Doctor of Philosophy (PhD)
EOR application in prolific deepwater Gulf of Mexico (DGOM) reservoirs has remained a challenge. Exorbitant well cost (>200M$) precludes having extensive injection patterns and very characteristics of the reservoirs themselves are partly to blame for negligible EOR activity in DGOM. We have been able to develop and demonstrate a novel design in the form of Single Well – Gas Assisted Gravity Drainage (SW-GAGD) process, which is potentially cost effective, at the same time ensuring very high oil recoveries. In this design, a single well acts as an injector as well as a producer, thereby minimizing well cost. The efficacy of the process has been demonstrated using partially scaled visual glass models and material balance calculations. The recovery factor is in the range of 70-80% in the immiscible mode and near 100% in the miscible mode at abandonment. Such high recoveries are as a result of highly efficient film flow aided gravity drainage process. Being a forced gravity drainage process, SW-GAGD is, however, an order of magnitude faster and thus expected to be an economically viable recovery process. For example, at just 2.5 SCCM (2.3 ft/day), the process was 23 times faster than pure gravity drainage for recovering 61% OOIP (ultimate recovery factor for pure gravity drainage). This process has also been shown to be immune to reservoir heterogeneities like vertical fractures, reservoir permeability layering and reservoir dip and hence laboratory results are more likely to be translatable to the field. In fact reservoir layering with low permeability layering near horizontal lateral was shown to improve the sweep and recovery efficiency compared to no layering case by 6-7% at abandonment. Among various models, semi-analytical Hagoort model was found to best represent forced gravity process in an analytical fashion. It used a non-dimensional form of solution with velocity incorporated in the gravity no. definition to account for forced gravity drainage process. A reasonable match was obtained for SW-GAGD recoveries, with slight under prediction of recoveries post breakthrough. This is attributed to non-consideration of film drainage, which is anticipated to play an important role, especially post breakthrough.
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Saikia, Bikash Deep, "Development of Single-Well Gas Assisted Gravity Drainage Process for Enhanced Oil Recovery" (2016). LSU Doctoral Dissertations. 4290.
Rao, Dandina N.