Ferrate(VI)-based hydraulic fracturing fluid for carbon dioxide sequestration and methods related thereto

Compositions, methods, and systems for treating a subterranean formation for carbon dioxide sequestration include introducing a ferrate(VI)-based hydraulic fracturing fluid into a subterranean formation. The ferrate(VI)-based hydraulic fracturing fluid comprises ferrate(VI) oxidizing agent having the formula M2FeO4, where M is an alkali metal or an alkaline earth metal, and an aqueous carrier fluid. Reacting the ferrate(VI) oxidizing agent with a surface of the subterranean formation increases a pore volume of pores therein and interacting the ferrate(VI) oxidizing agent with carbon dioxide (CO2) sequesters the CO2 with the ferrate(VI) oxidizing agent within the pores.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to oilfield production and, more particularly, to compositions, systems, and methods for carbon dioxide sequestration in a subterranean formation.

BACKGROUND OF THE DISCLOSURE

Carbon dioxide (CO2) sequestration (e.g., of free CO2) has recently been the subject of intense research and development activities in a number of fields, primarily due to its environmental impacts as a greenhouse gas. In this regard, significant pressure has been placed on various industries to decrease their CO2emissions in order to address the effects of global warming and ocean acidification. Indeed, the United Nations Climate Change Conference and the Paris Agreement have adopted efficient CO2reduction strategies to encompass CO2capture, utilization, and sequestration in a closed loop, with geological CO2sequestration being a critical initiative for permanent CO2storage.

Geological CO2sequestration effectiveness is dependent and limited by the particular type of geological formation, its depth horizon and reservoir extension, and its likelihood of CO2plume migration and leakage, among other geological and engineering long-term operational issues. Accumulated CO2volume within geological formations over time may suffer from plume migration and/or loss of cap rock seal capacity resulting in CO2leakage. Such migration and/or leakage may result in significant environmental, health, and societal effects. There is therefore a need for permanent sequestration with no liability of migration or leakage over many centuries.

A number of approaches have been implemented to capture CO2for transport and storage. For example, geological CO2storage in deep saline aquafers has also been identified as a viable means of CO2sequestration because they have substantial storage capacity (e.g., with up to 85% organic-rich formations), but leakage or plume migration of the CO2can enter water sources. CO2has also been used in depleted d hydrocarbon (fossil fuel) formation reservoirs during tertiary enhanced oil recovery (tEOR) operation, with the aim to permanently sequester at least a portion of the CO2therein, but have limited CO2storage capacity compared to saline aquafers. However, hydrocarbon formations may be more secure (e.g. from leakage and plume migration) compared to deep saline aquifers.

tEOR may involve “scrubbing” the walls of existing channels or fractures in a hydrocarbon geological formation with treatment fluids that, as of recently, may include one or more oxidizing agents. The inclusion of such oxidizing agents has demonstrated CO2sorption potential in addition to enhanced oil recovery. However, tEOR does not generally permanently alter the geology of the formation, such as by creating new or enhanced porosity in which CO2sorption may be enhanced.

SUMMARY OF THE DISCLOSURE

According to an embodiment consistent with the present disclosure, a method is provided including introducing a ferrate(VI)-based hydraulic fracturing fluid into a subterranean formation, reacting the ferrate(VI) oxidizing agent with a surface of the subterranean formation so as to increase a pore volume of pores therein, and interacting the ferrate(VI) oxidizing agent with carbon dioxide (CO2), so as to sequester the CO2with the ferrate(VI) oxidizing agent within the pores. The ferrate(VI)-based hydraulic fracturing fluid comprises ferrate(VI) oxidizing agent having the formula M2FeO4, where M is an alkali metal or an alkaline earth metal, and an aqueous carrier fluid.

In another embodiment consistent with the present disclosure, a ferrate(VI)-based hydraulic fracturing fluid is provided including a ferrate(VI) oxidizing agent having the formula M2FeO4, where M is an alkali metal or an alkaline earth metal, and an aqueous carrier fluid, the ferrate(VI)-based hydraulic fracturing fluid for use in reacting with a surface of a subterranean formation to increase a pore volume therein and interacting with carbon dioxide (CO2), so as to sequester the CO2within the pores.

