02-02-2013, 12:07 PM
Enhanced Oil Recovery: An Update Review
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Abstract:
With the decline in oil discoveries during the last decades it is believed that
EOR technologies will play a key role to meet the energy demand in years to come. This
paper presents a comprehensive review of EOR status and opportunities to increase final
recovery factors in reservoirs ranging from extra heavy oil to gas condensate. Specifically,
the paper discusses EOR status and opportunities organized by reservoir lithology
(sandstone and carbonates formations and turbiditic reservoirs to a lesser extent) and
offshore and onshore fields. Risk and rewards of EOR methods including growing trends in
recent years such as CO2 injection, high pressure air injection (HPAI) and chemical
flooding are addressed including a brief overview of CO2-EOR project economics.
EOR Status
Most of the current world oil production comes from mature fields. Increasing oil recovery from the
aging resources is a major concern for oil companies and authorities. In addition, the rate of
replacement of the produced reserves by new discoveries has been declining steadily in the last
decades. Therefore, the increase of the recovery factors from mature fields under primary and
secondary production will be critical to meet the growing energy demand in the coming years.
EOR in Sandstone Formations
It is well known that EOR methods have been extensively implemented in sandstone formations. In
general, sandstone reservoirs show the highest potential to implement EOR projects because most of
the technologies have been tested at pilot and commercial scale in this type of lithology. Additionally,
there are some fields where different EOR technologies have been evaluated successfully at pilot scale
demonstrating technical applicability of different EOR methods in the same field.
Thermal Methods
Cyclic steam injection (Huff & Puff), steamflooding and most recently Steam-Assisted Gravity
Drainage (SAGD) have been the most widely used recovery methods of heavy and extra-heavy oil
production in sandstone reservoirs during last decades. Thermal EOR projects have been concentrated
mostly in Canada, Former Soviet Union (FSU), U.S. and Venezuela, and Brazil and China to a lesser
extent. Steam injection began approximately 5 decades ago. Mene Grande and Tia Juana field in
Venezuela [40,41] and Yorba Linda and Kern River fields in California [42] are good examples of
steam injection projects over four decades. Some examples of recent steam injection projects reported
in the literature are the steamfloods in the Crude E Field in Trinidad [43], Schoonebeek oil field in
Netherlands [44] and Alto do Rodrigues in Brazil [45]. Although attempts to optimize steam injection
processes by using solvents [46], gases [47], chemical additives [48] and foams [49] have been
proposed, few of these methods have been tested in the field [38,50]). One example is the LASER (for
Liquid Addition to Steam for Enhancing Recovery) process, which consist in the injection of C5+
liquids as a steam additive in cyclic steam injection processes. Although the LASER process was
tested at pilot scale in Cold Lake [51] the process has not been expanded at a commercial scale. Steam
injection has also been tested in medium and light oil reservoirs being crude oil distillation and thermal
expansion the main recovery mechanisms in these types of reservoirs [52]. However, steam injection
in medium and light oil reservoirs has not contributed to EOR production worldwide.
Conclusions
Thermal methods, specifically steam injection, still dominate as the preferred EOR method for
heavy oil reservoirs. As of today, SAGD seems to be a technology only applicable to Canadian Oil
Sands and more specifically in the McMurray formation. High-pressure air injection (HPAI) represents
one of the thermal recovery processes showing an increased interest in recent years in both carbonate
and sandstone formations. However, HPAI field projects are still concentrated in the low permeable
dolomitic Red River formation of Montana and North and South Dakota. Lack of understanding and
dissemination of information regarding HPAI designs and risk mitigation have been probably
responsible for the limited number of cases deployed as full-field projects, despite significant success
in ongoing projects.