Microbially enhanced thermal oil recovery
A procedure and a system for recovering oil from now inaccessible oil containing geological units by triggering the deep biosphere microbial seed bank. Nutrient and thermal enhancement of germs in oil containing geological units allows for stimulation of inactive and/or dormant germs such they proliferate and create gasoline. The oil viscosity that’s decreased by warmth, together with the gas pressure generated by activated microbes that allows previously inaccessible oil to flow toward production wells.
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Oil reservoirs are geological units within the subsurface of the Earth that contain an accumulation of petroleum. The oil from the reservoirs is recovered or extracted to be used by a procedure commonly referred to as petroleum production. Traditional oilproduction normally involves two stages: primary recovery and secondary recovery. Primary recovery entails the use of organic in-reservoir high pressure forces to drive the flow of oil into petroleum production wells. Secondary recovery typically involvesthe maintenance of the high pressure by pumping fluids into the reservoir so that oil production can last.
In oil reservoirs that contain heavy oil or oil-sands (also known as tar sands, bitumen, or bituminous sands), the oil is too viscous to flow freely to the creation wells by traditional methods. Therefore, other means of oil production, suchas thermal retrieval strategies, must be used. Thermal recovery strategies involve heating the oil reservoirs to improve the mobility of the oil and thus the ease of its following extraction. The applied heat reduces the oil’s viscosity allowing itto flow to production molds. A good example of a commonly used thermal retrieval strategy in heavy oil recovery is the Steam-Assisted Gravity Drainage (SAGD) method.
The SAGD method involves the use of steam injection well 5 and manufacturing well 7 pairs, as depicted in FIGS. 1, 2 and 3 of the previous art. The steam injection well introduces steam into a clean sand area 8 of an oil reservoir. The injectedsteam migrates upwards until reaching geological units that prevent further migration of their vapor. The injected steam warms the reservoir to temperatures of about 200. degree. C., reducing the viscosity of the oil and allowing it to flow to theoil production molds. This can be referred to as the steam room 10, shown in FIGS. 2 AND 3. The steam is continually injected to reduce oil viscosity, easing the constant flow of oil towards the production molds, and to help displace the oilfrom the sand.
There are lots of drawbacks to the SAGD procedure. One big problem is that the SAGD steam-generation procedure has a negative environmental effect. For instance, the SAGD process is a huge contributor of greenhouse gas emissions. This is becauselarge amounts of natural gas has to be combusted to give the energy to heat water to create the steam. Not only does burning natural gas contribute significantly to greenhouse gas emissions, but it also represents an additional price for bitumen production.Furthermore, the SAGD process also consumes large amounts of water sources to the introduction of the vapor.
Since the production of steam would be the principal contributor to the environmental and financial effect of the SAGD system, the environmental efficacy of SAGD operations might be expressed in terms of the steam-to-oil ratio (Gates & Larter, 2014,incorporated herein by reference). The steam-to-oil ratio encircles both the environmental and financial cost of steam production in connection with the sum of crude oil resource that’s recovered. A reduce steam-to-oil ratio means fewer greenhouse gasemissions and improved environmental performance per unit of production.
The energy costs and greenhouse gas emissions associated with unconventional oil sands production and extraction, such as SAGD operations, are roughly 100-200percent greater compared to conventional oil production (“The Truth About Dirty Oil: IsCCS the Answer?” , Bergerson & Keith, Environmental Science & Technology, 2010, 44, 6010-6015, incorporated herein by reference). Therefore, new approaches and technologies for enhancing the environmental and economic performance in oil plantations extractionmust be developed to lower the steam-to-oil ratio associated with SAGD operations.
Production from conventional oil reservoirs is usually ineffective at extracting each of the available oil from the targeted area. Therefore, there are many strategies that aim to increase oil recovery. A number of these strategies include theuse of microorganisms in the subsurface.
Subsurface environments are parasitic habitats and include a wide array of parasitic taxa. FIG. 4 of the prior art shows a histogram of this abundance rank order of different microbial taxa at a subsurface environmental sample; accommodated fromPedros-Alio (2006)”Marine microbial diversity, can it be determined?” , Trends in Microbiology, Vol 14, Number 6, pp 257-263. The bars of the histogram are identical since they are very close together. The lighter shaded area 1 on the left of thehistogram signifies abundant taxa, and the darker shaded area 2 to the right signifies the rare taxa. Therefore, in certain environmental sample, there is frequently a large percentage of abundant and active microorganisms along with a variety of lowabundance, dormant or dormant germs. By way of instance, in certain microbial communities, one species might encompass up to 20% of the total cells present, whereas hundreds of rare species may collectively make up less than 1% of the total.
Microbially Enhanced Oil Recovery (MEOR) is a phrase to describe strategies for conventional oil production that target the use of microbial communities for enhancing and raising oil recovery from conventional oil reservoirs. MEOR is typicallyemployed following primary and secondary recovery. Together with MEOR, microbes are used in the conventional target areas of the reservoir to improve oil production. MEOR is believed to occur by an assortment of mechanisms associated with microbial metabolism in oilreservoirs, such as biosurfactant production, metabolism of oil, and production of gas as a metabolic by-product. Each of the processes cited above helps to raise the fluid mobility of their oil, leading to the production of the residual oilstill within the reservoir after primary and secondary recovery strategies.