In another embodiment consistent with the present disclosure, system is provided including a pump fluidly coupled to a tubular, the tubular extending into a subterranean formation and containing a ferrate(VI)-based hydraulic fracturing fluid, wherein the ferrate(VI)-based hydraulic fracturing fluid comprises ferrate(VI) oxidizing agent having the formula M2FeO4, where M is an alkali metal or an alkaline earth metal, and an aqueous carrier fluid, the ferrate(VI)-based hydraulic fracturing fluid for use in reacting with a surface of a subterranean formation to increase a pore volume therein and interacting with carbon dioxide (CO2), so as to sequester the CO2within the pores.

DETAILED DESCRIPTION

Embodiments in accordance with the present disclosure generally relate to oilfield production and, more particularly, to compositions, systems, and methods for CO2sequestration in an organic-rich subterranean formation using a hydraulic fracturing fluid comprising a ferrate(VI) oxidizing agent.

The current rate of CO2emission worldwide is almost 32 gigatons per year, and therefore a large portion of the emitted CO2must be stored and sequestered in available and proven geological formations for permanent sequestration with no liability of migration and/or leakage centuries. That is, CO2sequestration should result in permanent mineralization of the sequestered CO2. Physical locations for geological sequestration of the vast amount of emitted CO2are limited.

Hydrocarbons located in geological formations require twice as much oxygen as carbon to form CO2, increasing their mass and volume within the atmosphere considerably. As such, geological CO2sequestration may be most effective in an organic-rich source rock that can be treated and/or tailored to enhance or enlarge porosity (e.g., a permanent sink) and improve CO2sequestration capacity.

As provided in the present disclosure, it has been observed that ferrate(VI) can be used in hydraulic fracturing operations to create newly expanded porosity spaces and organic surfaces in organic-rich rock for enhanced CO2volume sequestration. Moreover, ferrate(VI) included in hydraulic fracturing operations can also provide enhanced oil and gas recovery.

Definitions

As used herein, the term “geological formation,” and grammatical variants thereof, refers to a subterranean (underground) geological formation.

As used herein, the terms “CO2sequestration” or “CO2storage,” and grammatical variants thereof, are used interchangeably and refer to the process of storing free CO2in a geological formation.

The term “proppant particulates” or simply “proppant” refers to solid particles used to prevent fractures from fully closing once hydraulic pressure is removed in a hydraulic fracturing operation. By keeping the fractures from fully closing, the proppant particulates form a proppant pack having interstitial spaces that act as conductive paths through which fluids produced from the formation may flow. As used herein, the term “proppant pack” refers to a collection of proppant particulates in a fracture, thereby forming a “propped fracture.”

As used herein, the term “porosity,” and grammatical variants thereof, refers to a percentage of pore volume or void space within a rock (e.g., subterranean formation) that can contain fluids. The term “fluids,” as used herein, refers to gases, liquids, and solids, particularly CO2fluids, as defined herein.

Ferrate(VI) is a strong oxidizing agent having a high oxidation/reduction (redox) potential that has been previously used for the removal of organic contaminants in wastewater treatment plants. However, the use of ferrate(VI) to increase the porosity of organic-rich geological formations, and during hydraulic fracturing operations, has not heretofore been explored to enhance organic surface sorption for improved CO2sequestration. Indeed, as described herein, the use of ferrate(VI) for enhancing CO2 sequestration capacity in organic-rich geological formations is improved compared to traditional oxidizing agents. Table 1 demonstrates the redox potential (E°, electronvolts (eV)) for various traditional oxidizing agents, as well as ferrate(VI).

As shown, ferrate(VI) oxidizing agent exhibits the highest redox potential compared to the family of oxidizers. Ozone exhibits a lesser, but similar, redox potential, but is damaging to the environment and human health. Differently, ferrate(VI) is a non-toxic, environmentally friendly oxidizing agent, giving no mutagenic/carcinogenic by-products. It should be that the oxidizing agents listed in Table 1 may be used in combination with ferrate(VI) oxidizing agent (e.g., bromate, hypochlorite, and the like), without departing from the scope of the present disclosure.

The ferrate(VI) oxidizing agent for use in the hydraulic fracturing fluids of the present disclosure has the following Formula: M2FeO4, where M is potassium (K) or sodium (Na), or other alkali metal or an alkaline earth metal. Accordingly, the term “ferrate(VI)” as used herein includes both potassium ferrate and sodium ferrate, unless otherwise specified.

The reaction product of ferrate(VI) in an aqueous base fluid, upon decomposition, yields oxygen, alkali hydroxide and ferric hydroxide/oxyhydroxide, as depicted in Reaction 1.

