Downhole tool with hydraulic timer

Abstract: A downhole tool apparatus such as a sampler (120) includes an operating mechanism (166) and a hydraulic timer (206). The hydraulic timer (206) is operably associated with the operating mechanism for providing a time delay prior to operation of the operating mechanism. The hydraulic timer includes a fluid flow restriction (214) and a spring biased piston (208) which pushes a predetermined volume of hydraulic fluid through the fluid flow restriction (214). An initiator valve (230) is located hydraulically in series with the fluid flow restriction (214). The time delay is provided by the time taken for the fluid to pass through the restriction. Thereafter the operating mechanism is effective.

Description: The present invention relates to a downhole tool, especially but not exclusively a sampler, which tool has a hydraulic timer for providing a time delay in the operation of the tool. Various prior art fluid sampling devices include hydraulic time delays built into the operational mechanism of the tools so as to slow the travel of the operating mechanism. An example of such a device is shown in our U.S. patent specification no. 4,903,765 to Zunkel, which shows a recent improvement in such fluid sampling tools, wherein the fluid sampling tool is constructed to have a time delay which starts when a valve of the tool first starts to move in response to pressure from the well. We have now devised an improved hydraulic timer means for a downhole tool apparatus. Both US-A-4766955 and US-A-4648470 disclose a downhole tool apparatus, comprising an operating mechanism; a hydraulic timer means, operably associated with said operating mechanism, for providing a time delay prior to operation of said operating mechanism, said timer means including a fluid flow restriction and a spring biased piston means for pushing a predetermined volume of hydraulic fluid through said fluid flow restriction; and an initiator valve located hydraulically in series with said fluid flow restriction, said initiator valve having a closed position wherein said hydraulic fluid is prevented from flowing through said fluid flow restriction, and an open position wherein said hydraulic fluid is permitted to flow through said fluid restriction. In US-A-4648470, the initiator valve is responsive to a pressure increase in the tubing from the surface. The present invention is characterised in that said initiator valve includes spring biasing means for biasing said initiator valve toward its said closed position, said initiator valve including a protruding valve stem; and said pressure responsive switching means includes a switching piston having a first side exposed to said outside zone and having a second side exposed to a low pressure chamber defined in said apparatus, said switching piston including abutment means abutting said protruding valve stem for moving said initiator valve to its said open position in response to an increase in fluid pressure in said outside zone. In order that the invention in its various aspects, may be more fully understood, embodiments thereof will now be described by way of example only with reference to the accompanying drawings, wherein: Figure 1 is a schematic block diagram depicting an embodiment of sampler apparatus of the present invention in place within a well which is to be sampled. Figures 2A-2H comprise an elevation sectioned view of an embodiment of the present invention. The apparatus of Figures 2A-2H utilizes a blocking valve to initially hydraulically block the sample valve. A hydraulic timer provides a second time delay prior to the opening of the blocking valve. FIG. 2H shows a pressure responsive switching means for starting the hydraulic timer in response to an increase in well pressure above a predetermined level. A disabling means seen in FIG. 2A prevents the trapping of a fluid sample at pressures above a predetermined level. The apparatus in FIGS. 2A-2H is shown in its initial position as it is being run into a well. FIGS. 3A-3H show the apparatus of FIGS. 2A-2H in its final position after it has been placed in a well and a well sample has been trapped therein. FIGS. 4A-4B illustrate a modification of the apparatus of FIGS. 2A-2H in which the hydraulic timer has been modified to utilize a compressed gas spring rather than the mechanical spring illustrated in FIGS 2E-2F. Detailed Description of The Preferred Embodiments Referring now to FIG. 1, a fluid sampling apparatus 10 is shown disposed in an oil or gas well 11 defined by a bore 12 which is typically lined with casing (not shown). The fluid sampling apparatus 10 is lowered and raised relative to the bore 12 on a slick line 14. It will be appreciated that the