CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority from U.S. Provisional Application No. 62/510,012, filed on May 23, 2017, the entire contents of which are hereby incorporated by reference herein. It is noted that a certified copy of U.S. Provisional Application No. 62/510,012 is publicly available from the WIPO database.

FIELD

[0001] The present specification relates generally to an apparatus, method, and reagent for detecting hydrocarbons, and more particularly to an organic solvent sensor for detecting hydrocarbons.

BACKGROUND

[0002] Hydrocarbon deposits are generally formed from the maturation of sedimentary organic matter which undergoes varying stages of alteration depending on its burial history. For example, deposited marine and organic sediments contain carbohydrates such as cellulose, lipids and proteins including lignin which are microbially degraded at low temperature to leave more resistant humic compounds. The humic compounds are products of microbial oxidation of more bioavailable molecules along a spectrum of polymerization, which leaves behind a mixture of high molecular weight paraffinic and aromatic compounds which transitions to kerogen over time and thermal treatment during burial. Catagenesis occurs as the reservoir temperature increases during burial and light, medium and heavy petroleum deposits are produced depending on the temperature and duration of kerogen degradation. In the example of the Athabasca oil sands, biological activity continues unabated in over its entire burial history where the deposits temperature during burial likely did not exceed 80°C and the extent to which kerogen was thermally degraded to petroleum may be less advanced relative to other deposits. In addition to this, ongoing microbial activity in heavy oil deposits represent another fraction of organic material in the form of cellular or extracellular biofilm matter which may contribute physically or chemically to the oleic viscosity.

SUMMARY

[0003] A well and method of reducing oil viscosity are provided. The method can be used in operation of the well as well as other applications calling for a reduction in oil viscosity. In an aspect of the invention, a method of treating hydrocarbons with natural enzymes to reduce their low-shear heavy oil viscosity is provided. The method can improve heavy oil mobility at in-situ reservoir temperatures. These enzymes used in the method can be mixed with water to form a solution and injected into oil reservoirs along with solution oxygen to act as an "Enzyme Flood" (also referred to as a flood mixture) which can mobilize heavy oil at lower costs, lower energy input and lower start-up times compared to thermal enhanced oil recovery (EOR) methods such as steam-assisted gravity drainage (SAGD). Depending on the dissolution products that are generated, the method can also be used to upgrade hydrocarbons in a surface processes by breaking down larger molecular weight hydrocarbons into lighter oils or other small degradation products.

[0004] A technique for enhanced oil recovery from heavy and shale oil reservoirs by breaking down their organic components is provided. The method involves reducing the overall oil phase viscosity and aiding its mobilization towards production wells. Enzymes used are generally natural and organic and operate at in-situ reservoir temperatures and consequently present the opportunity for heavy oil or shale oil production with significantly lower energy input and environmental impact. Depending on whether the dissolved hydrocarbon products are themselves hydrocarbons of lighter molecular weight these enzymes can also be used for bitumen upgrading in surface facilities. Humic compounds have been found to release Amino acids upon enzymatic dissolution and may represent a source for bioavailable organic molecules during microbial enhanced recovery coupled with an enzyme flood. A significant advantage of this process is the relatively benign biocompatibility of the enzymes injected with the natural environment as compared with traditional chemical injectants like surfactants or fracking fluid and their ability to provide incremental improvements in heavy oil production at lower reservoir temperatures. This technique may be especially important for the production of more kerogen-rich shale oils which are largely unproduced.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Reference will now be made, by way of example only, to the accompanying drawings in which:

[0006] Figure 1 is a schematic diagram of stages of kerogen transformation and

biogeochemical formation pathways of hydrocarbon reservoirs demonstrating spectrum of degradation from active biomass to heavy and light hydrocarbons;

[0007] Figure 2a is a schematic view of an enzyme flood heavy oil production using two parallel horizontal wells, one injection and another producer;

[0008] Figure 2b is a schematic view of an enzyme flood heavy oil production using

staggered vertical injection and production wells;

[0009] Figure 3 is a schematic view of a controlled injection of enzyme and oxygen to heavy oil process streams to meet viscosity specification;

