Abstract:
Heatable wellbore material, e.g., cements, polymers, composites, and epoxies, and systems and methods using heatable material, which, in certain aspects, are methods for cementing casing in a wellbore with such cement, the heatable material, in some aspects, being one or a combination of electrically resisteively heatable material, microwave heatable material, and/or material heatable by the application thereto of a magnetic field. This abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure and is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims, 37 C.F.R. 1.72( b ).

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention is directed to: wellbore operations; wellbore cement; wellbore cementing methods; methods for casing a well; methods for producing a well; such methods employing heatable cement; such methods having cement with resistively heatable electrically conductive material and/or inductively heatable material and/or microwave heatable material; in certain particular aspects, to providing a wellbore with a casing string having all or a portion thereof cemented with cement having electrically conductive nanomaterial therein that is heatable by imposing an electric current thereon thereby heating the cement; and to methods for wellbore operations using material (e.g., cements, polymers, composites, and/or epoxy systems) having resistively heatable electrically conductive material and/or inductively heatable material and/or microwave heatable material to facilitate heating, hardening, setting, and/or curing. 
         [0003]    2. Description of Related Art 
         [0004]    There are a multitude of known systems and methods for completing a wellbore for oil and gas production, including many known casing methods and methods for cementing casing in a wellbore. There are many known cements used in such systems and methods. 
         [0005]      FIG. 1  shows schematically and not to scale a typical cased wellbore with casing cemented in place in the wellbore with cement. The casing extends from an earth surface down to the bottom of the wellbore and the casing is usually cemented along its length. 
         [0006]    There have long been needs, recognized by the present inventor, for heatable cement for wellbore operations, for effective well completion methods and systems, and for enhanced methods and systems for producing fluids from a wellbore. 
       SUMMARY OF THE PRESENT INVENTION 
       [0007]    The present invention discloses cements and methods for using such cements. In certain aspect, using such cements for cementing casing in a wellbore, the methods including cementing at least a portion of a casing in a wellbore with cement that contains one or a combination of: resistively heatable electrically conductive material; inductively heatable material; microwave heatable material; and/or electrically conductive nanomaterial. 
         [0008]    The present invention discloses cements and methods for using such cements for cementing casing in a wellbore, the methods including cementing at least a portion of a casing in a wellbore with cement that contains electrically conductive nanomaterial. In certain aspects, the present invention discloses materials, systems, and methods for facilitating the hardening, setting, and/or curing of material within a wellbore (e.g., but not limited to, polymers, composites, epoxy systems, and cements) and/or within a wellbore structure (downhole or above ground) by employing material that contains one or a combination of: resistively heatable electrically conductive material; inductively heatable material; microwave heatable material; and/or electrically conductive nanomaterial. 
         [0009]    The present invention, in certain aspects, discloses a cased cemented wellbore and methods for making such a wellbore that has at least a part of, parts of, or all of the cement containing electrically conductive nanomaterial therein so that part, parts, or all of the cement is heatable by imposing an electric current on the electrically conductive nanomaterial resulting in resistive heating of the cement, and, if desired, things in contact with or near the cement. The current may be either alternating current or direct current. Such heating may also facilitate curing, solidifying, and/or setting of the cement. In one aspect, material (e.g., cement, polymer, composite, epoxy system) according to the present invention has nanomaterials therein which are electrically conductive, for example, and not limited to, electrically conductive nanotubes, nanographene, nanographene ribbons, and/or transformed nanomaterials and carbon nanomaterials, e.g., but not limited to, carbon nanotubes. Electrically conductive nanomaterial in embodiments of the present invention may include one or a variety of nanotubes, including, but not limited to single-walled nanotubes, multi-walled nanotubes, double walled nanotubes, and/or surface-modified nanotubes. “Nanomaterial” includes, without limitation, one, some or any combination of these materials and/or nanotubes. 
         [0010]    It is within the scope of the present invention to impose a magnetic field on inductively hetable material, to impose an electric current on electrically conductive material, and/or to impose an electrical current on electrically conductive nanomaterial in material (e.g., in cement, polymer, epoxy system) according to the present invention using any suitable magnetic field generator, induction coil apparatus, and/or power system and/or control system and/or connectors, connections, leads, metal tubulars themselves, wires and/or power cables, insulated or not, in the earth adjacent the material, in the material, on the exterior of a tubular and/or on the interior of a tubular. Optionally, electric current is sent via a transmitted wave or signal (with a wired system and/or wirelessly) to a suitable receptor for conversion to electrical current for application to the material. Optionally, a generator in the earth, in the wellbore, or in a tubular in the wellbore generates the needed electricity to produce heat. 
         [0011]    Heat generated in material (e.g., in cement, in polymers, in an epoxy system) according to the present invention and/or in systems according to the present invention can be used to heat the material and, in certain aspects, to heat things and materials either in contact with the material or in proximity to the material; e.g., but not limited to, tubulars (e.g., casing, collars, pipe, or tubing), fluid and/or materials in such tubular, fluid and/or materials outside a tubular, e.g. fluid or materials in an annulus between a tubular exterior and a wellbore or tubular exterior, and earth or formations adjacent the material; e.g., but not limited to, adjacent cement in a wellbore. 
         [0012]    Accordingly, the present invention includes features and advantages which are believed to enable it to advance wellbore technology and wellbore production technology. Characteristics and advantages of the present invention described above and additional features and benefits will be readily apparent to those skilled in the art upon consideration of the following description of preferred embodiments and referring to the accompanying drawings. 
         [0013]    Certain embodiments of this invention are not limited to any particular individual feature disclosed here, but include combinations of them distinguished from the prior art in their structures, functions, and/or results achieved. Features of the invention have been broadly described so that the detailed descriptions of embodiments preferred at the time of filing for this patent that follow may be better understood, and in order that the contributions of this invention to the arts may be better appreciated. There are, of course, additional aspects of the invention described below and which may be included in the subject matter of the claims to this invention. Those skilled in the art who have the benefit of this invention, its teachings, and suggestions will appreciate that the conceptions of this disclosure may be used as a creative basis for designing other structures, methods and systems for carrying out and practicing the present invention. The claims of this invention are to be read to include any legally equivalent devices or methods which do not depart from the spirit and scope of the present invention. 
         [0014]    What follows are some of, but not all, the objects of this invention. In addition to the specific objects stated below for at least certain embodiments of the invention, other objects and purposes will be readily apparent to one of skill in this art who has the benefit of this invention&#39;s teachings and disclosures. It is, therefore, an object of at least certain embodiments of the present invention to provide the embodiments and aspects listed above and: 
         [0015]    New, useful, unique, efficient, nonobvious systems and methods for completing a wellbore for fluid production therefrom; 
         [0016]    New, useful, unique, efficient, nonobvious wellbore casing cements which include inductively heatable material, electrically conductive material, and/or electrically conductive nanomaterial therein to heat the cement and, in some aspects, material and/or earth in contact with and/or adjacent the heated cement; 
         [0017]    New, useful, unique, efficient, nonobvious wellbore cements and systems and methods for cementing casing in a wellbore; and 
         [0018]    New, useful, unique, efficient, nonobvious systems and methods for heating all, a part of, or parts of cement that cements casing in a wellbore. 
