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|Title:||Scaling and Sensitivity Analysis of Gas-Oil Gravity Drainage EOR|
|Citation:||Proceedings of the 2008 SPE Asia Pacific Oil and Gas Conference and Exhibition, 20-22 October, 2008|
|Conference Name:||SPE Asia Pacific Oil and Gas Conference and Exhibition (2008 : Perth, Australia)|
|Abstract:||<jats:sec> <jats:title>Abstract</jats:title> <jats:p>Gas injection is one of the key enhanced oil recovery (EOR) methods. Significant volumes of the residual oil, remaining after earlier EOR methods, has been reported to be recovered through the gravity drainage mechanism, following the crestal gas injection in the horizontal, dipping or reef type oil reservoirs. The rate of oil recovery is controlled by the viscous/capillary/gravity forces, the rate of gas injection and oil production, the difference of oil and gas density, the oil relative permeability, the oil viscosity and number of other operational parameters. Risk analysis of these parameters helps to identify their relative dominance during gas-oil gravity drainage process. The interactions between various process controlling parameters is studied through development of scaling groups that govern the displacement process. Functional relationships between those scaling groups and their effect on the overall performance of immiscible gas-driven gravity drainage EOR are investigated in this study. This enables an estimation of fractional oil recovery for the combinations of scaling groups. The results of numerical sensitivity analysis through the reservoir simulations are presented to map the effective combinations of the dimensionless scaling groups for gas-oil gravity drainage EOR method.</jats:p> <jats:sec> <jats:title>Introduction</jats:title> <jats:p>Gas injection either in the immiscible or miscible mode (largely CO2) is the key process amongst the major contending methods of enhancing oil recovery. It can be carried out either in secondary or tertiary stage of the producing life of the reservoir in continuous mode, alternating cycles of water and gas or in gravity drainage mode. Continuous gas injection methods are largely impaired by the viscous instabilities, the severe gas-oil gravity segregation and the poor volumetric sweep efficiency. Moreover, the larger difference of the density between the injected gas and the in-situ reservoir fluid leads to severe gravity segregation effects. The cumulative effect is an uncontrolled gas flood front leading to the premature gas breakthrough in the producing wells and the unfavorable mobility ratio culminating into the severe viscous fingering. Further modifications in the injection modes could not completely eliminate these recovery impeding factors. Therefore, a method that uses the natural density based gravity segregation of the fluids to recover the bypassed oil in the unswept regions looks to be a more promising option.</jats:p> <jats:p>Gravity forces are recognized to play an important role at nearly every stage of the producing life of the reservoir, whether it is primary depletion, secondary water or gas injection scheme or tertiary enhanced or improved oil recovery methods. They always compete with the viscous (flow rate per unit area) forces and the capillary (ratio of the fluid/fluid forces to the grain size) forces occurring in porous media in addition to the vertical barriers in the form of heterogeneity. In presence of these impeding factors less dense fluid gets trapped in the producing zone, further diminishing the oil recovery performance. Conversely, gravity forces can be taken into advantage through the gravity drainage mechanism to maximize oil recovery from the oil bearing zone under investigation. A number of investigations carried out in the laboratories and in the field (Bangla et al., 1991; Chatzis et al., 1988; Da Sle and Guo, 1990; Kulkarni and Rao, 2006) suggest the significance of the gas-oil gravity drainage process in view of the higher oil recoveries obtained in contrast to the conventional gas injection EOR methods. Gravity drainage by gas injection is commonly implemented in either dipping or pinnacle reef type reservoirs. Current study focuses on the application of the gas-assisted gravity-drainage mechanism to a horizontal type reservoir through the combination of the vertical injectors and horizontal production wells.</jats:p> </jats:sec> </jats:sec>|
|Description:||©2003 – 2009 Society of Petroleum Engineers, All Rights Reserved|
|Appears in Collections:||Australian School of Petroleum publications|
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