[0010] Figure 4 is a chart showing results from samples of enzymatically treated bitumen samples at a shear rate of 0.1 1/s at room temperature;

[0011] Figure 5 is a chart showing original and post-treatment experimentally measured bitumen viscosities compared with pseudocomponent and simulated mixture viscosities as functions of temperature;

[0012] Figure 6 is a chart showing Oleic mixture viscosity as measured experimentally vs how it is simulated with a pseudocomponent reaction;

[0013] Figure 7a is a temperature profile in simulation including enzymatic reaction after 5 years of flooding;

[0014] Figure 7b is a bitumen viscosity profile in simulation including enzymatic reaction after 5 years of flooding; and

[0015] Figure 8 is a chart showing cumulative oil produced with the enzymatic reaction and without In both cases warm water at 40°C was injected over a period of 5 years.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0016] Referring to figure 1 , organic precursors of petroleum are shown at the top level. Each of the organic precursors have corresponding lytic enzymes which can cleave their bonds and degrade them into smaller products. Many of these same enzymes have been found to degrade some of the more recalcitrant compounds such as cellulose, lignin and the humic compounds. For example, washing humic compounds with cellulase has been found to release n-alkane and fatty acid products. The treatment of kerogen with typical aerobic hydrolytic enzymes has been little studied, likely because these enzymes are predominantly aerobic and would not elucidate further pathways of kerogen degradation at in-situ conditions. In the examples discussed in greater detail below, these aerobic enzymes are applied to the reduction of heavy oil and shale oil viscosities to the extent to which organic components all along the biodegradation spectrum are present in the oleic phase and are susceptible to enzymatic dissolution. It is to be appreciated by a person of skill in the art that organic and kerogenic components can contribute significantly to heavy oil viscosities by stabilizing asphaltene aggregates that control the colloidal viscous properties of bitumen.

[0017] It is to be appreciated by a person of skill in the art with the benefit of this description that the specific mix of enzymes to apply is not particularly limited and can vary based on various factors, such as the source rock composition and diagenic history of each deposit. As an example, the Athabasca and Peace River bitumen deposits with surrounding kerogenic shale deposits have suggested the Exshaw Formation includes source rock with Total Organic Content (TOC) varying from about 5-24wt% and almost original/immature H/C ratios in sections. The Exshaw Formation is a Type II kerogen derived from lipid-rich planktonic biomass deposited in marine conditions and thus is susceptible to lipase treatment. Since petroleum deposits derived from lacustrine and fluvial deltas often contain more terrestrial organic matter including cellulose and lignin, defined as Type III kerogen, cellulase/ligninase may be applicable for enzyme flooding. In general, any hydrolase or other digestive enzyme might be applicable towards the viscosity reduction of heavy and shale oils depending on their relative

biodegradation state. Some examples of the proposed enzymes include, but are not limited to, cellulases, ligninases, amylases, proteases, lipases, papain, pepsin, chitinases, saccharases, glucosidases, oxygenases, peroxidases, and hydrogenases/dehydrogenases.

[0018] Accordingly, several different classes of enzymes, each representing a large set of proteins with varied enzyme structure and activity. Since a large number of enzymes are aerobic, oxygen is often co-injected with the enzyme solution to enhance performance.

Furthermore, each class of enzyme exhibit peak activity at an optimal pH. For example, cellulases are most active at pH value of about 5 while lipases prefer a pH value of about 7.7. Optimal temperatures also vary for different enzymes, but in general most enzymes kinetics are fastest around 37°C. Additionally, since the effect of the enzyme solution on physical properties on interfacial properties such as wettabilities due to enzyme adsorption can affect performance, surfactants, chelants and other compounds can be added to the enzyme solution (also referred to as a flood mixture) to create a holistically optimal mixture. In a present embodiment, this flood mixture is heated with oxygen co-injection to about 40°C to take advantage of the combined improvement in enzyme activity and thermal reduction in bitumen viscosity. However, it is to be appreciated that variations are contemplated to further optimize the system.

