GB1445602A - Safety means for well flow control - Google Patents

Abstract

1445602 Controlling flow in wells SCHLUMBERGER TECHNOLOGY CORP 10 Aug 1973 38095/73 Heading E1F A system for terminating flow through a well conduit 10 comprises a first sub-surface valve 20 which closes in response to pressures in the conduit below a first level, and a second sub-surface valve 50 which closes in response to pressures in the conduit above a second level higher than the first level. The valve 20 is preferably above the valve 50 so that closing of one valve will cause the pressure to change so as to close the other valve. The valves may be closed, for example to test them, by closing surface valve 12, so that the pressure rises and valve 50 closes; then surface valve 12 is opened so that the pressure falls and valve 20 closes. The valves are locked when opened by respective locking balls 42, 95 held in place by shafts 34, 92 connected to bellows 40, 112 communicating with reservoirs 41, 120 containing compressible fluid. If the pressure falls below the first level, bellows 40 will have expanded far enough to release the locking balls 42-so that spring 42a urges valve member 33 onto seat 32; the valve is reopened by imposing from the surface a pressure great enough to restore the shaft 34 to a locking position. If the pressure rises, bellows 112 causes shaft 92 to move upwardly, pin 150 moving in a slot 151 in stem 93 of valve member 70; when the second level is exceeded the shaft will have moved so as to release locking balls 95 and the pin will have reached the end of slot 151 so that further movement compresses spring 153 and causes the valve member 70 to meet seat 57. If the pressure then rises above a third higher level, since the shaft 92 cannot move further upwardly, further contraction of the bellows causes resilient fingers 114 on adapter 110 to release the shaft 92; the valve is held closed by the pressure beneath it, until the pressure above it is raised to that value, when it is opened by the spring 153. Instead of being responsive to pressures the valves may be controlled by a prescribed range of flow rates being departed from. Specification 1445603 is referred to.