Abstract
A well system and method including applying suction to a wellhead housing outlet (8) to divert the flow of subterranean gas from flowing through a gas conduit through the wellhead housing (4). An operation can then safely be performed on a component (e.g. removing a hanger) of the wellhead apparatus. Well gas can be diverted to a flare system (200). Suction can be applied by a venturi system including eductors (104, 106). The method may include opening the gas conduit outlet once a pressure sensed at the conduit outlet is negative. Suction may also be applied to an upper outlet (14).
Claims
1. A method of controlling the flow of gas within a well system in gaseous communication with subterranean gas exiting a well bore, wherein the well system comprises: a wellhead apparatus, wherein: the wellhead apparatus defines a first gas conduit comprising a bottom end in gaseous communication with the subterranean gas exiting the well bore, and a top end distal the bottom end; wherein the first gas conduit is open to the atmosphere; the wellhead apparatus comprises a wellhead housing at the first gas conduit bottom end, wherein the wellhead housing is connected to the well bore, wherein the wellhead housing comprises at least one wellhead housing outlet, wherein the portion of the first gas conduit defined by the wellhead housing has a second end distal the first gas conduit bottom end, and wherein the at least one wellhead housing outlet is in gaseous communication with the first gas conduit intermediate said bottom end and said second end; and the wellhead apparatus comprises at least one upper outlet in gaseous communication with the first gas conduit intermediate the at least one wellhead housing outlet and the top end; the wellhead apparatus comprises a blowout preventer intermediate the wellhead housing and the at least one upper outlet, wherein the blowout preventer defines a portion of the first gas conduit; at least a portion of the exterior of the blowout preventer and/or the wellhead housing is exposed to the atmosphere; wherein the well system comprises a suction source in gaseous communication with the at least one wellhead housing outlet and the at least one upper outlet for applying suction to the at least one wellhead housing outlet and/or the at least one upper outlet to divert the flow of subterranean gas within the first gas conduit to the at least one wellhead housing outlet and/or the at least one upper outlet; the method comprising the step of: applying suction with the suction source to the at least one wellhead housing outlet and/or the at least one upper outlet to divert the flow of subterranean gas within the first gas conduit to the at least one wellhead housing outlet and/or the least one upper outlet to thereby control the flow of gas within the wellhead apparatus.
2. The method of claim 1, wherein the step of applying suction to the at least one wellhead housing outlet and/or the at least one upper outlet results in substantially no subterranean gas exiting to the atmosphere via the first gas conduit top end.
3. The method of claim 1, wherein the suction is applied by a venturi system comprising at least one eductor.
4. The method of claim 3, wherein the subterranean gas is diverted to a flare system connected to the venturi system.
5. The method of claim 1, wherein the wellhead apparatus further comprises at least one spool, wherein the at least one spool defines a portion of the first gas conduit, and wherein the at least one spool comprises the at least one upper outlet, the method comprising the step of: applying suction to the at least one wellhead housing outlet and to the at least one upper outlet to thereby divert the flow of subterranean gas within the first gas conduit to the at least one wellhead housing outlet and the at least one upper outlet to thereby control the flow of gas within the wellhead apparatus.
6. A well system comprising: a wellhead apparatus, wherein: the wellhead apparatus defines a first gas conduit comprising a bottom end in gaseous communication with subterranean gas exiting a well bore and a top end distal the bottom end, wherein the first gas conduit is open to the atmosphere; the wellhead apparatus comprises a wellhead housing at the first gas conduit bottom end, wherein the wellhead housing is connected to the well bore, wherein the wellhead housing comprises at least one wellhead housing outlet, wherein the portion of the first gas conduit defined by the wellhead housing has a second end distal the first gas conduit bottom end, and wherein the at least one wellhead housing outlet is in gaseous communication with the first gas conduit intermediate said bottom end and said second end; and the wellhead apparatus comprises at least one upper outlet in gaseous communication with the first gas conduit intermediate the at least one wellhead housing outlet and the top end; the wellhead apparatus comprises a blowout preventer intermediate the wellhead housing and the at least one upper outlet, wherein the blowout preventer defines a portion of the first gas conduit; at least a portion of the exterior of the blowout preventer and/or the wellhead housing is exposed to the atmosphere; a suction source in gaseous communication with the at least one wellhead housing outlet and the at least one upper outlet for applying suction to the at least one wellhead housing outlet and/or the at least one upper outlet to divert the flow of subterranean gas within the first gas conduit to the at least one wellhead housing outlet and/or the at least one upper outlet.
7. The well system of claim 6, wherein the system is configured so that substantially no subterranean gas exits to the atmosphere via the first gas conduit top end.
8. The well system of claim 6, wherein the suction source is a venturi system comprising at least one eductor.
9. The well system of claim 8, wherein the well system further comprises a flare system for receiving subterranean gas from the venturi system, wherein the flare system is in gaseous communication with the venturi system.
10. The well system of claim 9, wherein the flare system comprises a knock-out drum.
11. The well system of claim 6, wherein the wellhead apparatus further comprises at least one spool, wherein the at least one spool defines a portion of the first gas conduit, wherein the at least one spool comprises the at least one upper outlet.
