Abstract:
A method of drilling a slim hole and inserting a slotted liner into such hole drilled in an underground reservoir using jet-drilling. The method enables jet-drilling to be effective in unconsolidated subterranean formations, such as some petroleum reservoirs. The method enables fluid injection or production to be undertaken on individual jet-drilled holes or on groups of holes drilled laterally at different vertical intervals in a vertical well within an underground formation.

Description:
RELATED APPLICATIONS 
       [0001]    Priority is claimed from U.S. Provisional Application 61/272,547 filed Oct. 5, 2009 entitled “Jet-Drilling And Completion Process” listing Conrad Ayasse as inventor. Such provisional application is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to a method for recovering hydrocarbons from a well bore, and more particularly to a method for drilling lateral recovery bores in a vertical well using jet-drilling. 
       BACKGROUND 
       [0003]    Jet-drilling is an established rock drilling method. Lateral holes ranging in diameter from about 0.5 inches to 3 inches or more are drilled out laterally from a vertical wellbore and can extend horizontally for up to 100 meters or more into the formation. For petroleum recovery, these holes provide reservoir fluid flow channels and can increase petroleum recovery rates from a reservoir or they can be used to improve fluid infectivity into a formation as in a water disposal well. Jet-drilled holes are left as ‘open holes’ which means that there is no liner placed in the hole. 
         [0004]    Typically a coiled tubing from the surface is attached to a “shoe” and the shoe is located at the desired side-entry point in a vertical well. The shoe is a curved opening that abuts the well wall and contains a curved opening. A steel-drilling bit is lowered through the coiled tubing from the surface and is sufficiently flexible the make the sharp 90° bend at the shoe to reach the well wall. The drilling bit is activated from the surface and drills out a hole in the steel well wall and through any outer cement that may be placed outside the wall. After the drilling bit is withdrawn, a jet-drilling nozzle is lowered inside the coiled tubing. The nozzle is attached to a slim flexible jet-fluid delivery tubing conduit that can carry a high-pressure jet-drilling liquid from the surface to the nozzle. The Jet-drilling fluid can be formation water which is delivered to the nozzle at high pressure in the range of up to approximately 15,000 psi. The fluid exits the nozzle at the tip and blasts a hole in the rock ahead of the nozzle, while also exiting backwards from the side of the nozzle to provide a forward propulsion force. This latter force pulls the entire assembly forward as the hole advances in the rock. It also washes drilling debris back to the horizontal well, where it falls to the bottom of the vertical wellbore. In some operations, the shoe can be quickly rotated and/or lowered to enable horizontal holes to be drilled horizontally in any desired direction and at low cost relative to traditional large-diameter horizontal well drilling. 
         [0005]    In a consolidated rock the jet-drilled holes are stable and permanent. However, in an un-consolidated rock the hole can collapse and be of little use, so a way is needed to stabilize jet-drilled holes in un-consolidated rock formations. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention solves the problem of borehole collapse in unconsolidated formations. 
         [0007]    The method of the present invention provides for Jet-drilled boreholes in un-consolidated subterranean formation which are stabilized and remain permanently open by using the forward drive energy of a jet nozzle to drag a perforated liner into the borehole while the borehole is being drilled. 
         [0008]    At the completion of the jet drilling the jet-drilling nozzle and jet-fluid delivery tubing can be left in the borehole, or the tubing can be detached from the nozzle and recovered at the surface. The perforated liner may extend to the surface or be severed inside the vertical well. The liner perforation dimensions are chosen to enable exclusion of formation solids while permitting entry of formation fluids. 
         [0009]    Accordingly, in a first broad aspect of the method of the present invention for creating a borehole extending perpendicularly outwardly from a well bore, such method comprises the steps of: 
         [0010]    placing a shoe comprising a 90 degree curved member having an inner arcuate curved passage, to which a one end is affixed coiled tubing, against a side wall of said well bore; 
         [0011]    inserting a drilling bit into said coiled tubing, and thereby deflecting said drilling bit via said shoe against said side wall of said well bore; 
         [0012]    operating said drilling bit to drill through said side wall in said well bore, and thereafter removing said drilling bit; 
         [0013]    directing a jet drill member and attached perforated liner member, in which is located a jetting fluid feed line to said jet drill member, through said coiled tubing; and 
         [0014]    supplying a fluid under pressure to said jet drill member to drill a lateral borehole extending perpendicularly outwardly from said well bore. 