In addition to the generation of enhanced porosity in organic-rich formations for increased CO2sequestration volumetric space, the reaction between ferrate(VI) and organic-rich source rock generates Fe(III)(OH)3. Fe(III)(OH)3reacts positively in reducing the creation of acidic gases, such as H2S. H2S reacts to reduce Fe(III) to Fe(II), and the resultant Fe(II)(OH)2is available to react with CO2, leading to mineral carbonization into iron carbonate or siderate (FeCO3). The reaction is shown below as Reaction 2.

Accordingly, the use of ferrate(VI) oxidizing agent during a fracturing operation, as described herein, acts to synergistically enhance porosity in organic-rich source rock and produce a positive reaction byproduct for permanent CO2sequestration.

With reference toFIGS.1A-1D, illustrated is a schematic of a subterranean formation hydraulic fracturing system100treated with the ferrate(VI)-based hydraulic fracturing fluid of the present disclosure.FIGS.1A-ID are shown as a progression and, as provided above, like elements in the various figures may be denoted by like reference numerals for consistency. The circular portions of each ofFIGS.1A-ID are zoomed-in views of the properties and/or reactions taking place as part of the hydraulic fracturing system100, as described below.

Each ofFIGS.1A-ID depict a subterranean formation110. As shown inFIG.1A, the subterranean formation comprises organic-rich source rock112, shown in zoom in the circular portion ofFIG.1A. The organic-rich source rock112comprises long-chain hydrocarbons with or without entrapped short chain hydrocarbons and gases114. Referring now toFIG.1B, upon hydraulic fracturing of the formation110with ferrate(VI)-based hydraulic fracturing fluid, the organic-rick source rock112(FIG.1A) is oxidized into oxidized organic matter116by the ferrate(VI) oxidizing agent, shown in zoom in the circular portion ofFIG.1B. The oxidation of the organic matter116results in the creation of short-chained hydrocarbons (CnH4-n)118. With reference now toFIG.1C, at least a portion (e.g., a majority) of the short-chained hydrocarbons118(FIG.1B) may be recovered to the surface119. A portion of the short-chained hydrocarbons118may remain in the formation110(see zoomed portions ofFIGS.1C and1D). Simultaneous with hydraulic fracturing and cleaving of organic matter (FIG.1B), and as shown inFIG.1C, the ferrate(VI) oxidizing agent in the ferrate(VI)-based hydraulic fracturing fluid reacts with organic matter122(after oxidation) to enhance porosity (pore volume124) and spent oxidizing agent120forming byproducts, such as iron hydroxide/oxide, as described above. Referring now toFIG.1D, CO2is pumped into the formation110for storage between in the pore volume124. Upon reaction with CO2, the spent oxidizing agent120(iron hydroxide/oxide) is converted to iron carbonate (not labeled). It is to be noted that the size of organic matter122and spent oxidizing agent120will vary and are not necessarily uniform.

Accordingly, the present disclosure provides methods for introducing a ferrate(VI)-based hydraulic fracturing fluid into a subterranean formation comprising organic-rich source rock at a rate and pressure sufficient to create or enhance at least one fracture therein, reacting ferrate(VI) oxidizing agent with the organic-rich source rock to increase porosity of the organic-rich source rock, and introducing CO2to the organic-rich source rock to sequester the CO2therein. A reaction between spent ferrate(VI) and the CO2 may further result in mineral carbonation to iron carbonate. Hydrocarbons may be recovered as part of the hydraulic fracturing operation.

The ferrate(VI)-based hydraulic fracturing fluids of the present disclosure may be used to fracture and enhance porosity for CO2sequestration of organic-rich unconventional geological formations (e.g., shale, coal bed methane, tight gas) or organic-rich conventional geological formations (e.g., sandstone).

The ferrate(VI) oxidizing agent is aqueous soluble and, therefore, ferrate(VI)-based hydraulic fracturing fluids are comprised of an aqueous carrier fluid. The aqueous carrier fluid may include, but is not limited to, freshwater, acidified water, salt water, seawater, brine (e.g., a saturated salt solution), or an aqueous salt solution (e.g., a non-saturated salt solution), purified wastewater, and any combination thereof. In one or more instances, the aqueous carrier fluid is “slick water,” having a low viscosity of generally less than about 100 centipoise (cP), such as in the range of about 1 cP to about 100 cP, or from a lower limit of 1 cP, 10 cP, 20 cP, 30 cP, 40 cP, and 50 cP to an upper limit of 100 cP, 90 cP, 80 cP, 70 cP, 60 cP, and 50 cP, encompassing any value and subset therebetween.

