Application of Thermal Recovery Processes in Heavy Oil CarbonateReservoirs

Application of thermal processes in heavy oil carbonate reservoirs Swapan Kumar Das Swapan Kumar Das ConocoPhillips Co Search for other works by this author on: This Site Google Scholar Paper presented at the SPE Middle East Oil and Gas Show and Conference, Manama, Bahrain, March 2007. Paper Number: SPE-105392-MS https://doi.org/10.2118/105392-MS Published: March 11 2007 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Get Permissions Search Site Citation Das, Swapan Kumar. "Application of thermal processes in heavy oil carbonate reservoirs." Paper presented at the SPE Middle East Oil and Gas Show and Conference, Manama, Bahrain, March 2007. doi: https://doi.org/10.2118/105392-MS Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Search Dropdown Menu nav search search input Search input auto suggest search filter All ContentAll ProceedingsSociety of Petroleum Engineers (SPE)SPE Middle East Oil and Gas Show and Conference Search Advanced Search AbstractAs the demand for oil grows, the petroleum industry is expanding the technology envelope to access and exploit many unconventional resources. The current focus of all major oil companies is heavy oil in highly porous and permeable sandstone reservoirs (oil sand), which presents a significant opportunity. However, viscous oil trapped in carbonates (over 1.6 trillion bbl)1, potentially a huge resource for future, needs application of new technologies to be exploited economically.At present thermal processes like steam flooding and cyclic steam stimulation (CSS) are being used extensively for the recovery of moderately viscous heavy oil from sand stone reservoirs. Another thermal process, SAGD (steam assisted gravity drainage) is being used for the recovery of higher viscosity heavy oil and bitumen from oil sand. Some of these processes are apparently very successful with ultimate recovery over 80%.Application of thermal processes to the carbonates poses a different challenge. In general, thermal recovery in carbonates is highly energy intensive and hence, economically challenged. Due to adverse wettability (generally mixed or oil wet), lower matrix permeability, the anticipated recovery using thermal processes is much lower compared to sand stone reservoirs. With increased access of the reservoir through horizontal wells there is a possibility that these resources can be exploited economically. A simulation study has been undertaken to explore the possibility of application of thermal processes in carbonate reservoirs. Based on the results of this work, this paper presents different possible recovery options and examines the sensitivities of reservoir parameters on thermal recovery processes like CSS and SAGD in fractured carbonate heavy oil reservoirs. The results suggest that SAGD may be viable in some of these reservoirs.IntroductionThere are 20 known large carbonate reservoirs containing heavy oil and bitumen throughout the world, spread over a dozen of countries and at varying depth, temperature and API. In addition to these there are many smaller carbonate reservoirs containing heavy oil world wide, for example the Aruma zone in the Bahrain field2, Yates field in West Texas, carbonate reservoirs in cuba, etc. There are potentially many reservoirs worldwide which have not been fully evaluated yet. There are huge resource potentials in many of these reservoirs. It has been estimated that the Paleozoic carbonate deposits of northern Alberta, Canada, contains over a Trillion bbl bitumen in place.3,4,5 Some of these carbonate reservoirs are being produced currently, like Qarn Alam in Oman, Bati Raman in Turkey, Raspomare in Italy, etc. Deep reservoirs at higher temperature and higher oil mobility can be produced by primary production. In many cases primary production is short lived and ends up in high water cut and low recovery.At present many of the fractured carbonates are being exploited by CO2 injection either through CO2 flood or through the gravity stable displacement, which is some times referred to as GOGD (Gas Oil Gravity Drainage). The Weyburn project in Saskatchewan Canada and the Great Naigaran Reef area of Michigan are examples of those. In these reservoirs the oil is in the high twenties or low thirties in API gravity and does not fall in the heavy oil category. The Bati Raman heavy oil carbonate reservoir in Turkey is being exploited by CO2 flooding.Heterogeneity in Carbonate ReservoirsCarbonate reservoirs are in general very heterogenous, comprised of fractures and vugs, partially dolomatized, karsted, etc. The micro-porus carbonate matrix has very little permeability (only few mD) for flow of heavy oil through it. Fracture permeability lies in the Darcies and is the primary conduit for flow. This renders the flooding processe highly ineffective as the driving fluid takes the path of least resistance, i.e, the fractures, resulting in early breakthrough. Heterogeneities also create a distribution of oil saturation in the overall structure. The Weybarn filed of Saskatchewan, Canada comprises of two layers lower Vuggy and upper Marly6. As the name implies the vuggy is highly fractured, has higher permability and lower oil saturation and has been predominantly produced during the water flood. On the other hand Marly is less permeable and contain higher oil saturation as it was mostly by passed during water flood. Currently this is being produced by CO2 flood. Keywords: enhanced recovery, Upstream Oil & Gas, thermal process, injection, SAGD, imbibition, wettability, thermal method, steam-assisted gravity drainage, application Subjects: Improved and Enhanced Recovery, Thermal methods This content is only available via PDF. 2007. 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