Patent Description:
This disclosure relates to storing hazardous material in a subterranean formation and, more particularly, storing spent nuclear fuel in a subterranean formation.

Hazardous waste is often placed in long-term, permanent, or semi-permanent storage so as to prevent health issues among a population living near the stored waste. Such hazardous waste storage is often challenging, for example, in terms of storage location identification and surety of containment. For instance, the safe storage of nuclear waste (e.g., spent nuclear fuel, whether from commercial power reactors, test reactors, or even military waste) is considered to be one of the outstanding challenges of energy technology. Safe storage of the long-lived radioactive waste is a major impediment to the adoption of nuclear power in the United States and around the world. Conventional waste storage methods have emphasized the use of tunnels, and is exemplified by the design of the Yucca Mountain storage facility. Other techniques include boreholes, including vertical boreholes, drilled into crystalline basement rock. Other conventional techniques include forming a tunnel with boreholes emanating from the walls of the tunnel in shallow formations to allow human access. <CIT> discloses a hazardous material storage bank for nuclear waste containers below shale formations within the horizontal part of a well bore. <CIT> discloses the monitoring of radiation by sensors in a vertical borehole in a nuclear waste storage complex in a subterranean formation.

In a general implementation, the invention is covered by a hazardous material storage bank according to the set of claims.

The details of one or more implementations of the subject matter described in this disclosure are set forth in the accompanying drawings and the description below.

The present disclosure describes a hazardous material storage bank system, which includes one or more wellbores formed into a subterranean zone to provide long-term (e.g., tens, hundreds, or even thousands of years) storage of hazardous material (e.g., biological, chemical, nuclear, or otherwise) in one or more underground storage volumes storage containers. The subterranean zone includes multiple subterranean layers having different geological formations and properties. The storage containers may be deposited in a particular subterranean layer based on one or more geologic properties of that layer, such as low permeability, sufficient thickness, low brittleness, and other properties. In some aspects, the particular subterranean layer comprises a shale formation, which forms an isolative seal between the storage containers and another subterranean layer that comprises mobile water.

<FIG> are schematic illustrations of example implementations of a hazardous material storage bank system, e.g., a subterranean location for the long-term (e.g., tens, hundreds, or thousands of years or more) but retrievable safe and secure storage of hazardous material, during a deposit or retrieval operation according to the present disclosure. For example, turning to <FIG>, this figure illustrates an example hazardous material storage bank system <NUM> during a deposit (or retrieval, as described below) process, e.g., during deployment of one or more containers of hazardous material in a subterranean formation. As illustrated, the hazardous material storage bank system <NUM> includes a wellbore <NUM> formed (e.g., drilled or otherwise) from a terranean surface <NUM> and through multiple subterranean layers <NUM>, <NUM>, <NUM>, and <NUM>. Although the terranean surface <NUM> is illustrated as a land surface, terranean surface <NUM> may be a subsea or other underwater surface, such as a lake or an ocean floor or other surface under a body of water. Thus, the present disclosure contemplates that the wellbore <NUM> may be formed under a body of water from a drilling location on or proximate the body of water.

The illustrated wellbore <NUM> is a directional wellbore in this example of hazardous material storage bank system <NUM>. For instance, the wellbore <NUM> includes a substantially vertical portion <NUM> coupled to a radiussed or curved portion <NUM>, which in turn is coupled to a substantially horizontal portion <NUM>. As used in the present disclosure, "substantially" in the context of a wellbore orientation, refers to wellbores that may not be exactly vertical (e.g., exactly perpendicular to the terranean surface <NUM>) or exactly horizontal (e.g., exactly parallel to the terranean surface <NUM>). In other words, those of ordinary skill in the drill arts would recognize that vertical wellbores often undulate offset from a true vertical direction, that they might be drilled at an angle that deviates from true vertical, and horizontal wellbores often undulate offset from a true horizontal direction. Further, the substantially horizontal portion <NUM>, in some aspects, may be a slant wellbore or other directional wellbore that is oriented between exactly vertical and exactly horizontal. Further, the substantially horizontal portion <NUM>, in some aspects, may be a slant wellbore or other directional well bore that is oriented to follow the slant of the formation. As illustrated in this example, the three portions of the wellbore <NUM> - the vertical portion <NUM>, the radiussed portion <NUM>, and the horizontal portion <NUM> - form a continuous wellbore <NUM> that extends into the Earth.

The illustrated wellbore <NUM> has a surface casing <NUM> positioned and set around the wellbore <NUM> from the terranean surface <NUM> into a particular depth in the Earth. For example, the surface casing <NUM> may be a relatively large-diameter tubular member (or string of members) set (e.g., cemented) around the wellbore <NUM> in a shallow formation. As used herein, "tubular" may refer to a member that has a circular cross-section, elliptical cross-section, or other shaped cross-section. For example, in this implementation of the hazardous material storage bank system <NUM>, the surface casing <NUM> extends from the terranean surface through a surface layer <NUM>. The surface layer <NUM>, in this example, is a geologic layer comprised of one or more layered rock formations. In some aspects, the surface layer <NUM> in this example may or may not include freshwater aquifers, salt water or brine sources, or other sources of mobile water (e.g., water that moves through a geologic formation). In some aspects, the surface casing <NUM> may isolate the wellbore <NUM> from such mobile water, and may also provide a hanging location for other casing strings to be installed in the wellbore <NUM>. Further, although not shown, a conductor casing may be set above the surface casing <NUM> (e.g., between the surface casing <NUM> and the surface <NUM> and within the surface layer <NUM>) to prevent drilling fluids from escaping into the surface layer <NUM>.

As illustrated, a production casing <NUM> is positioned and set within the wellbore <NUM> downhole of the surface casing <NUM>. Although termed a "production" casing, in this example, the casing <NUM> may or may not have been subject to hydrocarbon production operations. Thus, the casing <NUM> refers to and includes any form of tubular member that is set (e.g., cemented) in the wellbore <NUM> downhole of the surface casing <NUM>. In some examples of the hazardous material storage bank system <NUM>, the production casing <NUM> may begin at an end of the radiussed portion <NUM> and extend throughout the substantially horizontal portion <NUM>. The casing <NUM> could also extend into the radiussed portion <NUM> and into the vertical portion <NUM>.

As shown, cement <NUM> is positioned (e.g., pumped) around the casings <NUM> and <NUM> in an annulus between the casings <NUM> and <NUM> and the wellbore <NUM>. The cement <NUM>, for example, may secure the casings <NUM> and <NUM> (and any other casings or liners of the wellbore <NUM>) through the subterranean layers under the terranean surface <NUM>. In some aspects, the cement <NUM> may be installed along the entire length of the casings (e.g., casings <NUM> and <NUM> and any other casings), or the cement <NUM> could be used along certain portions of the casings if adequate for a particular wellbore <NUM>. The cement <NUM> can also provide an additional layer of confinement for the hazardous material in containers <NUM>.

The wellbore <NUM> and associated casings <NUM> and <NUM> may be formed with various example dimensions and at various example depths (e.g., true vertical depth, or TVD). For instance, a conductor casing (not shown) may extend down to about <NUM> (<NUM> feet) TVD, with a diameter of between about <NUM>. <NUM> (<NUM> in. ) and <NUM> (<NUM> in. The surface casing <NUM> may extend down to about <NUM> (<NUM> feet) TVD, with a diameter of between about <NUM> (<NUM> in. ) and <NUM> (<NUM> in. An intermediate casing (not shown) between the surface casing <NUM> and production casing <NUM> may extend down to about <NUM> (<NUM> feet) TVD, with a diameter of between about <NUM> in. and <NUM> in. The production casing <NUM> may extend substantially horizontally (e.g., to case the substantially horizontal portion <NUM>) with a diameter of between about <NUM> (<NUM> in. ) and <NUM> (<NUM> in. The foregoing dimensions are merely provided as examples and other dimensions (e.g., diameters, TVDs, lengths) are contemplated by the present disclosure. For example, diameters and TVDs may depend on the particular geological composition of one or more of the multiple subterranean layers (<NUM>-<NUM>), particular drilling techniques, as well as a size, shape, or design of a hazardous material container <NUM> that contains hazardous material to be deposited in the hazardous material storage bank system <NUM>. In some alternative examples, the production casing <NUM> (or other casing in the wellbore <NUM>) could be circular in cross-section, elliptical in cross-section, or some other shape.