The ferrate(VI) oxidizing agent may be present in the ferrate(VI)-based hydraulic fracturing fluid in an amount sufficient to react with organic matter in an organic-rich source rock, which may depend accordingly on the particular type of organic-rich source rock, among other factors. In one or more embodiments, the concentration of ferrate(VI) oxidizing agent in the ferrate(VI)-based hydraulic fracturing fluid is in the range of about 0.1 millimolar (mM) to about mM of aqueous carrier fluid, such as from a lower limit of 0.1 mM, 1 mM, 10 mM, 20 mM, 30 mM, 40 mM, and 50 mM to an upper limit of 100 mM, 90 mM, 80 mM, 70 mM, 60 mM, and 50 mM, encompassing any value and subset therebetween.

In one or more instances the concentration of ferrate(VI) oxidizing agent in the ferrate(VI)-based hydraulic fracturing fluid may be based on the amount of organic matter in the subterranean formation into which the fracturing fluid is being introduced. In some embodiments, the amount of ferrate(VI) oxidizing agent introduced into a subterranean formation may be in a ratio of 0.1 gram (g) ferrate(VI) oxidizing agent to 1000 g of organic matter, such as a lower limit of 0.1 g to 500 g, or 10 g to 100 g, or 50 g to 100 g, or 100 g to 100 g of ferrate(VI) oxidizing agent to organic matter, encompassing any value and subset therebetween.

In some embodiments, the ferrate(VI)-based hydraulic fracturing fluid may comprise proppant particulates for creating proppant packs in produced fractures during hydraulic fracturing operations with the ferrate(VI)-based hydraulic fracturing fluid. Suitable materials for these proppant particulates may include, but are not limited to, sand, bauxite, gravel, ceramic material, glass material, polymeric material (e.g., ethylene-vinyl acetate or composite materials), polytetrafluoroethylene material, nut shell pieces, a cured resinous particulate comprising nut shell pieces, seed shell pieces, a cured resinous particulate comprising seed shell pieces, fruit pit pieces, a cured resinous particulate comprising fruit pit pieces, wood, composite particulates, and any combination thereof. Suitable composite particulates may comprise a binder and a filler material, wherein suitable filler materials may include, but are not limited to, silica, alumina, fumed carbon, carbon black, graphite, mica, titanium dioxide, barite, meta-silicate, calcium silicate, kaolin, talc, zirconia, boron, fly ash, hollow glass microspheres, solid glass, and the like, and any combination thereof.

In one or more embodiments, when included, the proppant particulates may be present in the ferrate(VI)-based hydraulic fracturing fluid in an amount in the range of about 0.5 pounds per gallon (ppg) to about 30 ppg by volume of the carrier fluid, such as about from a lower limit of about 0.5 ppg, 1 ppg, 5 ppg, 10 ppg, and 15 ppg to an upper limit of about 30 ppg, 25 ppg, 20 ppg, and 15 ppg, encompassing any value and subset therebetween.

The ferrate(VI)-based hydraulic fracturing fluid described herein may further comprise one or more optional additives including, but not limited to, a salt, a weighting agent, an inert solid, a fluid loss control agent, an emulsifier, a dispersion aid, a corrosion inhibitor, an emulsion thinner, an emulsion thickener, a viscosifying agent, a gelling agent, a surfactant, a particulate, a proppant, a gravel particulate, a lost circulation material, a foaming agent, a gas, a pH control additive, a breaker, a biocide, a bactericide, a crosslinker, a stabilizer, a chelating agent, a scale inhibitor, a gas hydrate inhibitor, an non-ferrate(VI) oxidizer, a reducer, a friction reducer, a clay stabilizing agent, and any combination thereof. Selected additive(s) should not interfere with the function of the ferrate(VI) oxidizing agent to enhance porosity for CO2 sequestration.

Accordingly, the present disclosure provides a ferrate(VI)-based hydraulic fracturing fluid comprising a ferrate(VI) oxidizing agent (e.g., potassium ferrate, sodium ferrate, or a combination thereof). The ferrate(VI)-based hydraulic fracturing fluid may additionally comprise proppant and/or one or more additives. The present disclosure further comprises ferrate(VI)-based hydraulic fracturing fluid may be used to fracture a subterranean formation comprising organic-rich source rock, recover hydrocarbons therefrom, react the ferrate(VI) oxidizing agent included in the ferrate(VI)-based hydraulic fracturing fluid with organic matter in the organic-rich source rock to expand (or create) pores therein and, thus, the porosity of the organic-rich source rock.

