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/ Executive summary This paper describes an approach undertaken for construction of the unique ERD well with Vertical section equal to 26112.7 m that targeted shallow (862.5 m TVD) Vikulovo reservoir – first of a kind well in Western Siberia. It unveils Main challenges and set of technologies and practices implemented to cope with these challenges. The paper also covers detailed engineering planning, QAQC of all processes, training of involved personnel that altogether resulted in a successful project execution with best KPI records. The project had following major challenges in place: ▪ Shallow reservoir TVD, hence severe problems with Downhole Weight Transfer, String Buckling, making impossible to get Running strings to target depths w/o rotation. ▪ Narrow Drilling window - ECD limitations. ▪ OBM rheology model mismatch with actual. To tackle aforementioned challenges, following measures have been undertaken: ▪ Advanced and thorough planning of Drilling programs with key Contractors; ▪ Real-Time Geomechanics Surveillance while drilling HZ section; ▪ Execution of QAQC program (Engineering and Operational); ▪ Support of Real Time Drilling Center; ▪ Fit for Purpose training of key involved office and Operational Personnel. ▪ Delivery of Performance of discussion sessions: DWOP, HAZID, L(logistics)OP, Lessons Learnt. As a main outcome, this project proved feasibility of drilling ERD wells in given regional Geological conditions, all due to implemented complex approach for engineering planning and operational execution similar achieving all targeted KPIs. Clear benefits are observed in minimization of Human Errors and associated NPT events from the Support of Real-Time Drilling Center that ensured correct decision-making process and Technologically Fail - Safe operations. Geomechanical studies revealed and proved in fact narrow WBS (Wellbore Stability) drilling window. This defined safe operational limits of Drilling parameters and helped to work out procedures for smooth drilling conditions. A number of technological issues have been addressed by Real-Time Geomechanics Surveillance that included: ▪ WBS (wellbore stability) analysis ▪ Hydraulic parameters monitoring in drilling and reaming modes ▪ Continuous hole cleaning analysis ▪ Tripping Speeds guidance Executed thorough QAQC campaign helped to minimize Engineering planning mistakes and Operational risks. Engineering QAQC implied well design external review by SMEs (subject matter experts) and general Peer and Technical reviews by Internal Engineering teams. Operational QAQC in its turn inferred audits, equipment selection and Upgrade, modifications, inspections, assembling and function tests verification against Industry and Company Standards. Successful execution of this technologically challenging ERD (3.03 SOR) well is the main achievement of the project. This well is first of a kind in Central part of Western Siberia region. Success of the project and its uniqueness was driven by complex integrated approach to project planning and execution. Achieved results truly prove effectiveness of this approach and implemented Best Practices.

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This paper presents the results of studying petrophysical and geomechanical properties of rocks by conducting thick-walled cylinder core tests (TWCT) - triaxial compression with flushing by various fluids. Experiments were carried out for a limited number of core samples from the Ourinskoe Field, which is a part of the Western Siberia oil and gas-bearing basin. In the framework of the study, various core testing schemes were applied, the results of experiments using different fluids for flushing were analyzed, and the optimal testing parameters (including loading rate, washing time, sample relaxation time, etc.) were selected. The result of the research is a detailed analysis of rock fragments removed by different fluids as a result of triaxial compression and subsequent destruction of a thick-walled cylinder. The paper presents the qualitative relations of the particle size distribution on the prevailing deformation patterns (elastic or plastic), analyzes some petrophysical properties of the strata that control the behavior of the system "rocks – fluid", and consider typical scenarios for TWCT experiments. The obtained experimental data served as an important source of additional information for assessing the draw-down pressure that controlled sand inflow into the wellbore, to determine its particle size distribution, as well as to calculate the size of the wire-wrapped filter liner completion for sand preventing.