[0019] Referring to figure 2a, a well for oil recovery is generally shown at 40. In the present embodiment, the well 40 includes an upper wellbore 50 and a lower wellbore 60. It is to be appreciated that the wellbore 50 and the wellbore 60 are not particularly limited. For example, the upper wellbore 50 is generally configured to inject an enzyme and oxygen into an oil deposit to generate dissolution products and the lower wellbore 60 is generally configured to collect the dissolution products.

[0020] Surface injection of enzymes into pipelines, such as the wellbore 50, can be controlled to reduce heavy oil viscosity to a desired predetermined viscosity. It is to be appreciated by a person of skill in the art with the benefit of this description that the manner by which the injection is controlled is particularly limited. For example, the injection can be controlled by adjusting dosing concentrations, oxygen contents or temperatures to achieve a predetermined viscosity. In the present embodiment, processed is configured to provide a calculated residence time and emulsification level to achieve the predetermined viscosity, as the enzyme activity is constrained by how much the solution contacts the oleic phase and the rate at which enzyme can diffuse into the oil.

[0021] It is to be appreciated by a person of skill in the art with the benefit of this description that variations are contemplated. For example, in some applications, the wellbore 50 and the wellbore 60 can be reversed such that the flood mixture of enzyme and oxygen is injected below the wellbore configured to collect the dissolution products. As another example of variation, instead of having horizontal wellbores as shown in figure 2a, staggered vertical injection and production wellbores can be used as shown in figure 2b. As yet another variation, the method can be modified for reducing bitumen viscosity in surface mining operations. In this

embodiment, the flood mixture can be sprayed over a mine site or mixed with the bitumen before upgrading to reduce viscosity and improve recovery. It is to be appreciated that in some applications where water and oxygen are present, such as a surface mining operation, enzymatic powder deposited over the site.

[0022] It will now become apparent to a person skilled in the art that this method provides a low energy alternative to conventional EOR techniques that call for high temperatures to reduce viscosity. Accordingly, the development of thinner or shallower reservoirs which would typically be uneconomic to produce using SAGD due to high energy requirements can be developed using this method. [0023] In addition, some oil sands deposits having carbonate or clastic reservoirs, which are typically less susceptible to thermal EOR techniques due to loss of steam to thief zones, geological heterogeneity, their depth and/or thickness and other geological factors can be mined using this technique. However, these reservoirs also have high permeability and water mobility, which results in the dispersion of enzyme in the water phase through these reservoirs.

Accordingly, using lower temperature floods supported by the enzymatic viscosity reduction ca be used to increase the yield from these deposits. After a period of months to years the enzymes can degrade and reach the producer well. Therefore, some of the injected organics will be recovered and may be reinjected or used as feedstock for production of more enzyme via fermentation.

[0024] Another potential embodiment may be an initial enzyme flood for a period of months to years as a "pre-soak" for more traditional thermal EOR techniques. For some enzymes, viscosity reduction occurs over a period of weeks and this period, may be sufficient to provide most of the viscosity reduction improvement achievable. After this period, the viscosity reduction rate decreases and the marginal reduction in viscosity for extending the period would not no longer be economically viable. The duration of the "pre-soak" is not particularly limited and can be varied based on several factors such as the enzyme kinetics, which can depend on the diffusive rate into the heavy oil and rates of dispersion through the reservoir. After the "pre-soak" period, a temperature "ramp-up" to steam temperatures or lower, in which would the enzymes would thermally denature but the bitumen viscosity would be reduced to an even lower final viscosity than would be observed without the initial enzyme flood. Accordingly, the enzyme flood can be used as a means of accelerating or enhancing SAGD, cyclic stean stimulation (CSS) or similar thermal EOR applications and potentially improving the overall recovery.