As illustrated, the wellbore <NUM> extends through subterranean layers <NUM>, <NUM>, and <NUM>, and lands in subterranean layer <NUM>. As discussed above, the surface layer <NUM> may or may not include mobile water. Subterranean layer <NUM>, which is below the surface layer <NUM>, in this example, is a mobile water layer <NUM>. For instance, mobile water layer <NUM> may include one or more sources of mobile water, such as freshwater aquifers, salt water or brine, or other source of mobile water. In this example of hazardous material storage bank system <NUM>, mobile water may be water that moves through a subterranean layer based on a pressure differential across all or a part of the subterranean layer. For example, the mobile water layer <NUM> may be a permeable geologic formation in which water freely moves (e.g., due to pressure differences or otherwise) within the layer <NUM>. In some aspects, the mobile water layer <NUM> may be a primary source of human-consumable water in a particular geographic area. Examples of rock formations of which the mobile water layer <NUM> may be composed include porous sandstones and limestones, among other formations.

Below the mobile water layer <NUM>, in this example implementation of hazardous material storage bank system <NUM>, is an impermeable layer <NUM>. The impermeable layer <NUM>, in this example, may not allow mobile water to pass through. Thus, relative to the mobile water layer <NUM>, the impermeable layer <NUM> may have low permeability, e.g., on the order of nanodarcy permeability. Additionally, in this example, the impermeable layer <NUM> may be a relatively non-ductile (i.e., brittle) geologic formation. One measure of non-ductility is brittleness, which is the ratio of compressive stress to tensile strength. In some examples, the brittleness of the impermeable layer <NUM> may be between about <NUM> MPa and <NUM> MPa.

As shown in this example, the impermeable layer <NUM> is shallower (e.g., closer to the terranean surface <NUM>) than the storage layer <NUM>. In this example rock formations of which the impermeable layer <NUM> may be composed include, for example, certain kinds of sandstone, mudstone, clay, and slate that exhibit permeability and brittleness properties as described above. In alternative examples, the impermeable layer <NUM> may be deeper (e.g., further from the terranean surface <NUM>) than the storage layer <NUM>. In such alternative examples, the impermeable layer <NUM> may be composed of an igneous rock, such as granite.

Below the impermeable layer <NUM> is a storage layer <NUM>. The storage layer <NUM>, in this example, may be chosen as the landing for the substantially horizontal portion <NUM>, which stores the hazardous material, for several reasons. Relative to the impermeable layer <NUM> or other layers, the storage layer <NUM> may be thick, e.g., between about <NUM> and <NUM> (<NUM> and <NUM> feet) of total vertical thickness. Thickness of the storage layer <NUM> may allow for easier landing and directional drilling, thereby allowing the substantially horizontal portion <NUM> to be readily emplaced within the storage layer <NUM> during constructions (e.g., drilling). If formed through an approximate horizontal center of the storage layer <NUM>, the substantially horizontal portion <NUM> may be surrounded by about <NUM> and <NUM> (<NUM> and <NUM> feet) of the geologic formation that comprises the storage layer <NUM>. Further, the storage layer <NUM> may also have no mobile water, e.g., due to a very low permeability of the layer <NUM> (e.g., on the order of milli- or nanodarcys). In addition, the storage layer <NUM> may have sufficient ductility, such that a brittleness of the rock formation that comprises the layer <NUM> is between about <NUM> MPa and <NUM> MPa. Examples of rock formations of which the storage layer <NUM> may be composed include: shale and anhydrite. Further, in some aspects, hazardous material may be stored below the storage layer, even in a permeable formation such as sandstone or limestone, if the storage layer is of sufficient geologic properties to isolate the permeable layer from the mobile water layer <NUM>.

In some examples implementations of the hazardous material storage bank system <NUM>, the storage layer <NUM> is composed of shale. Shale, in some examples, may have properties that fit within those described above for the storage layer <NUM>. For example, shale formations may be suitable for a long-term confinement of hazardous material (e.g., in the hazardous material containers <NUM>), and for their isolation from mobile water layer <NUM> (e.g., aquifers) and the terranean surface <NUM>. Shale formations may be found relatively deep in the Earth, typically <NUM> (<NUM> feet) or greater, and placed in isolation below any fresh water aquifers.

Shale formations, for instance, may include geologic properties that enhance the long-term (e.g., thousands of years) isolation of material. Such properties, for instance, have been illustrated through the long term storage (e.g., tens of millions of years) of hydrocarbon fluids (e.g., gas, liquid, mixed phase fluid) without escape of such fluids into surrounding layers (e.g., mobile water layer <NUM>). Indeed, shale has been shown to hold natural gas for millions of years or more, giving it a proven capability for long-term storage of hazardous material. Example shale formations (e.g., Marcellus, Eagle Ford, Barnett, and otherwise) has stratification that contains many redundant sealing layers that have been effective in preventing movement of water, oil, and gas for millions of years, lacks mobile water, and can be expected (e.g., based on geological considerations) to seal hazardous material (e.g., fluids or solids) for thousands of years after deposit.

Shale formations may also be at a suitable depth, e.g., between <NUM> and <NUM> (<NUM> and <NUM> feet) TVD. Such depths are typically below ground water aquifer (e.g., surface layer <NUM> and/or mobile water layer <NUM>). Further, the presence of soluble elements in shale, including salt, and the absence of these same elements in aquifer layers, demonstrates a fluid isolation between shale and the aquifer layers.

Another particular quality of shale that may advantageously lend itself to hazardous material storage is its clay content, which, in some aspects, provides a measure of ductility greater than that found in other, impermeable rock formations (e.g., impermeable layer <NUM>). For example, shale may be stratified, made up of thinly alternating layers of clays (e.g., between about <NUM>-<NUM>% clay by volume) and other minerals. Such a composition may make shale less brittle and, thus less susceptible to fracturing (e.g., naturally or otherwise) as compared to rock formations in the impermeable layer (e.g., granite or otherwise). For example, rock formations in the impermeable layer <NUM> may have suitable permeability for the long term storage of hazardous material, but are too brittle and commonly are fractured. Thus, such formations may not have sufficient sealing qualities (as evidenced through their geologic properties) for the long term storage of hazardous material.

The present disclosure contemplates that there may be many other layers between or among the illustrated subterranean layers <NUM>, <NUM>, <NUM>, and <NUM>. For example, there may be repeating patterns (e.g., vertically), of one or more of the mobile water layer <NUM>, impermeable layer <NUM>, and storage layer <NUM>. Further, in some instances, the storage layer <NUM> may be directly adjacent (e.g., vertically) the mobile water layer <NUM>, i.e., without an intervening impermeable layer <NUM>.

<FIG> illustrates an example of a deposit operation of hazardous material in the substantially horizontal portion <NUM> of the wellbore <NUM>. For example, as shown, a work string <NUM> (e.g., tubing, coiled tubing, wireline, or otherwise) may be extended into the cased wellbore <NUM> to place one or more (three shown but there may be more or less) hazardous material containers <NUM> into long term, but in some aspects, retrievable, storage in the portion <NUM>. For example, in the implementation shown in <FIG>, the work string <NUM> may include a downhole tool <NUM> that couples to the container <NUM>, and with each trip into the wellbore <NUM>, the downhole tool <NUM> may deposit a particular hazardous material container <NUM> in the substantially horizontal portion <NUM>.

The downhole tool <NUM> may couple to the container <NUM> by, in some aspects, a threaded connection. In alternative aspects, the downhole tool <NUM> may couple to the container <NUM> with an interlocking latch, such that rotation of the downhole tool <NUM> may latch to (or unlatch from) the container <NUM>. In alternative aspects, the downhole tool <NUM> may include one or more magnets (e.g., rare Earth magnets, electromagnets, a combination thereof, or otherwise) which attractingly couple to the container <NUM>. In some examples, the container <NUM> may also include one or more magnets (e.g., rare Earth magnets, electromagnets, a combination thereof, or otherwise) of an opposite polarity as the magnets on the downhole tool <NUM>. In some examples, the container <NUM> may be made from or include a ferrous or other material attractable to the magnets of the downhole tool <NUM>.

As another example, each container <NUM> may be positioned within the wellbore <NUM> by a wellbore tractor (e.g., on a wireline or otherwise), which may push or pull the container into the substantially horizontal portion <NUM> through motorized (e.g., electric) motion. As yet another example, each container <NUM> may include or be mounted to rollers (e.g., wheels), so that the downhole tool <NUM> may push the container <NUM> into the cased wellbore <NUM>.

