Overcoming Practical Artificial Lift Challenges to Produce Extra-Heavy Oil from a Deep Reservoir in Northern Kuwait

Abstract

Extra-heavy oil reserves in the Abdali field in Northern Kuwait exhibit a viscosity ranging from 6,000 to more than 15,000 cP at depths of ~9000 ft. Assuming a fully isolated tubing, the theoretical natural flow rate is less than 1.0 bbl/d. The viscosity profile shows an exponential trend inside the well reaching millions of centipoises at surface conditions. This paper investigates the lifting challenges and possible solutions for the efficient, practical and commercial production of these reserves. The study builds upon the findings presented in two previously published papers by Al-Murayri et al. (2024). A compositional EOS with a Pedersen (1987) viscosity model was used to accurately describe the properties of the oil, liquid solvent, and their mixture at different pressures and temperatures inside a vertical well. A correct fluid property description from PVT flash calculations was key for modelling the weight of the column, friction losses and the pressure distribution along the well. Jet Pump and ESP were considered. Other pumps were discarded either because of their incompatibility with the reservoir depth or due to their environmental footprint. Nodal analysis combined with advanced analytical calculations and numerical simulations were necessary to find feasible operating points for different well configurations. Abdali's oil must be diluted with liquid solvent at the bottomhole to reduce the viscous friction losses. Adding 70% mass fraction of liquid solvent reduces in-situ oil viscosity from 6,300 cP to 9 cP, and the viscosity at surface conditions from 3,000,000 cP to 65 cP. The proposed Jet Pump used the liquid solvent as power fluid. Its configuration ensured the desired BHP and liquid rate with good efficiency. The key parameters were the ratio of power fluid to the reservoir fluid, the pressure discharge, and the pump Nozzle diameter. ESP lifting necessitates a concentric tubing or a capillary tube for liquid solvent injection. A direct solvent injection into the annulus showed higher than target BHP due to the cumulative impact of the hydrostatic solvent column weight and the topside injection pressure. For the capillary tube, Bernoulli's equation proved that the hydraulic weight of the column is partially compensated with friction losses resulting in the desired BHP. It was shown that numerical simulations are necessary for nodal analysis of such a complex lift design. Prominent industrial well modelling packages cannot handle extra-heavy oil blends with liquid solvents due to a lack of EOS integration in their artificial lift design. This paper investigated a novel approach combining advanced analytical calculations with nodal analysis and numerical simulations to prove the feasibility of lifting a complex fluid mixture from a deep reservoir while capturing the flow dynamics from the bottomhole to the wellhead.