12. The method of claim 1, wherein the method of controlling the flow of gas within a well system is a method of performing a well operation on a component of the well system, wherein the step of applying suction with the suction source to the at least one wellhead housing outlet and/or the at least one upper outlet is to divert the flow of gas within the first gas conduit such that substantially no subterranean gas exits to the atmosphere via the first gas conduit top end, the method further comprising the step of: performing an operation on the component of the well system.
13. A method of opening a wellhead apparatus to the atmosphere, wherein the wellhead apparatus is part of a well system comprising: (i) the wellhead apparatus, wherein: the wellhead apparatus defines a first gas conduit comprising a bottom end in gaseous communication with subterranean gas exiting a well bore, and a top end distal the bottom end; wherein the first gas conduit is closed to the atmosphere; the wellhead apparatus comprises a wellhead housing at the first gas conduit bottom end, wherein the wellhead housing is connected to the well bore, wherein the wellhead housing comprises at least one wellhead housing outlet, wherein the portion of the first gas conduit defined by the wellhead housing has a second end distal the first gas conduit bottom end, and wherein the at least one wellhead housing outlet is in gaseous communication with the first gas conduit intermediate said bottom end and said second end; and the wellhead apparatus comprises at least one upper outlet in gaseous communication with the first gas conduit intermediate the at least one wellhead housing outlet and the top end; the wellhead apparatus comprises a blowout preventer intermediate the wellhead housing and the at least one upper outlet, wherein the blowout preventer defines a portion of the first gas conduit; at least a portion of the exterior of the blowout preventer and/or the wellhead housing is exposed to the atmosphere; (ii) a suction source configured to apply suction to the at least one wellhead housing outlet and/or the at least one upper outlet, and a pressure sensor for sensing the pressure within the first gas conduit; the method further comprising the steps of: applying suction to the at least one wellhead housing outlet and/or the at least one upper outlet; sensing the pressure within the first gas conduit with the pressure sensor; and once the pressure sensed with the pressure sensor is negative, opening the first gas conduit to the atmosphere at a point distal to the well bore.
14. A method of removing a hanger in a well system, wherein the well system comprises: (i) a wellhead apparatus including: a wellhead housing and a hanger, wherein the wellhead housing is in gaseous communication with subterranean gas exiting a well bore, wherein the wellhead housing is connected to the well bore, and wherein the wellhead housing comprises a first gas conduit and at least one wellhead housing outlet, wherein the first gas conduit has a first end in gaseous communication with the subterranean gas exiting the well bore and a second end distal the first end closed to the atmosphere, and the at least one wellhead housing outlet is in gaseous communication with the first gas conduit intermediate said first and second ends, wherein the hanger is positioned within the first gas conduit, and wherein at least a portion of the exterior of the wellhead housing is exposed to the atmosphere; and (ii) a suction source configured to apply suction to the at least one wellhead housing outlet, and a pressure sensor for sensing the pressure at the at least one wellhead housing outlet, wherein the method further comprises the steps of: applying suction to the least one wellhead housing outlet; sensing the pressure at the at least one wellhead housing outlet with the pressure sensor; once the pressure sensed by the pressure sensor is negative, opening the first gas conduit to the atmosphere at a point distal to the well bore; mounting a blowout preventer relative to the wellhead housing, and mounting at least one spool relative to the blowout preventer, wherein the at least one spool provides at least one upper outlet in gaseous communication with the first gas conduit; connecting the at least one upper outlet to the suction source, and applying suction to the at least one upper outlet; and removing the hanger from the wellhead apparatus.
15. The method of claim 1, wherein the method of controlling the flow of gas within a well system is a method of landing a hanger assembly in a well system, wherein the wellhead apparatus defines a hanger landing position within the first gas conduit which is intermediate the at least one wellhead housing outlet and the at least one upper outlet; wherein the method further includes the steps of: a. lowering a hanger assembly into the first gas conduit to its landing position, wherein the hanger assembly comprises a hanger and a hanger landing tool; b. decreasing the suction applied at the at least one upper outlet to thereby pull the hanger assembly into position via the at least one wellhead housing outlet until substantially no suction is applied through the at least one upper outlet; and c. holding the hanger assembly in place.
16. The method of claim 3, wherein the venturi system comprises at least a first suction system and a second suction system, wherein the first suction system is configured to apply suction to the at least one wellhead housing outlet, and the second suction system is configured to apply suction to the at least one upper outlet.
17. The method of claim 16, wherein the first suction system includes at least one choke manifold for controlling a pressure differential within the system.
18. The method of claim 1, wherein the wellhead apparatus further comprises one or more of: a ball valve, a mud cross, a tubing spool, a casing spool and an eductor spool.
