friction, and employs clay-free invert emulsion, complemented by managed pressure drilling (MPD) to control ECD. Then, downhole vibration sensors integrated into RSS enable predictive maintenance against tool fatigue. Next, drilling bit optimization based on formation strength analysis increases rate of penetration and extends bit life. Next, dual-telemetry xBolt (MWD) technology, combined with azimuthal gamma ray logging (LWD), which precisely reveals bed crossings and boundaries, optimizes wellbore placement. Finally, a specialized casing running tool and robust casing connection ensure successful deployment of 5.5-inchcasings in long laterals. These optimizations delivered outstanding outcomes. Several records were broken, such as the longest 4,875-meter horizontal slim-hole section drilled in a single bit run, with the average sweet zone drilling ratio of 96%, the longest single-run deployment of 5.5-inch and 4.5-inch hybrid casing at a depth of 8,157-meter, and a rapid 17-day drilling cycle without incidents. In recent years, numerous horizontal wells have extended beyond 4,000m in lateral length, achieving an average horizontal rate of penetration (ROP) exceeding 50m/h and an average drilling duration of within 20 days. Finally, These drilling optimizations deployed in the Duvernay shale project have notably reduced per-meter costs and enhanced drilling speed, setting a new benchmark within the Western Canadian unconventional project. These practices has set the stage for continued drilling of extended reach horizontal wells in the development of similar unconventional reservoirs.
Kong et al. (Mon,) studied this question.