In some embodiments, the ferrate(VI)-based hydraulic fracturing fluids disclosed herein (including mixing of the ferrate(VI) oxidizing agent and carrier fluid, optional proppant, and/or optional additives) can be mixed at a remote location from a well site and shipped to the well site or, in other embodiments, the ferrate(VI)-based hydraulic fracturing fluids can mixed at the well site. In some embodiments, the ferrate(VI)-based hydraulic fracturing fluids may be mixed and pumped on-the-fly. A person having ordinary skill in the art of designing such fluids with the benefit of this disclosure will be able to consider these factors and determine whether remote mixing or on-site mixing is most appropriate for a given operation.

In various embodiments, systems configured for delivering the ferrate(VI)-based hydraulic fracturing fluids described herein to a downhole location are described. In various embodiments, the systems can comprise a pump fluidly coupled to a tubular, the tubular containing the treatment fluids described herein.

The pump may be a high pressure pump in some embodiments. As used herein, the term “high pressure pump” will refer to a pump that is capable of delivering a ferrate(VI)-based hydraulic fracturing fluid downhole at a pressure of about 1000 psi or greater. A high pressure pump may be used when it is desired to introduce the ferrate(VI)-based hydraulic fracturing fluids to a subterranean formation at or above a fracture gradient of the subterranean formation, but it may also be used in cases where fracturing is not desired. In some embodiments, the high pressure pump may be capable of fluidly conveying solid particulate matter, such as the proppant particulates or solid additives described in some embodiments herein, into the subterranean formation. Suitable high pressure pumps will be known to one having ordinary skill in the art and may include, but are not limited to, floating piston pumps and positive displacement pumps.

In other embodiments, the pump may be a low pressure pump. As used herein, the term “low pressure pump” will refer to a pump that operates at a pressure of about 1000 psi or less. In some embodiments, a low pressure pump may be fluidly coupled to a high pressure pump that is fluidly coupled to the tubular. That is, in such embodiments, the low pressure pump may be configured to convey the ferrate(VI)-based hydraulic fracturing fluids to the high pressure pump. In such embodiments, the low pressure pump may “step up” the pressure of the ferrate(VI)-based hydraulic fracturing fluids before reaching the high pressure pump.

In some embodiments, the systems described herein can further comprise a mixing tank that is upstream of the pump and in which the ferrate(VI)-based hydraulic fracturing fluids are formulated. In various embodiments, the pump (e.g., a low pressure pump, a high pressure pump, or a combination thereof) may convey the treatment fluids from the mixing tank or other source of the treatment fluids to the tubular. In other embodiments, however, the ferrate(VI)-based hydraulic fracturing fluids may be formulated offsite and transported to a worksite, in which case the ferrate(VI)-based hydraulic fracturing fluid may be introduced to the tubular via the pump directly from its shipping container (e.g., a truck, a railcar, a barge, or the like) or from a transport pipeline. In either case, the ferrate(VI)-based hydraulic fracturing fluids may be drawn into the pump, elevated to an appropriate pressure, and then introduced into the tubular for delivery downhole.

In one or more aspects, the ferrate(VI)-based hydraulic fluids are delivered to a subterranean formation having a temperature in the range of about 5° C. to about 250° C., such as from a lower limit of about 0.5° C., 1° C., 25° C., 50° C., 75° C., 100° C., and 125° C. to an upper limit of about 250° C., 225° C., 200° C., 175° C., 150° C., and 125° C., encompassing any value and subset therebetween. The ferrate(VI)-based hydraulic fracturing fluids may further be delivered to a subterranean formation at a pressure in the range of about 1 bar to about 800 bar, such as from a lower limit of about 1 bar, 50 bar, 100 bar, 150 bar, 200 bar, 250 bar, 300 bar, 350 bar, and 400 bar to an upper limit of about 800 bar, 750 bar, 700 bar, 650 bar, 600 bar, 550 bar, 500 bar, 450 bar, and 400 bar, encompassing any value and subset therebetween.

Further, upon delivery of the ferrate(VI)-based hydraulic fluids, CO2injection into the subterranean formation may be performed. Alternatively, CO2injection may be performed simultaneously with the delivery of the ferrate(VI)-based hydraulic fluids. In yet another alternative, delivery of the ferrate(VI)-based hydraulic fluids may be performed in cycles with CO2injection.

