Patent Publication Number: US-11384280-B1

Title: Adsorption improved water in supercritical CO2 encapsulation for improved oil recovery

Description:
BACKGROUND 
     During primary oil recovery, oil inside an underground hydrocarbon reservoir is driven to the surface (for example, toward the surface of an oil well) by a pressure difference between the reservoir and the surface. However, only a fraction of the oil in an underground hydrocarbon reservoir can be extracted using primary oil recovery. Thus, a variety of techniques for enhanced oil recovery are utilized after primary oil recovery to increase the production of hydrocarbons from hydrocarbon-bearing formations. Some examples of these techniques include water flooding, chemical flooding, and supercritical CO 2  injections. 
     Supercritical CO 2  is an useful fluid for enhanced oil recovery applications due to its chemical and physical properties as well as providing the opportunity to introduce a greenhouse gas into a subterranean area. Supercritical CO 2  is miscible with hydrocarbons. Thus, when it contacts hydrocarbon fluid in a reservoir, the fluid is displaced from the rock surfaces and pushed toward the production well. Additionally, CO 2  may dissolve in the hydrocarbon fluid, reducing the viscosity of the hydrocarbon fluid and causing it to swell. This further enhances the ability to recover hydrocarbons and increase production. 
     SUMMARY 
     This summary is provided to introduce a selection of concepts that are further described in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter. 
     In one aspect, embodiments disclosed relate to an aqueous solution encapsulated by zeolite-templated carbon particles. 
     In another aspect, embodiments disclosed relate to a dispersion of capsules in critical or supercritical carbon dioxide, the capsules comprising an aqueous solution encapsulated by zeolite-templated carbon particles. 
     In yet another aspect, embodiments disclosed relate to a method of making a dispersion of aqueous solution capsules. The method includes providing a medium of critical or supercritical carbon dioxide, introducing the aqueous solution into the critical or supercritical carbon dioxide medium, and introducing a zeolite-templated carbon particle into the critical or supercritical carbon dioxide medium. 
     In another aspect, embodiments disclosed relate to a method of treating a hydrocarbon-bearing formation. The method includes introducing into a hydrocarbon-bearing formation a dispersion of aqueous solution capsules in a medium of critical or supercritical carbon dioxide. The aqueous solution capsules include an aqueous solution encapsulated by zeolite-templated carbon particles. 
     Other aspects and advantages of the claimed subject matter will be apparent from the following description and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  shows a simplified schematic of an embodiment capsule useful for treating hydrocarbon-bearing formations. 
         FIG. 2  shows a simplified schematic of an embodiment dispersion in use in a hydrocarbon-bearing formation. 
         FIG. 3  is a block flow diagram of an embodiment method of making a dispersion. 
         FIG. 4  is a simplified schematic of an embodiment hydrocarbon bearing formation. 
     
    
    
     DETAILED DESCRIPTION 
     Carbon dioxide (CO 2 ) is widely used in flooding processes for enhanced oil recovery. While it can be effective for oil recovery due to its affinity for hydrocarbons and its ability to be readily used in its supercritical state in hydrocarbon-bearing formations, it suffers from a number of challenges in its use. The density of CO 2  is less than many of the fluids present in subterranean formations, including water and the liquid and semi-solid hydrocarbons. Due to this reduced density, CO 2  has a tendency to seek upward-directed flow paths in the reservoir as it progresses away from the injection point and through the reservoir. This may lead to the introduced CO 2  preferentially bypassing portions of the reservoir and leaving portions of the reservoir untreated. This phenomenon is called “gravity override.” 
     The present disclosure relates to compositions and methods for increasing and maintaining the density of supercritical CO 2  by adding an aqueous solution encapsulated by zeolite-templated carbon (ZTC) particles to carbon dioxide in the critical or supercritical state (“SCCO2”). The SCCO2 dispersions described here provide a SCCO2 composition with increased density that does not suffer from the gravity override effect. Such compositions lead to improved sweep efficiency and enhanced oil recovery of the hydrocarbon-bearing formation. 