MEOR is typically tried as a tertiary recovery approach in conventional oil reservoirs. However, because of the unconventional nature of oil and oil sands and the unconventional production methods for generating this oil, MEOR strategiesare not frequently employed in heavy oil and oil sands.
MEOR may be put on the commonly-targeted area of a heavy oil or oil residues unit before or following the application of strategies such as the SAGD method. MEOR involves either (1) biostimulation, i.e., the injection of nutrition to stimulatethe native overriding and abundant taxa, or (2) bioaugmentation, i.e., the injection of foreign germs that are regarded as acceptable for the reservoir requirements.
The high temperature of the SAGD steam chamber sterilizes the conventional goal region of the oil sands reservoir. Therefore, when MEOR is employed for improving oil recovery in the SAGD steam chamber of a heavy oil sands reservoir, MEORmay just be implemented either before the steam is injected into the reservoir, or after the SAGD technique is full and the reservoir gets cooled down to low temperatures. U.S. patent application Ser. No. 14/070,095, incorporated herein by reference,describes a way of injecting foreign bacteria prior to injecting steam for part of SAGD for increasing the liquid mobility of oil at a heavy oil reservoir. Inside this technique, germs are introduced into the reservoir through both injection andproduction molds, prior to steam injection, to pre-condition the reservoir to get improved (shorter) beginning of the SAGD procedure.
No. 4,475,590, incorporated herein by reference, provides an example of biostimulation at a traditional oil reservoir in conjunction with waterflood technology. Waterflooding aims at displacing the residual oil at the reservoirwith water, in contrast to the steam that’s applied during the SAGD technique. Likewise U.S. Pat. Nos. 4,971,151, and 5,083,611, incorporated herein by reference, describe methods involving the injection of nutrition in the traditional oil reservoirsfor enhancing oil recovery.
All of these methods, but focus on the busy taxa present in high relative prosperity from the microbial communities that are adapted to local prevailing in situ conditions (temperature, geochemistry, salinity, mineralogy, etc.) and arereadily researched by microbiological procedures. Yet, in nearly every environment you will find parasitic seed banks that include several species or taxa of germs found in low relative prosperity. These microbial taxa can be inactive or dormant, andmay include dormant bacterial endospores. Microbial seed banks may constitute significantly less than 0.01percent of the total cells present, and frequently exist in a dormant condition. As such, they’re typically not detected or highlighted by most environmentalDNA extraction surveys, and other more traditional procedures for microbial characterization of petroleum reservoir surroundings.
Furthermore, the subsurface areas beyond the bounds of this SAGD steam room, for example inclined heterolithic strata (IHS), may comprise up to twice as much oil sands resource as the steam room region. However, production of theoil from the IHS region during SAGD is constrained. This IHS oil is interbedded with thin, but laterally extensive, low-permeability mudstone layers through which the steam can’t penetrate. Therefore, methods aside from gravity drainage are required todisplace the petroleum. The petroleum in the IHS is considered high quality and more precious than the oil in the steam room region since it’s less biodegraded and less viscous (“Effect of oil-water contacts, reservoir (dis)continuity, and reservoircharacteristics on spatial distribution of gas, water, and high-water” Fustic et al., 2013, Heavy Oil/Bitumen Petroleum Systems in Alberta & Beyond, Eds. F. J. Hein, J. Sutter, D. A. Leckie, and S. Larter, AAPG Memoir, p. 163-205., integrated hereinby reference in its entirety).
FIG. 5 shows a schematic of an example of a commonly-targeted geological unit in the subsurface of the Athabasca oil sands. The decrease region represents the target for steam room 10 positioning, that is the targeted region for SAGD. The upperregion signifies the IHS region 20, which contains oil which is not easily accessible by current methods. Restricted oil recovery is recorded from the IHS. The diagonal lines in the IHS region signify the laterally broad sand strata 30 interbeddedwith decimeter scale heavy oil or bitumen saturated laterally extensive porous sands. Above and beneath these areas are the low-permeability non-reservoir underseal 22 and secure 25.
FIG. 6 shows a Picture of an Athabasca Oil Sands outcrop near Fort McMurray in Alberta, Canada by Strobl et al. (1997) in the Canadian Society of Petroleum Geologists, Memoir 18, pp 375-391.
The geological unit revealed in FIG. 5 isrepresentative of this geological unit in the Athabasca Oil Sands. Referring back into FIG. 6, the snowy substantially parallel lines across the upper half of this geological unit represent the cartilage broad mud strata 30 of this IHS region 20, and havea slope of approximately six (6) to ten (10) degrees. The lowest limb extensive mudstone layer 35, as denoted by the arrow, defines the anticipated upper border of the SAGD steam chamber 10 (according to subsurface studies, Strobl et al.,1997, Strobl, 2013).
While means to increase oil recovery in the available areas, such as the SAGD steam room, are widely researched, use of the oil at the IHS layer remains challenging using present technologies. There are lots of initiatives to tryto access this oil, such as by attempting to split the mudstone in the IHS by geomechanical, electrical, Improved Solvent Extraction Incorporating Electromagnetic Heating (ESEIEH), or thermo-chemical methods to access the oil. But, theseapproaches have had a very limited success so far.
There is consequently a need to mitigate, if not overcome, the consequences of the prior art and to, preferably, develop a technique to produce oil or boost oil production from currently challenging IHS regions of oil reservoirs.
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