Abstract:
Long lateral wellbores are prepared for the production of hydrocarbons by preparing only a portion of the wellbore for production at a time, starting at a remote end of the long lateral wellbore. The prepared production section is produced until production becomes uneconomic before a further production section is prepared and produced.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates in general to wellbore completion and hydrocarbon production and, in particular, to a novel method of completing and producing long lateral wellbores. 
       BACKGROUND OF THE INVENTION 
       [0002]    When a well is drilled, production casing is set so that the well can be properly cemented and the production zone(s) do not have fluid communication with other geological strata. The production zone is logged and then the production casing is perforated so that oil and/or gas can be drained from the production zone into the production casing of the well. Traditionally, hydrocarbon wells were drilled vertically down to and through one or more hydrocarbon production zone(s). As shown in  FIG. 1 , a vertical wellbore  10  having a production casing  12  passes through a hydrocarbon production zone  14 . A plurality of perforations (not shown) formed in the production casing  12  using methods well known in the art permit hydrocarbons  16  to flow into the production casing  12 . The casing perforations also permit the production zone  14  to be treated to stimulate production by creating a plurality of fractures  18  in the production zone  12  using, for example, hydraulic fracturing techniques that are well known in the art. A production tubing  20  is used to deliver the hydrocarbons  16  to the surface. A packer  22  seals the annulus between the production tubing  20  and the production casing  12 . 
         [0003]    Vertical wellbores have now been substantially abandoned in favor of more productive lateral wellbores that provide more exposure to the production zone. Although the first recorded true lateral well was drilled near Texon, Tex. in 1929, new technology developed over the last decade has permitted lateral drilling techniques to rapidly evolve. Hydrocarbon wells are now drilled vertically to a point above the production zone and then curved so that the wellbore enters the production zone at an angle and continues laterally within the production zone for more in-zone exposure to the hydrocarbon bearing formation. Some production zones are up to 300 feet (91.5 meters) thick, or more, and with lateral drilling techniques casing can be run up to 8,000 ft. (2.44 kilometers) into the production zone, thus providing significantly more area for hydrocarbons to drain into the production casing. 
         [0004]      FIG. 2  is a schematic cross-sectional diagram of an exemplary prior art hydrocarbon well  30  with a lateral wellbore. Well know features such as the conductor and surface casing are not shown. A vertical section  32  of the hydrocarbon well  30  is drilled down into proximity of a production zone  14 , cased and cemented in a manner well known in the art. In many areas, the vertical section of the well may be 10,000 feet (3.05 kilometers) in length. In some areas the vertical section may exceed 10,000 feet (3.05 kilometers) in length. A curved section  34  of the hydrocarbon well  30  is then drilled into the production zone  14 . Once it is established that the curved section  34  is in the production zone  14 , a lateral wellbore  36  is drilled in a desired direction in as straight a path as possible within the production zone  14 . Recent innovations in work strings for completing lateral wellbores described in applicant&#39;s co-pending U.S. patent application Ser. No. 14/735,846 filed Jun. 10, 2015, the specification of which is incorporated herein by reference, permit lateral wellbores of at least 12,000 feet (3.66 kilometers) to be successfully completed. After the lateral wellbore  36  is drilled, a production casing  38  is run into the lateral wellbore  36 . The production casing  38  is generally “cemented in” before it is perforated for production. In any event, sections of the production casing  38  are perforated and stimulated using methods known in the art until an entire length of the production casing  38  has been perforated and the surrounding production zone  14  has been stimulated. A production tubing  42  is then run into the well and a packer  44  is set to seal the annulus. In a very long lateral bore, stimulation of the production  14  surrounding the lateral well bore  36  is a major undertaking and now costs more than drilling, casing and cementing the bore. Once stimulation and flow-back of stimulation fluids are completed, production of hydrocarbons from the wellbore  30  begins. In a shale basin such as found in the Bakken play, production is generally commercially viable for about 2 years, and may be extended by reworking the well using methods known in the art. 
         [0005]    While the lateral wellbore method has been commercially successful, the potential for innovative production strategies has yet to be realized. 
         [0006]    There therefore exists a need for a novel method of completing and producing long lateral wellbores. 
       SUMMARY OF THE INVENTION 
       [0007]    It is therefore an object of the invention to provide a novel method of completing and producing long lateral wellbores. 