Description
BRIEF DESCRIPTION OF DRAWINGS
(1) Examples of the invention will now be described by way of example with reference to the accompanying Figures, in which:
(2) FIG. 1 illustrates a first exemplary wellhead apparatus;
(3) FIG. 2 illustrates a second exemplary wellhead apparatus;
(4) FIG. 3 illustrates a first exemplary well system including the wellhead apparatus illustrated in FIG. 1;
(5) FIG. 4 illustrates a second exemplary well system including the wellhead apparatus illustrated in FIG. 2;
(6) FIG. 5 provides a schematic of a third exemplary well system;
(7) FIG. 6 provides a schematic of a fourth exemplary well system;
(8) FIG. 7 provides a schematic of a fifth exemplary well system;
(9) FIG. 8 provides a layout of a sixth exemplary well system;
(10) FIG. 9 provides a layout of a seventh exemplary well system;
(11) FIG. 10 provides a layout of the well system shown in FIG. 9;
(12) FIG. 11 provides a perspective view of the venturi system between the well head apparatus and the flare system of the well system shown in FIG. 9;
(13) FIG. 12 provides a perspective view of an exemplary flare system, when collapsed for towing;
(14) FIG. 13 provides a perspective view of the flare system of FIG. 13, as assembled;
(15) FIG. 14 provides a layout of an eighth exemplary well system;
(16) FIG. 15 provides a layout of a ninth exemplary well system;
(17) FIG. 16 provides a cross sectional view through an exemplary wellhead apparatus when landing a hanger;
(18) FIG. 17 provides a cross sectional view through an exemplary wellhead apparatus when landing a hanger;
(19) FIG. 18 provides a cross sectional view through an exemplary wellhead apparatus after the hanger has landed; and
(20) FIG. 19 provides a layout of a tenth exemplary well system.
(21) Preferred features, embodiments and variations of the invention may be discerned from the following Description which provides sufficient information for those skilled in the art to perform the invention. The following Description is not to be regarded as limiting the scope of the preceding Summary of the Invention in any way.
DESCRIPTION OF EMBODIMENTS
(22) Embodiments of the invention will now be described with reference to FIGS. 1 to 19. In the figures, like reference numerals refer to like features.
(23) Two wellhead apparatuses 1 are illustrated in FIGS. 1 and 2. The apparatus 1 of FIGS. 1 and 2 includes a wellhead housing 4 in gaseous communication with subterranean gas exiting a well bore 2. The wellhead housing 4 includes a first gas conduit 6 having a first end 7 in gaseous communication with the subterranean gas exiting the well bore 2 and a second end 9 distal the first end, and at least one wellhead housing outlet (or second gas conduit) 8 in gaseous communication with the first gas conduit 6 intermediate the first and second ends 7, 9. The at least one wellhead housing outlet (or second gas conduit) 8 extends perpendicularly to the longitudinal axis of the first gas conduit 6 and is in register with the first gas conduit 6. The wellhead housing 4 is in register with the well bore 2.
(24) As illustrated in FIGS. 1 and 2, the wellhead apparatus 1 also includes a blowout preventer (BOP) 10, and a number of spools including eductor spool 12 (eductor spool 12 is a spool having one transverse outlet). The first gas conduit 6 extends through the well head apparatus 1, passing through the BOP 10 and the eductor spool 12. Each of the wellhead housing 4, BOP 10 and eductor spool 12 are substantially in the form of an annulus, defining a central bore which provides the first gas conduit 6. The first gas conduit 6 is open to the atmosphere, as the eductor spool 12 is not capped. The wellhead apparatus 1 includes a bottom end 7 (which is also the wellhead housing first end), and a top end 11.
(25) At least one upper outlet (or third gas conduit) 14 is provided by the eductor spool 12 outlet, and the at least one upper outlet (or third gas conduit) 14 is in gaseous communication with the first gas conduit 6. The at least one upper outlet (or third gas conduit) 14 extends perpendicularly to the longitudinal axis of the first gas conduit 6 and is in register with the first gas conduit 6. The at least one upper outlet (or third gas conduit) 14 is located on the apparatus 1 distal to the wellbore 2 intermediate the at least one wellhead housing outlet (or second gas conduit) 8 and the wellhead apparatus top end 11.
(26) In FIG. 1, the wellhead housing 4 is a 2 kpsi wellhead housing 4 in two sections (the first section is typically about 180 mm long, and the second section about 533 mm long). Connected to the wellhead housing 2 is a crossover spool 16 (2 kpsi to 3 kpsi. The crossover spool 16 is typically about 230 mm long). Connected to the crossover spool 16 is a drilling spool 18 (3 kpsi. The drilling spool 18 typically includes a test port, and the spool 18 is typically about 305 mm long). Connected to the drilling spool 18 is BOP 10 (a 7 1/16″ blind ram, the BOP 10 is typically 270 mm long). Connected to the BOP 10 is spool 20 (a 7 1/16″ torus style annular, typically 534 mm long). Connected to spool 20 is an eductor spool 12 (made from a 9⅝″ casing with a 6″ low pressure side outlet flange which provides the at least one upper outlet (or third gas conduit) 14).
(27) In FIG. 2, the wellhead housing 4 includes 2″ side outlets (which provide the at least one wellhead housing outlet (or second gas conduit) 8). The wellhead housing 4 is typically about 500 mm long. Connected to the wellhead housing 4 is an adaptor spool 22 to connect the wellhead 4 to the BOP 10 (the adaptor spool is typically about 300 mm long). Connected to the adaptor spool 22 is a BOP 10 (a 11″ 3000 psi Dual Gate Ram or a 11″ 300 psi Single Gate Ram. The BOP 10 may include a test port. The BOP 10 is typically about 1000 mm long). Connected to the BOP 10 is an eductor spool 12 (made from a 9⅝″ casing with a 6″ low pressure side outlet flange which provides the at least one upper outlet (or third gas conduit) 14).