In some example implementations, the container <NUM>, one or more of the wellbore casings <NUM> and <NUM>, or both, may be coated with a friction-reducing coating prior to the deposit operation. For example, by applying a coating (e.g., petroleum-based product, resin, ceramic, or otherwise) to the container <NUM> and/or wellbore casings, the container <NUM> may be more easily moved through the cased wellbore <NUM> into the substantially horizontal portion <NUM>. In some aspects, only a portion of the wellbore casings may be coated. For example, in some aspects, the substantially vertical portion <NUM> may not be coated, but the radiussed portion <NUM> or the substantially horizontal portion <NUM>, or both, may be coated to facilitate easier deposit and retrieval of the container <NUM>.

<FIG> also illustrates an example of a retrieval operation of hazardous material in the substantially horizontal portion <NUM> of the wellbore <NUM>. A retrieval operation may be the opposite of a deposit operation, such that the downhole tool <NUM> (e.g., a fishing tool) may be run into the wellbore <NUM>, coupled to the last-deposited container <NUM> (e.g., threadingly, latched, by magnet, or otherwise), and pull the container <NUM> to the terranean surface <NUM>. Multiple retrieval trips may be made by the downhole tool <NUM> in order to retrieve multiple containers from the substantially horizontal portion <NUM> of the wellbore <NUM>.

Each container <NUM> may enclose hazardous material. Such hazardous material, in some examples, may be biological or chemical waste or other biological or chemical hazardous material. In some examples, the hazardous material may include nuclear material, such as spent nuclear fuel recovered from a nuclear reactor (e.g., commercial power or test reactor) or military nuclear material. For example, a gigawatt nuclear plant may produce <NUM> tons of spent nuclear fuel per year. The density of that fuel is typically close to <NUM> (<NUM> gm/cm<NUM> = <NUM>/liter), so that the volume for a year of nuclear waste is about <NUM><NUM>. Spent nuclear fuel, in the form of nuclear fuel pellets, may be taken from the reactor and not modified. Nuclear fuel pellets are solid, and emit very little gas other than short-lived tritium (<NUM> year half-life).

In some aspects, the storage layer <NUM> should be able to contain any radioactive output (e.g., gases) within the layer <NUM>, even if such output escapes the containers <NUM>. For example, the storage layer <NUM> may be selected based on diffusion times of radioactive output through the layer <NUM>. For example, a minimum diffusion time of radioactive output escaping the storage layer <NUM> may be set at, for example, fifty times a half-life for any particular component of the nuclear fuel pellets. Fifty half-lives as a minimum diffusion time would reduce an amount of radioactive output by a factor of <NUM> x <NUM>-<NUM>. As another example, setting a minimum diffusion time to thirty half-lives would reduce an amount of radioactive output by a factor of one billion.

For example, plutonium-<NUM> is often considered a dangerous waste product in spent nuclear fuel because of its long half-life of <NUM>,<NUM> years. For this isotope, <NUM> half-lives would be <NUM> million years. Plutonium-<NUM> has low solubility in water, is not volatile, and as a solid is not capable of diffusion through a matrix of the rock formation that comprises the illustrated storage layer <NUM> (e.g., shale or other formation). The storage layer <NUM>, for example comprised of shale, may offer the capability to have such isolation times (e.g., millions of years) as shown by the geological history of containing gaseous hydrocarbons (e.g., methane and otherwise) for several million years. In contrast, in conventional nuclear material storage methods, there was a danger that some plutonium might dissolve in a layer that comprised mobile ground water upon confinement escape.

Turning to <FIG>, an alternative deposit operation is illustrated. In this example deposit operation, a fluid <NUM> (e.g., liquid or gas) may be circulated through the wellbore <NUM> to fluidly push the containers <NUM> into the substantially horizontal wellbore portion <NUM>. In some example, each container <NUM> may be fluidly pushed separately. In alternative aspects, two or more containers <NUM> may be fluidly pushed, simultaneously, through the wellbore <NUM> for deposit into the substantially horizontal portion <NUM>. The fluid <NUM> can be, in some cases, water. Other examples include a drilling mud or drilling foam. In some examples, a gas may be used to push the containers <NUM> into the wellbore, such as air, argon, or nitrogen.

In some aspects, the choice of fluid <NUM> may depend at least in part on a viscosity of the fluid <NUM>. For example, a fluid <NUM> may be chosen with enough viscosity to impede the drop of the container <NUM> into the substantially vertical portion <NUM>. This resistance or impedance may provide a safety factor against a sudden drop of the container <NUM>. The fluid <NUM> may also provide lubrication to reduce a sliding friction between the container <NUM> and the casings <NUM> and <NUM>. The container <NUM> can be conveyed within a casing filled with a liquid of controlled viscosity, density, and lubricant qualities. The fluid-filled annulus between the inner diameter of the casings <NUM> and <NUM> and the outer diameter of the conveyed container <NUM> represents an opening designed to dampen any high rate of container motion, providing automatic passive protection in an unlikely decoupling of the conveyed container <NUM>.

In some aspects, other techniques may be employed to facilitate deposit of the container <NUM> into the substantially horizontal portion <NUM>. For example, one or more of the installed casings (e.g., casings <NUM> and <NUM>) may have rails to guide the storage container <NUM> into the wellbore <NUM> while reducing friction between the casings and the container <NUM>. The storage container <NUM> and the casings (or the rails) may be made of materials that slide easily against one another. The casings may have a surface that is easily lubricated, or one that is self-lubricating when subjected to the weight of the storage container <NUM>.

The fluid <NUM> may also be used for retrieval of the container <NUM>. For example, in an example retrieval operation, a volume within the casings <NUM> and <NUM> may be filled with a compressed gas (e.g., air, nitrogen, argon, or otherwise). As the pressure increases at an end of the substantially horizontal portion <NUM>, the containers <NUM> may be pushed toward the radiussed portion <NUM>, and subsequently through the substantially vertical portion <NUM> to the terranean surface.

Turning to <FIG>, another alternative deposit operation is illustrated. In this example deposit operation, the fluid <NUM> (e.g., liquid or gas) may be circulated through a tubular fluid control casing <NUM> to fluidly push the containers <NUM> into the substantially horizontal wellbore portion <NUM>. The fluid <NUM> may circulate through an end of the substantially horizontal portion <NUM> in the fluid control casing <NUM> and recirculate back to the terranean surface <NUM> in an annulus between the fluid control casing <NUM> and the casings <NUM> and <NUM>. In some examples, each container <NUM> may be fluidly pushed separately. The annulus between the fluid control casing <NUM> and the casings <NUM> and <NUM> may be filled with a fluid or compressed gas to reverse the flow of fluid <NUM>, e.g., in order to push the containers <NUM> back towards the terranean surface <NUM>. In alternative aspects, two or more containers <NUM> may be fluidly pushed, simultaneously, through the wellbore <NUM> for deposit into the substantially horizontal portion <NUM>. The fluid control casing <NUM> could be similar or identical to the production casing <NUM>. For that case, a separate tubular member could be enclosed in the wellbore <NUM> or within the production casing <NUM> to provide a return path for the fluid <NUM>.

In some aspects, the wellbore <NUM> may be formed for the primary purpose of long-term storage of hazardous materials. In alternative aspects, the wellbore <NUM> may have been previously formed for the primary purpose of hydrocarbon production (e.g., oil, gas). For example, storage layer <NUM> may be a hydrocarbon bearing formation from which hydrocarbons were produced into the wellbore <NUM> and to the terranean surface <NUM>. In some aspects, the storage layer <NUM> may have been hydraulically fractured prior to hydrocarbon production. Further in some aspects, the production casing <NUM> may have been perforated prior to hydraulic fracturing. In such aspects, the production casing <NUM> may be patched (e.g., cemented) to repair any holes made from the perforating process prior to a deposit operation of hazardous material. In addition, any cracks or openings in the cement between the casing and the drill hole can also be filled at that time.

