No abstract

This article describes an experience drilling a multilateral "fishbone" well with eight sidetracks and contains geological substantiation of this technology from the production-increase point of view as well as actual results of the eight-lateral well start up and operation. For fishbone wells where each wellbore is a sidetrack from the previous hole, one of the fundamental drilling aspects is kickoff from the parent wellbore. This article is based on the analysis of 114 kickoffs in production wells of the East Messoyakha field where kickoffs with a rotary steerable system (RSS) and performance drilling motor (PDM) were determined beneficial. Additionally, strength analysis and hydraulic calculations for drilling of the longest fishbone at the East Messoyakha field with an extended reach drilling (ERD) factor of 2.95 are discussed. Further, this article highlights the main potential of this technology development and its limitations during a further massive application.

The Vostochno-Messoyakhskoe field is the northernmost active continental field in the Russian Federation (Fig. 1). This field is located 250 km from the Arctic Circle, in the arctic climatic zone. Full production drilling only began in 2015 because of the field's geological complexity and lack of transportation structure. Weather conditions, such as strong winds and extremely low temperatures, can be hazardous to personnel and equipment. Additionally, this oil field has permafrost zones (400m from the surface) and low formation temperatures at the production zone. Also, because of permafrost zones, there is a high risk of thawing the wellhead formation. These conditions significantly affect which technologies can be applied during drilling and completion of the wells. Therefore, special cement designs are necessary to help reduce risks associated with low temperatures and permafrost zones in the Vostochno-Messoyakhskoe field. Production is further complicated by a gas layer at 720 to 820m true vertical depth (TVD) and high formation pore pressure. This can make the cement operations with the production casings difficult. While the TVD of the casing landing is not relatively deep, the measured depth (MD) in extended reach drilling (ERD) wells is significant (Fig. 2). ERD wells can challenge cement displacement efficiency (Sabins, 1990). Mud removal efficiency may not be enough to create a high-quality cement barrier and isolate formations from gas migration. Poor mud removal can affect future life of the wells and crude oil production. To perform remedial jobs, it is necessary to stop production for several days. Due to experience in performing remedial jobs in the Messoyakhskoe field, it is usually necessary to perform a few attempts of the remedial cementing operation to reach positive results. Therefore, the operator decided to utilize hydraulic packers to create a second barrier between the surface and production casings to help prevent gas migration to the surface, save time associated with remedial operations, and extend the life of future wells.