apparatus 10 can also be run on a tubing string, on a wire line, or below a packer as is well known to those skilled in the art. The well bore 12 is shown as intersecting a subsurface formation 16, the flow from which is to be sampled. Formation fluids from the formation 16 flow into the well 11 and are sampled by the fluid sampling apparatus 10. The sampling apparatus 10 is lowered from and controlled by various surface equipment schematically illustrated at 18, which is located at the surface of the well. Another particular environment in which the present invention can be used is in a large sample chamber of a perforate/test sampler tool which is placed in the well. The Embodiment of FIGS. 2 and 3 FIGS. 2 and 3 illustrate an embodiment of the fluid sampling apparatus of the present invention, which embodiment is generally designated by the numeral 120. The apparatus 120 is shown in FIGS. 2A-2H in its initial position, and is shown in FIGS. 3A-3H in its final position after a sample has been trapped therein. The fluid sampling apparatus 120 includes a body or housing 122. The body 122 is made up of a number of individual components threadedly connected together with suitable seals provided therebetween. From top to bottom, the components of the body 122 include upper end coupling 124, upper coupling adapter 126, upper oil chamber housing 128, intermediate adapter 130, sample chamber section 132, valve housing section 134, drain nipple 136, blocking means housing section 138, spring housing section 140, intermediate coupling 142, lower adapter 144, and lower end coupling 146. Defined in the body 122 are a sample chamber 148, an oil chamber 150, and an air chamber or dump chamber 152. A metering cartridge 154 is threadedly connected to drain nipple 136 at threaded connection 156 with an O-ring seal 158 being provided therebetween. Metering cartridge 154 carries an orifice means 160 which preferably is a device such as a Visco-Jet element of a type well known to the art. The orifice means 160 provides an impedance means 160 disposed in the body 122 between oil chamber 150 and air chamber 152 for impeding flow of hydraulic fluid which fills oil chamber 150 from the oil chamber 150 to the air chamber 152. The valve housing section 134 of body 122 has both a sample port 162 and a separate power port 164 defined therein. A sliding spool type sample valve means 166 is slidably received within a bore 168 of the valve housing section 134. The valve means 166 provides a means for being moved relative to the body 122 in response to outside pressure from the outside well zone 11 acting on the sample valve means 166. The sample valve means 166 also provides a means for communicating the sample port 162 with the sample chamber 148 after a predetermined first time delay after the pressure from outside well zone 11 begins moving the sample valve means 166. The valve means 166 includes an enlarged piston portion 172 having a seal 174 slidably received within a lower bore of valve housing section 134 below the port 164. Valve means 166 carries an upper sliding seal 176 which is received within the bore 168 initially above port 162. A seal 170 is also provided below the sample port 162 when the valve means 166 is in its initial position, thus isolating the sample port 162 from enlarged diameter piston 172 and its piston seal 174. Fluid pressure from the well 11 to move the piston 172 is provided through the separate power port 164. The portion of valve means 166 between seals 170 and 176 can be described as a first closure means for maintaining the sample port 162 sealed from the sample chamber 148 as the valve means 166 moves relative to the sample port 162 during a predetermined time delay. This time delay is determined by several factors, including the viscosity of the oil in oil chamber 150, the nature of the flow restriction provided by orifice means 160, and the physical distance through which the valve means 166 must move before the upper seal 176 passes the sample port 162. Valve means 166 carries another seal 178 spaced a distance above the seal 176. Located between seals 176 and 178 is a fill port 182 communicated with a sample fill passageway 184 communicated with the upper end of valve means 166. The fill port 182 and passageway 184 located between seals 176 and 178 can be described as an open means connected to the first closure means for providing a fluid conducting passageway between the sample port 162 and the sample chamber 148 after the predetermined time delay provided by the time necessary for the seal 176 to move past sample port 162. Finally, the valve means 166 carries a fourth seal 180 above the seal 178. An intermediate portion of the valve means 166 between seals 