The Pokur Suite Hard-to-Recover Reserves Development: Successful Achievement of Challenging ERD Wells Drilling and Completion Goals at North-Komsomolskoe Field

Abstract

Over the last years, operators get to think about hard-to-recover reserves in poorly consolidated reservoirs of Pokur formations saturated with highly viscous oil and complicated by underlying aquifers and gas capsmore frequently. Low level of knowledge about the reservoir makes it difficult to select an efficient completion technology for ERD wells. This paper describes a successful experience of construction and "complex" completion of wells, with application of various types of inflow control devices at the North-Komsomolskoye field. To solve the challenges of the North-Komsomolskoye field and to find an efficient development system, a decision was made to drill ERD wells with 1,500 and 2,000 m long horizontal sections, which, considering the vertical depth of ~1,120 m, already represents a challenge in terms of drilling and completion string running operations. The complicating factors dictate the necessity to select a completion system which effectively prevents sand production and limits the unwanted fluid inflow into the wellbore. The extensive calculations of drilling and completion running processes resulted in application of heavy-wall drill pipes with unusual for Russia 114.3 mm (4.5″) high-torque threaded connections used for drilling and completion assemblies running processes. The liner running operations are carried out using a power swivel: a device for running string (RS) rotation independently from the liner. Drilling of long horizontal sections is carried out with oil-based mud to significantly decrease the risks related to wellbore placement and stability issues. Considering the reservoir heterogeneity, a multizone completion system is used, with swellable packers. To enable packers’ activation, ensure proper displacement of OBM from the wellbore and reduce risks of counterflow emulsions formation, the well is displaced to brine with the use of multi-composition spacer fluids and a washpipe to ensure circulation via the filter liner shoe. One of the completion stage constituents is the laboratory-based selection of autonomous inflow control devices and valves along with validation of sand filters. The successfully performed completion stage in long horizontal sections provided very good results during wells operation: Higher flow rates vs. previously drilled wells. No water/gas breakthrough vs. wells completed only with filters. Absence of significant production of solids.