Understanding coning performance in a high-anisotropy reservoir: The Burgan reservoir case study

Abstract

Water cones largely dictate oil recovery in a typical bottom-water situation. Major parameters influencing coning include mobility ratio, producing rate, completion interval, and anisotropy. We conducted a systematic study to understand the influence of these and other parameters on coning. Our aim was to develop producing and completion rules for managing the Greater Burgan's Third Middle Sand (3MS) reservoir in Kuwait. The building blocks of our study were: (1) detailed geologic modeling using core and openhole log data, (2) geostatistical modeling for 3D sector modeling, (3) transient-pressure testing, (4) production logs, and (5) cased-hole saturation logs. Single-well, 2D radial models were built to understand various elements of coning for existing completions. We also explored alternative completions to mitigate coning. The study included the use of single- and dual-lateral wells and cone-reversal techniques. Follow up studies using a 3D-sector model confirmed some of the findings of single-well modeling. Results show that high anisotropy provides near piston-like displacement and, consequently, completing at the top of the bed appears prudent in a vertical well High producing rate tends to leave higher remaining oil saturation than those do at moderate rates. A combination of high-anisotropy and low- length-to-thickness ratio makes horizontal completions unattractive in the crestai area of the field.