         [0019]    New, useful, unique, efficient, nonobvious wellbore materials which include inductively heatable material, electrically conductive material, microwave heatable material, and/or electrically conductive nanomaterial therein to heat the wellbore material (e.g., cement, polymers, composites, epoxy systems, e.g., but not limited to, two-part epoxy systems) and, in some aspects, material and/or earth in contact with and/or adjacent the heated material; and 
         [0020]    New, useful, unique, efficient, nonobvious systems and methods for heating all, a part of, or parts of material in a wellbore e.g, but not limited to, cement that cements casing in a wellbore. 
         [0021]    The present invention recognizes and addresses the problems and needs in this area and provides a solution to those problems and a satisfactory meeting of those needs in its various possible embodiments and equivalents thereof. To one of skill in this art who has the benefits of this invention&#39;s realizations, teachings, disclosures, and suggestions, various purposes and advantages will be appreciated from the following description of certain preferred embodiments, given for the purpose of disclosure, when taken in conjunction with the accompanying drawings. The detail in these descriptions is not intended to thwart this patent&#39;s object to claim this invention no matter how others may later attempt to disguise it by variations in form, changes, or additions of further improvements. 
         [0022]    The Abstract that is part hereof is to enable the U.S. Patent and Trademark Office and the public generally, and scientists, engineers, researchers, and practitioners in the art who are not familiar with patent terms or legal terms of phraseology to determine quickly, from a cursory inspection or review. the nature and general area of the disclosure of this invention. The Abstract is neither intended to define the invention, which is done by the claims, nor is it intended to be limiting of the scope of the invention or of the claims in any way. 
         [0023]    It will be understood that the various embodiments of the present invention may include one, some, or all of the disclosed, described, and/or enumerated improvements and/or technical advantages and/or elements in claims to this invention. 
         [0024]    Certain aspects, certain embodiments, and certain preferable features of the invention are set out herein. Any combination of aspects or features shown in any aspect or embodiment can be used except where such aspects or features are mutually exclusive. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0025]    A more particular description of embodiments of the invention briefly summarized above may be had by references to the embodiments which are shown in the drawings which form a part of this specification. These drawings illustrate embodiments preferred at the time of filing for this patent and are not to be used to improperly limit the scope of the invention which may have other equally effective or legally equivalent embodiments. 
           [0026]      FIG. 1  is a schematic view—not to scale—of a prior art cased cemented wellbore. 
           [0027]      FIG. 2  is a schematic view—not to scale—of a cased cemented wellbore according to the present invention. 
           [0028]      FIG. 3  is a schematic view—not to scale—of a cased cemented wellbore according to the present invention. 
           [0029]      FIG. 4  is a schematic view—not to scale—of a cased cemented wellbore according to the present invention. 
           [0030]      FIG. 5A  is a schematic view—not to scale—of a cased cemented wellbore according to the present invention. 
           [0031]      FIG. 5B  is a schematic view—not to scale—of a cased cemented wellbore according to the present invention. 
           [0032]      FIG. 5C  is a schematic view—not to scale—of a cased cemented wellbore according to the present invention. 
           [0033]      FIG. 5D  is a schematic view—not to scale—of a cased cemented wellbore according to the present invention. 
           [0034]      FIG. 6  is a schematic view—not to scale—of a cased cemented wellbore according to the present invention. 
           [0035]      FIG. 7  is a schematic view—not to scale—of a cased cemented wellbore according to the present invention. 
           [0036]      FIG. 8A  is a side cross-sectional view of a well bore and a casing to be cemented therein having a cementing plug assembly installed in its initial position in the casing. 
           [0037]      FIG. 8B  is a view similar to  FIG. 8A , but showing the well bore and casing after a displacement plug of the cementing plug assembly has been released and landed on a float collar in the casing. 
           [0038]      FIG. 8C  is a view similar to  FIG. 8B , but showing the well bore and casing after a bottom plug of the cementing plug assembly has been released and landed on the displacement plug. 
           [0039]      FIG. 8D  is a view similar to  FIG. 8C , but showing the well bore and casing after a top plug of the cementing plug assembly has been released and landed on the bottom plug. 
           [0040]      FIG. 9A  is a fragmentary cross-sectional illustration of an embodiment of a step in a method according to the present invention. 
           [0041]      FIG. 9B  is a fragmentary cross-sectional illustration of an embodiment of a step in a method according to the present invention after the previous step. 
           [0042]      FIG. 9C  is a fragmentary cross-sectional illustration of an embodiment of a step in a method according to the present invention. 
           [0043]      FIG. 9D  is a fragmentary cross-sectional illustration of an embodiment of a step in a method according to the present invention after the previous step. 
           [0044]      FIG. 9E  is a fragmentary cross-sectional illustration of an embodiment of a step in a method according to the present invention after the previous step. 
           [0045]      FIG. 10A  is a side schematic view of a cementing system connected to a well head with suitable piping for making a cemented wellbore according to the present invention and includes a cement delivery system and well head. 
           [0046]      FIG. 10B  is a side schematic view of a cemented wellbore according to the present invention showing a casing with cement in an annular space with zones with different cement. 
           [0047]      FIG. 10C  is a side schematic view of a cemented wellbore according to the present invention showing a casing with cement in an annular space with zones with different cement. 
           [0048]      FIG. 11  a side schematic view of a cemented wellbore according to the present invention. 
           [0049]      FIG. 12  a schematic view of a system and method according to the present invention. Nanomaterial is not depicted to scale in any drawing. 
       
    
    
       [0050]    Certain embodiments of the invention are shown in the above-identified figures and described in detail below. Various aspects and features of embodiments of the invention are described below and some are set out in the dependent claims. Any combination of aspects and/or features described below or shown in the dependent claims can be used except where such aspects and/or features are mutually exclusive. It should be understood that the appended drawings and description herein are of certain embodiments and are not intended to limit the invention or the appended claims. On the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the invention as defined by the appended claims. In showing and describing these embodiments, like or identical reference numerals are used to identify common or similar elements. The figures are not necessarily to scale and certain features and certain views of the figures may be shown exaggerated in scale or in schematic in the interest of clarity and conciseness. 