     Capsules of Aqueous Solution 
     In one aspect, embodiment capsules disclosed relate to an aqueous solution encapsulated by zeolite-templated carbon particles.  FIG. 1  shows a simplified schematic of an embodiment capsule useful for treating subterranean formations.  FIG. 1  shows a capsule  100  having an aqueous solution  102  that is encapsulated by zeolite-templated carbon (ZTC) particles  104 . The aqueous solution  102  as given in capsule  100  has a solution diameter  106 . The ZTC particles  104  have a ZTC particle diameter  108 . The capsule  100  has a capsule diameter  110 . In the embodiment shown in  FIG. 1 , the surface  112  of the aqueous solution  102  is surrounded by a layer of ZTC particles  104  which form an encapsulating shell  114  around the aqueous solution  102  such that it is encapsulated. Several potential shapes of the ZTC particles  104  are represented, such as spherical  116 , pyramidal  118 , and cubic  120 . 
     Embodiment capsules include an aqueous solution. For embodiment capsules, the aqueous solution includes water. The water may comprise one or more known compositions of water, including distilled; condensed; filtered or unfiltered fresh surface or subterranean waters, such as water sourced from lakes, rivers or aquifers; mineral waters; gray water; run-off, storm or waste water; potable or non-potable waters; brackish waters; synthetic or natural sea waters; synthetic or natural brines; formation waters; production water; and combinations thereof. 
     In some embodiments, within the embodiment capsule the aqueous solution is in the form of a liquid, for example, a droplet or sphere. In such embodiments, the solution diameter may have a range of from about 10 nm (nanometers) to about 100 μm (micrometers), meaning the solution diameters have a D 1  of about 10 nm and a D 99  of about 100 μm. In some embodiments, the solution diameter may have a range of from about 10 nm to 200 nm. In other embodiments, the solution diameter may have a range of from about 10 μm to 100 μm. A D 1  value means that 1% of the solution diameters have a diameter of less than the D 1  value. A D 99  value means that 99% of the solution diameters have a diameter of less than the D 99  value. 
     Embodiment capsules also include a zeolite-templated carbon (ZTC) particle. In some such embodiments, the zeolite-templated carbon particle comprises zeolite-templated carbon (ZTC). The zeolite-templated carbon is made of carbon residue from the reduction of one or more olefin compounds in a zeolite structure, forming a 3-dimensional (3D) carbon matrix. 
     The zeolite-templated carbon particles may be made by a method that includes introducing an organic precursor gas made of an organic precursor for a chemical vapor deposition (CVD) period to a crystalline zeolite that is maintained at a CVD temperature such that the carbon-zeolite composite forms. The introduced organic precursor adsorbs via CVD into the crystalline zeolite. The organic precursor converts into carbon within the crystalline zeolite. Useful organic precursors for such a process may include propylene, ethanol and acetylene. The carbon within the crystalline zeolite forms a carbon template of the internal void structure of the zeolite. The zeolite templated carbon therefore takes the shape of a negative replica of the crystalline zeolite on a matrix scale. The method includes introducing a non-reactive gas for a thermal treatment period to the carbon-zeolite composite maintained at a thermal treatment temperature such that a thermally-treated carbon-zeolite composite forms. The carbon template of the zeolite within the crystalline zeolite converts into a thermally-treated carbon template of the zeolite. The method includes introducing an aqueous strong mineral acid mixture to the thermally-treated carbon-zeolite composite such that the zeolite templated carbon (ZTC) is freed from the zeolite structure. Additional details regarding the ZTC particles disclosed here may be found in U.S. Pat. No. 9,604,194, which is incorporated by reference in its entirety. 
     In other such embodiments, the previously-described ZTC particles comprise functionalized ZTC particles. In such embodiments, the ZTC particles may be functionalized with amines, hydroxyl groups, carboxylic acid groups, and combinations thereof, in order to increase their affinity for supercritical CO 2 . 
     In other such embodiments, the previously-described ZTC particle comprises doped ZTC particles. In some embodiments, the dopant for the ZTC particles is selected from the group consisting of oxygen, nitrogen, sulfur, iron, zinc, and combinations thereof. The use of such dopants may allow for the tuning of the degree of hydrophobicity of the doped ZTC particles. 
     On the macro-scale, embodiment zeolite-templated carbon particles may be any appropriate shape useful for encapsulating aqueous solutions. For example, as shown in  FIG. 1 , ZTC particles are shown as spherical ( 116 ), cubic ( 120 ), and pyramidal ( 118 ); however, geometric and non-geometric configurations are not limited except as to provide for an encapsulating surface for the aqueous solution. 