(28) FIGS. 3 and 4 illustrate well systems 100 including the wellhead apparatuses 1 illustrated in FIGS. 1 and 2. The well systems 100 each include a wellhead apparatus 1, a venturi system 102 and a flare system 200.
(29) Referring to FIG. 3, the venturi system 102 includes a first eductor 104 configured to apply suction to the at least one wellhead outlet (or second gas conduit) 8. In FIG. 3, the first eductor 104 is a 2″ Schutte & Koerting Style Eductor valve. The venturi system 102 also includes a second eductor 106 configured to apply suction to the at least one upper outlet (or third gas conduit) 14. In FIG. 3, the second eductor 106 is a 10″ Mathena Style Eductor valve. The venturi system 102 also includes at least one fluid compressor 110 configured to provide fluid to the first and second eductors 104, 106 to thereby provide a venturi effect. The fluid compressor 110 illustrated in FIG. 3 is a 900 Standard Cubic Feet per Minute Air Compressor. The system 100 illustrated in FIG. 3 also includes valves, including back pressure valve 112, and air choke manifolds 114 and 116. Air choke manifold 116 is adapted for high pressures. An 8″ blooie line connects to the at least one upper outlet (or third gas conduit) 14 (at eductor spool 12), and a 2″ bleed line connects the first eductor 104 to flare system 200. Flare system 200 includes a flare stack 202 and a flame arrestor 204. In FIG. 3, the venturi system 102 includes a first suction system 180 and a second suction system 190. The first suction system 180 includes an inlet at the at least one wellhead outlet 8 and an outlet at flare system 200. The first suction system 180 includes air choke manifold 116, and first eductor 104. The second suction system 190 includes an inlet at the at least one upper outlet 14 and an outlet at the flare system 200. The second suction system 190 includes second eductor 106.
(30) Referring to FIG. 4, the venturi system 102 includes a first eductor 104 configured to apply suction to the at least one wellhead housing outlet and the at least one upper outlet (or the second and third gas conduits) 8, 14. In FIG. 4, the first eductor 104 is a Mathena Style Valve. The first eductor 104 is able to apply suction to the at least one wellhead housing outlet and the at least one upper outlet (or the second and third gas conduits) 8, 14 through three point connector 122. The venturi system 102 also includes at least one fluid compressor 110 configured to provide fluid to the first eductor 104 to thereby provide a venturi effect. The fluid compressor 110 illustrated in FIG. 4 is a 900 Standard Cubic Feet per Minute Air Compressor. The system 100 illustrated in FIG. 4 also includes valves, including back pressure valve 112, air choke manifolds 114 and 116, and in line chokes 118 and 120. Air choke manifold 116 is adapted for high pressures. The outlet of the first eductor 104 is connected to flare system 200. Flare system 200 includes a flare stack 202, a flame arrestor 204 and a flare 206. The venturi system 102 includes a first suction system 180, a second suction system 190 and a third suction system 195. The first suction system 180 includes an inlet at the at least one wellhead outlet 8 and an outlet at the choke 120. The first suction system 180 includes air choke manifold 116 and choke 120. The second suction system 190 includes an inlet at the at least one upper outlet 14, and an outlet at the choke 118. The second suction system 190 includes choke 118. The third suction system 195 includes an inlet at the chokes 118 and 120, and an outlet at the flare system 200. The third suction system 195 includes connector 122, and first eductor 104.
(31) FIG. 15 illustrates the same well system 100 as shown in FIG. 4, except the well system 100 of FIG. 15 does not include an eductor spool 12, at least one upper outlet (or third gas conduit) 14, conduit extending between third gas conduit 14 and choke 118 (or second suction system 190), and BOP 10.
(32) FIG. 14 illustrates a simpler well system 100 including a wellhead apparatus 1, a venturi system 102 and a flare system 200. The venturi system 102 includes a first eductor 104 configured to apply suction to the at least one wellhead outlet (or second gas conduit) 8. In FIG. 14, the first eductor 104 is a 2″ Schutte & Koerting Style Eductor valve. The venturi system 102 also includes at least one fluid compressor 110 configured to provide fluid to the first eductor 104 to thereby provide a venturi effect. The fluid compressor 110 illustrated in FIG. 14 is a 900 Standard Cubic Feet per Minute Air Compressor. The system 100 illustrated in FIG. 14 also includes valves, including back pressure valve 112, and air choke manifolds 114 and 116. Air choke manifold 116 is adapted for high pressures. A 2″ bleed line connects the first eductor 104 to flare system 200. Flare system 200 includes a flare stack 202 and a flame arrestor 204. The venturi system 102 includes a first suction system which includes first eductor 104, valve 112 and manifolds 114 and 116.
(33) FIG. 19 illustrates a further well system 100, including a wellhead apparatus 1, a venturi system 102 and a flare system 200. In FIG. 19, the wellhead housing 4 is formed in two parts, with a spool situated directly below the BOP 10. The spool in the wellhead housing 4 includes a further wellhead housing outlet 8 (this outlet 8 is not connected to a pipe or line in the Figure), to provide a total of three wellhead housing outlets 8. It can be advantageous to include a spool in the wellhead 4 as the spool may provide a wider diameter outlet (for example a 4 inch outlet), which correspondingly allows for greater suction to be applied (this may be needed especially if the well produces high volumetric flow rates of gas). Similarly, use of more than one wellhead housing outlet 8 may increase the suction that is able to be applied at the wellhead housing 4.