         [0015]    In a further broad aspect of the method of the present invention of creating at least one lateral borehole extending perpendicularly outwardly from a pre-drilled vertical well bore drilled in an underground formation, such method comprises the steps of: 
         [0016]    attaching coil tubing to one end of a 90 degree curved member, said curved member having an inner arcuate curved passage, 
         [0017]    attaching an opposite end of said curved member against a side wall of said vertical well bore; 
         [0018]    inserting a drilling bit into said coiled tubing and into said curved member, and deflecting said drilling bit via said arcuate curved passage against said side wall of said well bore; 
         [0019]    operating said drilling bit to drill through said side wall in said vertical well bore, and thereafter removing said drilling bit from said curved member and said well bore; 
         [0020]    attaching a jet drill apparatus to a perforated liner member; 
         [0021]    locating a jetting fluid feed line co-axially within said perforated liner member, and coupling said fluid feed line to said jet drill apparatus so that said jet drill apparatus is in fluid communication therewith; 
         [0022]    directing said jet drill apparatus and attached perforated liner member, in which said jetting fluid feed line is co-axially located, through said coiled tubing and said curved member; and 
         [0023]    supplying a fluid under pressure to said jet drill apparatus via said jetting fluid feed line and drilling a lateral borehole extending perpendicularly outwardly from said vertical well bore. 
         [0024]    In yet a still further broad aspect of the method of the present invention of creating at least one lateral borehole extending perpendicularly outwardly from a pre-drilled vertical well bore drilled in an underground formation, such method comprises the steps of: 
         [0025]    attaching coil tubing to one end of a 90 degree curved member having an inner arcuate curved passage, 
         [0026]    attaching an opposite end of said curved member against a side wall of said vertical well bore; 
         [0027]    inserting a drilling bit into said coiled tubing and into said curved member, and deflecting said drilling bit via said arcuate curved passage against said side wall of said well bore; 
         [0028]    operating said drilling bit to drill through said side wall in said vertical well bore, and thereafter removing said drilling bit from said curved member and said well bore; 
         [0029]    coupling a jet drill apparatus to a jetting fluid feed line so as to be in fluid communication with each other; 
         [0030]    locating said jetting fluid feed line co-axially within a perforated liner member, and attaching said perforated liner member to said jet drill apparatus or said jetting fluid line so that said perforated liner member moves with said jet drill jet drill apparatus; and 
         [0031]    directing said jet drill apparatus and said perforated liner member in which said jetting fluid feed line is co-axially located, through said coiled tubing and said curved member; and 
         [0032]    supplying a fluid under pressure to said jet drill apparatus via said jetting fluid feed line and drilling a lateral borehole extending perpendicularly outwardly from said vertical well bore. 
         [0033]    In a refinement of each of the above methods, the method further comprising the step of detaching said jetting fluid feed line from said jet drill apparatus and removing said jetting fluid feed line from said lateral borehole. 
         [0034]    In an alternative refinement of each of the above methods, the method further comprises the step, after the step of supplying fluid under pressure to said jet drill member, of severing said coiled tubing at said side wall of said well bore. 
         [0035]    In a combination of refinements, the method of the present invention further comprises the steps, after the step of supplying fluid under pressure to said jet drill member and after the step of detaching said jetting fluid feed line from said jet drill member and removing said jetting fluid feed line from the lateral borehole, of severing said coiled tubing at said side wall of said well bore. 
         [0036]    Finally, in a further broad aspect of the invention, such invention comprises a method of recovering liquid hydrocarbons from an underground formation, comprising the steps of: 
         [0037]    (i) creating a vertical well; 
         [0038]    (ii) creating lateral boreholes extending perpendicularly outwardly from said vertical well by:
       (a) placing a shoe comprising a 90 degree curved member having an inner arcuate curved passage, to which at one end is affixed coiled tubing, against a side wall of said well bore;   (b) inserting a drilling bit into said coiled tubing, and thereby deflecting said drilling bit via said shoe against said side wall of said well bore;   (c) operating said drilling bit to drill through said side wall in said well bore, and thereafter removing said drilling bit;   (d) directing a jet drill member and attached perforated liner member, in which is located a jetting fluid feed line to said jet drill member, through said coiled tubing; and   (e) supplying a fluid under pressure to said jet drill member to drill a lateral borehole extending perpendicularly outwardly from said well bore;       
 
         [0044]    (iii) allowing hydrocarbons to flow into said lateral boreholes; and 
         [0045]    (iv) pumping said hydrocarbons to surface. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0046]    Further advantages and permutations will appear from the following detailed description of various non-limiting embodiments of the invention, taken together with the accompanying drawings, in which: 
           [0047]      FIG. 1  is a schematic view of a jet drilling apparatus being used in the method of the prior art, with a jet nozzle being used to drill toward the left-hand side of the page; 
           [0048]      FIG. 2  is a schematic view of a jet-drilling apparatus being used in the method of the present invention, showing the manner of inserting a perforated liner into a horizontal well bore utilizing a jet nozzle, with a jet nozzle being used to drill toward the left-hand side of the page; 
           [0049]      FIG. 3  is a schematic view of the completion of the vertical well when the perforated liners are terminated at the vertical well; 
           [0050]      FIG. 4  is a schematic view of a plurality of horizontally-drilled holes in a vertical well, each of said horizontal bores having a perforated liner; and 
           [0051]      FIG. 5  is a detail view of a single horizontal well of  FIG. 4  which has been drilled by the method of the present invention, showing a perforated liner being introduced to the horizontal wellbore during the jet-drilling process. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0052]    Similar items in each of  FIGS. 1-5  with identical function are identified with the same reference number. 
