A major development with multiple rigs delivering extensive multi-laterals encountered a pervasive mud-window issue within the reservoir. The resulting severe mud losses, extensive NPT and formation-damage was also deteriorating with time due to depletion. Conventional approaches to stem losses had failed and adoption of an energized mud-system with acceptable Effective Circulating Density (ECD) was not considered cost effective, pragmatic nor safe. Instead a novel application using Hollow-Glass-Spheres (HGS) was trialled, that demonstrated an effective and highly successful outcome. With 10 rigs drilling 60-70 wells per-year, each with 5,500 to 6,750m in the reservoir, quick resolution of the issue was required. For these reasons the Team at bp Russia looked carefully at alternatives that might fit the mud-window, but that offered a realistic approach for the environment and conditions in Eastern Siberia. The Team identified HGS as an approach to lighten the mud, often used for cementing ECD, application for drilling has been limited. For this approach we required an option with broad capabilities that could be scaled-up and exported to other development areas where such issues existed. This paper will report on the planning, delivery, and execution of a pilot on the Sb. field at TYNGD, in Eastern Siberia. Initially deployed on three wells, including multi-laterals, the paper will walk through the engineering considerations, during the planning and execution phases. Reporting comprehensively on the data gathered and the many lessons learned during the incremental and stepwise deployment. Data will be provided that demonstrated loss-free drilling was achieved where this had not occurred before, with a dramatic reduction in NPT, FLA needs and costs. The paper will also report on the post drilling productivity and comparison with offset wells drilled with conventional mud systems and suffering severe losses. The results of this pilot have beaten all expectations, there have been many insights and the Team are now looking to set a timetable to scale-up across the NOJV. Much has been learned, waste HGS material has been demonstrated to be an effective FLA pill in other sections of the well and centralisation of mud process may offer additional cost savings and improvements. Further efficiencies are expected to be achieved and potential across the Company portfolio could be a major game changer. HGS for cementing is well documented, application for drilling fluids has been less reported and almost exclusively applied to one-off sections/wells. The TYNGD application is novel as this is a major new development with 10 drilling rigs. Application is on multi-laterals and prior offset wells are available for direct comparison. The results of the approach demonstrate a new way of performing well construction in an effective manner for major Field Developments where losses are prevalent.

The paper describes the first deployment of HGS in Eastern Siberia as a mud additive. The technology was utilized for reducing drilling fluid density for prevention and mitigation of losses; while drilling through a producing reservoir section with low pore pressure, unconsolidated and fractured sands. The engineering considerations, fundamentals of the approach and major risks involved were reviewed with application to the Sredneboutobinskoye Oilfield as a pilot field application for broader future plans. Key planning, delivery and execution principles of the initial application will be reported in the paper. Initially deployed on three wells, including multi-laterals (Rylance et al., 2021), the paper will walk through the engineering considerations during the planning and execution phases. Key sections include the data gathered and the many lessons learned during the incremental and stepwise deployment. The paper will also report on post drilling productivity and comparisons with the offset wells drilled with conventional mud systems, which suffered severe losses. The results of this pilot have exceeded expectations. There have been many insights and the Team are now looking to set a timetable to scale-up across the Taas-Yuryakh Neftegazodobycha (TYNGD). After many hours of laboratories study and preparation works, the general plan was to reduce the static density and ECD to mitigate fluid losses. However, the applied results showed additional effects from HGS. Data will be provided that demonstrated loss-free drilling was achieved where this had not been the case before, with a material reduction in NPT, lost circulation material (LCM) needs and costs. Much has been learned, recovered HGS material has been demonstrated to be an effective LCM pill and centralization of mud processing may offer additional cost savings and improvements. Further efficiencies are also expected to be achieved and future potential is considerable. HGS for cementing is well documented, yet application for drilling fluids has been less well reported and almost exclusively related to single wells. The TYNGD application is innovative as this is a major development with 10 active drilling rigs. The application is on multi-laterals and offset wells are available for direct comparison. The results of the approach demonstrate a new way of performing well construction in an effective manner for major field developments where losses are prevalent.