For example, in the case of spent nuclear fuel as a hazardous material, the wellbore may be formed at a particular location, e.g., near a nuclear power plant, as a new wellbore provided that the location also includes an appropriate storage layer <NUM>, such as a shale formation. Alternatively, an existing well that has already produced shale gas, or one that was abandoned as "dry," (e.g., with sufficiently low organics that the gas in place is too low for commercial development), may be selected as the wellbore <NUM>. In some aspects, prior hydraulic fracturing of the storage layer <NUM> through the wellbore <NUM> may make little difference in the hazardous material storage capability of the wellbore <NUM>. But such a prior activity may also confirm the ability of the storage layer <NUM> to store gases and other fluids for millions of years. If, therefore, the hazardous material or output of the hazardous material (e.g., radioactive gasses or otherwise) were to escape from the container <NUM> and enter the fractured formation of the storage layer <NUM>, such fractures may allow that material to spread relatively rapidly over a distance comparable in size to that of the fractures. In some aspects, the wellbore <NUM> may have been drilled for a production of hydrocarbons, but production of such hydrocarbons had failed, e.g., because the storage layer <NUM> comprised a rock formation (e.g., shale or otherwise) that was too ductile and difficult to fracture for production, but was advantageously ductile for the long-term storage of hazardous material.

<FIG> are schematic illustrations of example implementations of a hazardous material storage bank system during storage and monitoring operations according to the present disclosure. For example, <FIG> illustrates the hazardous material storage bank system <NUM> in a long term storage operation. One or more hazardous material containers <NUM> are positioned in the substantially horizontal portion <NUM> of the wellbore <NUM>. A seal <NUM> is placed in the wellbore <NUM> between the location of the containers <NUM> in the substantially horizontal portion <NUM> and an opening of the substantially vertical portion <NUM> at the terranean surface <NUM> (e.g., a well head). In this example, the seal <NUM> is placed at an uphole end of the substantially vertical portion <NUM>. Alternatively, the seal <NUM> may be positioned at another location within the substantially vertical portion <NUM>, in the radiussed portion <NUM>, or even within the substantially horizontal portion <NUM> uphole of the containers <NUM>. In some aspects, the seal <NUM> may be placed at least deeper than any source of mobile water, such as the mobile water layer <NUM>, within the wellbore <NUM>. In some aspects, the seal <NUM> may be formed substantially along an entire length of the substantially vertical portion <NUM>.

As illustrated, the seal <NUM> fluidly isolates the volume of the substantially horizontal portion <NUM> that stores the containers <NUM> from the opening of the substantially vertical portion <NUM> at the terranean surface <NUM>. Thus, any hazardous material (e.g., radioactive material) that does escape the containers <NUM> may be sealed (e.g., such that liquid, gas, or solid hazardous material) does not escape the wellbore <NUM>. The seal <NUM>, in some aspects, may be a cement plug or other plug, that is positioned or formed in the wellbore <NUM>. As another example, the seal <NUM> may be formed from one or more inflatable or otherwise expandable packers positioned in the wellbore <NUM>.

Prior to a retrieval operation (e.g., as discussed with reference to <FIG>), the seal <NUM> may be removed. For example, in the case of a cement or other permanently set seal <NUM>, the seal <NUM> may be drilled through or otherwise milled away. In the case of semi-permanent or removable seals, such as packers, the seal <NUM> may be removed from the wellbore <NUM> through a conventional process as is known.

<FIG> illustrates an example monitoring operation during long term storage of the containers <NUM>. For example, in some aspects, it may be advantageous or required to monitor one or more variables during long term storage of the hazardous material in the containers <NUM>. In this example of <FIG>, the monitoring system includes one or more sensors <NUM> placed in the wellbore <NUM> (e.g., within the substantially horizontal portion <NUM>) and communicably coupled to a monitoring control system <NUM> through a cable <NUM> (e.g., electrical, optical, hydraulic, or otherwise). Although illustrated as within wellbore <NUM> (e.g., inside of the casings), the sensors <NUM> may be placed outside of the casings, or even built into the casings before the casings are installed in the wellbore <NUM>. Sensors <NUM> could also be placed outside the casing (e.g., casings <NUM> and/or <NUM>), or outside the fluid control casing <NUM>.

As shown, the sensors <NUM> may monitor one or more variables, such as, for example, radiation levels, temperature, pressure, presence of oxygen, a presence of water vapor, a presence of liquid water, acidity, seismic activity, or a combination thereof. Data values related to such variables may be transmitted along the cable <NUM> to the monitoring control system <NUM>. The monitoring control system <NUM>, in turn, may record the data, determine trends in the data (e.g., rise of temperature, rise of radioactive levels), send data to other monitoring locations, such as national security or environmental center locations, and may further automatically recommend actions (e.g., retrieval of the containers <NUM>) based on such data or trends. For example, a rise in temperature or radioactive level in the wellbore <NUM> above a particular threshold level may trigger a retrieval recommendation, e.g., to ensure that the containers <NUM> are not leaking radioactive material. In some aspects, there may be a one-to-one ratio of sensors <NUM> to containers <NUM>. In alternative aspects, there may be multiple sensors <NUM> per container <NUM>, or there may be fewer.

<FIG> shows another example monitoring operation during long term storage of the containers <NUM>. In this example, sensors <NUM> are positioned within a secondary horizontal wellbore <NUM> that is formed separately from the substantially vertical portion <NUM>. The secondary horizontal wellbore <NUM> may be an uncased wellbore, through which the cable <NUM> may extend between the monitoring control system <NUM> and the sensors <NUM>. In this example, the secondary horizontal wellbore <NUM> is formed above the substantially horizontal portion <NUM> but within the storage layer <NUM>. Thus, the sensors <NUM> may record data (e.g., radiation levels, temperature, acidity, seismic activity) of the storage layer <NUM>. In alternative aspects, the secondary horizontal wellbore <NUM> may be formed below the storage layer <NUM>, above the storage layer in the impermeable layer <NUM>, or in other layers. Further, although <FIG> shows the secondary horizontal wellbore <NUM> formed from the same substantially vertical portion <NUM> as the substantially horizontal portion <NUM>, the secondary horizontal wellbore <NUM> may be formed from a separate vertical wellbore and radiussed wellbore.

<FIG> shows another example monitoring operation during long term storage of the containers <NUM>. In this example, sensors <NUM> are positioned within a secondary vertical wellbore <NUM> that is formed separately from the wellbore <NUM>. The secondary vertical wellbore <NUM> may be a cased or an uncased wellbore, through which the cable <NUM> may extend between the monitoring control system <NUM> and the sensors <NUM>. In this example, the secondary vertical wellbore <NUM> bottoms out above the substantially horizontal portion <NUM> but within the storage layer <NUM>. Thus, the sensors <NUM> may record data (e.g., radiation levels, temperature, acidity, seismic activity) of the storage layer <NUM>. In alternative aspects, the secondary vertical wellbore <NUM> may bottom out below the storage layer <NUM>, above the storage layer in the impermeable layer <NUM>, or in other layers. Further, although shown placed in the secondary vertical wellbore <NUM> at a level adjacent the storage layer <NUM>, sensors <NUM> may be placed anywhere within the secondary vertical wellbore <NUM>. Alternatively, the secondary vertical wellbore <NUM> may, in some aspects, be constructed prior to wellbore <NUM>, thereby permitting monitoring by installed sensors <NUM> during construction of the wellbore <NUM>. Also, the monitoring borehole <NUM> could be sealed to prevent the possibility that material that leaks into borehole <NUM> would have a path to the terranean surface <NUM>.

<FIG> shows another example monitoring operation during long term storage of the containers <NUM>. In this example, sensors <NUM> are positioned within a secondary directional wellbore <NUM> that is formed separately from the wellbore <NUM>. The secondary directional wellbore <NUM> may be an uncased wellbore, through which the cable <NUM> may extend between the monitoring control system <NUM> and the sensors <NUM>. In this example, the secondary directional wellbore <NUM> lands adjacent the substantially horizontal portion <NUM> and within the storage layer <NUM>. Thus, the sensors <NUM> may record data (e.g., radiation levels, temperature, acidity, seismic activity) of the storage layer <NUM>. In alternative aspects, the secondary directional wellbore <NUM> may land below the storage layer <NUM>, above the storage layer in the impermeable layer <NUM>, or in other layers. Further, although shown placed in the secondary directional wellbore <NUM> at a level adjacent the storage layer <NUM>, sensors <NUM> may be placed anywhere within the secondary directional wellbore <NUM>. In some aspects, the secondary directional wellbore <NUM> may be used for retrieval of the containers <NUM>, for example, in case the wellbore <NUM> is inaccessible.