         [0008]    The invention therefore provides a method of producing hydrocarbons from a cased and cemented long lateral wellbore, comprising: preparing a first production section of the long lateral wellbore for production, the first production section having a length of less than a total length of the long lateral wellbore; producing hydrocarbons from the first production section until production from the first production section is uneconomic; setting a plug to plug off the first production section of the long lateral wellbore; preparing a next production section of the long lateral wellbore for production, the next production section having a length of less than a total length of the long lateral wellbore; producing hydrocarbons from the next production section until production from the next production section is uneconomic; if hydrocarbons have not been produced from the entire long lateral wellbore, plugging off the next production section of the long lateral wellbore; and repeating the steps of preparing a next production section and producing from the next production section until an entire length of the long lateral wellbore has been prepared for production and produced until production from the long lateral wellbore is uneconomic. 
         [0009]    The invention further provides a method of producing hydrocarbons from a cased and cemented long lateral wellbore, comprising: preparing a first production section of the long lateral wellbore for production, the first production section having a length of less than a total length of the long lateral wellbore; producing hydrocarbons from the first production section until production from the first production section is uneconomic; pulling production equipment from the long lateral wellbore; setting a plug to plug off the first production section of the long lateral wellbore; preparing a next production section of the long lateral wellbore for production, the next production section having a length of less than a total length of the long lateral wellbore; running the production equipment back into the long lateral wellbore; producing hydrocarbons from the next production section until production from the next production section is uneconomic; pulling the production equipment from the long lateral wellbore; pulling the plug from the long lateral wellbore; running the production equipment back into the long lateral wellbore until a packer is in an unperforated region between the first and next production sections of the long lateral wellbore; setting the packer in the unperforated region; installing a tubing at a wellhead of the long lateral well bore; pumping enhanced oil recovery flood fluid through the tubing into an annulus of a production casing of the long lateral wellbore, and hence down the annulus and through perforations in the production casing of the next production section; and producing hydrocarbons through a production tubing associated with the packer until the production of hydrocarbons is uneconomic. 
         [0010]    The invention yet further provides a method of producing hydrocarbons from a cased and cemented long lateral wellbore, comprising: drilling a plurality of long lateral wellbores from a single well pad; preparing a first production section of each of the long lateral wellbores for production, the first sections having a length of less than a total length of the respective long lateral wellbores; producing hydrocarbons from the first production sections of the respective long lateral wellbores until production from the respective first production sections becomes uneconomic; setting a plug to plug off the first production section of each of the respective long lateral wellbores; preparing a next production section of the respective long lateral wellbores for production, the respective next sections having a length of less than a total length of the respective long lateral wellbores; producing hydrocarbons from the respective next production sections until production from the respective next production sections becomes uneconomic; if hydrocarbons have not been produced from an entire length of the respective long lateral wellbores, plugging off the next production section of the respective long lateral wellbores; and repeating the steps of preparing a next production section and producing from the next production section until an entire length of the respective long lateral wellbores have been prepared for production and produced until production from the respective long lateral wellbores becomes uneconomic. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    Having thus generally described the nature of the invention, reference will now be made to the accompanying drawings, in which: 
           [0012]      FIG. 1  is a schematic cross-sectional diagram of an exemplary prior art vertical hydrocarbon well; 
           [0013]      FIG. 2  is a schematic cross-sectional diagram of an exemplary prior art lateral hydrocarbon well; 
           [0014]      FIG. 3  is a schematic-cross sectional diagram of a lateral hydrocarbon well with a first section completed for production using the method in accordance with the invention; 
           [0015]      FIG. 4  is a schematic-cross sectional diagram of the lateral hydrocarbon well shown in  FIG. 3  with a second section completed using the method in accordance with the invention; 
           [0016]      FIG. 5  is a schematic cross-sectional diagram of a portion of a lateral wellbore completed using a method in accordance with the invention. 