         [0051]    As used herein and throughout all the various portions (and headings) of this patent, the terms “invention”, “present invention” and variations thereof mean one or more embodiments, and are not intended to mean the claimed invention of any particular appended claim(s) or all of the appended claims. Accordingly, the subject or topic of each such reference is not automatically or necessarily part of, or required by, any particular claim(s) merely because of such reference. So long as they are not mutually exclusive or contradictory any aspect or feature or combination of aspects or features of any embodiment disclosed herein may be used in any other embodiment disclosed herein. The drawing figures present the embodiments preferred at the time of filing for this patent. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0052]    It is within the scope of the present invention, in any embodiment described below, to substitute for the electrically conductive nanomaterial, electrically conductive material that is sufficiently resistively heatable to effect the desired heating and/or microwave heatable material. It is within the scope of the present invention, in any embodiment described below, to substitute for the electrically conductive nanomaterial, inductively heatable material that is sufficiently inductively heatable to effect the desired heating and/or microwave heatable material; and in such embodiments, any power source below may be changed to a magnetic field apparatus useful in inductive heating, e.g., but not limited to, induction coil apparatuses and/or changed to a suitable apparatus for applying microwaves to microwave heatable material. It should also be understood that it is within the scope of the present invention to use a combination of any of these materials—electrically conductive material, inductively heatable material, microwave heatable material, and electrically conductive nanomaterial—in a single material in or for introduction into a wellbore, e.g., but not limited to, cements, polymers, ckomposites, and/or epoxy systems, including, but not limited to, two-part epoxy systems and, in certain particular aspects, in a single cement or in a single zone of a wellbore. 
         [0053]      FIG. 2  shows a cemented cased wellbore Q with electrically conductive nanomaterial NM (e.g., but not limited to, carbon nanotubes) throughout the cement. Electricity is imposed on the nanomaterial in the cement via leads A and B. As is true for any embodiment described below, the material NM may be replaced by, or used with, one or a combination of (combinations including any two or three of these materials or a combination of any one or two of them with electrically conductive nanomaterial) resistively heatable electrically conductive material; inductively heatable material; microwave heatable material. “Microwave heatable material” as used herein may include any of the nanomaterials disclosed or referred to herein that is microwave heatable. 
         [0054]      FIG. 3  shows a cemented cased wellbore R with electrically conductive nanomaterial NM (e.g., but not limited to, carbon nanotubes) in discrete portions X and Y of the cement. Electricity is imposed on the cement portion X via leads C and D and/or the cement portion Y by leads E and F (all leads going to a power source either in the well or at the surface). 
         [0055]    It is within the scope of the present invention to have any number of spaced-apart portions of cement in a wellbore (e.g., one, two, three, four or multiple portions throughout a wellbore or multiple spaced-apart portions in an area of a wellbore adjacent a particular formation) with electrically conductive nanomaterial therein so that any part of the wellbore and of adjacent formation can be selectively heated. 
         [0056]      FIG. 4  shows a perforated zone Z in a cased cemented wellbore S with electrically conductive nanomaterial NM in the cement adjacent the perforated zone. This part of the cement in the zone Z can be selectively heated via leads G and H with a power source PS at the surface or with a power source PC in the well, or with both. Any suitable AC or DC power source or sources may be used (as is true for any embodiment according to the present invention). It is believed that heating the formation FO around the zone Z may, in some cases, facilitate production from the formation. As is true for any embodiment of the present invention (including, but not limited to, those described above and below) instead of or in addition to the power source PS, depending on the material to be heated, a magnetic field apparatus may be used and/or an apparatus for applying microwaves to microwave heatable material may be used and the subject matter of the various drawing figures that shows a power source may be changed so that the power source is deleted and a magnetic filed source and/or microwave source is used. 
         [0057]      FIG. 5A  shows a cased cemented wellbore  1  with electrically conductive nanomaterial NM (not to scale) in cement T with one lead C at the bottom of the cement and extending up through the earth and one lead D extending through the earth to an upper part of the cement. 
         [0058]      FIG. 5B  shows a cased cemented wellbore  2  with electrically conductive nanomaterial NM (not to scale) in cement T with one lead E at the top of the cement and connected to the interior of the casing and one lead F extending through the earth to the bottom of the cement T. The lead E may be insulated and may pass through the casing to contact the cement. 
         [0059]      FIG. 5C  shows a cased cemented wellbore  3  with electrically conductive nanomaterial NM (not to scale) in cement T with one lead G at the top of the cement and connected to the interior of the casing and one lead H extending through the casing&#39;s interior to the bottom of the cement T. The leads may contact the casing itself or the leads may be insulated and may pass through the casing to contact the cement. 
         [0060]      FIG. 5D  shows a cased cemented wellbore  4  with electrically conductive nanomaterial NM (not to scale) in cement T with one lead K at the top of the cement and passing through or connected to the interior of the casing and one lead L extending through the earth to the bottom of the cement T. The lead K may contact the casing itself or the lead K may be insulated and may pass through the casing to contact the cement. 
         [0061]    Power may be supplied to the leads of the systems of  FIGS. 5A-5D  via a surface power generator PG (see e.g.  FIG. 5A ) or via a power generator PE in the earth (see  FIG. 5B ), or via a power generator PR within the casing (see  FIG. 5C ). Optionally, a power source PU either at the surface, as shown, or in the casing or in the earth (not shown) receives a wave or signal from an appropriate device or system and converts the wave or signal to electric power for application to the leads K and L. Power may be supplied to any system or cement according to the present invention with any of the power sources of  FIGS. 5A-5D . When inductively heatable material is used instead or in addition to cement, a magnetic field is applied the inductively heatable material via a surface apparatus or via an apparatus in the earth, or via an apparatus within the casing. Optionally, such an apparatus either at the surface or in the casing or in the earth receives a wave or signal from an appropriate device or system and converts the wave or signal to power for application of the magnetic field. When microwave heatable material is used instead of or in addition to cement and/or inductively heatable material, microwaves are applied the inductively heatable material via a surface apparatus or via an apparatus in the earth, or via an apparatus within the casing. Optionally, such an apparatus either at the surface or in the casing or in the earth receives a wave or signal from an appropriate device or system and converts the wave or signal to power for application of the microwaves. 
         [0062]    As is true of any wellbore, any system and any method according to the present invention, a cased wellbore according to the present invention, as exemplified by the wellbores in the drawing figures hereof, can be made with any known drilling and completion method that involves the cementing of casing in a wellbore, including, but not limited to, typical drilling and cementing operations and also, without limitation, casing drilling methods, rotary drilling methods, top drive drilling methods and coiled tubing drilling methods. 
         [0063]      FIG. 6  shows a wellbore  60  according to the present invention in the earth  67 . Casing  61  is cemented in the wellbore  60  with cement  62 . Portions  63 ,  64  and  65  of the cement  62  have electrically conductive nanomaterial NM therein. The portions  63 ,  64 ,  65  are spaced-apart any desirable distance and they may be located adjacent different earth formations. There may be the three portions shown or, according to the present invention, there may be two or any number of such portions at any part of or throughout the wellbore. 
         [0064]    A power supply  66  supplies electrical current to the nanomaterial NM in the portions  63 ,  64 ,  65 . All portions can be heated simultaneously; one or two portions may be selectively heated; or the portions may be sequentially heated from top to bottom or from bottom to top. 