178 and 180 can be described as a second closure means connected to the open means 182, 184 for sealing the sample chamber 148 from the sample port 162 after the seal 180 of the open means has moved past the sample port 162 to a final closed position of the valve means 166 wherein a fluid sample is sealed in the sample chamber 148. A selective blocking means or selective closure means 186 is disposed in the body 122 between the oil chamber 150 and air chamber 152 for initially isolating the oil chamber 150 from the air chamber 152 to hydraulically block the sample valve means 166 against movement in response to pressure in the well 11. The blocking means 186 is further characterized as a means for communicating the oil chamber 150 and the dump chamber 152 independently of a value of a pressure differential between the well 11 and the dump chamber 152, thus permitting well fluid pressure to move the sample valve means 166. The selective blocking means 186 includes a blocking valve 188 shown in FIG. 2E in its closed position wherein the oil chamber 150 and air chamber 152 are isolated from each other, and shown in FIG. 3E in its open position wherein the oil chamber 150 and air chamber 152 are communicated with each other. The blocking valve 188 is a sliding sleeve type valve which includes a cylindrical valve body 190 received within a bore 192 of blocking means housing section 138 with an O-ring seal 193 being provided therebetween. Valve body 190 includes a downwardly extending neck portion 194. A valve passage 196 extends through the valve body 190 to a radially extending valve port 198 which communicates with the outer surface of the neck portion 194. The blocking valve 188 also includes a sliding sleeve 200. A pair of O-ring seals 202 and 204 are carried by the neck portion 194 on opposite sides of valve port 198, so that when the sleeve 200 is in the closed position shown in FIG. 2E the valve port 198 is sealingly blocked by sleeve 200. The fluid sampling apparatus 120 includes a timer means generally designated by the numeral 206 which is associated with and may be considered a part of the selective blocking means 186, for providing a predetermined time delay prior to a time at which the blocking valve 188 moves to its open position to communicate the oil chamber 150 and air chamber 152. The timer means 206 illustrated in FIGS. 2A-2H is a hydraulic timer means including a timing piston 208 biased by mechanical spring 210 against a volume of oil trapped in a lower oil chamber 212. Timing piston 208 carries an O-ring seal 209 closely received within a bore 211 of lower oil chamber 212. The spring biased piston 208 pushes a predetermined volume of oil contained in lower oil chamber 212 through a Visco Jet type of fluid flow restriction or restricted orifice 214 into a lower air chamber or dump chamber 216. The amount of time delay provided by the timer means 206 is dependent upon the volume of oil in oil chamber 212, the physical properties of the oil, the spring force exerted by spring 210, and the flow restriction provided by fluid flow restriction 214. These parameters can be adjusted to provide the desired time delay. The purpose of the timer means 206 is to allow the fluid sampling apparatus 120 to be lowered into its final position within the well 11 as illustrated in FIG. 1 prior to the time at which the blocking valve 188 opens to permit the sample valve means 166 to move downward within the body 122 so as to permit the sample chamber 148 to be filled with a well fluid sample. The timer means 206 includes a lost motion linkage 218 having members 220 and 222 connected to the valve sleeve 200 and the timing piston 208, respectively. This lost motion linkage 218 causes the valve sleeve 200 to be pulled to its open position only after the timing piston 208 has moved through a predetermined distance relative to the body 122. The members 220 and 222 include overlapping projections 224 and 226, respectively, which are engaged with each other after the timing piston 208 has moved through a predetermined distance, and after which engagement the members 220 and 222 move together to pull the valve sleeve 200 to an open position. Referring now to FIG. 2H, the fluid sampling apparatus 120 further includes a mechanical initiating means 228 for starting the hydraulic timer means 206. The mechanical initiating means 228 includes an initiator valve 230 located hydraulically in series with the fluid flow restriction 214 of the hydraulic timing means 206. Initiator valve 230 is communicated with fluid flow restriction 214 through a passageway 232 defined through the lower adapter 144 of body 122. The initiator valve 230 is mounted in the lower end of lower adapter 144. Initiator