     Embodiment zeolite-templated carbon particles may be any appropriate size for encapsulating aqueous solutions. Based upon the configuration or geometry of the form of the ZTC particle, the particle size may be determined by a center-traversing axis parallel with its longest length. So, for example, a sphere may be measured by its diameter; a cube by its diagonal. In some embodiments, the zeolite-templated carbon particles have a particle size in a range of from about 10 to about 200 nm, meaning the ZTCs have a D 1  of about 10 nm and a D 99  of about 200 nm. A D 1  value means that 1% of the ZTC particles have a diameter of less than the D 1  value. A D 99  value means that 99% of the particles have a diameter of less than the D 99  value. 
     In some embodiments, the zeolite-templated carbon particles are hydrophobic. In such embodiments, the water contact angle of embodiment ZTC particles is from about 90° to about 180°. In some embodiments, the water contact angle of embodiment ZTC particles is less than 150°, such as less than 120°. 
     In some embodiments, the density of the zeolite-templated carbon particles is the same or greater than the density of water. In such embodiments, the density of water is from about 1.0 to 1.2 g/mL (grams per milliliter), generally corresponding to the density of water under formation conditions. 
     As described, embodiment capsules include an aqueous solution that is encapsulated by ZTC particles. The aqueous solution is surrounded by the ZTC particles and does not disperse into the medium hosting the capsules. In embodiment capsules, the aqueous solution and the ZTC particles are as previously described. 
     In some embodiments, capsules have a capsule size range, which is effectively the diameter of the capsule, from about a few nanometers to a few millimeters. In such embodiments, the capsule diameter may have a range of from about 10 nm (nanometers) to about 100 μm (micrometers), meaning the capsules have a D 1  of about 10 nm and a D 99  of about 100 μm. In some embodiments, the capsule diameter may have a range of from about 10 nm to 200 nm. In other embodiments, the capsule diameter may have a range of from about 10 μm to 100 μm. The capsule size range for a given embodiment capsule should be approximately the same in all directions of the roughly spherical shape; however, variations in configuration between a given ZTC particle and another may provide some statistically insignificant differences in determined capsule size range based on one diameter versus another. 
     Embodiment capsules have a density in a range of from about 0.9 to about 1.2 g/mL. 
     Dispersion of Capsules in Super/Critical Co 2    
     In another aspect, embodiments disclosed relate to a dispersion of the embodiment capsules previously described.  FIG. 2  shows a simplified schematic of an embodiment dispersion in use in a hydrocarbon-bearing formation. A hydrocarbon-bearing formation  200  has pores  206  throughout. An embodiment dispersion within pores  206  may include CO 2  in the critical or supercritical state (“SCCO2”)  202  and capsules  204 . Arrows (not labeled) show the direction of flow of the embodiment dispersion through the hydrocarbon-bearing formation. 
     In embodiment dispersions, a medium of SCCO2 suspends the prior-discussed embodiment capsules. The critical temperature for carbon dioxide is approximately 31.1° C.; the critical pressure is approximately 8.38 MPa (megapascals). In some embodiment dispersions, the carbon dioxide is in a critical state. In some other embodiment dispersions, the carbon dioxide is in a supercritical state. Embodiment dispersions may include SCCO2 in a temperature range of from about 50° C. to about 100° C. Embodiment dispersions may include SCCO2 in a pressure range of from about 1500 psi (pounds per square inch) to about 5000 psi. 
     In some embodiment dispersions, the carbon dioxide medium may have a purity of at or greater than 90%. The purity of the carbon dioxide is determined before introduction of the capsules into the embodiment dispersion, the introduction of water into the carbon dioxide, or the introduction of the carbon dioxide into a subterranean formation, as any contact may introduce external impurities into the critical or supercritical carbon dioxide. In some embodiment dispersions, the carbon dioxide medium may have a density in a range of from about 0.8 to 0.9 g/mL. 
     Embodiment dispersions also include capsules as previously described. The capsules are stable in the SCCO2 environment. The ZTC particle and aqueous solution do not physically or chemically degrade or disassociate due to the presence of the SCCO2. 
     Embodiment dispersions may include a percent volume of water as compared to the total volume of water and SCCO2. Embodiment dispersions may include from about 60 to 70 vol. % of water. A greater water content contributes to an increased density of embodiment dispersions, as water has a greater density than SCCO2 at formation conditions. 
     Embodiment dispersions may include any suitable amount of ZTC particles. In some embodiments, dispersions may include up to 5.0 wt. % of ZTC particles in terms of the total weight of the dispersion. Embodiment dispersions may have a lower limit of about 1.0, 1.5, 2.0, or 2.5 wt. % ZTC, and an upper limit of about 5.0, 4.5, 4.0, 3.5, or 3.0 wt. % ZTC, where any lower limit may be used in combination with any mathematically compatible upper limit. 
