TAILINGS

FIELD OF THE INVENTION

[0001] The subject matter disclosed herein relates to methods for recovering oil and water from oil sands tailings. More specifically, oils sands tailings are sent to a drying apparatus.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application is entitled to the benefit of Provisional Patent Application Serial No. 61/668,081 filed July 5, 2012, and titled METHODS FOR RECOVERING OIL AND WATER FROM OIL SANDS TAILINGS. The above listed application is herein incorporated by reference.

BACKGROUND OF THE INVENTION

[0003] Oil sands are naturally occurring mixtures of sand, clay, water, and about 10-12 % by weight of oil deposits. The oil may be bituminous petroleum, or in some areas, such as the Orinoco Belt in Venezuela, it may be heavy or extra-heavy crude oil. Aqueous-based methods to extract oil from oil sands include Clark Hot Water Extraction (CHWE) or steam-assisted gravity-drainage ("SAGD").

[0004] In CHWE, the oil sands are mined from the surface. Hot water at about 50-80 °C is added to the oil sands to form a slurry. The slurry is then transferred to a flotation vessel. The slurry may be agitated or aerated to break-up oil sands agglomerates and encourage frothing. The slurry is then allowed to settle, wherein the solids settle to the bottom and the oil and any entrained air will float to the slurry surface. The bitumen froth is skimmed of the top of the slurry and recovered. The recovered bitumen froth may comprise about 30% water and 10% solids by weight. The CHWE process requires about 7 to 9 barrels of water for every produced barrel of oil.

[0005] In SAGD, two parallel horizontal wells are drilled. The upper well injects steam into the geological formation, and the lower well collects the heated crude oil or bitumen that flows out of the formation along with water from the condensation of the injected steam. This condensed steam and oil are pumped to the surface wherein the oil is separated, leaving an oily/water mixture known as

"produced water". Roughly three barrels of this oily and bituminous containing process water are produced per barrel of recovered oil. The SAGD produced water normally contains about 1-60% solids and has a temperature of about 95 °C.

[0006] Both the CHWE and SAGD processes generate large amounts of process water contaminated with substantial amounts of suspended and emulsified oil, bitumen and other impurities like salts, silica, etc. Recovery and reuse of the water are needed to reduce operational costs and to minimize environmental concerns. The process water is eventually recycled for reuse in the extraction processes, but it must first be clarified and separated from substantial amounts of suspended and emulsified oil, bitumen and other impurities like salts, silica, etc. Despite recycling, most of the process water ends-up as fluid tailings, or Oil Sands Tailings Water ("OSTW"). These tailings are the unusable materials that remain after all the valuable fractions have been removed. The tailings are mostly water with some oil and a substantial amount of sandy solids. The OSTW are transferred to tailing ponds where sedimentation occurs. Once the OSTW are in the tailings ponds, the sand quickly settles. Fine tailings suspended in the ponds take about two years to settle and form Mature Fine Tails ("MTF"). MTF are about 33 % solids by weight.

[0007] The Energy Resources Conservation Board, an independent agency of the government of Alberta, CA, has issued Directive 074 to regulate tailings associated with oil sands. A main goal of the directive is to lay out criteria for oil sands operators to follow to reduce the amount of fluid tailings produced.

BRIEF DESCRIPTION OF THE INVENTION

[0008] Methods are disclosed wherein water and oil from oil sands tailings are immediately recovered, thereby reducing the overall water and oil consumption in the extraction process. The methods may also be employed using oil sands tailings water from oil sands tailings ponds, thereby allowing operators to reduce the volume of their existing tailings ponds.

