Monobore Completion Design: Classification, Applications, Benefits and Limitations

摘要

A monobore completion is a simple completion design that uses the same internal diameter from the bottom of the well to surface. This may be accomplished by cementing a string of casing in a well, or by having tubing stabbed into a polished bore receptacle on a casing liner the same size as the tubing. Monobore completions have been applied extensively in oil and gas fields around the world, both onshore and offshore, from very low reservoir flow to extremely high production rates, since the late 1980s. They have proven beneficial due to their simplicity and cost savings. This study summarizes an extensive literature review of monobore completions and categorizes the monobore completions as slimhole, big bore or special function applications.;This study also evaluates the well inflow impact of the 4 1/2-in. openhole multistage sleeve monobore completion employed in the North Kuwait Jurassic Gas field for HPHT wells compared to the previous completion using 3 1/2-in. tubing and 5 1/2-in. liners. The inflow evaluation was made for both volatile oil and gas condensate fluids found in this reservoir. Reservoir depletion was modeled to determine flowing life for the conventional completion versus the monobore design.;The results of the modeling indicate production rate for the volatile oil case is the same in both completion designs, conventional and monobore, while in the gas condensate case the production rate is slightly higher for the monobore completion. As the monobore completion is larger, it reaches an unstable flow condition more quickly than the conventional design. However the multistage completion methodology allows all zones to be stimulated and contribute to flow, and can be equipped with a velocity string to sustain flow.