           [0017]      FIG. 6  is a schematic cross-sectional diagram of the lateral hydrocarbon well shown in  FIG. 4  configured for enhanced oil recovery using the method in accordance with the invention; 
           [0018]      FIG. 7  is a schematic cross-sectional diagram of the lateral hydrocarbon well shown in  FIG. 4  configured in another way for enhanced oil recovery using the method in accordance with the invention; 
           [0019]      FIG. 8  is a schematic cross-sectional diagram of a detail of a lateral hydrocarbon well configured for enhanced oil recovery in accordance with the invention; and 
           [0020]      FIG. 9  is a schematic diagram of lateral hydrocarbon wells drilled using methods in accordance with the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0021]    The invention provides a method of completing lateral wellbores that leverages the potential of long lateral wellbores enabled by current lateral boring and completion equipment and techniques. Lateral wellbores in excess of 12,000 linear feet (3.66 kilometers) may now be drilled and completed. In accordance with the invention, such wellbores are completed in two or more production sections, and hydrocarbon is produced from each production section until production from that production section is exhausted or no longer commercially viable. In accordance with a further aspect of the invention, 2 or more lateral wellbores are drilled from the same drill pad and each wellbore is produced in production sections until all the wellbores in each pad have been produced. In accordance with a yet a further aspect of the invention, perforation and stimulation of each production section is carefully planned to permit the respective production sections to be re-stimulated if desired. In accordance with yet a further aspect of the invention, enhanced oil recovery (EOR) is practiced within a lateral wellbore by pumping EOR flood fluids down a work string into a first production section and producing hydrocarbons up the annulus of the production casing from a second production section, or pumping EOR flood fluids down the annulus of the production casing into the second production section and producing hydrocarbons up the work string from the first production section. 
         [0022]      FIG. 3  is a schematic-cross sectional diagram of a lateral hydrocarbon well  100  having a production casing  101 , with a first production section  102  completed for production using the method in accordance with the invention. Modern drilling techniques permit very long lateral wellbores to be drilled and completed. This permits hydrocarbon deposits under natural bodies of water such as rivers  104  and/or cities  106  to be exploited without inconvenience or disturbance to surface features. In accordance with the method, after the long lateral wellbore is drilled, cased and cemented, only the first production section  102  at the farthest reach of the production casing  101  is perforated and stimulated for production. A length the first production section  102  is a matter of design choice and may depend on any one or more of a number of factors including; a production potential of the production zone  14 ; current or projected price for hydrocarbon products to be produced from the production section; current investment funds available for production stimulation treatments; availability of stimulation service providers; desired lifetime of the entire well; etc. In general each production section  102  has a recommended length of 2,000′-4,000′ (600-1,200 meters), or at most less than the entire length of the lateral wellbore of the hydrocarbon well  100 . Keeping production section  102  at a length of 4,000′ (1,200 meters) or less permits service providers to achieve a more focused stimulation treatment, which results in better production per linear foot of wellbore. Each production section  102  may also have a different length, as described below in more detail. An operator may decide to have 3 production sections in a 12,000 ft. lateral wellbore. The furthest production section out from the vertical wellbore may be 3,000′ in length. The second production section may be 4,000′ in length, and the last section would therefore be about 5,000′ in length. 
         [0023]    After the first production section  102  of production casing  101  has been prepared for production using production casing perforation and formation stimulation techniques well known in the art, flow-back of stimulation fluids is performed in accordance with methods that are also known in the art. After flow-back, production from the hydrocarbon well  100  may commence. Depending on the production formation  14 , hydrocarbon may be initially produced up the production casing  101 . After production up the production casing  101  is not viable, a production tubing  108  is then run into the well. A packer  110  is set to seal the annulus around the production tubing  108  and production from the hydrocarbon well  100  continues or commences. A pump assisted lift may be required to produce hydrocarbons from the production section  102 , as understood by those skilled in the art. Production from the production section  102  continues until production from that production section is no longer commercially viable. 