[0009] Oil Sands Tailings Water (contaminated with oil products, Mature Fine Tails, Ultra-Fine Tails and other materials) will be fed into a vacuum drying apparatus (this mixture can include chemistries to properly bind the material prior to drying), the dried material will be released from the apparatus to be sent to a disposal site (land fill, mines, etc.) and the water/oil mixture will be fed into an oil/water separation apparatus. The oil (separated in the oil/water separation apparatus) will be released to be reclaimed in the Upgrading and/or Extraction facility of the plant (this oil can be mixed with chemistries to aid the reclaiming/upgrading process), the water will be sent to a water clarifying device (Air Flotation, Etc.) to be combined with water chemistries to aid in the clarification of the water. The product/effluent water (from the clarifying device), depending on water quality can be fed into an Ultra Purifying process to allow for quick utilization of the water in the upgrading/extraction/utilities/SAGD portions of the plant. This combined recycling/reclamation process will reclaim the materials in the tailings water; reclaim the tailings water to be recycled (via evaporation and/or clarification and/or ultra- purification) and reclaim the oil in the tailings water to be upgraded at the facility.

[0010] In one embodiment, a method for recovering water and oil from tailings is disclosed. The method may comprise feeding the tailings to a drying apparatus, wherein the tailings are separated to form a concentrated tailings product and a fluid stream. The fluid stream may be recovered. Suitable drying apparatuses include, but are not limited to, nutsche filters, horizontal plate filters, filter presses, tube filters, bag filters, leaf filters, centrifugal filters, rotary drum filters, disk filters, and cartridge filters. In yet another embodiment, a vacuum may be applied to the drying apparatus. In another embodiment, the drying apparatus is mounted on a mobile skid or frame so that it may be moved between tailings ponds and operated at the tailings pond site.

[0011] In another embodiment, the method may comprise using a water separator to separate said fluid stream into an oil stream and an aqueous stream. Suitable water separators include, but are not limited to, gravity separators or parallel plate separators. The aqueous stream may be further processed by sending it to a clarification device. Suitable clarification devices include dissolved gas flotation (DGF) or dissolved air flotation (DAF) devices. The clarified aqueous stream may be fed to an ultra water purification process. Suitable ultra water purification processes include, but are not limited to, microfiltration, ultrafiltration, reverse osmosis, and biofiltration.

[0012] In another embodiment, the tailings are tailings from a hydrocarbon extraction or mining process. In another embodiment, the tailings may be oil sands tailings. In yet another embodiment, at least a portion of the tailings may be from a tailings pond. The concentrated tailings product may have an average shear strength of equal to or greater than about 10 kPa. Such tailings are suitable as trafficable deposits as required under Directive 074.