         [0065]      FIG. 7  shows a wellbore  70  according to the present invention in the earth  77 . Casing  71  is cemented in the wellbore  70  with cement  72 . Portions  73 ,  74  and  75  of the cement  72  have electrically conductive nanomaterial NM therein. The portions  73 ,  74 ,  75  are spaced-apart any desirable distance and they may be located adjacent different earth formations. There may be the three portions shown or, according to the present invention, there may be two or any number of such portions at any part of or throughout the wellbore. 
         [0066]    A power supply  76  (within the earth as shown or at the surface or within the wellbore—as is true for the power supply  66 ) supplies electrical current to the nanomaterial NM in the portions  73 ,  74 ,  75 . All portions can be heated simultaneously; one or two portions may be selectively heated; or the portions may be sequentially heated from top to bottom or from bottom to top. 
         [0067]    As shown in  FIG. 7 , the density (or concentration) of nanomaterial NM in the portion  73  is less than the density of nanomaterial NM in the portion  74 ; and the density of nanomaterial NM in the portion  75  is denser than that of the nanomaterial NM in the portion  74 . In one aspect, it is possible to heat the portion  75  faster than the portions  74  and  73  due to the presence of more nanomaterial per unit volume in the portion  75 ; and/or it is possible to heat the portion  75  to a higher temperature than the other two portions for the same reason. It is to be understood that heating of the portions  63 - 65  and/or  73 - 75 , can, according to the present invention, be used to heat the earth in contact with or adjacent these portions and/or to heat the casing adjacent these portions and/or the contents of the casing adjacent these portions. 
         [0068]    The power supplies  66  and  76  and the leads, cables, connections, etc. for them may be any power source or supply and leads, etc. disclosed herein. Any control system may be used with the power supplies  66  and  76 , e.g. like the control system CS  FIG. 10A  or any of the options disclosed for the system CS. 
         [0069]    The present invention provides improvements to various existing wellbore cementing methods. In one aspect, the present invention provides methods which in some ways are similar to those disclosed in U.S. Pat. No. 5,829,523, incorporated fully herein for all purposes. In certain embodiments of the present invention, in cementing casing or liners (both referred to hereinafter as “casing”) in well bores (sometimes referred to as “primary cementing”), a cement slurry containing electrically conductive nanomaterial is pumped downwardly through the casing to be cemented and then upwardly into the annulus between the casing and the walls of the well bore. Upon setting, the cement bonds the casing to the walls of the well bore and restricts fluid movement between formations or zones penetrated by the well bore. Prior to this, the casing is suspended in a well bore and both the casing and the well bore are filled with drilling fluid. In order to reduce contamination of the cement slurry at the interface between it and the drilling fluid, a cementing plug for sealingly engaging the inner surfaces of the casing is pumped ahead of the cement slurry whereby the cement slurry is separated from the drilling fluid as the cement slurry and drilling fluid ahead of it are displaced through the casing. The cementing plug wipes the drilling fluid from the walls of the casing and maintains a separation between the cement slurry and drilling fluid until the plug lands on a float collar attached near the bottom end of the casing. 
         [0070]    The cementing plug which precedes the cement slurry and separates it from drilling fluid is referred to herein as the “bottom plug.” When the predetermined required quantity of the cement slurry has been pumped into the casing, a second cementing plug, referred to herein as the “top plug”, is released into the casing to separate the cement slurry from additional drilling fluid or other displacement fluid used to displace the cement slurry. When the bottom plug lands on the float collar attached to the casing, a valve mechanism opens which allows the cement slurry to proceed through the plug and the float collar upwardly into the annular space between the casing and the well bore. The design of the top plug is such that when it lands on the bottom plug it shuts off fluid flow through the cementing plugs which prevents the displacement fluid from entering the annulus. After the top plug lands, the pumping of the displacement fluid into the casing is continued whereby the casing is pressured up and the casing and associated equipment including the pump are pressure tested for leaks or other defects. 
         [0071]    The present invention provides, in certain aspects, methods which include releasing a first displacement plug (e.g., but not limited to, as in U.S. Pat. No. 5,829,523) into the casing which is selectively openable after landing on a float collar. A first displacement fluid is then pumped behind the first displacement plug while measuring the quantity of the first displacement fluid being pumped until the first displacement plug is displaced through the casing and lands on a float shoe contained in the casing. The first displacement plug is caused to open, and a cement slurry which has nanomaterials therein (any cement according to the present invention) is pumped into the casing in a predetermined quantity required to fill the annulus between the exterior of the casing and the walls of the well bore with the cement slurry. After the predetermined quantity of cement slurry is pumped into the casing, a top cementing plug is released into the casing. A second displacement fluid is then pumped behind the top cementing plug to displace the cement slurry through the casing and through the open displacement plug into the annulus. The second displacement fluid is pumped in a quantity substantially equal to the quantity of the first displacement fluid as measured during the displacement of the first displacement plug thereby ensuring that the cement slurry is not under or over displaced in the annulus. 
         [0072]    As shown in  FIGS. 8A-8D , a well cementing plug assembly (any known suitable assembly, e.g., but not limited to, as shown in U.S. Pat. No. 5,829,523) is illustrated and generally designated by the numeral  810 . The plug assembly  810  is shown positioned within a string of casing  812  which is suspended in a well bore  814  preparatory to being cemented therein. The plug assembly  810  is in its initial position in the casing  812  whereby it is releasably connected to the lower end of a string of drill pipe or a conventional circulation tool  816 . The casing  812  includes a conventional float collar  824  connected therein near the bottom thereof. A conventional float shoe  832  is connected to the bottom end of the casing  812  separated from the float collar  824  by a distance  830 . 
         [0073]    In one version of a cementing plug assembly  810 , the assembly has a selectively operable displacement plug  818  which is releasably connected to a selectively operable bottom cementing plug  820 . The bottom cementing plug  20  is in turn releasably connected to a top cementing plug  822 . The top cementing plug  822  is releasably connected to the drill pipe or circulation tool  816 . 
         [0074]    The displacement plug  818  and bottom cementing plug  820  are both separately closed and released by dropping different sizes of releasing plugs, e.g., balls, therein and then increasing the differential fluid pressures exerted on the plugs to predetermined differential fluid pressures which cause their release as will be described further herein below. When the displacement plug  818  lands on the float shoe  824  and when the bottom plug  820  lands on the displacement plug  818 , the plugs are separately caused to open. That is, the displacement and bottom plugs are opened by again increasing the differential fluid pressures exerted on them to predetermined differential fluid pressures. The top cementing plug  822  is also closed and released by dropping a releasing plug, e.g., a drill string or tubing plug, therein and exerting a predetermined differential fluid pressure thereon. 