(34) In FIG. 19 two of the wellhead housing outlets 8 are connected to a high pressure line and then to first eductors 104. First eductors 104 are configured to apply suction to the at least one wellhead housing outlet 8. Fluid is provided to the first eductors 104 from fluid compressor 110 via air choke manifold 114 to thereby provide a venturi effect. The high pressure line also includes an inline choke 121 to control the gas flowing through the line, and a three point connector 123 to combine the gas flowing from the two wellhead housing outlets 8. In line with the connector 123 is air choke manifold 116 and in-line choke 120. The venturi system 102 in FIG. 19 includes a first suction system 180, which includes first eductors 104, inline chokes 121 and 120, three point connector 123, and air choke manifold 116. The outlet of the first suction system is provided by inline choke 120.
(35) The venturi system 102 also includes a second eductor 106 configured to apply suction to the at least one wellhead housing outlet 8 and to an at least one upper outlet 14 (which is provided by an eductor spool 12) through three point connector 122. The line (or pipe) to the at least one upper outlet 14 also includes an inline choke 118. The venturi system 102 includes a second fluid compressor 110 configured to provide fluid to the second eductor 106 via air choke manifold 114 to thereby provide a venturi effect. Both fluid compressors 110 in FIG. 19 also include back pressure valves 112.
(36) The venturi system 102 in FIG. 19 includes a second suction system 190, which includes inline choke 118. The venturi system 102 in FIG. 19 also includes a third suction system 195, which includes second eductor 106, and three point connector 122.
(37) The outlet of the second eductor 106 is connected to flare system 200 (alternatively, the outlet of the third suction system 195 is connected to the flare system 200). Flare system 200 includes a flare stack 202, a flame arrestor 204 and a flare 206.
(38) The layout illustrated in FIG. 19 may also include a further eductor in the second suction system (not shown), which may be connected to a third fluid compressor or to one of the two fluid compressors 110 illustrated. The layout may also further include at least one further eductor (not shown) in series with either the first or second eductors 104, 106 to thereby increase the suction applied to the at least one wellhead housing outlet 8 or to the at least one upper outlet 14. The layout may also further include an additional upper outlet 14 (not shown) to thereby allow greater suction to be applied above the BOP 10. The first suction system 180 may also include at least one further air choke manifold between the first eductors 104 and the at least one wellhead housing outlets 8 (this may be important to assist in regulating the pressure around the wellhead housing 4).
(39) The well system 100 illustrated in FIG. 5 includes wellhead apparatus 1, including eductor spool 12 having an outlet providing the at least one upper outlet (or third gas conduit) 14, a BOP 10, and a wellhead housing 4 including an outlet providing at least one wellhead housing outlet (or second gas conduit) 8. The eductor spool 12, BOP 10 and wellhead housing 4 define a first gas conduit which is open to the atmosphere and which is in gaseous communication with subterranean gas exiting a well bore 2. The at least one wellhead housing outlet (or second gas conduit) 8 includes a 2″ isolation valve 30, and the at least one upper outlet (or third gas conduit) 14 includes a 4″ isolation valve 32.
(40) The well system 100 illustrated in FIG. 5 also includes a venturi system 102. The venturi system includes a first eductor 104 configured to apply suction to the at least one wellhead outlet (or second gas conduit) 8 and at least one upper outlet (or third gas conduit) 14. The first eductor 104 is able to apply suction to the at least one wellhead outlet (or second gas conduit) 8 and at least one upper outlet (or third gas conduit) 14 through three point connector 122. The three point connector 122 connects to the at least one upper outlet (or third gas conduit) 14 via a 4″ line, within which a 4″ choke valve 118 is positioned. The three point connector 122 connects to the at least one wellhead housing outlet (or second gas conduit) 8 via a 2″ line, within which a 2″ choke valve 120, and choke manifold 116 is positioned. Connecting the 2″ choke valve 120 to the three point connector 122 is a 4″ to 2″ pipe reducer 128. A first suction system 180 may be comprised of the choke manifold 116 and choke valve 120. A second suction system 190 may be comprised of the choke valve 118. A third suction system 195 may be comprised of the connector 122 and the first eductor 104.
(41) The venturi system 102 also includes two fluid compressors 110, each of which is a 900 Standard Cubic Feet per Minute Air Compressor. The presence of two fluid compressors 110 in the venturi system 102 provides redundancy should one fluid compressor 110 fail. The fluid compressors 110 are configured to provide fluid to the first eductor 104 to thereby provide a venturi effect. Each fluid compressor 110 includes a check valve 130 and valve 132 connected to a 2″ line. The 2″ line connects to first eductor 104 via check valve 134 and 4″ to 2″ pipe reducer 136.
(42) The well system 100 also includes a flare system 200 in gaseous communication with the outlet of the first eductor 104. The flare system 200 includes a knock-out drum 210 (to slow the flow rate of gas exiting the eductor 104), flare stack 202, flare arrestor 204 and flare 206.