[0025] . In the described embodiment, organic enzymes are used to mobilize heavy or shale oils during enhanced recovery with less carbon intensity and energy input required compared to traditional steam-based EOR techniques. The likely embodiment would be as a warm water flood around 40°C wherein enzymes would be mixed with pH optimal water on surface and injected into the reservoir while simultaneously producing mobilized bitumen and other dissolution products. This may also be coupled with a microbial enhanced oil process. The produced water surface facilities could be almost identical to standard SAGD water treatment as the enzyme solution could be separated from the oleic phase in the Free Water Knock-Out (FWKO) and water treating train to be rejuvenated and recycled. There may be an opportunity for companies to brew their digestive enzymes on surface in bioprocess reactors (Colla 2011 ) using food wastes from camp and other relatively inexpensive organic inputs. Oxygen could be co-injected using toe/heel strings with similar completions to SAGD injection wells. The ideal well configuration would depend on the reservoir geology but potential flood patterns are presented in the figures below. Referring to figure 3 a system for processing heavy oil in accordance with an embodiment is generally shown at 100. In the present embodiment, an enzyme and oxygen are injected into a stream of heavy oil. The amount of enzyme and oxygen injected into the heavy oil stream can be controlled using valves 110 and 120, respectively. In the present embodiment, the valves 110 and 120 are controlled using a controller 130, such as a microprocessor. In other embodiments, the valves 110 and 120 can also be manually controlled. Accordingly, in some embodiments, viscosity sensors can be used to measure the viscosity so that the controller can control the valves 110 and 120.

[0026] The heavy oil flow passes a mixer 140 where the oil, enzymes and oxygen are mixed before entering a storage tank 150. In the storage tank, the aqueous phase and nonaqueous phase can separate allowing for subsequent removal of the two phases independently. It is to be appreciated by a person of skill in the art with the benefit of this description that the period of time the mixture is stored in the storage tank is not limited and can be varied depending on the desired reduction in viscosity. In the present embodiment, the storage tank 150 further includes an optional heater 160, which can be used to increase the temperature of the heavy oil for further viscosity reduction and/or improving the reaction rate. In the present embodiment, the heater 160 is controlled by the controller 130. In other embodiments, the heater 160 can be manually controlled or connected to a thermostat to regulate the temperature of the heavy oil in the storage tank 150.

[0027] Referring to table 1 , various enzyme mixtures were prepared used. Preliminary jar samples were prepared by combining 5ml_ Bitumen with 44ml_ de-ionized water, 15ml_ pickling vinegar and two pills of digestive enzymes with the composition presented in table 1 . The pH immediately after preparation is approximately 6. The six jar samples were created, placed on a rotating rack for agitation and left at room temperature and data was collected every five days a 2ml_ sample was collected from each jar and tested on a rheometer at room temperature to produce three viscosity curves each, resulting in 18 viscosity curves averaged for each time point. Viscosities were measured as a function of shear rate and consequently the lowest zero- shear viscosity value has been presented below, being most analogous to the shear conditions during reservoir displacement. Table 1. Composition of One Capsule Digestive Enzyme Mixture

j Compound j Mass (mg) Activity 1 j Pancrealipase (Sus scro fa-Pancreas) 148

Contains: Amylase j - 37000 USP 1

Protease I - 37000 USP 1

Lipase I - 2960 USP 1

j Cellulase {Aspergillus niger) 0.16 12000 FCC CU 1 j Papain (Carica Papaya) 2 50000 FCC PU i

\ Pepsin A (Sus scrofa - Stomach) 0.05 500 FCC PU

\ Fruit Bromelain {Ananas comosus) 50 1800 M FCC PU ί

[0028] Referring to figure 4, after 10 days of enzyme treatment the low-shear bitumen viscosity was measured to be 33.8% lower than the initial viscosity. This result is contrary to what may be expected from soaking bitumen in a solution of acetic acid since treatment of bitumen with formic acid, the C1 carboxylic relative of acetic acid, amongst others is a well- developed technique for hardening bitumen by accelerating oxidative aging and increasing the effective asphaltene fraction by increasing its colloidal solvation constant. Accordingly, enzyme treatment provides concomitant physical and chemical processes effecting the colloidal structure/viscosity of the bitumen samples simultaneous with the enzymatic action, but the enzyme activity is the most cause of viscosity reduction.