         [0075]    Both the casing  812  to be cemented and the well bore  814  are usually filled with drilling fluid prior to commencing primary cementing operations. After suspending the casing string  812  in the well bore  814  and positioning the cementing plug assembly  810  within the casing  812  as shown in  FIG. 8A , a releasing plug RP of a predetermined relatively small size is dropped into and caused to be moved in a known manner through the drill string or circulation tool  816 , through the plug assembly  810  and into the displacement plug  818 . The releasing plug closes the displacement plug  818  and a first predetermined differential fluid pressure is then exerted on the displacement plug  818  which causes its release from the assembly  810 . A first displacement fluid, such as drilling fluid, is pumped behind the closed displacement plug so that the displacement plug is moved through the casing and lands on the float collar  824  as shown in  FIG. 8B . The displacement plug  818  slidably and sealingly engages the walls of the casing  812  as it is moved through the casing and it separates and prevents mixing of the fluids on its opposite sides, i.e., drilling fluid  826  below the displacement plug  818  which was in the casing prior to the release of the displacement plug  818  and the first displacement fluid  828  above the displacement plug  818 . Optionally, as the displacement plug  818  is moved through the casing  812 , the quantity of the first displacement fluid being pumped is measured by a volume meter, a pump stroke counter or other volume measurement device whereby when the displacement plug  818  lands on the float collar  824 , the total quantity of displacement fluid required to move the displacement plug  818  from the assembly  810  to the float shoe is known. 
         [0076]    When the displacement plug  818  lands on the float collar  824 , the movement of the displacement plug  818  and the flow of the first displacement fluid is stopped whereby the pressure within the casing  812  above the displacement plug  818  is increased. Such pressure increase is seen in the displacement fluid pressure indicated at the surface whereby the drilling rig operator knows the displacement plug  818  has landed and can then observe or otherwise determine the total quantity of the first displacement fluid pumped. Thereafter, the first displacement fluid pressure is increased by continued pumping until a second predetermined differential fluid pressure is reached which opens the displacement plug  818  in a manner which will be described herein below. 
         [0077]    A length  830  of the casing  812  extends between the float collar  824  and the float shoe  832  attached to the bottom end of the casing  812 . The length of casing  830  between the float collar  824  and the float shoe  832  is known in the art as the shoe track and will be referred to hereinafter as the shoe track  830 . During the travel of the displacement plug  818  from the assembly  810  to the float collar  824 , the drilling fluid  826  below the displacement plug  818  is displaced through the float collar  824 , through the shoe track  830  and through the float shoe  832  into the annulus  834  between the casing  812  and the walls of the well bore  814 . Once the displacement plug  818  has landed on the float collar  824 , the total quantity of the first displacement fluid pumped has been measured and the displacement plug  818  has been opened, a second releasing plug of a predetermined medium size as compared to the first releasing plug is dropped into the bottom cementing plug  820  whereby the bottom cementing plug  820  is closed. A cement slurry  836  is then pumped through the drill string or circulation tool  816  whereby a third predetermined differential fluid pressure is exerted on the bottom cementing plug  820  and it is released. The cement slurry contains electrically conductive nanomaterial NMT (not shown to scale; any such nanomaterial disclosed herein according to the present invention). The cement slurry  836  is pumped into the casing  812  behind the bottom plug  820  in a predetermined quantity required to fill the annulus  834 . As the bottom plug  820  moves through the casing  812 , the first displacement fluid  828  is displaced through the displacement plug  818 , through the float collar  824 , through the shoe track  830 , through the float shoe  32  and into the annulus  834 . The cement slurry  836  is pumped, and if necessary displaced, into the casing  812  until the bottom plug  820  lands on the displacement plug  818  as shown in  FIG. 8C . The pumping or displacement of the cement slurry  836  is then continued to increase the fluid pressure exerted on the bottom cementing plug  820  until a fourth predetermined differential fluid pressure is reached which causes the bottom cementing plug  820  to open and the cement slurry  836  to flow through it, through the displacement plug  818 , through the float collar  824 , through the shoe track  830 , through the float shoe  832  and into the annulus  834 . 
         [0078]    When the predetermined quantity of cement slurry  836  has been pumped into the casing  812 , a third releasing plug of a predetermined large size as compared to the second releasing plug is dropped into the top cementing plug  822  which closes the top cementing plug  822 . A second displacement fluid  838 , which preferably is the same as or at least has very similar properties to the first displacement fluid  828  used, is pumped behind the top cementing plug  822 . The fluid pressure exerted on the top cementing plug  822  by the second displacement fluid  838  is increased to a fifth predetermined differential fluid pressure which causes the top cementing plug  822  to be released. Thereafter, a quantity of the second displacement fluid  838  substantially equal to the previously measured quantity of the first displacement fluid  828  is pumped. The pumped quantity of the second displacement fluid  838  is preferably measured using the same flow meter or other measuring device which was used to measure the quantity of the first displacement fluid thereby assuring that the two quantities are the same or substantially the same. 
         [0079]    The cement slurry  836  is displaced through the casing  812 , through the bottom cementing plug  820 , through the displacement plug  818 , through the float collar  824 , through the shoe track  830  and through the float shoe  832  into the annulus  834  as shown in  FIG. 8D . When the top cementing plug  822  lands on the bottom cementing plug  820 , the top cementing plug terminates the flow of the second displacement fluid  838  and prevents it from flowing into the shoe track  830  or the annulus  834 . The pumping of the measured quantity of the second displacement fluid  838  allows the rig operator to know that the top plug  822  has landed whereupon the operator can proceed to pressure test the casing  812  and associated equipment. The cement slurry  836  in the annulus  834  and the shoe track  830  is then allowed to set whereby the casing  812  and shoe track  30  are cemented in the well bore. Thereafter, the displacement plug  818 , the cementing plugs  820  and  822 , the internals of and set cement in float collar  824 , the set cement in the shoe track  830  and the internals of and set cement in the float shoe  832  are all drilled out of the casing  812  whereupon the well is completed or additional well bore is drilled below the casing  812 . 
         [0080]    In accordance with certain aspects of the present invention, the quantity of the second displacement fluid  838  utilized for displacing the top cementing plug  822  and the cement slurry  836  through the casing  812  and into the annulus  834  is a quantity substantially equal to the quantity of the first displacement fluid  828  measured when the displacement plug  818  was displaced through the casing  812  with the first displacement fluid  828 . The first and second displacement fluids are preferably the same or very similar fluids, e.g., drilling fluid, and are preferably measured by the same flow meter or other measuring device to ensure as much as possible that the quantities of the first and second displacement fluids are equal or at least substantially equal. Thus, the quantity of the second displacement fluid  838  required to displace the cement slurry  836  into the annulus  834  and land the top cementing plug  822  is positively determined. 
         [0081]    It is within the scope of the present invention that some operators may prefer to omit the use of the bottom cementing plug  820 , and instead utilize a two plug assembly consisting of the displacement plug  818  and the top cementing plug  820 . Also it is within the scope of the present invention that the displacement plug and one or two cementing plugs used be released from the surface separately in any suitable manner and do not necessarily need to be releasably connected in an assembly as described above. 
         [0082]    A wellbore made as in  FIGS. 8A-8D  may have any device or system described herein for imposing a current on the nanomaterial in the cement. 
