Range of operability of gas-assisted gravity drainage process

Document Type

Conference Proceeding

Publication Date

1-1-2008

Abstract

The gas-assisted gravity drainage (GAGD) process is being developed to overcome the limitations of, and as an alternative to, the conventional WAG process. In our recent paper (SPE 110132) we have presented the visual model results to demonstrate the feasibility of the GAGD process and the various mechanisms responsible for the high recoveries achieved. In this paper, we present visual and quantitative results from the physical model experiments to demonstrate the various modes of operability of GAGD, its applicability to fractured reservoirs, the effect of oil viscosity and a comparison of its performance with WAG and CGI processes. A Hele-Shaw type model - consisting of two parallel glass plates (23′ × 13" × %" in size) with %" gap between them filled with Ottawa silica sand - has been used in all experiments with a perforated plastic tube serving as the horizontal production well placed at the bottom of the model. Vertical tubes were placed at different depths in the model to serve as gas injectors. The presence of fractures was simulated by placing cylindrical shaped fine wire mesh tubes into the sandpack. Separate models were built to study the effect of gas injection rate, depth, CGI, WAG, huff-and-puff, toe-to-heel, oil viscosity and wettability. This paper presents video images of the GAGD process in operation in various modes and discusses the quantitative results of these experiments that led us to conclude that, with the exception of toe-to-heel operation, the GAGD process yielded positive results in all the tests with oil recoveries ranging from 54% to 83% OOIP. This study demonstrates improved GAGD oil recoveries over CGI and WAG, in fractured model over homogeneous, in oil-wet media over water-wet, thereby signifying the potential for wide applicability of the process in both secondary and tertiary modes. Copyright 2008, Society of Petroleum Engineers.

Publication Source (Journal or Book title)

Proceedings - SPE Symposium on Improved Oil Recovery

First Page

935

Last Page

946

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