Abstract: In a subterranean well having a production tubing string outwardly circumscribed by a brine-filled casing annulus, a specially designed combination casing pressure relief and kill valve is supported within a side pocket mandrel installed in the production tubing, the valve having inlet ports communicated with the casing annulus. During an initial production phase of the well, when the casing annulus/production tubing pressure differential reaches a first pressure differential set point of the valve due to a brine temperature increase, a pressure relief portion of the valve opens to admit a relatively low flow rate of annulus brine to the tubing string, thereby relieving the annulus pressure, and then closes to reseal the annulus. When it later becomes necessary to temporarily kill the well, kill fluid is pumped into the casing annulus. As the annulus pressure increases, the first valve set point is reached and the pressure relief portion of the valve opens.

Abstract: A gas lift valve for use in a continuous flow operation which has an externally biased bellows which is pressurized internally to open the valve. A noncompressible liquid surrounds the bellows and flows upwardly through a passage about the valve stem into a dome in the valve which is pressurized to a predetermined pressure to resist movement of the bellows and opening of the valve. Fluid passes through a series of labyrinth rings formed on the valve stem adjacent the passage into the dome to dampen valve movement. An O-ring seal on the valve stem below the passage into the dome engages and seals off the passage if excessive pressure expands the bellows to a predetermined point such that the bellows will be protected from rupture by the noncompressible liquid trapped about the bellows. A snubber ring of nonmetallic material is positioned about the lower end of the valve stem to limit lateral movement of the valve ball in the seat.

Abstract: Disclosed is a circulating valve for use in a well. The circulating valve includes at least one valve plug initially blocking flow through the valve which moves to a retained position permitting flow through the valve upon the application of a predetermined pressure differential across the valve plug. This abstract is neither intended to define the scope of the invention, which, of course, is measured by the claims, nor is it intended to be limited in any way.