         [0053]      FIG. 1  shows a jet-drilling nozzle  1  being used in the jet-drilling method of the prior art, typically reserved for consolidated formations, having a jet-fluid delivery tube  2 , which is caused to create a hole  10  in a formation  20 . 
         [0054]    Interstitial space  3  within hole  10  conducts fluids to surface (not shown) when the hole  10  is stable, such as for consolidated rock, but which hole  10  will become blocked with the collapse of the hole when rock in the formation  20  is unconsolidated. 
         [0055]    In operation, jetting fluid  4  exits the front of the nozzle  1  and blast the rock in formation  20  to create an open hole  10 . Jetting fluid  5  which exits the nozzle  1  from the side of nozzle  1  creates a forward drive force that pulls nozzle  1  and the jet-fluid delivery tube  2  forward, while simultaneously flushing the drilling debris back along open interstitial space  3  to a vertical well  12  where it can fall to a sump. 
         [0056]      FIG. 2  shows the method of the present invention for drilling a bore  10  in a formation using a jet-drilling nozzle  1  and jet-fluid delivery tubing  2 , while simultaneously inserting a perforated well liner  6  into the resulting bore  10  in formation  20 . Perforated liner  6  is attached directly or indirectly to jet-nozzle  1 . Again, in operation, jetting fluid  4  exits the front of the nozzle  1  and blasts rock in formation  20  to create an open hole  10 . Jetting fluid  5  which exits the nozzle  1  from the side of nozzle  1  creates a forward drive force that pulls nozzle  1  and the jet-fluid delivery tube as well as the perforated liner  6  attached to the jet-nozzle  1  forward, while simultaneously flushing the drilling debris back along open interstitial space  3  to a vertical well  12  where it can fall to a sump. 
         [0057]    Perforated liner  6  is of a design that will permit the entry of fluids, such as liquid hydrocarbons, but not solids. Such design may comprise a series of small apertures or perforations within perforated liner  6 , or a combination of apertures in combination with screens (not shown). However, other designs of perforated liners  6  may be used as are known to persons of skill in the art. A fluid flow space  7  inside the perforated liner  6 , for delivering produced fluids to the vertical well  12  and thence to the surface, is provided. This fluid flow space  7  is enlarged upon the (optional) detachment of jet-fluid delivery tubing  2  from jet nozzle  1  and removal of the jet-fluid delivery tubing  2  to surface at the completion of the borehole drilling and liner insertion process. 
         [0058]    Referring to  FIG. 2  and  FIG. 3 ,  FIG. 3  depicts a completed vertical well  12 , having a series of individual separate left-side lateral bores  10  each with an associated perforated liner  6  and a similar series of individual separate right-side lateral bores  10 , each likewise having an associated perforated liner  6 . Each of lateral bores  10  and the respective associated perforated liners  6  terminate at the vertical well  12 . In order for this to have occurred, after the step of terminating the supply of the jet fluid  4 , 5  to the jet drilling nozzle  1  upon each lateral borehole  10  being drilled, the jet drill nozzle  1  is decoupled from the jet fluid delivery tubing  2  via known methods such as unscrewing, or decoupling via a “on-off” tool (not shown), and the jet fluid delivery tubing  2  is removed from the borehole  10 , leaving the perforated liner  6  remaining in borehole  10 . Packers  30 ,  32 , and  34  isolate various zones A, B, C and D respectively in vertical well bore  12 . Hydrocarbons flowing into boreholes  10  are collected in respective isolated zones A, B, C, and D of vertical wellbore  12 . Feeding tubes B′, C′, and D′ deliver fluids to surface from respective zones B, C, and D. 