(43) The well system 100 illustrated in FIG. 6 is the same as the system 100 illustrated in FIG. 5, except that the wellhead housing 4 includes a further outlet 34 with associated valves (including a check valve). The wellhead housing outlet 34 is connected to a mud pump 36 and then to storage tank 38.
(44) The well system 100 illustrated in FIG. 7 is the same as the system 100 illustrated in FIG. 6, except that the mud pump 36 connects to two storage tanks 38.
(45) The well system 100 illustrated in FIG. 8 is similar to the system 100 illustrated in FIG. 6. In this system there is again two fluid compressors 110 connected to first eductor 104 via control valve 114 (which may be a choke manifold). The first eductor 104 is connected to the at least one wellhead outlet (or second gas conduit) 8 and at least one upper outlet (or third gas conduit) 14 via a 4″ blooie line which branches at three point connector 122. The line connecting the three point connector 122 to the at least one upper outlet (or third gas conduit) 14 includes a choke and isolator valve 118. A 2″ line connects the three point connector 122 to the first gas conduit 8, and within this line is positioned a 2″ choke and isolator valve 120 and a choke manifold 116. A further outlet extends from the wellhead housing, and this outlet is connected to a mud pump 36 and then to a storage tank 38. The well system 100 illustrated in FIG. 8 also includes a blowout preventer hydraulic power unit (BOP HPU) 40 connected to the BOP 10 in wellhead apparatus 1 and a generator 42 to power the BOP HPU 40.
(46) The well system 100 illustrated in FIGS. 9-11 is similar to the system 100 illustrated in FIG. 8. The well system 100 includes a well head apparatus 1 including at least one wellhead outlet (or second gas conduit) 8 extending from the wellhead housing 4, and at least one upper outlet (or third gas conduit) 14 extending from an eductor spool 12. An 8″ blooie line connects the at least one upper outlet (or third gas conduit) 14 to a flare system 200, and within the blooie line is located a three point connector 122 and a first eductor 104. The 8″ blooie line is substantially straight and substantially parallel to the ground. The three point connector is connected to a 3″ choke line to the at least one wellhead outlet (or second gas conduit) 8 through choke manifold 116. The system 100 also includes three fluid compressors 110 (air compressors capable of 900 cubic feet per minute at 150 psi) configured to provide fluid to the first eductor 104 through a 2″ air hose (including an air control manifold 114) to thereby provide a venturi effect. The venturi system 100 further includes a second eductor 138 positioned between the choke manifold 116 and the second gas conduit 8, and a third eductor 140 connected between the 8″ blooie line and the third gas conduit 14. The fluid compressors 110 are configured to provide fluid to the second and third eductors 138, 140 (including through an air control manifold 142) to thereby provide a venturi effect. Use of three eductors 104, 138, 140 may advantageously provide improved suction, especially over longer line distances. A further outlet extends from the wellhead housing, and this outlet is connected to a mud pump 36 (capable of pumping 417 L per minute at 450 psi) and then to skid mounted storage tanks 38. The well system 100 illustrated in FIGS. 9-11 also includes a blowout preventer hydraulic power unit (BOP HPU) 40 connected to the BOP 10 in wellhead apparatus 1 and a generator 42 to power the BOP HPU 40. The flare system 200 is connected to a pump 46 (especially a 4″ transfer pump capable of pumping at 1200 L per minute)) via a 4″ suction hose to a skid mounted storage tank 44.
(47) An exemplary flare system 200 is illustrated in FIGS. 12 and 13. The flare system 200 is trailer mounted. The flare system 200 includes a knock-out drum 210 (for slowing the flow rate of gas exiting the eductor 104), flare stack 202 and flare 206. The flare system 200 also includes an inlet 214 for introduction of the gas to be flared, an igniter gas 216 for the flare, a control panel 218 and stabilizing legs 220. When assembled, the flare system 200 may be more than 10 metres high. Consequently, the system 200 may be collapsible for movement. The system 200 may include a stack elevation drive 222 for raising and lowering the flare stack.
(48) Methods of the present invention are described below with reference to various systems described above, especially the systems 100 illustrated in FIGS. 4 and 14. However, a skilled person would readily be able to adapt the methods described below for use with systems 100 described in the other Figures.
(49) The system 100 described in FIG. 4 may be used in performing a well operation on a component of the wellhead apparatus 1. In this method, valve 118 is closed, but valves/manifolds 114, 116 and 120 are open. The fluid compressor 110 is active and is providing fluid to the first eductor 104 to thereby provide a venturi effect. Consequently, suction is being applied to the at least one wellhead outlet (or second gas conduit) 8 (but not to the at least one upper outlet (or third gas conduit) 14 as valve 118 is closed) such that substantially all subterranean gas flows through the at least one wellhead outlet (or second gas conduit) 8. At this time, an operation on the component of the wellhead apparatus 1 may be performed (such as removing the eductor spool 12 and BOP 10).