[0029] An "enzyme flood" reservoir simulation was performed to assess how viscosity reduction may scale up from the results shown in figure 4 to an oil field. A one acre five-point flood pattern was defined with the properties shown in table 2 distributed uniformly over the grid blocks. Relative permeability curves were taken from a reference simulation of a very similar heavy oil SAGD process.

[0030] In the simulation a warm water flood was conducted with 250 m3/day injected at 40°C over a period of 5 years. Oxygen, enzyme and two oleic pseudocomponents (Pseudol and Pseudo2) were defined in order to model the viscosity reduction reaction. Oxygen was injected at its maximum solubility of 0.0375mol% at 2000kPa along with 0.01 mol% enzyme which was the bare minimum to model a meaningful reaction. The simulation was initialized with 3mol% Pseudol in the oleic phase with the same properties as the original bitumen. Pseudol was created to set a lower bound on the extent to which the bitumen viscosity was reduced as otherwise the reaction would proceed continuously and not match the desired viscosity kinetic curve. Therefore, Psuedo2 was created with a viscosity defined to match the desired oleic mixture viscosity after the reaction is complete. Model reaction rates linear were modelled using the frequency factor fit assuming 1 st order oxygen and enzyme consumption kinetics and the reaction form:

1 Pseudol + 1 Enzyme + 1 0 ₂ → 1 Pseudo2 + 2 H ₂ 0

[0031] The enzyme kinetics measured were at 22°C while the reservoir flood was simulated at 40°C to provide an additional thermal viscosity reduction. Accordingly, the results of the simulation will be conservative and are shown in figures 5 and 6.

[0032] The molecular weight of Pseudo2 was varied to ensure the above reaction has mass balance error <1 e-6. The pseudocomponent viscosity was fit such that the bitumen viscosity approaches the experimentally measured value as the mole fraction of Pseudo2 approached 0.03 as shown in Figure 4 above. Two simulations were run, one including oxygen and enzyme with the injected warm water and another with pure warm water, the reaction and bitumen-like Pseudol being present in both simulations.

[0033] Referring to figures 7a and 7b, the corner blocks with the injectors are at the lowest viscosity thanks to being at the injection temperature, at this point in the simulation all of the bitumen in the reservoir has had its viscosity reduced enzymatically (mole fraction of Pseudol in oleic phase is zero everywhere) and consequently the viscosity gradient is entirely due to the thermal gradient between injectors and producer. In this embodiment, warm water/oxygen/ enzyme injectors are present on the four corners with a production well at the center. Upon comparing the simulation results with and without the enzymatic reaction it was found that the warm water alone was insufficient to produce even a small amount of bitumen.

[0034] Referring to figure 8, it is shown that the use of enzymes dramatically increases the production of oil from a well at lower temperatures. Accordingly, it is possible that the utilization of enzymes for bitumen viscosity reduction may make warm water flooding feasible where it may not have been possible.

[0035] Various advantages will now be apparent to a person of skill in the art. Of note is the ability to extract heavy oils from an oil deposit using little energy. As another example of an advantage, the method can be used to reduce the viscosity of heavy oil in any application including facilitating the processing of heavy oil.

[0036] Organic enzymes are used to mobilize heavy or shale oils during enhanced recovery with less carbon intensity and energy input required compared to traditional steam-based EOR techniques. For example, a warm water flood around 40°C wherein enzymes would be mixed with pH optimal water on surface and injected into the reservoir while simultaneously producing mobilized bitumen and other dissolution products. This may also be coupled with a microbial enhanced oil process. The produced water surface facilities could be almost identical to standard SAGD water treatment as the enzyme solution could be separated from the oleic phase in the Free Water Knock-Out (FWKO) and water treating train to be rejuvenated and recycled. In addition, digestive enzymes can be brewed on surfaces in bioprocess reactors using food wastes from camp and other relatively inexpensive organic inputs. Oxygen could be co-injected using toe/heel strings with similar completions to SAGD injection wells. The specific well configuration is no particularly limited and can depend on the reservoir geology.

[0037] While specific embodiments have been described and illustrated, such embodiments should be considered illustrative only and should not serve to limit the accompanying claims.