         [0059]    Perforated liner  6  will be of sufficient material strength and thickness to resist collapse of unconsolidated rock in a borehole  10 . For such reason liner  6  will typically be of a hard, but somewhat flexible material, such as Kevlar, to permit bending from the vertical to the horizontal. In some cases steel may need to be used in instances where it is desired that fluid flow into borehole  10  via such liner  6  for subsequent collection, particularly if borehole diameter is small and liner  6  must accordingly be as thin as possible to preserve borehole diameter and at the same time have numerous and sufficiently-sized perforations to allow ingress of fluid. However the perforations are of insufficient size and number to weaken the liner  6  to a sufficient extent that liner  6  has insufficient strength to substantially resist collapse due weight of to unconsolidated rock in formation  20 . 
         [0060]      FIG. 4  is a view of a vertical well  12  similar to the vertical well  12  of  FIG. 3 , but without the use of packers  30 ,  32 , or  34 , having similar lateral boreholes  10 . Jet drilled boreholes  10  within vertical well  12 , permit the separate injection of fluids into formation  20  via coil tubing  40 , or alternatively permit the flow of fluids from the formation  20  through perforated liners in boreholes  6 , through curved arcuate “shoes”  42 , and thereafter via coil tubing  40  to surface. 
         [0061]      FIG. 5  is a detailed view of a borehole  10  shown in  FIG. 4  at the time of drilling is the borehole  10  of  FIG. 4 , and is perhaps best illustrative of the method of the present invention for creating lateral boreholes  10  extending perpendicularly outwardly from a well bore  12 . 
         [0062]    In this regard  FIG. 5  shows a vertical well  12  drilled in subterreanean formation  20 . Shoe  42 , having coil tubing  42  attached thereto has been placed against the steel vertical well side wall  12 ′ of vertical well  12  at the desired entry point during the initial drilling of aperture  16  in steel vertical well side wall  12 ′ (as described below). Perforated liner  6  is coupled to an non-perforated liner segment  50 , which may extend to surface within coil tubing  40 , to collect liquid hydrocarbons which may have drained into borehole  10 . 
       Example 1 
       [0063]    The method of the invention in creating a borehole in a non-consolidated rock formation  20  will now be described, with reference to  FIG. 5 . 
         [0064]    Firstly, in order to ready the vertical well  12  for the borehole drilling operation shown in  FIG. 5  an initial first series of steps of creating an aperture  16  in the side of a vertical well  12  is carried out, and is hereinafter described as follows. 
         [0065]    A shoe  42 , which is affixed at the end of a coiled tubing  40 , is placed against the steel vertical well side wall  12 ′ of vertical well  12  at the desired entry point. Shoe  42  is a steel device having a 90 degree curved inner arcuate passage  43 , as shown in  FIG. 5 . A drilling bit (not shown), typically of steel or titanium-coated steel, is lowered from the surface into the coiled tubing  40  and is deflected at the shoe  42  from the vertical to the horizontal direction. The steel drilling bit drills out an aperture  16  through the vertical well steel sidewall  12 ′ and through any cement that may have been emplaced outside vertical well  12 , and reaches into the rock formation  20 . The steel drilling bit is thereafter retracted, and the assembly described in  FIG. 1 , namely a jet nozzle  1  with a jet fluid delivery tube  2 , and an attached perforated liner  6 , is lowered into the coiled tubing  40  for the purpose of jet-drilling a horizontal borehole  10  in formation.  20 , extending perpendicularly outwardly from vertical well  12 . The jet-drilling assembly comprising high-pressure jet nozzle  1  with an attached jetting liquid delivery tubing  2  permits the nozzle  1  to spray liquid  4 ,  5  in two main directions: ahead with liquid spray  4  to pulverize rock and create a borehole  10 , as well as direct liquid spray  5  sideways and backwards to provide a driving force that moves the jet nozzle  1 , jetting fluid delivery tubing  2 , and attached perforated liner  6  forward and into borehole  10 , while simultaneously flushing drilling debris back towards the vertical well  12  along coiled tubing  40 , and to surface or to a sump in the vertical well. Drilling pressures with respect to supplied fluid  4 , 5  may be up to 15,000 psi or even higher. 
