Patent Publication Number: US-2015060077-A1

Title: Integrated packer and fluid cross-over subassembly for gas injection and fluid removal in a well

Description:
FIELD OF THE INVENTION 
     In oil and gas production environments, wells often produce gases and liquids, the liquids having a higher density than the gases. If liquids are not produced out of the well&#39;s bore, they can accumulate and eventually their weight will act against innate pressure in the well&#39;s producing formation, and cause the well&#39;s production to slow or stop. Additionally, some produced liquids are valuable commodities, and producers would like to recover them to surface for further processing and sale. 
     BACKGROUND OF THE INVENTION 
     Deviated wellbores are a special example of this phenomenon, since an enormous surface area communicating from the production zone to the well&#39;s bore is provided along the horizontal section of the wellbore, at roughly the same elevation. This can exacerbate problems with removal of produced liquids, and as well can provide in essence a large bottom-hole reservoir of collected liquids (when compared to a non-deviated well). 
     DESCRIPTION OF PRIOR ART 
     In the prior art, quite a few techniques are available to remove fluids from a wellbore, including mechanical pumps, jet pumps, and of particular note, high velocity gas streams achieved by constraining the diameter or carrying volume of a production conduit within a well&#39;s bore so that exiting gas is forced to take the low-volume conduit to surface, resulting in a high velocity exit—those systems are aimed at causing the high-velocity exiting gases to carry comingled fluid with the gases in order to produce the fluids in the same high velocity stream. 
     A variation on that theme, which is proposed for use in a deviated or horizontal well production situation, is disclosed in U.S. Pat. No. 8,006,756 granted to Mazzanti (“Mazzanti &#39;756”). First, Mazzanti &#39;756 contains a discussion of a prior art gas lift system of the prior art in connection with its FIG. 2. Essentially, a narrow conduit or tubing string is inserted into the deviated well terminating at or above the deviation (where the wellbore bends toward horizontal). A packer is deployed to seal the annulus between the well&#39;s casing and the outer surface of the narrow conduit. Gas under pressure from surface is flowed down the annulus to above the packer, and can enter the narrow conduit through a gas lift valve. The pressurized gas comingles with fluids which have collected in the well&#39;s bore below the packer and upward into the narrowed conduit, and flows to surface bearing comingled fluids with it. 
     Mazzanti &#39;756 discloses an improved alternative, which provides for injection of pressurized gas into the production zone of the deviated wellbore well beyond the bend to horizontal through the central conduit of a concentrically arranged two-tube system. The outer tube is packed and sealed off to the casing above the bend, and pressurized gas is introduced through the inner conduit to the wellbore below the packer. This pressurized gas together with formation pressure is sufficient to force comingled gas and produced liquids up the well&#39;s bore via the annular space between the outer surface of the inner tube and the inner surface of the outer tube of the concentrically arranged tube system. This lift is used to raise liquids to a reservoir above the packer formed of the packer, the well&#39;s casing, and the outer surface of the concentrically arranged two-tube system, and then a conventional pump is used to raise liquids to surface. This is a complex multi-stage system. 
     SUMMARY OF THE INVENTION 
     The invention includes a subassembly for insertion in a production string inside a cased deviated well to permit the injection of pressurized gas down the annulus (between the outer wall of an inner or core conduit in the tubing and the inner wall of an outwardly concentrically deposed conduit or the wellbore&#39;s inner wall) of the string for substantially all of its vertical portion with a passageway communicating in a sealed fashion from the annulus into the central bore at or just below the point where the well is deviated (to horizontal); similarly, fluid flow from the wellbore&#39;s lower, deviated portion into the annulus including commingled pressurized gas delivered along the above passageway, flows uphole in that annulus to the crossover sub, where it is directed into the core passage in the tubing string. The advantage is that the higher velocity attained in the vertical portion upward bound more efficiently moves fluids out of the well to surface (including produced fluids) using the pressurized gas introduced during the operation; this occurs with the simultaneous advantage of efficient delivery of the high pressure gas to the lower end of the conduit inside the core tubing, permitting the operation to take place where the outer wall of the annulus is perforated or otherwise open to formation. 