     Embodiment dispersions may have a bulk density suitable for mitigating gravity override. Such dispersions may have a bulk density of from about 0.9 to 1.1 g/mL at formation conditions. Embodiment dispersions may include in a range of from about 50 to 70 vol. % of embodiment capsules. 
     Method of Forming a Dispersion 
     In another aspect, embodiments disclosed here relate to a method of making the previously-described dispersion.  FIG. 3  is a block flow diagram of an embodiment method of making a dispersion  300 . 
     The method  300  may include providing a medium of critical or supercritical carbon dioxide  302 . In some embodiments, providing the medium may include introducing SCCO2 into a subterranean formation. In such cases, the dispersion may be produced in situ, that is, within the formation to be treated with the dispersion. As such, the treatment of the formation and the creation of the dispersion occur virtually simultaneously. In other embodiments, the dispersion is fabricated outside of a subterranean formation, such as on the surface or in a production facility. 
     The method  300  may include introducing water into the SCCO2 such that an emulsion of water in CO 2  forms  304 . Embodiment SCCO2 may be in a temperature in in a range of from about 50° C. to about 100° C. and a pressure in a range of from about 1500 psi to about 5000 psi when water is introduced. The water may be introduced to SCCO2 by any suitable means in which the previously described temperatures and pressures may be maintained. For example, the water may be introduced by a pump configured to introduce fluids at a temperature and pressure greater than the temperature and pressure of the SCCO2, such by using a high pressure syringe pump. The water/SCCO2 may then be mixed using vigorous stirring to form am emulsion. If ZTC particles are already present in the CO 2  as a dispersion, then the ZTC particles encapsulate the aqueous solution and the dispersion forms. 
     Upon introducing an aqueous solution into a SCCO2 medium, an emulsion of water droplets in SCCO2 may be formed. However, such emulsions may not be stable for extended periods because water and SCCO2 naturally separate due to differences in polarity of the two fluids. 
     The method  300  may include introducing ZTC particles into the SCCO2  306 . The SCCO2 medium in embodiment dispersions may be in a temperature in a range of from about 50° C. to about 100° C. and a pressure in a range of from about 1500 psi to about 5000 psi when ZTC particles are added. Embodiment ZTC particles may be added to embodiment dispersions as a dry powder. Embodiment ZTC particles may be added to the CO 2  medium under vigorous stirring to evenly disperse the ZTC particles. The dispersion may then be stirred for about 30 to 60 minutes. 
     In some embodiments, the water is added to the SCCO2 prior to the addition of the ZTC particles to the SCCO2. If water is present in the SCCO2 medium and an emulsion is already present, the embodiment dispersion may immediately form. The zeolite-templated carbon particles described previously may be provided to the emulsion to encapsulate aqueous solution present, thereby mitigating the polarity difference, stabilizing the aqueous solution in the SCCO2 medium, and forming the dispersion from the emulsion of water and SCCO2. In some embodiments, the ZTC particles are added to the SCCO2 prior to the addition of the water to the SCCO2. If the aqueous solution is not present in the SCCO2 medium, then a dispersion of ZTC particles in the SCCO2 is formed. In some embodiments, the water and ZTC particles may be introduced to the SCCO2 medium simultaneously. 
     When introduced into an aqueous solution in SCCO2 emulsion, hydrophobic particles, such as the previously-described zeolite-templated carbon particles, may collect at the interfaces between the aqueous solution and the SCCO2, if water is already present in the SCCO2 medium. If water is not present, the ZTC particles will likely be distributed fairly evenly throughout the SCCO2 medium until water is present. When the aqueous solution is introduced, however, the ZTC particles will tend to aggregate on the surface of the aqueous solution even though they are hydrophobic. As the zeolite-templated carbon particles collect at the aqueous/SCCO2 interface, a layer of ZTC particles aggregate around the aqueous solution, as shown in  FIG. 1 . This ZTC layer serves to encapsulate the aqueous solution. 
     Although not wanting to be bound by theory, it is believed that due to the hydrophobic nature of the embodiments of the zeolite-templated carbon particles, Van der Walls forces between the CO 2  molecules in the SCCO2 and surfaces of the zeolite-templated carbon particles may be strong. This may have the effect of CO 2  molecules adsorbing to surfaces of the zeolite-templated carbon particles at SCCO2 conditions. As such, CO 2  molecules may pack more tightly near the surface of a capsule as compared to molecules in the bulk SCCO2 medium. This may result in an increase in the bulk density of SCCO2/capsule dispersion, which will mitigate the gravity override issue when in use in a formation or reservoir. 