valve 230 includes a valve seat insert 234 threadedly connected to the lower end of lower adapter 144 and having a tapered valve seat 236 defined thereon. Initiator valve 230 also includes a poppet 238 biased by valve spring 240. Poppet 238 has a tapered surface 242 defined thereon which when engaged with valve seat 236 will block the passageway 232. Initiator valve 230 is shown in FIG.2H in an closed position and in figure 3H in an open position wherein fluid may flow downward through the fluid flow restriction 214, the passageway 232, and through a poppet passageway 244. It is noted that the valve spring 240 biases the poppet 238 toward a closed position in which a lower end 246 of the poppet 238 extends downward through the valve seat insert 234. The lower end coupling 146 carries an engagement spool 248 which has an engagement surface 250 defined on the upper end thereof. The engagement spool 248 has a pressure responsive piston 274 extending downward therefrom and received within a bore 276 with an O-ring seal 278 provided therebetween. An air chamber 280 is defined below the piston seal 278. The air chamber 280, which is initially at substantially atmospheric pressure when the tool is assembled, is separated from the fluid in the well by a rupture disk 282 which closes a radial port 284. The rupture disk 282 and piston 274 associated with the engagement spool 248 collectively provide a pressure responsive switching means for starting the hydraulic timer means 206 in response to an increase in well pressure to a predetermined level at which the rupture disk 282 is designed to rupture. This pressure responsive switching means includes the switching piston 274 having its upper end exposed to the low pressure chamber 216. The rupture disk 282 provides a means for initially isolating the switching piston 274 from the well fluid pressure until that well fluid pressure reaches a predetermined level at which the rupture disk 282 ruptures thus allowing well fluid to enter the atmospheric chamber 280 thus creating an upward pressure differential across the piston 274. Thus, the hydraulic timer means 206 is not necessarily started prior to placement of the tool in the well 11. The rupture disk 282 can be designed so that it will rupture only after the tool has been lowered to a certain depth within the well 11. The advantage of this activation method is that no metering time will be used until the tool experiences a significant pressure level. This means that no metering time will be wasted while the tool is being rigged up to be placed in the well. When the timer 206 is started as just described, moving the spring biased poppet 238 to the open position illustrated in FIG. 2H, this permits the spring biased timing piston 208 to begin pushing hydraulic fluid from the lower oil chamber 212 through the fluid flow restriction 214 into the dump chamber 216. The hydraulic timer means 206 is constructed so as to provide sufficient time, for example, for the fluid sampling apparatus 120 to be lowered to its desired position within the well 11 before the blocking valve 188 is opened to permit a fluid sample to be taken. Preferably with this version of the tool 120 having the mechanical initiating means 228, the hydraulic timer 206 is started at a preselected point, e.g. at a certain depth, within the well, and the hydraulic timer 206 does not finish displacing the entire volume of hydraulic fluid through the fluid flow restriction 214 until after the tool has been completely run to its final position within the well 11. The hydraulic timer 206 is designed so as to provide a sufficient time delay so that there is plenty of time for the tool to be placed at its final depth in the well before the blocking valve 188 is opened and the sample valve means 166 begins to move to allow a sample of well fluid to flow into the sample chamber 148. The metering time provided by the hydraulic timer means 206 is typically within the range of from two to ten hours. The metering time for the sample valve 166 to move from a closed to an open position after it begins moving is typically about five minutes. Both of these times can of course be adjusted by varying the construction of the apparatus. Looking now at the upper end of the apparatus 120 as seen in FIGS. 2A-2C, the sample chamber 148 is initially filled with oil above a floating piston 250. There is a restricted orifice 252 mounted in the intermediate adapter 130. The sample chamber 148 is communicated through the restricted orifice 252 with an upper air chamber or upper dump chamber 254. A second floating piston 256 is initially located in the lower end of air chamber 254. When the sample valve means 166 moves downward relative to body 122 to