     In an embodiment, a crossover subassembly is provided for inclusion in a production tubing stream in a well, comprising a body with an upper end with: (i) a first connection to an upper central tube above the body; (ii) a second connection to an annulus between the outer surface of the upper central tube and the inner surface of another conduit, which may be the well&#39;s casing or a secondary tubing string; and with a lower end with: (i) a third connection to a lower central tube below the body; and (ii) an opening or fourth connection to an annulus between the outer surface of the lower central tube and the inner surface of another conduit, which may be the well&#39;s casing or a secondary tubing string. The subassembly has: at least two passageways through the body: a first passageway communicating between the first connection and the opening or fourth connection; a second passageway communicating between the second connection and the third connection; and a packer or seal between the body and the well&#39;s casing or secondary tubing string, to isolate the wellbore above the subassembly from the wellbore below the subassembly. 
     Another embodiment provides a method for producing fluids from a deviated well with by injecting pressurized gas from surface down a conduit formed of an upper annulus between the outer surface of an upper central tubing string and the inner surface of a second conduit through which the central tubing string is strung, which may be the well&#39;s casing or a secondary tubing string from surface equipment to a seal between the outer surface of the upper central tubing string and the inner surface of a cross-over subassembly thus sealing the annulus to the inner wall of the second conduit at the subassembly, then through a passageway through the body of the cross-over subassembly to which the upper annulus is attached at the top of the subassembly in communication through the subassembly to a lower central tubing string extending into the deviated portion of the well&#39;s bore and then producing fluids from the deviated portion of the well&#39;s bore below the seal on the subassembly&#39;s body up the annulus between the inner surface of the well&#39;s bore where it is in communication with a formation through which the well was made and the outer surface of the lower central tubing string and then through a second passageway through the subassembly&#39;s body into the upper central tubing string and then to surface equipment. 
     Although the invention has been described in terms of preferred embodiments, those skilled in the art will recognize that modifications and changes may be made while remaining in the scope and spirit of the invention claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a schematic diagram, not to scale, showing flow-paths for introduced gas and produced fluids in a simple deviated wellbore. 
         FIG. 2  shows a diagram, not to scale, showing mechanical features, conduits and flow directions for introduced gas and produced fluids at the device of the invention (i.e. not “in situ” the well-bore) 
         FIGS. 3   a  and  3   b  show a cross-section of two examples of the cross-over subassembly of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     When lifting fluids from a horizontal well&#39;s horizontal portion of its bore, typically where the bore is open to production, using pressurized gas lift with gas under pressure from surface introduced to the well, it is desirable that the pressurized gas be delivered as deeply into the well as possible to mix and comingle with fluids collected in the bore for as much distance in the bore as possible. Since the well&#39;s bore may be open to the production zone over much of its length, this means it is desirable to have the pressurized gas delivered in a conduit such as a tube, and not in the annulus between a tubing string and the well&#39;s bore&#39;s face. 
     In this invention, in the deviated (horizontal) part of the well&#39;s bore we deploy a conduit  10  with its open bottom end  20  in communication with the wellbore  90  within its horizontal or deviated portion. Conduit  10  is at its top end  30  connected to and in communication with the crossover subassembly  50 . In operation, the crossover subassembly  50  will be sealed with a packer  55  to the casing  110  of the vertical portion of the wellbore (or to some functionally equivalent tubing string if the well has multiple completions—not shown). Within the crossover subassembly  50 , a passageway  60  which communicates with conduit  10  also communicates with the annular space above the packer  55  between the casing  110  and another tubing  70  to surface equipment (not shown). Similarly, a passageway  65  communicates between an upper tubing  70  and the annulus between the wellbore  90  and the outer surface of the lower conduit  10  below packer  55 . 
     As can be seen, high pressure gas from surface (downward arrows  80 ) flow from surface equipment (not shown) down the annulus between casing  110  and conduit  70  through packer  55  and subassembly  50  into conduit  10 , and then out the lower end of conduit  10  into the wellbore. There, the pressurized gas comingles with fluids in the horizontal portion of the wellbore  90  and flow toward surface in the annulus between the wellbore  90  and the outer surface of tubing  10 , into the subassembly  50  past packer  55  and into the upper conduit  70  (shown by arrows  85 ) to collection facilities at surface (not shown). This accomplishes two things: delivery of pressurized gas well into the horizontal portion of the wellbore  90 , and delivery up the vertical portion of the production string at high velocities in small-diameter tubing  70 .