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A downhole tool such as a tester valve originally constructed to operate with a compressible gas spring may be modified to operate with a compressible liquid spring. The volume of a spring chamber is increased. A differential area of a power piston is decreased. A flow restriction in a metering cart

A downhole tool such as a tester valve originally constructed to operate with a compressible gas spring may be modified to operate with a compressible liquid spring. The volume of a spring chamber is increased. A differential area of a power piston is decreased. A flow restriction in a metering cartridge associated with the spring chamber is increased. Also, a relief valve is provided to allow fluid to be relieved from the tool into the well annulus upon expansion of the compressible liquid due to heating as the tool is lowered into a well if the expansion of liquid exceeds the available volume in the tool.

대표청구항 ▼

A downhole tool apparatus, comprising: a housing; a well annulus pressure responsive power piston means disposed in said housing and acting against a compressible liquid substantially completely filling a spring chamber of said housing, said spring chamber containing a volume of said compressible li

A downhole tool apparatus, comprising: a housing; a well annulus pressure responsive power piston means disposed in said housing and acting against a compressible liquid substantially completely filling a spring chamber of said housing, said spring chamber containing a volume of said compressible liquid large enough to be compressed by an amount equal to a displacement of said power piston means; a liquid-filled equalizing chamber defined in said housing and communicated with said well annulus; a restricted passageway communicating said spring chamber and said equalizing chamber; a floating piston disposed in said equalizing chamber and dividing said equalizing chamber into a first zone and a second zone, said first zone being substantially completely filled with said compressible liquid and said second zone being substantially completely filled with well annulus fluid and in communication with the exterior of said housing; one-way relief valve means disposed in said floating piston, for relieving liquid from said first zone to said second zone when said compressible liquid expands in said spring chamber due to heating as said apparatus is lowered into a well and pressure of said compressible liquid in said first zone exceeds well annulus fluid pressure in said second zone due to said expansion. A method of substituting a compressible liquid spring for a compressible gas spring in a downhole tool, said method comprising the steps of: (a) providing an original downhole tool constructed to operate by means of a well annulus pressure responsive power piston acting against a compressible gas disposed in a spring chamber; (b) modifying said original tool by increasing a volume of said spring chamber; and (c) after step (b), substantially completely filling said spring chamber with a volume of compressible liquid sufficient so that said liquid may be compressed by an amount equal to a displacement of said power piston upon operation of said power piston.