Successful Drilling Well on Middle Jurassic Formation with Severe Geotechnical Conditions on West-Yurkharovskoe Field

Abstract

The paper describes the engineering and technology solutions that used in the well with non-standard casing design and geological conditions on West-Yurkharovskoe field. Drilling characterized by low ROP, high risks of downhole tool failure and problems with wellbore stability. The geological structure is quite complex with coal-zone, high-pressure zones with abnormal pore pressure equal 2.2 g/cm3 and high temperature 125°C of Middle Jurassic formations that limited the choice of applicable tools and demand the optimal solutions in planning. For successful accomplishment of the project objectives and minimization runs number was carried detailed analysis geological data, possible complications, experience of drilling wells on West-Yurkharovskoe field. Depending on the tasks and goals are set, the following selection was made: – Downhole tool which have to ensure possibility to drill section with heavy mud and can work with high temperature on bottom; – Drill bit design optimization which can ensure high ROP; – RSS with bit 241mm in tie-back section; – For the first time in Russia was used special liner hanger system which greatly reduces the risk of prematurely setting the hanger while RIH in heavy mud. Integrated approach and close working relationship has lead to next results: – Optimal combination rotary steerable system with new drill bit design allowed to increase average ROP for the whole run in liner is 9.4 m/h, that helped to reduce total drilling time by 268% then average results according to previous wells; – Drilling section 241.3mm, 165.1mm, 155.6mm in one run with demanding geological conditions; – Successful using for the first time in Russia special liner hanger system which allowed achieved bottom without prematurely setting in heavy mud with density equal 2.18 g/cm3; – Implementation liner packer. The packer designed to withstand the extreme wellbore conditions. The packer will provide an effective annular seal between the top of the liner and the casing, thus preventing possible formation breakdown, loss of cement slurry and gas migration above the liner top during cement cure. Successful accomplishment of the project objectives with demanding geological conditions have been achieved due to utilization new completion systems and downhole tools, which was applicable to borehole conditions. This experience allows to get one step closer to making the well construction for Jurassic formation deposits profitable and achievable more longer horizontal section.