allow fluid from the well 11 to flow through the sample port 162 into the sample chamber 148, the oil initially filling sample chamber 148 above the floating piston 250 is forced relatively slowly upwardly through the restricted orifice 252 into the dump chamber 254 below the second floating piston 256. The purpose of the dual floating piston arrangement on the upper end of FIG. 2 is to keep the well fluid entering the sample chamber 148 from experiencing a significant pressure drop as the sample chamber 148 fills. If the fluid experiences a large enough pressure drop, the gas in the sample can flash, degrading the quality of the sample. An additional feature seen near the upper end of FIG. 2A is a disabling means 258 for disabling the fluid sampling apparatus 120 when pressure in the well 11 exceeds a predetermined level. The body 122 has a pressure relief passage 260 defined therein and communicated with the well 11. The pressure relief passage 260 may be considered to include a cartridge passage 261 through a rupture disk cartridge 262 and a bore 264 through upper coupling adapter 126 which is communicated with the dump chamber 254. Thus, the pressure relief passage 260 communicates the well 11 outside the body 122 with the dump chamber 254 and across floating piston 256 with the sample chamber 148. The disabling means 258 includes a rupture disk 266 held by a threaded disk insert 268 in the cartridge 262 so that the rupture disk 266 blocks the pressure relief passage 260. The rupture disk 266 is constructed to rupture when the pressure differential between the well 11 and the substantially atmospheric pressure contained in dump chamber 254 exceeds a predetermined level above which it is undesirable to trap a sample of fluid. If the fluid sampling apparatus 122 encounters pressure within the well 11 in excess of the level at which the rupture disk 266 is designed to rupture, the disk 266 will rupture thus allowing well fluid pressure to be communicated to the dump chamber 254 and across the floating piston 256 to the hydraulic fluid initially contained in the sample chamber 148 above the floating piston 250. Thus, when the sample valve means 166 later is moved downward, a fluid sample will not flow through the sample port 162 and into the sample chamber 148. This is because the well fluid pressure will be present on both sides of the floating piston 250 thus balancing well fluid pressure across the sample chamber 148. Thus, the disabling means 258 prevents the trapping of a fluid sample in the sample chamber 148 at a pressure in excess if the predetermined pressure at which the rupture disk 266 is designed to rupture. This is a significant safety feature. For example, if a sample is trapped at too high a pressure, the gases from the sample may leak past the seals defining the sample chamber 148 when the fluid sampling tool 120 is pulled out of the well 11. If those gases contain poisonous components, this presents a safety hazard to personnel operating the well. Also, the laboratory equipment utilized to remove and test the fluid samples may not be able to satisfactorily handle samples above a certain pressure. Again, the proper selection of rupture disk 266 will insure that samples are not inadvertently trapped at pressures in excess of those which can be safely handled. It will be appreciated that the disabling means 258 is useful on tools other than the sampling tool disclosed herein. It could be used on any tool designed to operate in response to well pressure. The fluid sampling tool 120 can generally be described as having a body 122 with a low pressure chamber 148 defined therein, and having a first port 162 defined through the body 122. The floating piston 250 can be generally described as a pressure responsive operating mechanism 250 disposed in the body 122 and having its lower side communicated with the well through the port 162 and having its upper side communicated with the low pressure chamber 148. The rupture disk 266 placed in the pressure relief passage 260 thus provides a disabling means for disabling the apparatus when fluid pressure in the well exceeds the predetermined level at which the rupture disk 266 will rupture. When the rupture disk 266 ruptures, fluid pressure from the well is communicated to the low pressure zone 148 and thus to the upper side of the floating piston operating mechanism 250. The general manner of operation of fluid sampling apparatus 120 is as follows. The apparatus 120 is shown in FIGS. 2A-2H in its initial position in which it is lowered into the well. The apparatus is shown in FIGS. 3A-3H in its final position after the hydraulic timer 206 has opened the blocking valve 188 and allowed the sample valve means 166 to slide