         [0024]      FIG. 4  is a schematic-cross sectional diagram of the lateral hydrocarbon well  100  shown in  FIG. 3  with a second production section  112  of the production casing  101  completed using the method in accordance with the invention. Once production from production section  102  is no longer viable, the production tubing  108  and packer  110  are pulled from the well and a re-stimulation of section  102  may be performed to prolong production. Alternatively, a plug  114  is set in the unperforated interval “u” of the production casing  101 , where the packer  110  had been set. Perforating equipment (not shown) is then run into the production casing  101  and the production second section  112  is perforated and stimulated until an entire length of the second section  112  of the production casing  101  is prepared for production. A length of the unperforated section “u” left between the sections  102  and  112  is preferably at least one production casing joint (40′-12.2 m) in length and may be up to two casing joints in length. A length of the new production section  112  may be determined using production information collected during production from production section  102 . Consequently, new production section  112  may be longer, shorter, or the same length as production section  102  depending on production targets and any other factor relevant to operation of the hydrocarbon well  100 . An operator may also consider changing the stimulation treatment or service provider when stimulating the second production section  112  to determine the efficacy of a different treatment/service provider because production yields from the production sections  102  and  112  provide a direct comparison of stimulation efficacy since production from each section is from the same wellbore in the same production zone. Once stimulation and flow-back of stimulation fluids are completed, the production tubing  108  and the packer  110  are then run back into the wellbore and the packer  110  is reset. Production from the second production section  112  then commences and continues until the production from production section  112  is no longer economically viable, at which time the production section  112  may be plugged off, and the process of preparing another production section may be repeated until the entire lateral wellbore has been produced. Alternatively, enhanced oil recovery (EOR) may be performed, as described below with reference to  FIGS. 6-8 , or re-stimulation of production sections  102  and  112 , or production section  112  alone, may be performed as described below with reference to  FIG. 5 . 
         [0025]      FIG. 5  is a schematic cross-sectional diagram of a portion of one of the lateral wellbores  100  with a production casing  101  in the production zone  14  completed using a method in accordance with a further aspect of the invention. In accordance with the invention, initial perforation and stimulation of each production section  102 ,  112  (see  FIG. 4 ) of the lateral wellbore  100  is carefully planned with consideration to the potential of re-stimulation the respective production sections  102 ,  112  at a later date when a second stimulation procedure may be used to extend a life of the production section(s)  102 ,  112 . Since re-stimulation must be done down a work string, which limits the flow rate of stimulation fluids, careful consideration must be given to the length of perforations that can be re-stimulated taking into account the distance of the production section  102 ,  112  from the wellhead, the diameter of the production casing  101 , which determines a diameter of the work string that may be used, pressure loss in the work string, etc. Consequently, unperforated intervals “uu” are left between perforated runs  140  where fractures  150  are created by stimulation fluids. The unperforated intervals “uu” are long enough to ensure that stimulation fluids are unlikely to migrate down a backside of the production casing  101  during the re-stimulation procedure as this could have detrimental effects that would require expensive remediation. 
         [0026]      FIG. 6  is a schematic-cross sectional diagram of the lateral hydrocarbon well  100  shown in  FIG. 4  configured for enhanced oil recovery (EOR) using the method in accordance with the invention. After section  112  has been produced, or substantially produced, EOR may be considered to extract remaining hydrocarbon from the production zone  14  in production sections  102 ,  112 . In accordance with one aspect of the invention EOR may be performed by removing the production tubing  108  and the packer  110  shown in  FIG. 4 . The plug  114  is also removed (see  FIG. 4 ). A work string  200  and packer  202  are then run into the well  100  until the packer  202  can be set in the unperforated interval “u” between production sections  102  and  112  where the plug  114  had been set. In one embodiment the work string  200  is the work string described in applicant&#39;s above-referenced U.S. patent application Ser. No. 14/735,846, though if the run through the lateral bore is not too long coil tubing or jointed tubing such as Hydril® PH6® may be used as the work string  200 . Once the packer  102  is set, an EOR flood fluid  210  such as, for example, carbon dioxide (CO 2 ), liquid nitrogen (LN 2 ), compressed natural gas (CNG), water (H 2 O), or brine is pumped from the surface down the work string  200 . The pressurized flood fluid enters the production zone  14  through the perforations in the production casing  101  of production section  102 . As the pressurized EOR flood fluid enters the production formation  14 , remaining hydrocarbon  220  is urged along a path of least resistance through the perforations in section  112  and up the annulus of the production casing  101  to the surface where it is produced through a production tubing  230  installed at the wellhead  240 . Using this method, EOR fluids are pumped into section  102  until the EOR flood fluid flows up the annulus of the production casing  101  to the wellhead  240 . 
