Gas-assisted gravity drainage GAGD process for enhanced oil recovery: A comprehensive review and field applications

Document Type

Conference Proceeding

Publication Date

1-1-2017

Abstract

The Gas-Assisted Gravity Drainage (GAGD) process has been suggested to improve oil recovery in both secondary and tertiary recovery through immiscible and miscible injection modes. In contrast of Continuous Gas Injection (CGI) and Water-Alternative Gas (WAG), the GAGD process takes advantage of the natural segregation of reservoir fluids to provide gravity-stable oil displacement and improve oil recovery. In the GAGD process, the gas is injected through vertical wells to formulate a gas cap to allow oil and water drain down to the horizontal producer (s). The GAGD process has been invented based on experimental work at Louisiana State University. Limited studies have been conducted to test its effectiveness in real oil field evaluations. In this paper, a comprehensive literature review was presented to summarize all the references about the GAGD process concepts, principles, and field-scale evaluations. Particularly, the paper presents introduction about the gas injection approaches for Enhanced Oil recovery, the physical model description and evaluation of the GAGD Process Physical Model, the factors influencing the GAGD process in addition to review of all the field-scale evaluation studies. Moreover, the validation of the GAGD process in field-scale application was fully discussed with focusing the light on its weak points with respect to the optimal decision of application for maximum oil recovery. In one study, sensitivity analysis, production optimization, and uncertainty assessment have been also included and clarified in this paper. The paper ended with field-scale compositional simulations of continuous and cyclic CO2 injection modes through the GAGD process in a heterogeneous sandstone oil reservoir in South Rumaila oil field. It was noticed the effectiveness of the GAGD process to improve oil recovery to promising levels. It was also concluded that cyclic GAGD process was much better than the continuous one for higher oil production, smaller gas injection, and smaller injection pressure.

Publication Source (Journal or Book title)

Society of Petroleum Engineers - SPE/IATMI Asia Pacific Oil and Gas Conference and Exhibition 2017

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