downward within the body 122 thus filling the sample chamber 148. As previously noted, the hydraulic timer means 206 is started by the mechanical initiation means 228 upon rupture of the rupture disk 282. This starts a first predetermined time period which may be on the order of two to ten hours prior to the time at which the locking valve 188 is opened. This first time interval allows the fluid sampling apparatus 120 to be lowered into the well 11 to its desired location at which the well 11 is to be sampled. When the hydraulic timer means 206 does open blocking valve 188, the external well pressure acting through power port 164 acts downward on the piston 172 shearing shear pins 167 and slowly pulling the sample valve means 166 downward within the body 122 as hydraulic fluid from oil chamber 150 slowly meters through the restricted orifice 160 into the air chamber 152. When the seam 176 moves below sample port 162 well fluid flows through fill port 182 and fill passage 184 into the sample chamber 148 below the floating piston 250. The floating piston 250 moves upward forcing the hydraulic fluid which initially fills sample chamber 148 above floating piston 250 through the restricted orifice 252 into the upper dump chamber 254 below second floating piston 256. Prior to the time seal 178 passes sample port 162, there is sufficient time for the sample chamber 148 to completely fill with a sample of well fluid. When the valve 166 reaches its final position as illustrated in FIGS. 3C-3D, the seals 178 and 180 are on opposite sides of sample port 162 thus sealing the well fluid sample within the sample chamber 148. There is a significant advantage to the apparatus 120 having separate sample port 162 and fill port 164 rather than having a single port which serves the dual function of permitting the sample to flow into the sample chamber and communicating well pressure with the piston to actuate the sliding sample valve. The annular space 274 (see FIG. 3D) above the piston of the valve means 166 is not in communication with the sample chamber 148, and thus there is much less compression of the fluid in the sample chamber 148 necessary to move the valve means 166 upward to a position wherein the sample can be removed through the sample port 162. Thus, there is less degradation of the well fluid sample. Seals 170, 176, 178 and 180 collectively provide a seal means between the sample valve means 166 and the body 122 for isolating the sample chamber 148 from the annular portion 274 of the oil chamber 150 above the enlarged diameter piston 172, and also for isolating the sample chamber 148 from both the sample port 162 and the power port 164 after the sample chamber 148 is filled with sample fluid from the sample port 162. The Embodiment Of FIGS. 4A-4B FIGS. 4A-4B show a modified version of the apparatus like that of FIGS. 2 and 3 in which the mechanical spring 210 of the hydraulic timer means 206 has been replaced with a compressed gas spring. The valve body has been modified and is now designated by the numeral 400. Valve body 400 has upper portion 402, reduced diameter intermediate portion 404, and further reduced diameter neck portion 406. Valve passage 408 extends downward into valve body 400 and intersects radially extending valve ports 410. Intermediate portion 404 carries first and second O-ring seals 412 and 414. Intermediate portion 404 is closely received in a bore 416 of a modified blocking means housing section 418. A gas fill port 420 is disposed through housing section 418 and is closed by a threaded plug 422 having O-ring seal 424. In the position shown in FIGS. 4A-4B the seals 412 and 414 are on opposite sides of fill port 420 thereby blocking fill port 420. A gas chamber 426 within spring housing section 140 has already been filled with nitrogen gas at a pressure in the range of about 3448 to about 6895 KN/m 2 (about 500 to about 1000 psi). This pressure acts downward on the circular area within O-ring seal 209 of timing piston 206, thus providing a compressed gas spring acting against timing piston 206. The gas chamber 426 is filled in the following manner during assembly of the apparatus. A gas fill valve (not shown) is connected to fill port 420 in place of the plug 422. Prior to making up a threaded connection 428 between drain nipple 136 and housing section 418, the valve body 400 is only partially inserted into bore 416 with seal 414 being located in bore 416 above fill port 420. Sleeve 200 is already in place over neck portion 406 thus closing valve port 410. The thread 428 is partially made up to hold the valve body 400 in the position just described. The gas chamber 426 then is filled with pressurized nitrogen gas and afterward the thread 428 is completely