         [0083]    Referring to  FIG. 9A , a method  910  according to the present invention is illustrated for cementing a wellbore  912  which employs a system that includes a shoe  914  defining a passage  914   a  that is coupled to an end of a tubular member  916  defining a passage  916   a . The tubular member  916  includes one or more tubular members threadably coupled end to end. The other end of the tubular member  916  is coupled to an end of a float collar  918  including a float  918   a . The other end of the float collar  918  is coupled to an end of a tubular member  920  defining a passage  920   a . Centralizers  922   a ,  922   b , and  922   c  are coupled to the exteriors of the tubular members,  916  and  918 . More generally, the system may include any number of centralizers. The other end of the tubular member  920  is coupled to a fluid injection assembly  924  defining a passage  924   a  and radial passages  924   b ,  924   c , and  924   d , and including retaining pins  924   e  and  924   f . The fluid injection head  924  is commonly referred to as a cementing head. A bottom cementing plug  926  and a top cementing plug  928  are retained within the passage  924   a  of the fluid injection assembly  924  by the retaining pins  924   e  and  924   f . The bottom cementing plug  926  typically includes a longitudinal passage that is sealed off by a frangible diaphragm. 
         [0084]    During operation, as illustrated in  FIG. 9A , drilling mud  930  is circulated through the wellbore  912  by injecting the drilling mud into the fluid injection assembly  924  through the radial passage  924   b . The drilling mud  930  then passes through the passages  924   a ,  920   a ,  918   a , and  914   a  into the annulus between the tubular member  920 , the float collar  918 , the tubular member  916 , and the shoe  914 . As illustrated in  FIG. 9B , the bottom cementing plug  926  is then released and a spacer fluid  932  followed by a cement slurry  934  are injected into the injection assembly  924  through the radial passage  924   c  behind and above the bottom cementing plug. The cementing slurry  934  contains sufficient electrically nanomaterial NML (not shown to scale) that upon the imposition of an electric current thereon, the nanomaterial NML is resistively heated which in turn heats cement resulting from setting and hardening of the cement slurry  934 . As illustrated in  FIG. 9C , the top cementing plug  928  is then released and a displacing fluid  936  is injected into the injection assembly  924  through the radial passage  924   d  behind and above the top cementing plug. As illustrated in  FIG. 9D , the continued injection of the displacing fluid  936  displaces the bottom cementing plug  926  into contact with the float collar  918  and breaks the frangible membrane of the bottom cementing plug thereby causing the cement slurry  934  to flow into the annulus between the wellbore  912  and the shoe  914 , the tubular member  916 , the float collar  918 , and the tubular member  920 . As illustrated in  FIG. 9E , the continued injection of the displacing fluid  936  then displaces the top cementing plug  928  downwardly until the top cementing plug impacts the bottom cementing plug  926 . The float element  918   a  of the float collar  918  prevents back flow of the cement slurry  934  into the tubular member  920 . The cement slurry  934  may then be allowed to cure. 
         [0085]    A wellbore made as in  FIGS. 9A-9E  may have any device or system described herein for imposing a current on the nanomaterial in the cement. 
         [0086]    As shown in  FIG. 10A , a wellbore  1000  according to the present invention has multiple zones (Sectors  1 ,  2 ,  3 ) with different cements  1027 ,  1026 ,  1025 , respectively, according to the present invention which can be any cement disclosed herein according to the present invention. Electrically conductive nanomaterial is represented schematically by the material NME, NMF, NMG (may be different materials, similar materials, at the same or at different concentrations; not to scale). The cements can be prepared off site, or, as shown, can be mixed in the field and delivered through pumps  1011  into a manifold  1012 . The manifold is connected to a well head at  1013 . As appropriate, a suitable valve (or valves)  1014  is interposed between them. The cement is delivered under suitable pressures at selected flow rates. The nature of the cement is variable and the cements  1025 - 1027  may each be any cement disclosed herein according to the present invention; and they may each be a different cement, any two of them may be the same, or they may all three be the same. It is to be understood that a wellbore according to the present invention may have any multiple number of cement zones, although only three are depicted in  FIG. 10A . Optionally, a supply apparatus  1010  may supply different cements and/or other fluids to be used in the cementing process. In certain aspects, two or three different cements and/or fluids may be pumped into the well to complete the cementing job. The manifold  1012  is used to deliver these cements and/or fluids into the well. The pump  1011  is connected with suitable supplies of various fluids for delivery into the well. 
         [0087]    At the wellhead, an optional flow meter  1015  measures the rate of flow which can be expressed in barrels per minute. This is the rate of flow of the cement and/or fluid delivered into the well. The density of the fluid can also, optionally, be measured at the wellhead by a transducer  1016 . Density may be indicated in pounds per gallon. As appropriate, a fluid analysis device  1017  may be incorporated to make other measurements regarding the cement and/or fluid. Transducers  1015 ,  1016  and device  1017  form output data which is input town analysis and control system CS which controls the flow of the cement and/or fluid (the control system CS may be any suitable known control system, including, but not limited to, those disclosed in prior patents referred to herein). Any wellbore and method disclosed herein according to the present invention may have one or more of the control systems CS. Pressure at the wellhead may be measured by a device  1018  and may be expressed in pounds per square inch. The pressure device  1018  may be calibrated up to several thousand psi. Pressures in this range are not uncommon. 
         [0088]    The wellhead  1013  is connected to a completion string in a wellbore  1020 . The wellbore  1020  may, according to the present invention, be cased or open hole, and is represented in a very general form in  FIG. 10A . While there may be multiple completion strings,  FIG. 10A  shows a representative single completion string in the well. This is the string of pipe (or casing) to be cemented in place in the well; this string of pipe can enclose a separate tubing string or strings to conduct produced fluids, e.g. oil and/or gas, to the surface. This string can be uniform from top to bottom, but it can also be made in different sections. To this end, an upper section is identified by the numeral  1021 . This section is casing or tubing of a specific diameter and flow characteristic and has a certain length and extends to a selected depth in the bore hole. The number  1022  identifies a second section which is serially connected to a third section  1023 . The sections  1021 ,  1022 , and  1023  jointly comprise the completion string. They may be identical and to that degree only a single section need be mentioned. On the other hand, when they are different, they may be different lengths and may be formed of different diameters of casing, tubing, and/or pipe. As an example, the string can taper wherein the top section is relatively large in diameter and the bottom section  1023  is much smaller in diameter. The string terminates at a bottom located opening  1024  which can be fitted with various and sundry known landing nipples supported by packers, bridge plugs and the like; they have been omitted for sake of clarity in the description of the string and the associated equipment. 