FIG.2shows an illustrative schematic of a system that can deliver the ferrate(VI)-based hydraulic fracturing fluids of the present disclosure to a downhole location, according to one or more embodiments. It should be noted that whileFIG.2generally depicts a land-based system, it is to be recognized that like systems may be operated in subsea locations as well. As depicted inFIG.2, system200may include mixing tank210, in which the ferrate(VI)-based hydraulic fracturing fluids of the embodiments herein may be formulated. The ferrate(VI)-based hydraulic fracturing fluids may be conveyed via line212to wellhead214, where the ferrate(VI)-based hydraulic fracturing fluids enter tubular216, tubular216extending from wellhead214into subterranean formation218. Upon being ejected from tubular216, the ferrate(VI)-based hydraulic fracturing fluids may subsequently penetrate into subterranean formation218. Pump220may be configured to raise the pressure of the ferrate(VI)-based hydraulic fracturing fluids to a desired degree before introduction into tubular216. It is to be recognized that system200is merely exemplary in nature and various additional components may be present that have not necessarily been depicted inFIG.2in the interest of clarity. Non-limiting additional components that may be present include, but are not limited to, supply hoppers, valves, condensers, adapters, joints, gauges, sensors, compressors, pressure controllers, pressure sensors, flow rate controllers, flow rate sensors, temperature sensors, and the like.

Although not depicted inFIG.2, the ferrate(VI)-based hydraulic fracturing fluid or a portion thereof may, in some embodiments, flow back to wellhead214and exit subterranean formation218. In some embodiments, the ferrate(VI)-based hydraulic fracturing fluid that has flowed back to wellhead214may subsequently be recovered and recirculated to subterranean formation218, or otherwise treated for use in a subsequent subterranean operation or for use in another operation or industry.

While various embodiments have been shown and described herein, modifications may be made by one skilled in the art without departing from the scope of the present disclosure. The embodiments described here are exemplary only, and are not intended to be limiting. Many variations, combinations, and modifications of the embodiments disclosed herein are possible and are within the scope of the disclosure. Accordingly, the scope of protection is not limited by the description set out above, but is defined by the claims which follow, that scope including all equivalents of the subject matter of the claims.

EXAMPLE EMBODIMENTS

Embodiment A: A method comprising: introducing a ferrate(VI)-based hydraulic fracturing fluid into a subterranean formation, wherein the ferrate(VI)-based hydraulic fracturing fluid comprises ferrate(VI) oxidizing agent having the formula M2FeO4, where M is an alkali metal or an alkaline earth metal, and an aqueous carrier fluid; reacting the ferrate(VI) oxidizing agent with a surface of the subterranean formation so as to increase a pore volume of pores therein; and interacting the ferrate(VI) oxidizing agent with carbon dioxide (CO2), so as to sequester the CO2with the ferrate(VI) oxidizing agent within the pores.

Embodiment B: A ferrate(VI)-based hydraulic fracturing fluid comprising ferrate(VI) oxidizing agent having the formula M2FeO4, where M is an alkali metal or an alkaline earth metal, and an aqueous carrier fluid, the ferrate(VI)-based hydraulic fracturing fluid for use in reacting with a surface of a subterranean formation to increase a pore volume therein and interacting with carbon dioxide (CO2), so as to sequester the CO2within the pores.

Embodiment C: A system comprising: a pump fluidly coupled to a tubular, the tubular extending into a subterranean formation and containing a ferrate(VI)-based hydraulic fracturing fluid, wherein the ferrate(VI)-based hydraulic fracturing fluid comprises ferrate(VI) oxidizing agent having the formula M2FeO4, where M is an alkali metal or an alkaline earth metal, and an aqueous carrier fluid, the ferrate(VI)-based hydraulic fracturing fluid for use in reacting with a surface of a subterranean formation to increase a pore volume therein and interacting with carbon dioxide (CO2), so as to sequester the CO2within the pores.

Each of Embodiments A, B or C may have one or more of the following additional elements in any combination:

Element 1: wherein M is potassium or sodium.

Element 2: wherein the ferrate(VI) oxidizing agent is present in a concentration in the range of 0.1 mM to 100 mM of the aqueous carrier fluid.

Element 3: wherein the subterranean formation comprises an organic matter content in the range of 1% to 60% by weight.

Element 4: wherein the ferrate(VI) oxidizing agent is present in a concentration ratio of 1 gram of ferrate(VI) oxidizing agent to 100 grams of organic matter content.