made up thus pushing valve body 400 down to the position of FIG 4A blocking fill port 420. Then the gas fill valve is removed and plug 422 is put in place. The gas chamber 426 preferably has a volume such that the gas expands on the order of about thirty percent as the timing piston 206 moves through its full length of travel. A primary advantage of the compressed gas spring of FIG. 4 as compared to the mechanical spring of FIG. 2 is that the gas spring is more reliable at elevated temperatures. The gas spring design is limited only by the temperature resistance of seals associated with gas chamber 426. Those seals are preferably formed of a Vitron material capable of resisting temperatures up to about 260°C (500°F). Mechanical springs, by contrast, start to become less predictable at temperatures above about 149°C (300°F). It is noted that the embodiments of the fluid sampling apparatus of the present invention can be operated in an inverted position. The various embodiments of the present invention provide a very reliable design for a fluid sampling apparatus. This is so because the tools involve the use of tremendous hydraulically induced forces to drive the sample valve mechanism thus insuring the opening and closing of the sample valve mechanism. The fact that the operating forces are so high greatly reduces the susceptibility of the tool to operational problems associated with sand or other debris in the sample valve means that is in contact with the well bore fluids. Another significant advantage of each of the systems described above is that the activation mechanisms are completely removed from well bore fluid and contamination which might affect their performance or reliability. The hydraulic timer mechanism offers the advantage of not being adversely affected by elevated temperatures which would disable most electronic devices. An important basic concept which has been utilized in the versions of this tool is the use of a clean oil system to control tremendous forces created by a hydraulic area which is driven by a differential pressure between well bore hydrostatic pressure and the atmospheric pressure inside an air chamber. Thus it is seen that the apparatus of the present invention readily achieves the ends and advantages mentioned as well as those inherent therein. While certain preferred embodiments of the invention have been illustrated and described for purposes of the present disclosure, numerous changes in the arrangement and construction of parts may be made by those skilled in the art.

Claims: A downhole tool apparatus (120), comprising an operating mechanism (166); a hydraulic timer means (154, 186, 206), operably associated with said operating mechanism (166), for providing a time delay prior to operation of said operating mechanism, said timer means including a fluid flow restriction (214) and a spring biased piston means (208) for pushing a predetermined volume of hydraulic fluid through said fluid flow restriction (214); an initiator valve (228) located hydraulically in series with said fluid flow restriction (214), said initiator valve (228) having a closed position wherein said hydraulic fluid is prevented from flowing through said fluid flow restriction (214), and an open position wherein said hydraulic fluid is permitted to flow through said fluid flow restriction (214); and pressure responsive switching means (248A) for moving said initiator valve to its said open position and thereby starting said hydraulic timer means (154, 186, 206) in response to an increase in pressure in an outside zone (11) outside said apparatus (120) to a predetermined level; characterised in that said initiator valve (228) includes spring biasing means (240) for biasing said initiator valve (228) toward its said closed position, said initiator valve including a protruding valve stem (246); and said pressure responsive switching means (248A) includes a switching piston (274) having a first side exposed to said outside zone (11) and having a second side exposed to a low pressure chamber (216) defined in said apparatus, said switching piston including abutment means (250) abutting said protruding valve stem for moving said initiator valve (228) to its said open position in response to an increase in fluid pressure in said outside zone. Apparatus according to claim 1, further comprising rupture disk means (282) for initially isolating said switching piston (274) from said outside zone until pressure in said outside zone reaches said predetermined level.

Inventors: BECK HAROLD K, SCHULTZ ROGER L, BECK, HAROLD K., SCHULTZ, ROGER L.
Applicants: HALLIBURTON CO, HALLIBURTON COMPANY
Application year: 1991
Main classification: E21B49
IPC codes: E21B41, E21B34, E21B49