         [0089]    In general, pipe extends to the bottom or nearly so where cement is delivered from the opening  1024 . Cement flows into the annular space and is delivered into the space to complete the cementing job. This space has been represented in very general form in  FIG. 10A  and will be understood to be that portion of the wellbore where cement is to be delivered, and may, as desired, be defined and isolated by packers or bridge plugs. The annular space may also be temporarily or permanently filled with other fluids either before or after the cement, all for the purpose of completing the cement job and assuring that the cement bond between the string and well bore is completed in the desired fashion. The space is therefore set forth in very general form on the exterior of the string. This fact remains true even should there by multiple tubing strings to multiple zones along the well. 
         [0090]    A flow meter  1015  and the other devices and transducers are may be input into the system CS which may include, as needed, a computer or computers and may be accessible on site and/or remotely. Graphic displays may be provided. 
         [0091]    In one aspect, the annular space is filled by cement, cements, and/or fluids which are delivered serially. In one aspect, a first cement is pumped out the opening  1024  at the bottom end of the pipe and is a first cement  1044  which has a measured volume and hence stands to a certain height in the annular space and it is located above a subsequent amount of cement  1045 . In one aspect, three cements are pumped into the annular space. As shown in  FIG. 10B  the cement  1044  has been moved upwardly. The cement  1045  has moved upwardly and it is supported by a third cement  1046  which has introduced therebelow, flowing into the annular space The three cements thus stand one on the other. There may be some interface between them and/or they may flow with a relatively sharp separation. 
         [0092]    The cements may be isolated by adjacent slugs of other materials which can aid and assist in positioning the cements at the desired locations in the wellbore. This desired location may be delineated by suitable packers and bridge plugs. As is true for any embodiment herein, the cement (or any part thereof) may be heated to facilitate its curing, solidifying, and/or setting 
         [0093]    A wellbore made as in  FIGS. 10A-10C  may have any device or system described herein for imposing a current on the nanomaterial in the cement. 
         [0094]    As depicted in  FIG. 11 , a tubular string  1112  (such as a production, injection, drill, test or coiled tubing string) has been installed in a wellbore  1114  cased with casing  1124  cemented with cement  1126 . The cement  1126  may be any cement according to the present invention which has sufficient electrically conducting nanomaterial NMA (not shown to scale) that, upon imposition of electric current thereon, heats the cement, and/or the casing, the interior of the casing, and/or the tubing, the interior of the tubing and/or the earth formation adjacent the casing. An electrical power generator  1116  is interconnected in the tubular string  1112 . The generator  1116  generates electrical power from flow of fluid (represented by arrow  1118 ) through an internal flow passage  1120  of the tubular string  1112 . Optionally, the generator  1116  is disposed on an interior wall of the casing. 
         [0095]    The fluid  1118  is shown as flowing upwardly through the tubular string  1112  (as if the fluid is being produced), but it should be clearly understood that a particular direction of flow is not necessary in keeping with the principles of the invention. The fluid  1118  could flow downwardly (as if being injected) or in any other direction. Furthermore, the fluid  1118  could flow through other passages (such as an annulus  1122  formed radially between the tubular string  1112  and the wellbore  1114 ) to generate electricity, if desired. 
         [0096]    The generator  1116  is illustrated as being electrically connected with lines  1131  and  1132  to the casing, but it is within the scope of the present invention for any connection, lines, cables, wireless apparatus, etc. disclosed herein to be used to connect the generator  1116  to the casing, or through the casing to the cement. 
         [0097]      FIG. 12  illustrates a method  1200  according to the present invention in which material  1202  (“PRIMARY MATERIAL IN OR FOR USE IN A WELLBORE”) which has within it material  1204  that is heatable by the application of energy to it (“HEATABLE MATERIAL”). Energy is applied to the heatable material by an energy source  1206  (“ENERGY SOURCE”). The energy source  1206  is, as shown, spaced apart from the material  1202  or (as shown with the dotted lines) the energy source  1206  is in contact with the material  1202 . 
         [0098]    The material  1202  may be any material used in wellbore operations, including, but not limited to, drilling fluid, fracturing fluid, cement, polymers, composites, epoxy, epoxy systems, and two-part epoxies. The heatable material  1204  may be any known energy heatable material, e.g., but not limited to, microwave heatable material, resistively heatable electrically conductive material, and inductively heatable material heatable by the application of a magnetic field. The heatable material may be nanomaterial. The energy source may be any suitable source of energy, including, but not limited to, apparatus for applying microwaves, magnetic field apparatus such as apparatus with an induction coil, and a power source of electrical current. 
         [0099]    In certain aspects of the present invention wellbores according to the present invention and methods according to the present invention employ a power source for imposing an electric current on electrically conductive nanomaterial. It is within the scope of the present invention to use any suitable known power source, battery, generator, capacitor, motor, or storage device for supplying the electrical current, including, but not limited to, those disclosed in U.S. Pat. Nos. 7,242,103; 7,699,102; 7,002,261; 7,133,325; 7,814,993; 7,717,167; 6,717,283; 6,672,409; 6,672,382; 6,554,074; 6,504,258; 6,470,970; 6,424,079; 6,179,052; 6,020,653; 5,995,020; 5,965,964; 5,626,200; 5,202,194; 4,416,000; 4,415,823; 4,215,426; 4,015,234; 3,968,387; and 3,448,305 and in each prior reference cited in each of these patents—all said patents and said references incorporated fully herein for all purposes; and the control systems, communications systems, cabling, wireless transmission apparatus etc. disclosed in these applications and patents, when suitable, may be used with the wellbores and the methods of the present invention. 
         [0100]    It is within the scope of the present invention to use one, two, three or greater multiples of any energy source, etc. disclosed herein for a single wellbore, including, but not limited to, those of  FIGS. 5A-5D  and  FIG. 11 . It is also to be understood that the wellbore of  FIG. 11  may have multiple zones with heatable material, with one or more energy sources. Any energy source used with embodiments according to the present invention that is movable may be selectively moved to any desired point in a wellbore or in a tubular (e.g., casing) to apply energy (electric current, magnetic field, and/or microwaves) at any desired location. 
         [0101]    The present invention, therefore, provides in at least certain embodiments methods for cementing casing in a wellbore, the methods in certain aspects including cementing all of or at least a portion of a tubular, e.g., but not limited to, casing in a wellbore with cement that contains electrically conductive nanomaterial. 
         [0102]    The present invention, therefore, provides in at least certain embodiments methods for heating cement in a wellbore, the methods in certain aspects including imposing an electrical current on at least a portion of cement, said at least a portion of cement containing electrically conductive nanomaterial that is heated upon the imposition of the electrical current, the cement being any cement used in a wellbore and, in one aspect, cement that cements casing in a wellbore. 
         [0103]    The present invention, therefore, provides in at least certain embodiments methods for heating cement in a wellbore, the methods in certain aspects including methods for heating casing cemented in a wellbore with cement, the methods including imposing an electrical current on all of or at least a portion of cement that cements casing in a wellbore, said cement containing electrically conductive nanomaterial that is heated upon the imposition of the electrical current resulting in heating of the nanomaterial, said heating of the nanomaterial causing heating of the casing. 