[0013] In yet another method, at least a portion of the recovered fluid stream is reused in said hydrocarbon extraction or mining process. The oil stream separated from the fluid stream may be fed to the oil upgrading section of the extraction process. Alternatively, the oil stream may be used on site to operate the drying apparatus. The aqueous stream may be recycled for reuse in the hydrocarbon extraction or mining process, or upgrading for use as utility water.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 (FIG. 1) shows one embodiment of recovering oil and water from oil sands tailings.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0015] Figure 1 (FIG. 1) shows one embodiment recovering oil and water from oil sands tailings. The process may be a batch or continuous process and may be automated. Tailings comprising water, fine clays, silts, left-over bitumen, salts and soluble organic and inorganic compounds, and fine or ultra-fine tailings are obtained directly from the oil extraction or mining process or from a tailing pond (2). Tailings from a tailing pond may also comprise mature fine tailings. Mature fine tailings ("MFT") are fluid tailings made from fine tailings that settle over the course of several months or years. The solids-content is about 30 wt% based on a total MTF weight. The tailings (4) are fed to a drying apparatus (6). In the drying apparatus (6), the solid particles, such as sand, silt, clay, mature fine tailings, and fine tailings are dried to form a concentrated tailings product, or cake (8). Persons of ordinary skill in the art will recognize that the cake will have a larger solids-content than the tailings fed to the apparatus, but some moisture may be present in the cake. A suitable drying apparatus is a cake filter. Such filters are well known in the art and include, but are not limited to, nutsche filters, horizontal plate filters, filter presses, tube or bag filters, leaf filters, centrifugal filters, rotary drum filters, disk filters, and cartridge filters. A vacuum may be applied or maintained using any conventional method, such as steam jets or vacuum pumps. Vacuum drying has the added advantage of lowering the boiling point of water and any solvents or bitumen in the tailings, thereby decreasing the temperature required to produce the cake. Optionally the vacuum drying process may occur at elevated temperatures. The concentrated tailings product, or cake, may have an average shear strength of greater than 10 kPa, making it suitable for direct disposal (10) under Directive 074. Fluid from the drying apparatus (6) may be sent to an oil/water separator (14). The fluid may be a mixture of oil and water and may be a vapor, a liquid, or a vapor/liquid mixture. Suitable water separators are well known by those of skill in the art and include, but are not limited to, gravity separators and parallel plate separators. Oil from the oil/water separator is reclaimed (16) and sent elsewhere for further processing or use (18). The reclaimed oil (16) may even be suitable to power or heat the dryer apparatus. Water from the oil/water separator (20) is sent to a water-clarifying device (22), such as a dissolved gas flotation (DGF) or dissolved air flotation (DAF). After leaving the water clarifying device (22), the water may be recycled and used as process water (24), for example in cooling towers or boiler systems, or reused in the oil extraction or mining process. Optionally, the water from the water clarifying device is subject to ultra water purification (26), such as, microfiltration, ultrafiltration, reverse osmosis, or biofiltration before it is used as process water (24), or it may be discharged directly to the environment (not shown). Some recovery processes may add various water treatment chemicals, and process chemicals at various points in the recovery process (FIG. 1). The details of these chemicals and their uses have been omitted for the sake of brevity, but are well known to those of skill in the art. Accordingly, these and other minor differences in recovery processes do not affect the scope of the invention.

[0016] Oil Sands Tailings Water [about 25,000 gpm (contaminated with oil products, Mature Fine Tails, Ultra-Fine Tails and other materials; about 20-30% solids, 1-3% oil/bitumen & 70-80 % water)] will be fed into a continuous/batch vacuum drying process (this mixture can include chemistries to properly bind the material prior to drying). The vacuum drying process may utilize a filter press. The filter press may be of any design, including, but not limited to, flush-plate, plate and frame, or recessed plate designs. The concentrated tailings product, or cake, (>10 kPa) will be released from the drying apparatus to be sent to a disposal site (land fill, mines, etc.). The water/oil mixture (about 97% water and 3% oil) will be fed into an oil/water separation apparatus. The oil [about 3% of the 25,000 gpm stream (separated in the oil/water separation apparatus)] will be released to be reclaimed in the Upgrading and/or Extraction facility of the plant. This oil may be mixed with chemistries to aid the reclaiming/upgrading process. The water will be sent to a water clarifying device (Air Flotation, Etc.) to be combined with water chemistries to aid in the clarification of the water [Total mg/1 TSS varies on which pond is being recycled]. The product/effluent water [Potentially <200 mg/1 of TSS (from the clarifying device)], depending on water quality can be fed into an Ultra Purifying process (to reach boiler spec water) to allow for quick utilization of the water in the upgrading/extraction/utilities/SAGD portions of the plant or the product/effluent water (from the water clarifying device) can be used directly in the upgrading/extraction/utilities/SAGD portions of the plant without Ultra Purifying. This combined recycling/reclamation process will reclaim the materials in the tailings water (MFTs, solids, etc.); reclaim the tailings water to be recycled (via evaporation and/or clarification and/or ultra-purification) and reclaim the oil in the tailings water to be upgraded at the facility.

[0017] This combined recycling/reclamation process will reclaim the contaminated Fines, Mature Fine Tails, Ultra-Fine Tails and other materials in the tailings water ponds; reclaim the tailings water to be recycled (via evaporation and/or clarification and/or ultra-purification) and reclaim the oil in the tailings water fines to be upgraded at the facility. This will insure that the Oil Sands companies are able to reach their Directive 74 and Containment initiatives that have been given to them by the government.