         [0066]    In the operation of this invention, perforated liner  6  is attached at or nearby the jet nozzle  1  as shown in  FIGS. 2 and 5 . Liner  6  and jetting-liquid delivery tubing  2  which is inside the liner  6  are fed in at the surface as the assembly of nozzle  1 , jetting-liquid feed line  2  and perforated liner  6  simultaneously advance in the borehole  10  while jet-drilling. 
         [0067]    When the jet-drilling is completed, there are several choices. 
         [0068]    Firstly, the jet drilling assembly comprising the jet nozzle  1 , jetting fluid delivery tubing  2 , and perforated liner  6  can be left in the borehole  10 , and the liner  4  and coiled tubing  40  can be put on production at the surface. Any borehole hole collapse will be limited by the perforated liner and fluids which enter the liner  6  and flow to the surface or to a pump placed downhole. The jetting fluid delivery tubing  2  inside liner  6  provides only minor obstruction to fluid flow in either direction since there will remain ample open fluid flow area  7  inside the liner  6 . 
         [0069]    Alternatively, in a more preferred embodiment, the jetting-liquid delivery tubing  2  is detached from nozzle  1  as described above, or alternatively by a break-away device or procedure such as strong pulling on the delivery tubing  2 . This will leave the liner  6  completely clear, and the shoes  42  can also be removed. Therefore the invention can be employed for fluid production from a reservoir  20  or for fluid injection as may occur in water disposal, and it may be employed in both consolidated rock or un-consolidated rock. The material of construction for the liner  6  must have sufficient strength to hold back sand from borehole collapse and sufficient flexibility to make the sharp turn from vertical to horizontal at the shoe  42 . A number of materials are candidates, such as steel mentioned above, but also perforated Kevlar tubing, particularly where fluid (such as water) is being supplied to borehole  10  and not being withdrawn. In order to maintain maximum strength a favored embodiment for perforation is small holes of a size appropriate to exclude sand or other grains, but to permit fluid passage. The methodologies for determining the maximum perforation size are well known to those skilled in the art. 
         [0070]      FIG. 3  shows the embodiment wherein the coil tubing  40  and shoe  42  (see  FIG. 5 ) is severed at the vertical well  12 . Fluids entering the vertical wellbore  12  from boreholes  10   a  &amp;  10   b  admix in the annular space of the vertical well  12  with access to the surface. These fluids are segregated from others by a packer  30 . Fluids entering from holes  10   c  &amp;  10   d  are admixed in annular space B, and can rise to the surface via tubing B′ and are segregated by packers  30  &amp;  32 . Fluids entering from boreholes  10   e  and  10   f  admix in annular area C, and get to the surface via tubing C′ and are segregated by packers  32  &amp;  34 . Finally, fluids entering vertical well  12  via boreholes  10   g  and  10   h  admix in annular area D, and get to the surface via tubing D′, and are segregated by packer  34  and the bottom of the vertical well  12 ″. Therefore segregated fluid flow to and from multiple zones A, B, C, and D can be achieved, even in un-consolidated or poorly-consolidated formations. This can be exploited in certain enhanced oil recovery processes. For example in a gravity-stable miscible gas flooding project, solvent gas can be injected in an upper zone and oil produced from a lower zone. 
       Example 2 
       [0071]    A preferred embodiment for maximizing the oil recovery rate at low cost is to eliminate the packers  30 ,  32 , &amp;  34  and tubings B′, C′ and D′ shown in  FIG. 3  and let fluids flow into the wellbore  12  from all boreholes  10   a - 10   f . The mixture can then be pumped to the surface via a standard production tubing. The jet-liquid feed line  2  can be pulled out and the perforated liner  6  cut at the intersection of the vertical well bore  12  and borehole  10 , or such feed line  2  can be left in place. 
       Example 3 
       [0072]    In this example, as shown in  FIG. 4  and  FIG. 5 , the shoe  42  and coiled tubing  40  assembly is retained after creation of aperture  16  and drilling of boreholes  10 , and each liner  6  that is emplaced in the jet-drilled borehole  10  while drilling thereby retains direct access via coil tubing  40  to the surface. The jet-liquid feed line  2  can be left in the liner  6  or removed as described in Example 1. Details of this embodiment are shown in  FIGS. 4 and 5 . This embodiment provides the greatest flexibility because every jet-drilled wellbore  10  is individually accessible and can have many uses. This configuration eliminates the need for downhole packers. 
         [0073]    Although the disclosure describes and illustrates preferred embodiments of the method of the present invention, it is understood that the invention is not limited to these particular embodiments. Many variations and modifications will now occur to those skilled in the art. For a full definition of the invention, reference is to be made to the appended claims.