<FIG> is a schematic illustration of another example implementation of a hazardous material storage bank system according to the present disclosure. <FIG> illustrates an overhead schematic diagram of an hazardous material storage bank system <NUM> that illustrates an example configuration of wellbores that can be formed or used to store hazardous material, such as spent nuclear fuel, biological material, or chemical material. Hazardous material storage bank system <NUM> includes a vertical wellbore <NUM> (viewed from above here) with multiple horizontal wellbores <NUM> extending therefrom. In this example, four horizontal wellbores <NUM> may be formed from the single vertical wellbore <NUM>.

The example hazardous material storage bank system <NUM> shows a storage bank that can provide long-term (e.g., millions of years) storage for a volume of hazardous material greater than, for example, the hazardous material storage bank system <NUM>. For instance, each horizontal wellbore <NUM> may be substantially similar to the substantially horizontal portion <NUM> shown in <FIG>, which can store one or more containers <NUM> of hazardous material. Each horizontal wellbore <NUM> may be formed in the storage layer <NUM> or below the storage layer <NUM> to provide a sufficient seal against the diffusion of hazardous output in the event of a leak from the one or more containers. Thus, in the example of hazardous material storage bank system <NUM>, hazardous material may be stored more efficiently, as only a single vertical wellbore <NUM> need be formed to account for multiple horizontal wells <NUM>.

<FIG> is another schematic illustration of another example implementation of a hazardous material storage bank system according to the present disclosure. <FIG> illustrates an overhead schematic diagram of an hazardous material storage bank system <NUM> that illustrates an example configuration of wellbores that can be formed or used to store hazardous material, such as spent nuclear fuel, biological material, or chemical material. In this example, the system <NUM> includes a vertical wellbore <NUM> with multiple lateral wellbores <NUM> formed from the vertical wellbore <NUM>. The lateral wellbores <NUM>, in this example, are substantially parallel to each other in a "pitchfork" pattern (or other pattern, such as an "F" pattern, crow's foot pattern, or otherwise). Each lateral wellbore <NUM> may be formed in the storage layer <NUM> or below the storage layer <NUM> to provide a sufficient seal against the diffusion of hazardous output in the event of a leak from the one or more containers. In addition, each lateral wellbore <NUM> may be or include a storage area for containers <NUM>.

<FIG> are schematic illustrations of an example implementation of a hazardous material container according to the present disclosure. <FIG> illustrate isometric, vertical cross-section, and horizontal cross-section views, respectively, of a hazardous material container <NUM>. In some aspects, the hazardous material container <NUM> may be similar to the illustrated container <NUM> and usable in the hazardous material storage bank system <NUM>, the hazardous material storage bank system <NUM>, or other hazardous material storage bank system according to the present disclosure. The hazardous material container <NUM> may be used to store chemical hazardous material, biological hazardous material, nuclear hazardous material, or otherwise. For example, in the illustrated implementation, the hazardous material container <NUM> stores spent nuclear fuel in the form of spent nuclear fuel rods <NUM>.

As illustrated, the hazardous material container <NUM> includes a housing <NUM> (e.g., a crush-proof or crush resistant housing) that encloses a volume <NUM> to store the hazardous material. In this example, the spent nuclear fuel rods <NUM> are positioned in the housing <NUM> prior to sealing of the hazardous material container <NUM>. Each spent nuclear fuel rod <NUM> comprises multiple spent nuclear fuel pellets <NUM>. For example, the spent nuclear fuel pellets <NUM> contain most of the radioisotopes (including the tritium) of the spent nuclear fuel removed from a nuclear reactor. To form the spent nuclear fuel rods <NUM>, the fuel pellets <NUM> are surrounded by zirconium tubes, just as in the reactor. These tubes offer an additional level of containment. The tubes can be mounted in the original fuel assemblies, or removed from those assemblies for tighter packing for the spent nuclear fuel rods <NUM>. The tubes are placed in sealed capsules to form the rods <NUM>, typically <NUM> (<NUM> feet) long, with a diameter large enough to store a substantial number of fuel pellets <NUM>, yet small enough to permit placement in the housing <NUM>.

In some aspects, the housing <NUM> (and other components of the hazardous material container <NUM>) may be formed from metals or ceramics that, for example, have very high resistance to corrosion or radioactivity (e.g., zirconium or its alloy zircaloy, stainless steel, titanium, or other low corrosion materials). In addition, in some aspects, a storage area into which the container <NUM> is placed may be filled or partially filled with nitrogen, argon, or some other gas that reduces danger of corrosion to the housing <NUM> and other components of the container <NUM>.

Further, the dimensions of the housing <NUM> (and hazardous material container <NUM>, generally) may be designed to fit in a wellbore, such as the wellbore <NUM>. Example dimensions of the housing <NUM> may include a length, L, of between <NUM> and <NUM> (<NUM> and <NUM> feet), and, in the case of a substantially square housing <NUM>, side width, W, of between <NUM> and <NUM> (<NUM> and <NUM> inches). The housing <NUM>, in alternative aspects, may have a substantially circular horizontal cross-section diameter of between about <NUM> and <NUM> (<NUM> and <NUM> in. In some examples, the hazardous material container <NUM> (and container <NUM>) may be sized (e.g., length and width/diameter) for efficient deposit and retrieval into and from the wellbore <NUM>. For example, the length, L, may be determined based on, e.g., the radius dimension of the radiussed portion <NUM>, to ensure that the hazardous material container <NUM> may be moved through the radiussed portion <NUM> and into the substantially horizontal portion <NUM>. As another example, the width, W, may be determined based on a diameter of one or more of the casings in the wellbore <NUM>, such as the surface casing <NUM> and the production casing <NUM>.

The illustrated hazardous material container <NUM> also includes a connector portion <NUM>, which is shown on one end of the housing <NUM> but may be formed on both ends as well. In some aspects, the connector portion <NUM> may facilitate coupling of the hazardous material container <NUM> to a downhole tool (e.g., downhole tool <NUM>) to permit deposit and retrieval of the hazardous material container <NUM> from storage in a wellbore. Further, the connector portion <NUM> may facilitate coupling of one hazardous material container <NUM> to another hazardous material container <NUM>. The connector portion <NUM>, in some aspects, may be a threaded connection. For example, a connector portion <NUM> on one end of the housing <NUM> may be a male threaded connection while a connector portion <NUM> on the opposite end of the housing <NUM> may be a female threaded connection. In alternative aspects, the connector portion <NUM> may be an interlocking latch, such that rotation (e.g., <NUM> degrees or less) may latch (or unlatch) the housing <NUM> to a downhole tool or other hazardous material container <NUM>. In alternative aspects, the connector portion <NUM> may include one or more magnets (e.g., rare Earth magnets, electromagnets, a combination thereof, or otherwise) which attractingly couple to, e.g., a downhole tool or another hazardous material container <NUM>.

Referring generally to <FIG>, <FIG>, <FIG>, the example hazardous material storage bank system (e.g., <NUM>, <NUM>, and otherwise) may provide for multiple layers of containment to ensure that a hazardous material (e.g., biological, chemical, nuclear) is sealingly stored in an appropriate subterranean layer. In some example implementations, there may be at least twelve layers of containment. In alternative implementations, a fewer or a greater number of containment layers may be employed.

First, using spent nuclear fuel as an example hazardous material, the fuel pellets are taken from the reactor and not modified. They may be made from sintered uranium dioxide (UO<NUM>), a ceramic, and may remain solid and emit very little gas other than short-lived tritium. Unless the pellets are exposed to extremely corrosive conditions or other effects that damage the multiple layers of containment, most of the radioisotopes (including the tritium) will be contained in the pellets.

Second, the fuel pellets are surrounded by the zircaloy tubes of the fuel rods, just as in the reactor. As described, the tubes could be mounted in the original fuel assemblies, or removed from those assemblies for tighter packing.

Third, the tubes are placed in the sealed housings of the hazardous material container. The housing may be a unified structure or multi-panel structure, with the multiple panels (e.g., sides, top, bottom) mechanically fastened (e.g., screws, rivets, welds, and otherwise).

Fourth, a material (e.g., solid or fluid) may fill the hazardous material container to provide a further buffer between the material and the exterior of the container.

Fifth, the hazardous material container(s) are positioned (as described above), in a wellbore that is lined with a steel or other sealing casing that extends, in some examples, throughout the entire wellbore (e.g., a substantially vertical portion, a radiussed portion, and a substantially horizontal portion). The casing is cemented in place, providing a relatively smooth surface (e.g., as compared to the wellbore wall) for the hazardous material container to be moved through, thereby reducing the possibility of a leak or break during deposit or retrieval.