Element 5: wherein the ferrate(VI)-based hydraulic fracturing fluid comprises an additional oxidizing agent selected from the group consisting of chlorine, hypochlorite, chlorine dioxide, perchlorate, ozone, hydrogen peroxide, dissolved oxygen, permanganate, bromate, and any combination thereof.

Element 6: wherein the ferrate(VI)-based hydraulic fracturing fluid further comprises an additive selected from the group consisting of a salt, a weighting agent, an inert solid, a fluid loss control agent, an emulsifier, a dispersion aid, a corrosion inhibitor, an emulsion thinner, an emulsion thickener, a viscosifying agent, a gelling agent, a surfactant, a particulate, a proppant, a gravel particulate, a lost circulation material, a foaming agent, a gas, a pH control additive, a breaker, a biocide, a bactericide, a crosslinker, a stabilizer, a chelating agent, a scale inhibitor, a gas hydrate inhibitor, an non-ferrate(VI) oxidizer, a reducer, a friction reducer, a clay stabilizing agent, and any combination thereof.

Element 7: wherein the aqueous carrier fluid is selected from the group consisting of freshwater, acidified water, salt water, seawater, brine, or an aqueous salt solution, purified wastewater, and any combination thereof.

Element 8: further comprising introducing the ferrate(VI)-based hydraulic fracturing fluid into the subterranean formation at a pressure to induce one or more fractures.

Element 9: further comprising introducing CO2into the subterranean formation simultaneously with the ferrate(VI)-based hydraulic fracturing fluid.

Element 10: further comprising alternating introduction of CO2into the subterranean formation with introducing the ferrate(VI)-based hydraulic fracturing fluid.

By way of non-limiting example, exemplary combinations applicable to Embodiment A include: any one, more than one, or all of Elements 1-8 and 9, without limitation; any one, more than one, or all of Elements 1-8 and 10, without limitation.

By way of non-limiting example, exemplary combinations applicable to Embodiment B include: any one, more than one, or all of Elements 1-7, without limitation.

By way of non-limiting example, exemplary combinations applicable to Embodiment C include: any one, more than one, or all of Elements 1-7, without limitation.

To facilitate a better understanding of the embodiments described herein, the following examples of various representative embodiments are given. In no way should the following examples be read to limit, or to define, the scope of the present disclosure.

EXAMPLES

In this Example, the reaction of ferrate(VI) oxidizing agent with organic-rich source rock (“OM-Rock”) (S1-S4) was evaluated against a control OM-Rock having no ferrate(VI) oxidizing reactant (C1) for CO2update. Four different concentrations of ferrate(VI) oxidizing agents were used to measure the concentration of CO2uptake capacity. The reaction conditions are provided in Table 2, in which OM-Rock (120 milligrams (mg)) was dispersed in 15 mL of four different concentrations (millimolar (mM)) of potassium ferrate (K2FeO4) solutions in a scintillation glass vial and heated at 90° C. for 2 hours. The solid product was separated through filtration or centrifuge and the obtained powder was dried to remove excess water from the samples.

Thermogravimetric analysis (TGA) was performed using an SDT 650 thermal analyzer (TA Instruments (New Castle, Delaware)) equipped with gas lines (N2and CO2). Samples C1 and S1-S4 in the amount of 50-60 mg (variation due to the testing equipment, with minimal or no influence on results) were loaded in a pan and activated at 120° C. for 20 minutes (min) under N2flow at 100 milliliters per min (mL/min). The temperature was thereafter reduced to 40° C. and dry CO2gas was flowed over the samples for 60 min at 100 mL/min. The amount of CO2that was sorbed by the samples was measured. The results are shown inFIG.3.

As shown inFIG.3, CO2uptake capacity of each of S1-S4 (reacted with ferrate(VI)) is greater than C1 (unreacted) at 40° C. Moreover, the CO2uptake capacity increased with increasing ferrate(VI) concentration (i.e., compared to C1, S1 showed an increase in uptake of CO2of 60%, S2 of 132%, S3 of 320%, and S4 of 390%). Notably, the oxidative reaction of OM-Rock and ferrate(VI) results in the generation of iron(III)hydroxide as a byproduct in addition to cleaving of organic matter, as described above.

In this Example, various surface qualities, as well as CO2adsorption, of the reaction of ferrate(VI) oxidizing agent with OM-Rock (S5) was evaluated against a control OM-Rock having no ferrate(VI) oxidizing reactant (C1, identical to Example 1) for CO2update. In this Example, sample S6 was prepared by dispersing OM-Rock (120 mg) in 15 mL of a 10.1 mM concentration of a K2Fe4solution in a scintillation glass vial, and heated at 90° C. for 2 hours. The solid product was separated through filtration or centrifuge and the obtained powder was dried to remove excess water from the samples.