         [0027]      FIG. 7  is a schematic-cross sectional diagram of the lateral hydrocarbon well  100  shown in  FIG. 4  configured in another way for EOR using the method in accordance with the invention. In this configuration, the production tubing  108  and the packer  110  are left in the well and EOR flood fluid  210  is pumped down the annulus through tubing  232  installed at the wellhead  240 . Since the production casing  101  is unperforated above production section  112 , the EOR flood fluid  210  is forced through the perforations in production section  112  into the production zone  14 . Hydrocarbons  220  in the production zone  14  are urged by the EOR flood fluid  210  along the path of least resistance through the perforations in production section  102 , where they enter the production casing  101 . The hydrocarbons  220  are contained by the packer  106  and are forced up the production tubing  108  to the surface. Generally after an initial production period, there is no longer enough downhole pressure to force hydrocarbons  220  to the surface whether under normal production conditions or under EOR. Consequently, a pump is required to move the hydrocarbons  220  to the surface, an example of which is explained below in more detail with reference to  FIG. 8 . 
         [0028]      FIG. 8  is a schematic cross-sectional diagram of a more detailed example of a lateral hydrocarbon well  100  configured for EOR in accordance with the invention.  FIG. 8  is not drawn to scale. As shown in  FIG. 8 , a lateral wellbore  100  with four production sections  102 ,  112 ,  133  and  144 . Each of the production sections  102 ,  112 ,  133  and  144  are separated by an unperforated region “u”. Each unperforated region “u” being at least one casing joint in length, as described above with reference to  FIG. 3 . In this example, all four production sections  102 ,  112 ,  133  and  144  have been perforated, stimulated and produced. The production tubing  108  and packer  106  are then pushed down the production casing  101  past production section  144  and the packer  106  is set in the unperforated region “u” between production sections  144  and  133 . As explained above with reference to  FIG. 7 , EOR flood  210  fluid is then pumped down the annulus from the wellhead  240  (see  FIG. 7 ). The EOR flood fluid  210  is forced through perforations in the production section  144  and into the production zone  14 . Hydrocarbons remaining in the production zone  14  are urged along a path of least resistance through the perforations in production sections  133 ,  112  and  102  and into the production casing  101 . The hydrocarbons  220  are lifted to the surface through the production tubing  108  by a plunger pump  260 . A sucker rod string  250  drives the plunger pump  260 , which is connected to the end of the production tubing  108 . The plunger pump  260  lifts the hydrocarbons  220  to the surface in a manner well known in the art. The sucker rod string is reciprocated by a balanced beam pump jack, commonly referred to as a “nodding donkey”, (not shown) in a manner well known in the art. 
         [0029]      FIG. 9  is a schematic diagram of lateral hydrocarbon wells drilled using methods in accordance with a further aspect of the invention. In accordance with this aspect of the invention hydrocarbon wells are concentrated on well pads  300   a - c , which are located in convenient and unobtrusive locations, such as public road allowances off main rural roads, or the like, to minimize environmental impact while maximizing year round access. Each pad accommodates at least 2 hydrocarbon wells. In this example, each well pad  300  accommodates 4 lateral wells  301 , though the number of wells  301  on a well pad  300  is a matter of design choice dependent on at least: location, formation boundaries, lease holder rights and investment funds. Each of the wells  301  on each well pad  300  may be drilled in succession or at different times. Each well  301  has a lateral wellbore  302  that is drilled as long as possible given the limitations of: lease holder rights, production zone boundaries, and lateral wellbore completion equipment and technology. Lateral wellbores  302  cross paths but do not directly intersect, to provide a “network” of drainage within the production zone. Since current completion technology permits the completion of very long lateral wellbores  300 , they may be used to extract hydrocarbons underlying surface features such as a lake or reservoir  320 ; a river  330 ; a city, town or village  340 ; farm land  350 ; forest or recreational land  360 ; wet land (not shown) or the like. The network of drainage provided by the lateral wellbores is also suitable for EOR, since once produced some of the lateral wellbores  102  can be used as EOR flood fluid wellbores while others are used as EOR production bores. 
         [0030]    The methods in accordance with the invention also permit an operator to close in a well when oil prices make production uneconomical. Once a currently producing section is depleted, it can be plugged and the well closed in until prices recover. Since the cased wellbore above the plug is not perforated, the well can be brought back online without any difficulty when oil prices recover to economic production levels. 
         [0031]    The invention has been described with specific reference to wellbores in excess of 8,000′. However, the invention is equally applicable to lateral wellbores that are less than 8,000′ long. The scope of the invention is therefore intended to be limited solely by the scope of the appended claims.