Sixth, the cement that holds or helps hold the casing in place, may also provide a sealing layer to contain the hazardous material should it escape the container.

Seventh, the hazardous material container is stored in a portion of the wellbore (e.g., the substantially horizontal portion) that is positioned within a thick (e.g., <NUM>-<NUM> (<NUM>-<NUM> feet) seam of a rock formation that comprises a storage layer. The storage layer may be chosen due at least in part to the geologic properties of the rock formation (e.g., no mobile water, low permeability, thick, appropriate ductility or non-brittleness). For example, in the case of shale as the rock formation of the storage layer, this type of rock may offers a level of containment since it is known that shale has been a seal for hydrocarbon gas for millions of years. The shale may contain brine, but that brine is demonstrably immobile, and not in communication with surface fresh water.

Eighth, in some aspects, the rock formation of the storage layer may have other unique geological properties that offer another level of containment. For example, shale rock often contains reactive components, such as iron sulfide, that reduce the likelihood that hazardous materials (e.g., spent nuclear fuel and its radioactive output) can migrate through the storage layer without reacting in ways that reduce the diffusion rate of such output even further. Further, the storage layer may include components, such as clay and organic matter, that typically have extremely low diffusivity. For example, shale may be stratified and composed of thinly alternating layers of clays and other minerals. Such a stratification of a rock formation in the storage layer, such as shale, may offer this additional layer of containment.

Ninth, the storage layer may be located deeper than, and under, an impermeable layer, which separates the storage layer (e.g., vertically) from a mobile water layer.

Tenth, the storage layer may be selected based on a depth (e.g., <NUM> to <NUM>,<NUM> ft. ) of such a layer within the subterranean layers. Such depths are typically far below any layers that contain mobile water, and thus, the sheer depth of the storage layer provides an additional layer of containment.

Eleventh, example implementations of the hazardous material storage bank system of the present disclosure facilitate monitoring of the stored hazardous material. For example, if monitored data indicates a leak or otherwise of the hazardous material (e.g., change in temperature, radioactivity, or otherwise), or even tampering or intrusion of the container, the hazardous material container may be retrieved for repair or inspection.

Twelfth, the one or more hazardous material containers may be retrievable for periodic inspection, conditioning, or repair, as necessary (e.g., with or without monitoring). Thus, any problem with the containers may be addressed without allowing hazardous material to leak or escape from the containers unabated.

<FIG> is a schematic illustration of another example implementation of a hazardous material storage bank system according to the present disclosure. <FIG> illustrates an example implementation of a hazardous material storage bank system <NUM>, which includes hazardous material storage bank system <NUM> includes a wellbore <NUM> formed (e.g., drilled or otherwise) from a terranean surface <NUM> and through multiple subterranean layers <NUM>, <NUM>, <NUM>, and <NUM>. The illustrated wellbore <NUM> is a directional wellbore in this example of hazardous material storage bank system <NUM>. For instance, the wellbore <NUM> includes a substantially vertical portion <NUM> coupled to a radiussed or curved portion <NUM>, which in turn is coupled to a substantially horizontal portion <NUM>.

Generally, such components of the hazardous material storage bank system <NUM> are substantially the same as similarly-named components of hazardous material storage bank system <NUM>. For example, the illustrated wellbore <NUM> has a surface casing <NUM> positioned and set around the wellbore <NUM> from the terranean surface <NUM> into a particular depth in the Earth. For example, the surface casing <NUM> may be a relatively large-diameter tubular member (or string of members) set (e.g., cemented) around the wellbore <NUM> in a shallow formation. For example, in this implementation of the hazardous material storage bank system <NUM>, the surface casing <NUM> extends from the terranean surface through a surface layer <NUM>. The surface layer <NUM>, in this example, is a geologic layer comprised of one or more layered rock formations. In some aspects, the surface layer <NUM> in this example may or may not include freshwater aquifers, salt water or brine sources, or other sources of mobile water (e.g., water that moves through a geologic formation). In some aspects, the surface casing <NUM> may isolate the wellbore <NUM> from such mobile water, and may also provide a hanging location for other casing strings to be installed in the wellbore <NUM>. Further, although not shown, a conductor casing may be set above the surface casing <NUM> (e.g., between the surface casing <NUM> and the surface <NUM> and within the surface layer <NUM>) to prevent drilling fluids from escaping into the surface layer <NUM>.

As illustrated, a production casing <NUM> is positioned and set around the wellbore <NUM> downhole of the surface casing <NUM>. Although termed a "production" casing, in this example, the casing <NUM> may or may not have been subject to hydrocarbon production operations. Thus, the casing <NUM> refers to and includes any form of tubular member that is set (e.g., cemented) in the wellbore <NUM> downhole of the surface casing <NUM>. In some examples of the hazardous material storage bank system <NUM>, the production casing <NUM> may begin at an end of the radiussed portion <NUM> and extend throughout the substantially horizontal portion <NUM>.

As shown, cement <NUM> is positioned (e.g., pumped) around the casings <NUM> and <NUM> in an annulus between the casings <NUM> and <NUM> and the wellbore <NUM>. The cement <NUM>, for example, may secure the casings <NUM> and <NUM> (and any other casings or liners of the wellbore <NUM>) through the subterranean layers under the terranean surface <NUM>.

As illustrated, the wellbore <NUM> extends through subterranean layers <NUM>, <NUM>, and <NUM>, and lands in storage layer <NUM>. As discussed above, the surface layer <NUM> may or may not include mobile water. Subterranean layer <NUM>, which is below the surface layer <NUM>, in this example, is a mobile water layer <NUM>. Below the mobile water layer <NUM>, in this example implementation of hazardous material storage bank system <NUM>, is an impermeable layer <NUM>. The impermeable layer <NUM>, in this example, may not allow mobile water therethrough. Thus, relative to the mobile water layer <NUM>, the impermeable layer <NUM> may have low permeability, e.g., on the order of nanodarcy permeability. Additionally, in this example, the impermeable layer <NUM> may be a relatively non-ductile (i.e., brittle) geologic formation. Below the impermeable layer <NUM> is a storage layer <NUM>. The storage layer <NUM>, in this example, may be chosen as the landing for the substantially horizontal portion <NUM>, which stores the hazardous material, for several reasons. Relative to the impermeable layer <NUM> or other layers, the storage layer <NUM> may be thick, e.g., between about <NUM> and <NUM> (<NUM> and <NUM> feet) of TVD. Thickness of the storage layer <NUM> may allow for easier landing and directional drilling, thereby allowing the substantially horizontal portion <NUM> to stay within the storage layer <NUM> during formation (e.g., drilling). If formed through an approximate horizontal center of the storage layer <NUM>, the substantially horizontal portion <NUM> may be surrounded by about <NUM> and <NUM> (<NUM> and <NUM> feet) of the geologic formation that comprises the storage layer <NUM>. Further, the storage layer <NUM> may also have no mobile water, e.g., due to a very low permeability of the layer <NUM> (e.g., on the order of milli- or nanodarcys). In addition, the storage layer <NUM> may have sufficient ductility, such that a brittleness of the rock formation that comprises the layer <NUM> is between about <NUM> MPa and <NUM> MPa. Examples of rock formations of which the storage layer <NUM> may be composed include: shale and anhydrite.

In some examples implementations of the hazardous material storage bank system <NUM>, the storage layer <NUM> is composed of shale. Shale, in some examples, may have properties that fit within those described above for the storage layer <NUM>. For example, shale formations may be suitable for a long-term confinement of hazardous material and for their isolation from mobile water layer <NUM> (e.g., aquifers) and the terranean surface <NUM>. Shale formations may be found relatively deep in the Earth, typically <NUM> (<NUM> feet) or greater, and placed in isolation below any fresh water aquifers.

Hazardous material storage bank system <NUM> also includes a work string <NUM> (e.g., tubing, coiled tubing, wireline, or otherwise) that is extendable through the wellbore <NUM> to deposit (e.g., pump) a hazardous slurry <NUM> into a portion of the wellbore <NUM> (e.g., the substantially horizontal portion <NUM>). The hazardous material slurry <NUM> comprises a mixture of a hardenable material <NUM> and hazardous material <NUM>. For example, the hardenable material <NUM> may be cement, a cementitious material, resin, concrete, adhesive, grout, or other hardenable (e.g., over a known time duration). The hazardous material <NUM> may be, for example, biological material, chemical material, or nuclear material such as spent nuclear fuel pellets.

