Doctor of Philosophy (PhD)
Currently, the Water-Alternating-Gas (WAG) process is the most widely practiced horizontal mode gas injection process in the industry. Although this process is conceptually sound, it has resulted in low (5 – 10%) oil field recoveries. Conversely, the gravity stable mode of gas injection has carved its niche as one of the most effective methods of gas injection EOR in the dipping reservoirs and pinnacle reefs. The Gas Assisted Gravity Drainage (GAGD) process is therefore being developed at LSU to extend these highly successful gravity stable applications to horizontal type reservoirs. The dissertation attempts to address six key questions: (i) do we continue to ‘fix the problems’ of gravity segregation in the horizontal gas floods or find an effective alternative?, (ii) is there a ‘happy-medium’ between single-slug and WAG processes that would outperform both?, (iii) what are the controlling multiphase mechanisms and fluid dynamics in gravity drainage processes?, (iv) what are the mechanistic issues relating to gravity drainage?, and (v) how can we model the novel GAGD process using traditional analytical and empirical theories and (vi) what are the roles of the classical displacement, versus drainage in the GAGD process? The original contributions of this work to the existing literature are summarized as: (i) first demonstration of the GAGD concept through high pressure experimentation, (ii) experimental demonstration of the superior oil recovery performance of the GAGD process in secondary (immiscible recovery range: 62.3% to 88.56% ROIP) and tertiary (immiscible recovery range: 47.3% to 78.9% ROIP) processes, in both miscible (avg. secondary and tertiary miscible recoveries: near 100% ROIP) and immiscible modes, and in varying wettability and rock types, (iii) experimental verification of the hypothesis that the GAGD process is largely immune to the deteriorating effects of reservoir heterogeneity and that the presence of vertical fractures possibly aid the GAGD oil recoveries, (iv) experimental demonstration of the possibility of premature gas breakthrough does not mean end of the GAGD flood, (v) preliminary mechanistic and dynamic differences between the drainage and displacement phenomenon have been identified and a new mechanism to characterize the GAGD process fluid mechanics has also been proposed.
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Kulkarni, Madhav M., "Multiphase mechanisms and fluid dynamics in gas injection enhanced oil recovery processes" (2005). LSU Doctoral Dissertations. 62.
Dandina N. Rao