Particle Impingement, Corrosivity Testing and 3D Numerical Modelling for High Rate Gas Wells

Abstract Wellbore production or injection rates can be constrained by tubing restrictions if not considered in the design phase of the wellbore. In contrast to surface facilities, debottlenecking of wellbore restrictions require costly workovers especially in challenging environments. The concept of high rate hybrid bore design is an engineering solution that can be considered by operators to achieve maximum rate subject to reservoir conditions while optimizing equipment inventory and long lead requirements. A hybrid well is a variable bore with restricted diameters around the reservoir and surface sections of the well and larger diameter across 85% of the production conduit. The restricted sections of the wellbore are designed to meet specific reservoir inflow objectives such as controlled drawdowns, optimized drilling requirements and standard surface and safety equipment such as slim safety valves and wellhead systems. A successful hybrid well design integrates tubing stress analysis, lab wear, corrosivity and erosion test data that are matched to field data using combined wellbore hydraulics, flow assurance, 3D imaging and numerical finite element modelling as shown in this work. Due to variation in flow path for such high rate wells, wellbore erosion modelling around load bearing crossover well equipment is critical. Impingement testing using tribometer, ASTM G76-18 protocols with synthetic aluminum oxide particles at varying velocities and impingement angles are used to estimate expected wear conditions for various alloys used in such well design. All identified alloys are further tested for fluid corrosivity at varying pH, pressures and temperatures that are representative of operating conditions along the production tubing. The best alloy that meets load bearing requirements from tubing stress analysis is combined with results from corrosivity, impingement angles and 3D scar characterization for selecting the final well design especially for high risk erosion well crossover equipment. This design approach incorporates expected material properties into a total system hydraulic model to establish a maximum sub erosion gas rate that complies with tubing stress analysis results to maximize value and well lifespan operators. Numerical analysis using 3D finite element modelling is performed for specific well equipment such as choke and safety valves. A key outcome is that optimum well design is achieved based on actual material testing with defined parameters such as maximum allowable wall losses, sub erosion gas limits, erosion velocity ratios and annual tolerable erosion limits. A combination of numerical simulation models, analytical well performance tools, extended velocity models eliminates design restrictions from methods such as the API-14RE c-factors that can constrain production rates. The Hybrid technology requires critical mechanical assessment and material testing using lab and field data to ensure achieving the maximum potential from this design.