Extended-Reach Drilling Hits Mainstream To Squeeze Difficult Reservoirs

Though expensive and complex, extended-reach drilling (ERD) is moving more into the mainstream as the industry is driven to develop frontier reserves in fragile environments like the Arctic where drilling from shore to off-shore targets reduces a project’s infrastructure costs and environmental footprint. A form of directional drilling, ERD is also being used increasingly to tap into hard-to-produce reservoirs, making viable projects that might otherwise be written off as noncommercial. This article highlights how the Russian Far East became the ERD epicenter in the past decade, given ExxonMobil and Rosneft’s extensive use of ERD in developing Arctic resources offshore Sakhalin Island, and how ERD is becoming more widely used in regions as diverse as the Gulf of Thailand, off-shore Brazil, and the Arab Gulf. By definition, an extended-reach well (ERW) is one in which the ratio of the measured depth (MD) vs. the true vertical depth (TVD) is at least 2:1 (PetroWiki). An ERW differs from a horizontal well in that the ERW is a high-angle directional well drilled to intersect a target point, a feat requiring specialized planning to execute well construction. ExxonMobil subsidiary Exxon Neftegas Limited (ENL), which operates the Sakhalin-1 license area offshore Russia’s Sakhalin Island (Fig. 1), has been pushing the limits of ERD for nearly 2 decades with innovative technologies and sophisticated well planning, making the Sea of Okhotsk a place where any ERD drilling record set today may easily be broken tomorrow. Russia’s state-owned Rosneft (which has a 20% stake in Sakhalin-1) owns bragging rights for having drilled the longest ERW well on record to date. Rosneft announced in November 2017 it had drilled a 15000-m horizontal ERW from the offshore Orlan gravity-base platform at Chayvo field situated in 14 m water depth in the Sea of Okhotsk, topping four previous records set between 2013 and 2015 that had reached between 12450 m and 13500 m (Fig. 2). In a news release at the time, Rosneft called the well “super complex with a DDI [directional drilling index] of 8.0 and a 14129-m stepout.” The release went on to say that the Sakhalin-1 Consortium could (as of the 2017 announcement) claim to have drilled nine out of the world’s 10 longest ERD wells. According to Rosneft, the project had set five world records for measured depth of wells between 2013 and 2017. In April 2015, development well O-14 was drilled with a length of 13500 m. That broke a 2014 record when the 13000-m Z-40 well was completed. In 2013, records were announced for wells Z-43 and Z-42 which were drilled, respectively, in April and in June 2013 with lengths of 12450 m and 12700 m. Rosneft credited ExxonMobil’s patented “Fast Drill” drilling optimization process that can increase rates of penetration (ROP) by up to 400% as a significant innovation contributing to the ERD success story at Sakhalin-1. One of the largest foreign direct investments in Russia, Sakhalin-1 operates under a production sharing agreement (PSA) with its license area off the northeastern coast of Sakhalin Island, comprising the Chayvo, Odoptu, and Arkutun Dagi fields.