In operation, the work string <NUM> may deposit (e.g., through pumping) the hazardous material slurry <NUM> in the substantially horizontal portion <NUM> of the wellbore <NUM>. Over time, the hardenable material <NUM> in the slurry <NUM> may harden, thereby substantially trapping and sealing the hazardous material <NUM> within the hardened slurry and in the wellbore <NUM>. The hazardous material <NUM> may thus be sealed in the hardened material <NUM>, within the wellbore <NUM>, and within the storage layer <NUM>, providing multiple layers of containment of any output from the hazardous material <NUM>. The hardening time can be set to be short, or it could be set to a longer period (years or decades) to facilitate early retrieval, if it is determined that easier retrieval during the first few years would be advantageous.

Although not shown, once the deposit operation is completed, a seal (e.g., seal <NUM>) may be placed in the wellbore <NUM> uphole of the hardened slurry. Further, once sealed, a monitoring system (e.g., as shown and described with reference to one or more of <FIG>) may be installed in system <NUM> to monitor one or more variables associated with the hazardous material <NUM> (e.g., temperature, radioactivity, water vapor, oxygen, seismic activity, tampering or otherwise).

<FIG> are flowcharts that illustrate example methods <NUM>, <NUM>, and <NUM>, respectively, associated with storing hazardous material. Turning to method <NUM>, this example method for storing hazardous material may be performed with or by, e.g., hazardous material storage bank system <NUM> as described with reference to <FIG> and <FIG>. Alternatively, method <NUM> may be performed by another hazardous material storage bank system in accordance with the present disclosure.

Method <NUM> may begin at step <NUM>, which includes moving a storage container through an entry of a wellbore that extends into a terranean surface. The storage container encloses a hazardous material, such as chemical, biological, or nuclear waste, or another hazardous material. In some aspects, the storage container may be positioned in the entry directly from a mode of transportation (e.g., truck, train, rail, or otherwise) which brought the hazardous material to the site of the wellbore. In some aspects, a packaging of the hazardous material during transport is not removed for movement of the storage container into the entry. In some aspects, such transport packaging is only removed as the storage container fully enters the wellbore.

Method <NUM> may continue at step <NUM>, which includes moving the storage container through the wellbore that includes a substantially vertical portion, a transition portion, and a substantially horizontal portion. In some aspects, the wellbore is a directional, or slant wellbore. The storage container may be moved through the wellbore in a variety of manners. For example, a tool string (e.g., tubular work string) or wireline may include a downhole tool that couples to the storage container and moves (e.g., pushes) the storage container from the entry to the horizontal portion of the wellbore. As another example, the storage container may ride on rails installed in the wellbore, e.g., a cased wellbore. As yet another example, the storage container may be moved through the wellbore with a wellbore tractor (e.g., motored or powered tractor). In another example, the tractor could be built as part of the storage container. As yet a further example, the storage container may be moved through the wellbore with a fluid (e.g., gas or liquid) circulated through the wellbore.

Method <NUM> may continue at step <NUM>, which includes moving the storage container into a storage area located within or below a shale formation. For example, the horizontal portion of the wellbore may include or be coupled to the storage area and may be formed through a shale seam within a subterranean zone. In some aspects, the shale may include one or more geologic qualities that provide for a fluidic seal (e.g., gas and liquid) against the escape of any hazardous material beyond the shale formation (e.g., vertically or horizontally). In alternative aspects, the storage area may be formed in the horizontal portion of the wellbore in a rock formation that is not shale, but shares particular geologic characteristics with shale (e.g., anhydrite, and other formations). For example, the rock formation of the storage area may be relatively impermeable, with permeability values less than <NUM> millidarcys (and even down to nanodarcys). As another example, the rock formation may be ductile, having a brittleness of less than about 10MPa so as to prevent or help prevent fracturing that can allow hazardous material leaks therethrough. Brittleness, as used herein in example implementations, is the ratio of compressive stress of the rock formation to tensile strength of the rock formation. As another example, the rock formation may be relatively thick, with thickness proximate the storage area of between about <NUM> and <NUM> (<NUM> and <NUM> feet) (although less thick and more thick formations are also contemplated by the present disclosure). As another example, the rock formation may be composed of clay or other organic material, e.g., of about <NUM>-<NUM>% weight by volume, to help ductility.

Method <NUM> may continue at step <NUM>, which includes forming a seal in the wellbore that isolates the storage portion of the wellbore from the entry of the wellbore. For example, once the storage container is moved into the storage area (or after all storage containers are moved into the storage area), a seal may be formed in the wellbore. The seal may be a cement plug, an inflatable seal (e.g., packer), or other seal or combination of such seals. In some aspects, the seal is removable so as to facilitate a subsequent retrieval operation of the storage container.

Method <NUM> may continue at step <NUM>, which includes monitoring at least one variable associated with the storage container from a sensor positioned proximate the storage area. The variable may include one or more of temperature, radioactivity, seismic activity, oxygen, water vapor, acidity, or other variable that indicates a presence of the hazardous material (e.g., within the wellbore, outside of the storage container, in the rock formation, or otherwise). In some aspects, one or more sensors may be positioned in the wellbore, on or attached to the storage container, within a casing installed in the wellbore, or in the rock formation proximate the wellbore. The sensors, in some aspects, may also be installed in a separate wellbore (e.g., another horizontal or vertical wellbore) apart from the storage area.

Method <NUM> may continue at step <NUM>, which includes recording the monitored variable at the terranean surface. For example, variable data received at the one or more sensors may be transmitted (e.g., on a conductor or wirelessly) to a monitoring system (e.g., control system <NUM>) at the terranean surface. The monitoring system may perform a variety of operations. For example, the monitoring system may record a history of one or more of the monitored variables. The monitoring system may provide trend analysis in the recorded variable data. As another example, the monitoring system may include one or more threshold limits for each of the monitored variables, and provide an indication when such threshold limits are exceeded.

Method <NUM> may continue at step <NUM>, which includes determining whether the monitored variable exceeds a threshold value. For example, the one or more sensors may monitor radioactivity in the wellbore, e.g., an amount of radiation released by the hazardous material, whether in alpha or beta particles, gamma rays, x-rays, or neutrons. The sensors, for instance, may determine an amount of radioactivity, in units of measure of curie (Ci) and/or becquerel (Bq), rads, grays (Gy), or other units of radiation. If the amount of radioactivity does not exceed a threshold value that, for example, would indicate a large leak of hazardous nuclear material from the storage container, then the method <NUM> may return to step <NUM>.

If the determination is "yes," method <NUM> may continue at step <NUM>, which includes removing the seal from the wellbore. For example, in some aspects, once a threshold value (or values) is exceeded, a retrieval operation may be initiated by removing the seal. In alternative aspects, exceeding of a threshold value may not automatically trigger a retrieval operation or removal of the wellbore seal. In some aspects, there may be multiple monitored variables, and a "yes" determination is only made if all monitored variables exceed their respective threshold values. Alternatively, a "yes" determination may be made if at least one monitored variable exceeds its respective threshold value.

Method <NUM> may continue at step <NUM>, which includes retrieving the storage container from the storage area to the terranean surface. For example, once the seal is removed (e.g., drilled through or removed to the terranean surface), the work string may be tripped into the wellbore to remove the storage container (or containers) for inspection, repair, or otherwise. In some aspects, rather than removing the seal from the wellbore to retrieve the storage container, other remedial measures may be taken. For example, if the determination is "yes" in step <NUM>, rather than recovering the hazardous material, a decision might be made to improve the seal. This could be done, for example, by injecting a cement or other sealant into the borehole to fill the space previously filled with gas.

Turning to method <NUM>, this example method for storing hazardous material may be performed prior to, for example, method <NUM>. For example, in some aspects, the wellbore into which the storage container is moved in method <NUM> is formed primarily for the storage of hazardous material. Alternatively, the wellbore may have been formed prior to execution of method <NUM> and, in some aspects, years or decades prior to execution of method <NUM>. For instance, the wellbore may have been initially formed with a primary purpose of hydrocarbon production.

Method <NUM> may begin at step <NUM>, which includes forming (e.g., drilling) the wellbore from the terranean surface to the rock formation. In some aspects, the rock formation is shale or other rock formation that includes geologic characteristics suitable for hazardous material storage.

