Method and apparatus for gas-lift operations in oil wells

Claim 2

A gas-lift system for use in a well bore containing a production conduit and an injection conduit, comprising a hollow body member having an intake portion and an outlet portion for providing a flow path between said conduits, a first normally open valve means disposed in said body member and closeable in response to pressures in said injection conduit greater than a first preselected pressure to block said flow path, and a second normally closed valve means disposed in said body member and openable in response to pressures in said injection conduit greater than a second preselected pressure.

Claim 3

A gas-lift system for use in a well bore containing a production conduit and an injection conduit, comprising a hollow body member having an intake portion and an outlet portion for providing a flow path between said conduits, a first normally open valve means disposed in said body member and closeable in response to pressures in said injection conduit greater than a first preselected pressure, and a second normally closed valve means disposed in said body member and openable in response to pressures in said injection conduit greater than a second preselected pressure, said second preselected pressure being less than said first preselected pressure.

Claim 4

A gas-lift system for use in a well bore containing a production conduit and an injection conduit, comprising a hollow body member having an intake portion and an outlet portion for providing a flow path between said conduits, a first normally open valve means disposed in said body member and closeable in response to pressures in said injection conduit greater than a first preselected pressure, and a second normally closed valve means disposed in said body member and openable in response to pressures in said injection conduit greater than a second preselected pressure, said second preselected pressure being less than said first preselected pressure.

Claim 5

The system described in claim 2, wherein said first valve means includes a first seat member disposed in said body member intermediately of said intake and outlet portions thereof, a first shutoff member for shutoff engagement with said first seat member to interrupt fluid flow through said body member, and first driving member for urging said first shutoff member from said first seat member in response to a dome force substantially equal to said first preselected pressure.

Claim 6

The system described in claim 3, wherein said first driving member is responsive to pressures in said injection conduit greater than said first preselected pressure to longitudinally contract and draw said first shutoff member into sealing engagement with said first seat member.

Claim 7

The system described in claim 4, wherein said first seat member is located intermediately of said first driving member and said intake portion of said body member.

Claim 8

The system described in claim 5, wherein said first seat member is an annular body member disposed about said flow path in said hollow body member, and wherein said first shutoff member is an elongate member extending through said annular body member and having one end fixed to said first driving member and having a shutoff head portion at the other end positioned intermediately of said annular body member and said intake portion of said hollow body member for fluidtight engagement with said annular body member.

Claim 9

The system described in claim 6, wherein said first driving member is longitudinally distended by said dome force therein to unseat said head portion of said first shutoff member from said annular body member when said pressures in said injection conduit are less than said first preselected pressure.

Claim 10

The system described in claim 7, wherein said first driving member is longitudinally compressed by pressures in said injection conduit greater than said first preselected pressure to draw said head portion of said first shutoff member into fluidtight engagement with said annular body member.

Claim 11

The system described in claim 8, wherein said first valve means is located in said hollow body member intermediately of said intake portion thereof and said second valve means.

Claim 12

The system described in claim 8, wherein said second valve means is located in said hollow body member intermediately of said intake portion thereof and said first valve means.

Claim 13

The system described in claim 10, further including check means for closing said hollow body member in response to pressure in said production conduit greater than pressure in said injection conduit.

Claim 14

The check means described in claim 11, comprising first normally closed check valve assembly interconnected in said body member between said first and second seat members and openable in response to pressure in said injection conduit greater than pressure in said production conduit.

Claim 15

The check means described in claim 12, further comprising second normally closed check valve assembly interconnected in said body member between said outlet portion thereof and said first seat member.

Claim 16

The system described in claim 13, wherein said first valve means further comprises spring means for urging said head portion of said first shutoff member into engagement with said annular body member.

Claim 17

The system described in claim 8, further comprising a third bypass valve means arranged in said well bore below said hollow body member for intercommunication between said conduits, plugging means in said injection conduit below said bypass valve means, and an upwardly openable check valve means disposed in said production conduit below said bypass valve means.

Claim 18

The system described in claim 15, wherein said bypass valve means comprises a normally closed control valve openable in response to a preselected third pressure in said injection conduit.

Claim 19

The system described in claim 15, wherein said bypass valve means comprises a manually openable valve means.

Claim 20

The system described in claim 17, wherein said bypass valve means further includes a normally closed control valve openable in response to a preselected third pressure in said injection conduit.

Claim 21

The system described in claim 18, further including another upwardly openable check valve means disposed in said production conduit above said bypass valve means.

Claim 22

In a gas-lift valve assembly for use in a well bore containing a production conduit and an injection conduit and including a hollow body member having an intake portion for communication with said injection conduit and an outlet portion for communication with said production conduit, a first seat member disposed in said body member, a first shutoff member disposed in said body member, and a first pressure-responsive member urging said fiRst shutoff member into engagement with said first seat member and responsive to pressures in said injection conduit greater than a first preselected pressure to disengage said first shutoff member from said first seat member, the improvement in combination therewith comprising blocking means responsive to pressures in said injection conduit greater than a second preselected pressure greater than said first preselected pressure for blocking fluid flow through said hollow body member.

Claim 23

In a gas-lift valve assembly for use in a well bore containing a production conduit and an injection conduit and including a hollow body member having an intake portion for communication with said injection conduit and an outlet portion for communication with said production conduit, a first seat member disposed in said body member, a first shutoff member disposed in said body member, and a first pressure-responsive member urging said fiRst shutoff member into engagement with said first seat member and responsive to pressures in said injection conduit greater than a first preselected pressure to disengage said first shutoff member from said first seat member, the improvement in combination therewith comprising blocking means responsive to pressures in said injection conduit greater than a second preselected pressure greater than said first preselected pressure for blocking fluid flow through said hollow body member.

Claim 24

The improvement described in claim 20, wherein said blocking means passes fluid flow through said hollow body member when the pressures in said injection conduit are greater than said first preselected pressure but not greater than said second preselected pressure.

Claim 25

The blocking device described in claim 21, further comprising a second seat member interconnected with said hollow body member, a second movable shutoff member for engaging said second seat member, and a driving means responsive to a dome force substantially equal to said second preselected pressure for urging said second shutoff member from said second seat member.

Claim 26

The blocking device described in claim 22, wherein said driving means moves said second shutoff member toward said second seat member in response to pressures in said injection conduit greater than said second preselected pressure.

Claim 29

The method described in claim 24, wherein said gas is injected through said first flow path into said production conduit at a second pressure less than said first pressure.

Claim 30

The method described in claim 25, wherein said first pressure is greater than the hydrostatic pressure in said liquid-filled injection conduit adjacent said first path, and wherein said second pressure is less than said first pressure but greater than the pressure in said production conduit.

Claim 31

The method described in claim 26, including the step of reducing the pressure of said gas injected into said injection conduit to said second pressure after said liquid in said injection conduit has declined below said first flow path, and opening said first flow path in response to said reduction of said gas pressure in said injection conduit below said first pressure.

Claim 32

The method described in claim 27, including the step of closing said second flow path after opening said first flow path in said well bore.