Integrated approach to modeling gravel packs in horizontal wells

Abstract

Gravel packing has routinely been used as a sand control method in open-hole horizontal wells. With the advances in drilling technology in recent years, horizontal wells with lengths ranging from 2,000 to 6,000 ft have become more common. Executing these open-hole gravel-pack jobs (alpha-beta packs) has been a challenge.Although scattered attempts have been made to separately understand different parts of the gravel-pack process, the industry still lacks a tool that accurately models the complete process and aids in successfully designing these jobs. This paper presents a pseudo-3D modeling tool, which models the complete gravel-pack process and accounts for fluid flow and gravel settling in different flow paths. The presented simulator tracks the fluid flow and gravel concentration from the wellhead down through the workstring, crossover ports, open-hole and screen-washpipe annuli, and then back to the surface through the washpipe and casing-workstring annulus. In the open-hole section, flow through the different annuli is considered and fluid is distributed based on the frictional resistances of the respective annuli. The simulator calculates the bed height based on equilibrium velocity model, which constitutes the alpha wave part of the packing. During the beta wave, dehydration packing is achieved with fluid leaking off into the screen-washpipe annulus. The simulator also models fluid flow through complex flow paths like crossover ports, pressure attenuators, shifting tools, etc. Thus, it can be used to evaluate the impact of different tools and fluid configurations on the success of the job and subsequently optimize the job design. The paper also presents two case histories of gravel-pack jobs in long horizontal wells where the simulator was successfully used to design and execute the job. These case histories highlight the design methodology and show how, with proper calibration, the simulator can be an effective design tool and significantly increase the success rate of gravel-pack jobs in horizontal wells. Copyright 2008.