         [0104]    The present invention, therefore, provides in at least certain embodiments methods for heating contents of a tubular in a wellbore, the wellbore including cement therein, the methods in certain aspects including heating the contents within a wellbore (including, but not limited to contents within a tubular within a wellbore, including but not limited to the contents of casing or of tubing within a wellbore, including but not limited to the contents of tubing within casing in a wellbore, the methods including: imposing an electrical current on all of or at least a portion of cement in a wellbore, the wellbore having contents or a tubular within the wellbore having contents, said cement containing electrically conductive nanomaterial heated upon the imposition of the electrical current resulting in heating of the nanomaterial, said heating of the nanomaterial causing heating of the contents in the wellbore or causing heating of the tubular (e.g., tubing or casing), said heating resulting in heating of the contents. In such methods, incertain aspects, the contents is fluid, the fluid being one of drilling fluid, oil, gas, and water. 
         [0105]    The present invention, therefore, provides in at least certain embodiments methods for heating earth formation adjacent cement in a wellbore, the cement in the wellbore or the cement around casing in the wellbore, the methods including: imposing an electrical current on all of or on at least a portion of cement that cements casing in a wellbore, said at least a portion of cement containing electrically conductive nanomaterial that is heated upon the imposition of the electrical current; said heating of the electrically conductive nanomaterial causing heating of the cement which in turn heats earth formation adjacent the cement. In certain aspects, such a method in which the earth formation contains fluid to be produced through the wellbore heating the earth formation heats the fluid to be produced. 
         [0106]    The present invention, therefore, provides in at least certain embodiments methods for cementing a string of casing disposed in a well bore which includes a float collar connected near the bottom end thereof include the steps of: releasing a first displacement plug into said casing which is selectively openable after landing on said float collar; pumping a first displacement fluid behind said first displacement plug until said first displacement plug is displaced through said casing and lands on said float collar; causing said first displacement plug to open; pumping a cement slurry into said casing in a predetermined quantity required to fill the annulus between the exterior of said casing and the walls of said well bore with said cement slurry, said cement slurry containing electrical conductive nanomaterial which, upon the imposition of an electric current thereto, is resistively heatable; and releasing a top cementing plug into said casing and pumping a second displacement fluid behind said top cementing plug to displace said cement slurry through said casing and through said open displacement plug into said annulus. Such methods may include allowing the cement to set forming solid cement, and imposing an electric current on said electrical conductive nanomaterial to resistively heat the electrically conductive nanomaterial thereby heating the cement and/or imposing an electric current on said electrical conductive nanomaterial to resistively heat the electrically conductive nanomaterial thereby facilitating the setting of the cement. 
         [0107]    The present invention, therefore, provides in at least certain embodiments methods for cementing a tubular string in a wellbore, the methods including making a wellbore in the earth, placing a tubular string in the wellbore, introducing cement into a space between an exterior of the tubular string and an interior of the wellbore, the cement containing electrically conductive nanomaterial which is resistively heatable, and allowing the cement to set. In such methods the cement can include amounts of different cements each different cement located generally at a different location in the space, and, optionally, each different cement having a different concentration of electrically conductive nanomaterial. 
         [0108]    The present invention, therefore, provides in at least certain embodiments methods for heating cement that is in a wellbore and/or cement cementing casing in a wellbore, the methods including: imposing an electrical current on all of or on at least a portion of the cement, said cement containing sufficient electrically conductive nanomaterial so that the cement is heated upon the imposition of the electrical current, the electrical current supplied by a power source, the electrical current being one of alternating current and direct current, and, optionally, the power source controlled on-site or remotely by a control system. In such a method the power source may be any wired or wireless power source or generator, fixed or movable, and may be controlled by a control system that is one of on-site accessible and remotely accessible. 
         [0109]    The present invention, therefore, provides in at least certain embodiments methods for heating cement that is in a wellbore and/or that is cementing casing in a wellbore, the methods including: imposing an electrical current on all of or on at least a portion of cement, said cement containing sufficient electrically conductive nanomaterial that the cement is heated upon the imposition of the electrical current; the electrical current supplied by a power source, the power source being located within earth formation adjacent the casing, within the cement, within the wellbore, at an earth surface, within the wellbore, or within the casing. 
         [0110]    The present invention, therefore, provides in at least certain embodiments methods for heating cement that is in a wellbore or that is cementing casing in a wellbore, the methods including: imposing an electrical current on the cement, said cement containing electrically conductive nanomaterial that is heated upon the imposition of the electrical current, the cement including spaced-apart amounts of different cements each different cement located generally at a different location in the wellbore, and heating the different cements at the same time or at different times. Such methods may include one or some, in any possible combination, of the following: the different cements are one on top of the other and the heating is done from top to bottom of cements so that a lowermost cement is heated last or the different cements are one on top of the other and the heating is done from bottom to top of the different cements so that a lowermost cement is heated first; and/or each different cement has a different concentration of electrically conductive nanomaterial. 
         [0111]    The present invention, therefore, provides in at least certain embodiments methods for cementing casing in a wellbore, the method including cementing a casing in a wellbore with cement that contains electrically conductive nanomaterial, the cement comprising a plurality of spaced-apart cements each with a different concentration of electrically conductive nanomaterial. 
         [0112]    The present invention, therefore, provides wellbores with cement therein, the cement containing heatable electrically conductive nanomaterial. In certain aspects, the wellbore is cased with casing and the cement is heatable to heat the cement and/or to heat the casing an/or to heat things or fluids in contact with or near the heated cement and/or in contact with or near the casing. 
         [0113]    In conclusion, therefore, it is seen that the present invention and the embodiments disclosed herein and those covered by the appended claims are well adapted to carry out the objectives and obtain the ends set forth. Certain changes can be made in the subject matter without departing from the spirit and the scope of this invention. It is realized that changes are possible within the scope of this invention and it is further intended that each element or step recited in any of the following claims is to be understood as referring to the step literally and/or to all equivalent elements or steps. The following claims are intended to cover the invention as broadly as legally possible in whatever form it may be utilized. The invention claimed herein is new and novel in accordance with 35 U.S.C. §102 and satisfies the conditions for patentability in §102. The invention claimed herein is not obvious in accordance with 35 U.S.C. §103 and satisfies the conditions for patentability in §103. The prior text of this specification is in accordance with the requirements of 35 U.S.C. §112. The inventor may rely on the Doctrine of Equivalents to determine and assess the scope of their invention and of the claims that follow as they may pertain to apparatus and/or methods not materially departing from, but outside of, the literal scope of the invention as set forth in the following claims. All patents and applications identified herein are incorporated fully herein for all purposes. It is the express intention of the applicant not to invoke 35 U.S.C. §112, paragraph 6 for any limitations of any of the claims herein, except for those in which the claim expressly uses the words ‘means for’ together with an associated function. In this patent document, the word “comprising” is used in its non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not excluded. A reference to an element by the indefinite article “a” does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one of the elements.