Method <NUM> may continue at step <NUM>, which includes installing a casing in the wellbore that extends from at or proximate the terranean surface, through at least a portion of the wellbore. In some aspects, the casing may be installed an entire length of the wellbore (e.g., through a vertical portion, a transition portion, and a horizontal or slant portion of the wellbore.

Method <NUM> may continue at step <NUM>, which includes cementing the casing to the wellbore. In some aspects, the cement may be installed throughout an entire length of the wellbore. Alternatively, only a portion of the casing may be cemented in the wellbore.

Method <NUM> may continue at step <NUM>, which includes producing hydrocarbon fluid from the rock formation, through the wellbore, and to the terranean surface. In some aspects, the wellbore and casing may first be completed, e.g., perforated and hydraulically fractured, prior to production of hydrocarbon fluids. In some aspects, prior to or subsequent to completing the wellbore, it may be determined that there is insufficient hydrocarbons in the rock formation for economical production.

Method <NUM> may continue at step <NUM>, which includes shutting in the wellbore. In some aspects, shutting in the wellbore may include cementing the wellbore though at least a portion of its entire length. Thus, in such aspects, prior to step <NUM> of method <NUM>, the wellbore may be re-formed (e.g., drilled out) to remove the cementing or other seal. In some aspects, step <NUM> may not be performed, as step <NUM> from method <NUM> may be initiated directly after production of hydrocarbons in step <NUM> is completed.

Turning to method <NUM>, this example method for storing hazardous material may be performed with or by, e.g., hazardous material storage bank system <NUM> as described with reference to <FIG>. Alternatively, method <NUM> may be performed by another hazardous material storage bank system in accordance with the present disclosure.

Method <NUM> may begin at step <NUM>, which includes forming a vertical portion of a wellbore from a terranean surface into a subterranean zone. Method <NUM> may continue at step <NUM>, which includes forming a transitional portion of the wellbore, from the vertical portion, through the subterranean zone. Method <NUM> may continue at step <NUM>, which includes forming a horizontal portion of the wellbore, from the transitional portion, into or beneath a rock formation. The rock formation may be comprised of shale or other rock formation with appropriate geologic characteristics (e.g., permeability, ductility, thickness and/or claim or organic material composition) that evidence a fluid seal between the rock formation and a subterranean layer that includes mobile water. In some alternative aspects, however, the formed wellbore may be a substantially vertical wellbore, with no transition or horizontal portion.

Method <NUM> may continue at step <NUM>, which includes pumping a hardenable slurry that includes a mixture of a hardenable material and a spent nuclear fuel material into the horizontal portion of the wellbore (or vertical portion if no horizontal portion). The hardenable material may include, for example, a cementitious material, a hardenable resin or epoxy, concrete, grout, or other flowable material that hardens into a solid over a defined period of time. The spent nuclear fuel, e.g., nuclear fuel pellets, may be mixed into the hardenable material such that when the hardenable material hardens, the spent nuclear fuel pellets are rigidly contained in the hardened slurry.

<FIG> is a schematic illustration of an example controller <NUM> (or control system) for an on-board fuel separation system. For example, the controller <NUM> can be used for the operations described previously, for example as or as part of the monitoring control system <NUM>. For example, the controller <NUM> may be communicably coupled with, or as a part of, a hazardous material storage bank system as described herein.

The controller <NUM> is intended to include various forms of digital computers, such as printed circuit boards (PCB), processors, digital circuitry, or otherwise that is part of a vehicle. Additionally the system can include portable storage media, such as, Universal Serial Bus (USB) flash drives. For example, the USB flash drives may store operating systems and other applications. The USB flash drives can include input/output components, such as a wireless transmitter or USB connector that may be inserted into a USB port of another computing device.

The controller <NUM> includes a processor <NUM>, a memory <NUM>, a storage device <NUM>, and an input/output device <NUM>. Each of the components <NUM>, <NUM>, <NUM>, and <NUM> are interconnected using a system bus <NUM>. The processor <NUM> is capable of processing instructions for execution within the controller <NUM>. The processor may be designed using any of a number of architectures. For example, the processor <NUM> may be a CISC (Complex Instruction Set Computers) processor, a RISC (Reduced Instruction Set Computer) processor, or a MISC (Minimal Instruction Set Computer) processor.

In one implementation, the processor <NUM> is a single-threaded processor. In another implementation, the processor <NUM> is a multi-threaded processor. The processor <NUM> is capable of processing instructions stored in the memory <NUM> or on the storage device <NUM> to display graphical information for a user interface on the input/output device <NUM>.

The memory <NUM> stores information within the controller <NUM>.

The storage device <NUM> is capable of providing mass storage for the controller <NUM>. In various different implementations, the storage device <NUM> may be a floppy disk device, a hard disk device, an optical disk device, a tape device, flash memory, a solid state device (SSD), or a combination thereof.

The input/output device <NUM> provides input/output operations for the controller <NUM>.

The features described can be implemented in digital electronic circuitry, or in computer hardware, firmware, software, or in combinations of them. The apparatus can be implemented in a computer program product tangibly embodied in an information carrier, for example, in a machine-readable storage device for execution by a programmable processor; and method steps can be performed by a programmable processor executing a program of instructions to perform functions of the described implementations by operating on input data and generating output. The described features can be implemented advantageously in one or more computer programs that are executable on a programmable system including at least one programmable processor coupled to receive data and instructions from, and to transmit data and instructions to, a data storage system, at least one input device, and at least one output device. A computer program is a set of instructions that can be used, directly or indirectly, in a computer to perform a certain activity or bring about a certain result.

Storage devices suitable for tangibly embodying computer program instructions and data include all forms of non-volatile memory, including by way of example semiconductor memory devices, such as EPROM, EEPROM, solid state drives (SSDs), and flash memory devices; magnetic disks such as internal hard disks and removable disks; magneto-optical disks; and CD-ROM and DVD-ROM disks.

To provide for interaction with a user, the features can be implemented on a computer having a display device such as a CRT (cathode ray tube) or LCD (liquid crystal display) or LED (light-emitting diode) monitor for displaying information to the user and a keyboard and a pointing device such as a mouse or a trackball by which the user can provide input to the computer. Additionally, such activities can be implemented via touchscreen flat-panel displays and other appropriate mechanisms.

The features can be implemented in a control system that includes a back-end component, such as a data server, or that includes a middleware component, such as an application server or an Internet server, or that includes a front-end component, such as a client computer having a graphical user interface or an Internet browser, or any combination of them. Examples of communication networks include a local area network ("LAN"), a wide area network ("WAN"), peer-to-peer networks (having ad-hoc or static members), grid computing infrastructures, and the Internet.

While this specification contains many specific implementation details, these should not be construed as limitations on the scope of any inventions or of what may be claimed, but rather as descriptions of features specific to particular implementations of particular inventions.

A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made without departing from the scope of the disclosure as set out in the claims. For example, example operations, methods, or processes described herein may include more steps or fewer steps than those described. Further, the steps in such example operations, methods, or processes may be performed in different successions than that described or illustrated in the figures. Accordingly, other implementations are within the scope of the following claims.

Claim 1:
A hazardous material storage bank system (<NUM>) comprising:
a first wellbore (<NUM>) extending into the Earth and comprising an entry at least proximate a terranean surface (<NUM>), the first wellbore comprising a vertical portion (<NUM>), a transition portion (<NUM>), and a horizontal portion (<NUM>);
a storage area coupled to the horizontal portion of the first wellbore, the storage area within or below a rock formation (<NUM>), the storage area vertically isolated, by the rock formation, from a subterranean zone that comprises mobile water (<NUM>);
a storage container (<NUM>) positioned in the storage area, the storage container sized to fit from the first wellbore entry through the vertical portion, the transition portion, and the horizontal portion of the first wellbore, and into the storage area, the storage container comprising an inner cavity sized to enclose nuclear waste;
a seal (<NUM>) positioned in the first wellbore, the seal isolating the storage portion of the first wellbore from the entry of the first wellbore;
a monitoring system comprising:
a plurality of sensors (<NUM>) positioned proximate the storage container in the subterranean formation, at least one sensor of the plurality of sensors comprising a radioactivity sensor, wherein the plurality of sensors are positioned within a second wellbore (<NUM>, <NUM>, <NUM>) that is formed separately from the first wellbore (<NUM>), and
a monitoring control system (<NUM>) communicably coupled to the plurality of sensors to receive radioactivity data from the at least one sensor.