Surface Area Measurement:

OM-Rock having no ferrate(VI) oxidizing reactant (C1, identical to Example 1) and OM-Rock reacted with ferrate(VI) (S5) were subjected to N2adsorption-desorption measurement at 77 K to determine the changes in the surface area and pore size distribution. N2isotherms were collected using Autosorb iQ (high vacuum physisorption/chemisorption analyzer, Anton Paar) which is capable of measuring changes in the specific surface area below 0.01 m2/g. Referring toFIGS.4A and4B, the N2adsorption-desorption isotherms reveal that S5 shows higher adsorption volume of N2after oxidation of OM-Rock. The Brunauer-Emmett-Teller (BET) surface area calculated from the N2isotherms for both samples is shown inFIGS.4A and4B. Samples C1 and S5 show surface areas of 11 m2/g and 28 m2/g, respectively, which is about a 250% increase upon reaction with ferrate(VI). The increase in the surface area demonstrates the effect of ferrate(VI) oxidation on enhancing the surface area of the organic matter; that is, the overall connected porosity increases in the source rocks. The hysteresis in both isotherms suggests that the pore width is in the mesoporous range. However, sample S5 shows higher N2adsorption at low pressure which confirms that the oxidation reaction is creating new multi, sub-microns size of connected porosity.

Pore Size Distribution

Referring now toFIGS.5A and5B, the oxidation of OM-Rock reacted with ferrate(VI) (sample S5) demonstrates enhanced pore size and distribution while increasing the surface area and the bulk source rock pore volume. The data collected from the N2isotherms at 77 K (FIGS.4A,4B) was used to calculate the various pore size distribution and the bulk pore volume for C1 and S5, as shown inFIGS.5A and5B. Quenched Solid Density Functional Theory (QSDFT) equilibrium model (slit pores) was employed to determine pore volume and pore size distribution. The pore volume for C1 and S5 was 0.011 cm3/g and 0.024 cm3/g, respectively, showing an almost double pore volume upon the oxidative reactions.

In this Example, the effect of ferrate(VI) on the CO2adsorption-desorption characteristics was evaluated through the isothermal gas sorption analysis at 273 K and 1 bar. CO2isotherms were collected using Autosorb iQ (high vacuum physisorption/chemisorption analyzer, Anton Paar). As shown inFIG.6, the CO2adsorption capacity of OM-Rock (C1) was found to be 1.06 mg/g. The improvement in the CO2adsorption capacity was observed after the OM-Rock was reacted with ferrate(VI) (S5), measuring 11.87 mg/g. Without being bound by theory, it is believed that a higher CO2capacity in CO2adsorption-desorption measurement compared to the CO2-TGA measurement (Example 1) is due to degassing of samples carried out under ultra-high vacuum.

The pore size distribution and pore volume of OM-Rock (C1) and OM-Rock reacted with ferrate(VI) (S5) were calculated from the CO2adsorption isotherms, as shown inFIGS.7A and7B. The pore volume (CO2) was 0.008 cm3/g and 0.021 cm3/g for OM-Rock (C1) and OM-Rock reacted with ferrate(VI) (S5), respectively. The surface area (CO2) was 23.2 m2/g and 61.5 m2/g for OM-Rock (C1) and OM-Rock reacted with ferrate(VI) (S5), respectively. As shown, the pore volume was increased by 262% and the surface area was improved by 265% upon reaction with ferrate(VI) (S5).

In this example, the heat of adsorption was measured of OM-Rock (C1) and OM-Rock reacted with ferrate(VI) (S5) at 273K, which provides information about the CO2binding affinity with the source rock matrix. The higher the heat of adsorption, the better the CO2binding on the substrate (rock formation). The CO2adsorption-desorption isotherms measured at three different temperatures of 265K, 273K, and 298K to calculate the heat of CO2adsorption. The results are shown inFIG.8. OM-Rock (C1) demonstrated a heat of adsorption in range of 24.4-22 kJ/mol, whereas OM-Rock reacted with ferrate(VI) (S5) demonstrated a much higher heat of adsorption in the range of 39.2-30.6 kJ/mol, showing the effect of ferrate(VI) on improving the CO2-philic sites in OM-Rock.