     Method of Use in a Hydrocarbon-Bearing Formation 
     In another aspect, embodiments disclosed here relate to a method of using the previously-described embodiment dispersion in a hydrocarbon-bearing formation. As shown in  FIG. 2 , the embodiment dispersion comprising the embodiment capsules are shown traversing the pore structure of a reservoir. 
     As shown in  FIG. 3 , an embodiment method may include introducing the previously-described embodiment dispersion that comprises the embodiment capsules in SCCO2 into a subterranean formation, such as a hydrocarbon-bearing formation  308 . Embodiment methods may include introducing a previously-formed embodiment dispersion having the previously-described embodiment capsules into a subterranean formation. In other embodiments, components of the dispersion may be introduced separately, meaning that the SCCO2, aqueous solution and ZTC particles may each be introduced separately into the formation, and embodiment dispersions may be formed in the subterranean formation in situ. Components of the dispersion may be added to the formation in any order. If introduced into the formation separately, the ZTC particles may be added as a dry powder or they may be suspended in a suitable solvent, such as crude oil, hydrocarbon fractions, such as naphtha, kerosene or diesel, or SCCO2. The ZTC particles may also be suspended in water provided it has surfactants to assist in suspension of the ZTC particles. 
       FIG. 4  is a diagram that illustrates a well environment  400  in accordance with one or more embodiments. Well environment  400  includes a subsurface  410 . Subsurface  410  is depicted having a wellbore wall  411  both extending downhole from a surface  405  into the subsurface  410  and defining a wellbore  420 . The subsurface also includes target formation  450  to be treated. Target formation  450  has target formation face  455  that fluidly couples target formation  450  with wellbore  420  through wellbore wall  411 . In this case, casing ( 412 ) and coiled tubing  413  extend downhole through the wellbore  420  into the subsurface  410  and towards target formation  450 . 
     With the configuration in  FIG. 4 , the previously-described embodiment dispersion that comprises the embodiment capsules in critical or supercritical carbon dioxide may be introduced into the subsurface  410  and towards target formation  450  via a pump  417  through the coiled tubing  413 . In another embodiment, as previously described, the dispersion may be formed in situ, meaning components of the dispersion (CO 2 , aqueous solution, ZTC particles) may be introduced into the subsurface  410  separately via the pump  417  through the coiled tubing  413 , forming the dispersion inside the target formation  450 . In such embodiments, multiple pumps may be used to separately inject components of the dispersion. 
     Hydrocarbon-bearing formations may include any oleaginous fluid, such as crude oil, dry gas, wet gas, gas condensates, light hydrocarbon liquids, tars, and asphalts, and other hydrocarbon materials. Hydrocarbon-bearing formations may also include aqueous fluid, such as water and brines. Hydrocarbon-bearing formations may include formations with pores sizes of from about 100 nm to 100 μm. As such, embodiment capsules have sizes in an appropriate range to traverse pores of hydrocarbon-bearing formations. Embodiment dispersions may be appropriate for use in different types of subterranean formations, such as carbonate, shale, sandstone and tar sands. 
     Embodiments of the present disclosure may provide at least one of the following advantages. As described previously, embodiment dispersions may have greater density than bulk supercritical CO 2 . As such, embodiment dispersions may not have the gravity override challenges associated with SCCO2 in enhanced oil recovery applications. The SCCO2 dispersion may traverse deeper into target formations to treat portions of the formation that have not been treated or that have been bypassed. The compositions and methods disclosed here may result in in higher oil recovery and increased oil production. 
     When the word “approximately” or “about” are used, this term may mean that there can be a variance in value of up to ±10%, of up to 5%, of up to 2%, of up to 1%, of up to 0.5%, of up to 0.1%, or up to 0.01%. 
     Although only a few example embodiments have been described in detail, those skilled in the art will readily appreciate that many modifications are possible in the example embodiments without materially departing from the envisioned scope. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims. In the claims, means-plus-function clauses are intended to cover the structures described as performing the recited function and not only structural equivalents, but also equivalent structures. Thus, although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface, in the environment of fastening wooden parts, a nail and a screw may be equivalent structures. It is the express intention of the applicant not to invoke 35 U.S.C. § 112 (f) for any limitations of any of the claims, except for those in which the claim expressly uses the words ‘means for’ together with an associated function.