Extended Reach Drilling (ERD) Technology Enables Economical Development of Remote Offshore Field in Russia

Abstract

Abstract Advanced extended reach drilling (ERD) and completion technologies were successfully tested in a challenging remote Russian Far East location to prove feasibility of land based development for the offshore Chayvo field. Chayvo is located 8–11 km off the eastern coast of Sakhalin Island in the Sea of Okhotsk. Development plans using offshore platforms were marginally economic because of arctic design and operating conditions. Two ERD wells were drilled in a pilot program to measured depths of 9,375 m and 10,182 m. Horizontal displacements of the wells were 8,419 m and 9,246 m at a true vertical depth (TVD) of 2,613 m. These first two Chayvo ERD wells represent record wells for ExxonMobil and are currently the 7th and 4th longest ERD wells in the world. Other highlights include the first 13–5/8 in. casing installation using "mud-over-air" flotation and record coiled tubing runs. Absence of drilling data between the land-based surface location and the reservoir made planning Chayvo ERD wells difficult. ERD well design was based on a systematic planning approach through study of local Russian and worldwide geometric offset wells and application of ExxonMobil proprietary technologies (Integrated Hole Quality/Quantitative Risk Assessment). A comprehensive directional plan was developed to successfully intersect the reservoir target objective at a precise depth and location. Wells were drilled using rotary steerable systems (RSS) and polycrystalline diamond cutter (PDC) bits. Formation evaluation was achieved using logging while drilling (LWD) tools from surface to total depth (TD). Multiple challenges including tight schedules, international logistics and adverse weather conditions were overcome prior to spudding the first well. The team quickly adapted to actual well conditions (i.e. fracture gradients, wellbore stability, and high torque) while drilling. The now proven feasibility of ERD technology at this location will help make a once marginal "high-cost" project economic. Introduction ERD wells were drilled in several fields around the world1–7; each project had justification for the increased technical risk, required research work and upfront capital expenditure. Figure 1 shows the Chayvo onshore wellsite from which the first two pilot ERD wells, Chayvo Z-6 and Z-4, were drilled. The success of these two wells proved the feasibility of developing the northern portion of Chayvo field, shown in Figure 2, with ERD wells and creates significant opportunities for the Sakhalin 1 consortium:Enhances project economics through application of ERD technologyReduces or eliminates the capital cost of large offshore structuresOffsets high offshore operating costs with lower onshore costReaches additional resources from the same infrastructureReduces environmental exposure of project Critical to the success of the Sakhalin drilling program is utilization of evolving ERD well technology. Several initiatives were put in place to identify and progress specific technologies deemed beneficial to the project's successful implementation. This project will rely on best available technology but given the duration of the drilling program, several new or enhanced technologies will ultimately have significant impact on wells drilled during the program.