(50) In an alternative, the system 100 described in FIGS. 3 and 4 may be used in performing a well operation on a component of the wellhead apparatus 1. In this method, all valves/manifolds (e.g. 114, 116, 118 and 120) are open. The fluid compressor 110 is active and is providing fluid to the first eductor 104 (and to the second eductor 106 in the system of FIG. 3) to thereby provide a venturi effect. Consequently, suction is being applied to the at least one wellhead outlet (or the second gas conduit) 8 and to the at least one upper outlet (or the third gas conduit) 14 such that substantially all subterranean gas flows through the at least one wellhead outlet (or second gas conduit 8) and the at least one upper outlet (or third gas conduits 14). At this time, an operation on the component of the wellhead apparatus 1 may be performed (such as landing a hanger).
(51) The system 100 described in FIG. 14 may be used in a method of opening a wellhead housing 4 to the atmosphere. In this method, the system 100 illustrated in FIG. 14 includes a pressure sensor for sensing the pressure in the conduit between the first eductor 104 and the at least one wellhead outlet (or second gas conduit) 8, and a pressure sensor for sensing the pressure within or adjacent to the first gas conduit 6. Furthermore, first gas conduit 6 is closed to the atmosphere at the start of this method. First, air choke manifolds 114 and 116 are closed. The wellhead housing 4 outlet valves are opened, and the pressure within or adjacent the first gas conduit 6 is noted using the sensor. If the pressure within the first gas conduit 6 exceeds the working pressure of the line connected to manifold 116, then the wellhead pressure is bled off until choke manifold 116 is fully open. Subterranean gas exiting the well bore 2 is now able to pass through the at least one wellhead outlet (or second gas conduit) 8 and to the flare system 200 via first eductor 104. Compressed air from fluid compressor 110 is then allowed to pass to first eductor 104 by opening air choke manifold 114. The pressure in the conduit between the first eductor 104 and the at least one wellhead outlet (or second gas conduit) 8 is monitored, and once the pressure reading becomes negative the flow of subterranean gas exiting the well bore 2 and entering the first gas conduit 6 is controlled, as is the flow of gas within the wellhead housing 4. At this time, the first gas conduit 6 is opened to the atmosphere (for example by removing the wellhead bonnet). A component of the wellhead apparatus 1 (such as the BOP 10) may then be installed or serviced.
(52) A method of removing a hanger will now be described with reference to FIGS. 15 and 4. First, referring to FIG. 15. In this method, the system 100 illustrated in FIG. 15 may include a pressure sensor located at choke manifold 116, and a pressure sensor located in the first gas conduit 6, distal to the well bore 2. Furthermore, first gas conduit 6 is closed to the atmosphere at the start of this method, and a hanger is located within the wellhead apparatus 1. First, air choke manifolds 114 and 116, and in line choke 118, are closed. In line choke 120 is opened. The wellhead housing 4 outlet valves are opened, and the wellhead pressure is noted using the sensor located at choke manifold 116. If the wellhead pressure exceeds the working pressure of the line connected to manifold 116, then the wellhead pressure is bled off until choke manifold 116 is fully open. Subterranean gas exiting the well bore 2 is now able to pass through the at least one wellhead outlet (or second gas conduit) 8 and to the flare system 200 via first eductor 104. Compressed air from fluid compressor 110 is then allowed to pass to first eductor 104 by opening air choke manifold 114. The pressure reading at the pressure sensor is monitored, and once the pressure reading becomes negative the first gas conduit 6 may be opened to the atmosphere (for example by removing the wellhead bonnet). The pressure sensor in the first gas conduit 6 may be monitored during the bleed down and eductor 104 start up operations to determine whether the hanger and any associated flow control valves or penetrations are leaking. A BOP 10 may then be installed, followed by an eductor spool 12, having an outlet providing at least one upper outlet (or third gas conduit) 14. The at least one upper outlet (or third gas conduit) 14 is then connected to choke 118. The system 100 illustrated in FIG. 4 is now provided.
(53) The hanger may now be removed from the wellhead apparatus 1. When performing this step, it is advantageous to minimise the pressure differential between the top and bottom of the hanger while ensuring the volume in the first gas conduit 6 above the eductor spool 12 is kept free of gas. If the pressure differential is too high when the hanger is pulled from its seat, then the gas velocity at that time may be high enough to pull the hanger seals from their grooves on the hanger. To minimise the exposure of the hanger seals to excessive gas velocities, the following methods may be used.
(54) A. If no completion is attached to the hanger: (i) Remove any back pressure valve or two way check valve; (ii) Install a hanger handling joint with an in-line valve installed; (iii) Open the in-line valve, creating an air flow path through the handling tool to the at least one wellhead outlet (or second gas conduit) 8; (iv) Open the air choke 118 to create maximum suction at the at least one upper outlet (or third gas conduit) 14; (v) If possible, pull the hanger free mechanically; (vi) If the hanger is tight, it may be possible to create upward force on the bottom of the hanger by closing the in-line valve in the hanger handling tool and reducing the suction pressure at the at least one wellhead outlet (or second gas conduit) 8 (by closing the air choke 116 in a controlled manner). This should be done very carefully since the hanger may pop free creating potential for a gas vent on the workfloor or the handling tool to jumping upwards; (vii) Once the hanger is free of its seat, the in-line valve in the hanger should be closed and the air flow through the at least one wellhead outlet (or second gas conduit 8) and the at least one upper outlet (or third gas conduit) 14 should be held as close to balance as feasible; (viii) The hanger may be removed from the well at this time.