[0018] The reclaimed MFT/water/oil, with a very small amount of chemistry, created product (Diesel) at the test site to power the mechanical process of this application. The process may be mobilized to be moved between ponds and remotely operated via operational personnel. Unlike the typical MFT recovery process, the current invention does not require extreme amounts of polymer. The current invention also reduces the amount of fresh water required, such as river water, as a large portion of the process water maybe recycled and reused. Also, this process will help the Oil Sands companies meet Directive 74 ahead of schedule, if properly implemented.

[0019] Methods are disclosed wherein water and oil from oil sands tailings are immediately recovered, thereby reducing the overall water and oil consumption in the extraction process. The methods may also be employed using oil sands tailings water from oil sands tailings ponds, thereby allowing operators to reduce the volume of their existing tailings ponds.

[0020] Oil Sands Tailings Water (contaminated with oil products, Mature Fine Tails, Ultra-Fine Tails and other materials) will be fed into a vacuum drying apparatus (this mixture can include chemistries to properly bind the material prior to drying), the dried material will be released from the apparatus to be sent to a disposal site (land fill, mines, etc.) and the water/oil mixture will be fed into an oil/water separation apparatus. The oil (separated in the oil/water separation apparatus) will be released to be reclaimed in the Upgrading and/or Extraction facility of the plant (this oil can be mixed with chemistries to aid the reclaiming/upgrading process), the water will be sent to a water clarifying device (Air Flotation, Etc.) to be combined with water chemistries to aid in the clarification of the water. The product/effluent water (from the clarifying device), depending on water quality can be fed into an Ultra Purifying process to allow for quick utilization of the water in the upgrading/extraction/utilities/SAGD portions of the plant. This combined recycling/reclamation process will reclaim the materials in the tailings water; reclaim the tailings water to be recycled (via evaporation and/or clarification and/or ultra- purification) and reclaim the oil in the tailings water to be upgraded at the facility.

[0021] In one embodiment, a method for recovering water and oil from tailings is disclosed. The method may comprise feeding the tailings to a drying apparatus, wherein the tailings are separated to form a concentrated tailings product and a fluid stream. The fluid stream may be recovered. Suitable drying apparatuses include, but are not limited to, nutsche filters, horizontal plate filters, filter presses, tube filters, bag filters, leaf filters, centrifugal filters, rotary drum filters, disk filters, and cartridge filters. In yet another embodiment, a vacuum may be applied to the drying apparatus. In another embodiment, the drying apparatus is mounted on a mobile skid or frame so that it may be moved between tailings ponds and operated at the tailings pond site.

[0022] In another embodiment, the method may comprise using a water separator to separate said fluid stream into an oil stream and an aqueous stream. Suitable water separators include, but are not limited to, gravity separators or parallel plate separators. The aqueous stream may be further processed by sending it to a clarification device. Suitable clarification devices include dissolved gas flotation (DGF) or dissolved air flotation (DAF) devices. The clarified aqueous stream may be fed to an ultra water purification process. Suitable ultra water purification processes include, but are not limited to, microfiltration, ultrafiltration, reverse osmosis, and biofiltration.

[0023] In another embodiment, the tailings are tailings from a hydrocarbon extraction or mining process. In another embodiment, the tailings may be oil sands tailings. In yet another embodiment, at least a portion of the tailings may be from a tailings pond. The concentrated tailings product may have an average shear strength of equal to or greater than about 10 kPa. Such tailings are suitable as trafficable deposits as required under Directive 074.

[0024] In yet another method, at least a portion of the recovered fluid stream is reused in said hydrocarbon extraction or mining process. The oil stream separated from the fluid stream may be fed to the oil upgrading section of the extraction process. Alternatively, the oil stream may be used on site to operate the drying apparatus. The aqueous stream may be recycled for reuse in the hydrocarbon extraction or mining process, or upgrading for use as utility water.

[0025] This written description uses examples and figures to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.

[0026] What is claimed is: