High-Angle Gravel-Pack Completion Studies

Abstract

A two-part study was conducted to define optimal gravel-pack procedures for some high-angle well completions in an area operated by Chevron U.S.A. Inc. In the first part of the study, gravel slurries were pumped through a I,080-ft [329-m] tubing string to simulate actual slurry transport conditions in high-angle wells. The tubing string had an inclination of 80° [1.4 rad] from vertical. Measurements were made to determine suitable viscosity and solids concentration for effective gravel transport. In the second part of the study, a full-scale cased-hole completion model was constructed. Gravel slurries that had satisfactory transport performance were tested for packing characteristics in the model well bore (completion interval). The need for special completioninterval geometry to obtain satisfactory packs was investigated.Results showed that high-viscosity carrier fluids (600 to 700 cp [0.6 to 0.7 Pa's]) with high gravel concentrations (15 Ibm/gal [1797 g/ dm 3 ]) provide good transport, but they are unsuitable for use in completion intervals in wells with angles of 80° [1.4 rad] from vertical. Satisfactory transport and improved packing were achieved with lower carrier viscosity and concentration (300 to 400 cp, 4 Ibm/gal [0.3 to 0.4 Pa' s, 479 g/dm 3]). Special liner-tailpipe (washpipe) geometry considerations reported by previous investigators are required in conjunction with the optimal slurry properties defined in this study.Completion operations designed from results of this study have satisfactorily met general placement criteria. Field experience to date has been in wells with inclinations up to 80 ° [1.4 rad] from vertical.

An Overview of Gravel-Packed Completions

“…The recommended minimum ratio of wash-pipe OD to screen ID is 0.8. 2 This recommendation has been followed.…”