(55) B. If a completion is attached to the hanger (i.e. a tubing string extends from the hanger into the well bore 2): (i) Closing the tubing string extending into the well bore 2; (ii) With suction being applied through the at least one wellhead outlet (or second gas conduit) 8 and the pressure below the hanger negative, install a hanger handling joint; (iii) Open air choke 118 to create maximum suction at the at least one upper outlet (or third gas conduit) 14; (iv) If possible, pull the hanger free mechanically; (v) If the hanger is tight, it may be possible to create upward force on the bottom of the hanger by reducing the suction pressure at the at least one wellhead outlet (or second gas conduit) 8 (by closing the air choke 116 in a controlled manner). This should be done very carefully since the hanger may pop free creating potential for a gas vent on the workfloor or the handling tool to jumping upwards; (vi) Once the hanger is free of its seat, the air flow through the at least one wellhead outlet (or second gas conduit) 8 and the at least one upper outlet (or third gas conduit) 14 should be held as close to balance as feasible; (vii) The hanger may be removed from the well at this time.
(56) A method of landing a hanger assembly 50 will now be described with reference to FIG. 4 and with reference to FIGS. 16 to 18 (which provide a cross sectional view through the wellhead apparatus 1 illustrated in FIG. 4 as the hanger is landing). The method includes the steps of lowering the hanger assembly 50 (which includes the hanger 50 and a hanger landing tool (not shown))—see FIG. 16. Next, the suction applied at the at least one upper outlet (or third gas conduit) 14 is decreased to thereby pull the hanger assembly 50 into position with the wellhead housing 4 until substantially no suction is applied through the at least one upper outlet (or third gas conduit) 14—FIG. 17. Then the hanger assembly 50 need only be held in place—FIG. 18. After this, components such as the hanger landing tool, the eductor spool 12 and the BOP 10 may be removed from the wellhead apparatus 1. The first gas conduit may be closed to the atmosphere (such as by installing a wellhead bonnet). The venturi system 100 may also be disconnected from the wellhead housing 4.
(57) To minimise the exposure of the hanger seals to excessive gas velocities, the following methods may be used.
(58) A. If a completion is attached to the hanger 50 (i.e. a tubing string extends from the hanger 50 into the well bore 2): (i) Closing the tubing string extending into the wellbore 2; (ii) With suction being applied at the at least one wellhead outlet (or second gas conduit) 8 and the at least one upper outlet (or third gas conduit) 14, begin lowering the hanger into the wellhead assembly 1; (iii) The suction at the at least one wellhead outlet (or second gas conduit) 8 and the at least one upper outlet (or third gas conduit) 14 should be kept as close to balance as possible to minimize air flow across the hanger seals; (iv) With the hanger at the landing position, the suction at the at least one upper gas outlet (or third gas conduit) 14 should be reduced in a controlled manner by closing valve 118. This creates downward force on the hanger assembly 50, pulling the hanger 50 into its seat. Once seated, the hanger 50 may be locked in place (if tie down bolts are available) or held in place with suction (if a tie down bolts are not available and a lock down ring is used); (v) With the hanger in place and negative pressure at the at least one wellhead outlet (or second gas conduit) 8 confirmed, the BOP equipment may be removed and the wellhead bonnet installed; (vi) The wellhead 4 outlet valve may be closed and the suction at the at least one wellhead outlet (or second gas conduit) 8 may cease; (vii) The venturi system 100 may be disconnected from the wellhead apparatus 1.
(59) B. If no completion is attached to the hanger assembly 50: (i) With the suction at the at least one wellhead outlet (or second gas conduit) 8 and the at least one upper outlet (or third gas conduit) 14 running and as close to balance as possible, the hanger assembly 50 (which includes a handling tool and in-line valve), is lowered into the wellhead apparatus 1. The in-line valve should be open initially, to create an air flow path that is not across the hanger seals; (ii) Once the hanger assembly 50 is at its landing position, the in-line valve is closed and the valve 118 closed in a controlled manner. This creates maximum downward force on the hanger assembly 50, ensuring the hanger assembly 50 is properly seated; (iii) The BOP 10 pipe rams are closed and a pressure test performed to verify that the hanger 50 is not leaking; (iv) The BOP 10 pipe rams are opened, the hanger in-line valve opened and the hanger handling tool removed; (v) A two way check valve is then be installed and tested using the blind rams on the BOP 10; (vi) The BOP 10 is removed and the wellhead bonnet installed; (vii) The wellhead bonnet should then be pressure tested against the two-way check valve; (viii) Once a successful pressure test is obtained, the two way check valve may be removed and replaced with a back pressure valve or left open, as per the Operator's requirements; (ix) The wellhead 4 outlet valve may be closed and the suction at the at least one wellhead outlet (or second gas conduit) 8 may cease; (x) The venturi system 100 may be disconnected from the wellhead apparatus 1.
(60) Reference throughout this specification to ‘one embodiment’ or ‘an embodiment’ means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearance of the phrases ‘in one embodiment’ or ‘in an embodiment’ in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more combinations.
(61) In compliance with the statute, the invention has been described in language more or less specific to structural or methodical features. It is to be understood that the invention is not limited to specific features shown or described since the means herein described includes preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims appropriately interpreted by those skilled in the art.
