CA2135951A1 - Safety valve controller method and apparatus - Google Patents

Abstract

Method and apparatus for opening and closing surface safety valves and a surface controlled subsul face safety valve used on a controller for oil and gas wells. The valves are ope:ned and closed in a timed and predetermined sequence thereby to reduce wear and extend the life of the surface controlled subsurface safety valve.

Description

21 35gSl SAFETY VALVE CO~rROLLER METHOD AND APPARATUS
INTRODUCTION
This invention relates to a method and apparatus for controlling the opening and closing of surface a.nd surface controlled subsurface safety valves as used on oil and gas wells and, more ~dl~i~Uldlly, to opening and closing such valves in an - :.".,-l;. A11y controlled sequence.
BACKGROUND OF THE INVENTION
Oil and gas well ~hristmas trees mounted on the wellhead include surface safety valves ("SSV's") that can be closed r ~n qfir~lly in the event ofunsafe pressures, leakage, flowline rupture, fire, ~alLll~Lu~ or other hazardous15 conditions. In addition to surface safety valves, surface controlled subsurface safety valves (SCSSV's) are installed in the production tubing below ground level and can also be ~llt~mofirAlly closed to shut in the well. The SCSSV's are particularly important if the surface safety valves or the wellhead is damaged or mAlfilnf tir~nc Since the SCSSV is located in the tubing string, l~ld~ llL or repair of the SCSSV is difficult and expensive. When the SCSSV is closed, .1.~o,A.l-li..l. of the SCSSV is possible due to the throttling effect of the SCSSV and high pressure fluid flow.
Accordingly, it is desirable to limit the 11..~ that occurs when the SCSSV is closed under con~litions of high pressure fluid flow. To that end, it is desirable to limit any closing of the SCSSV when fluid flow through the SCSSVis taf.~ing place to those situatiorls where closing due to safety ~'Ull~ is 30 necessary. When testing the sy~tem, for example, it would be preferable to provide for the closing action without flow Ll~ LIllu~ and, likewise, it would be ~ 213SgSl preferable that the SCSSV be opened only when there is no fluid flow a~ auuu~l-. This will extend the life of the SCSSV and make repair or cclll~,.l. less frequent.
SUMMARY OF THE INVENTION
According to one aspect of the invention, there is provided an ac~ used witll a safety contrûller, said ~., ".~ being charged with hydraulic fluid on one side of a piston and a gas operable on the lû opposite side of said piston, said gas being ûperable to maintain pressure on said hydraulic fluid, said hydraulic fluid being operable to maintain opening pressure on a surface controlled subsurface safety valve.
According to a further aspect of the invention, there is provided a 15 dual pressure pump assembly operably comnected between first and second hydraulic circuits, said first hyd~^aulic circuit being charged by a first movable plunger and said second circuit l~eing charged by a second stationary plumger, said first and second plungers being concentric.
Accordmg to a further aspect of the invention, there is provided an adjustable time delay choke comlected with a control circuit of a surface controlled subsurface safety valve dump v~lve, said choke being operable tû delay the pressure loss from said control ~,ircuit thereby to defer closing of said subsurface safety valve.
According to a further aspect of the invention, there is provided a safety valve controller for opening and closing a subsurface safety valve and a surface safety valve comprising a hydraulic circuit connected between said surface and subsurface safety valves, said circuit allowing the closing of said surface safety valve without closing sai~l subsurface safety valve.

21~59~1 According to yet a. further aspect of the invention, there is provided an interlock valve operable within the hydraulic circuit of a safety valve controller, said interlock valve acting to allow the operling of a surface safety valve only after the opening of a surface controll~ d subsurface safety valve.
s According to yet a further aspect of the invention, there is provided a method of opening a closed sulface controlled subsurface safety valve and closed surface safety valve used in cont] oller safety valves for oil and gas wells, said method comprising first opening said surface controlled subsurface safety valve 10 and, thereafter, opening said surl`ace safety valve in a ~ sequence and at a ~Irl1rlr.",;". .I time following said opening of said subsurface safety valve.
According to still yet a further aspect of the invention, there is provided a method of closing surface controlled subsurface safety valve and a 15 surface safety valve used in a colltroller for safety valves of oil and gas wells in a rlrl I l l il lrd sequence, said method comprising initially closing said surface safety valve and, thereafter, closing said surface controlled subsurface safety valve after an adjustable ~l~d.t.,l.li..~d and adjustable period of time following said closure of said surface safety valve.
BRIEF DESCRlPTION OF THE SEVE~AL VIEWS OF T~F ~RAWINGS
A specific ~IIIb~ ' of the invention will now be described, by way of example only, with the use of drawings in which:
Figure 1 is a schernatic of the hydraulic circuit of the safety valve controller according to the inven~ion;
Figure 2 is a cross-sectional view of a reserve oil saver valve as 30 used with the hydraulic circuit of Figure 1;

213~951 Figure 3A, 3B an~l 3C are 11;..~.a,., -~;. cross-sectional views of the stored oil :~rc -~ l with its in!dicator as used with the hydraulic crrcuit of Figure 1;
Figure 4 is a cross-sectional view of the open pilot auto override as used with the hydraulic circuit Or Figure 1;
Figure 5 is a cross-sectional view of the pumping interlock valve as used with the hydraulic circuit oi` Figure 1;
Figure 6 is a cross-sectional view of the dual pressure pump assembly used with the hydraulic circuit of Figure 1;
Figure 7 is a cross-sectional view of a dual pilot dump valve used with the hydraulic circuit of Figure 1; and Figure 8 is a cross-sectional view of a single pilot dump valve used with the hydraulic circuit of Figulre 7.
DESCRIPTION OF SPI~CIFIC EMBQPII~ENT
With reference to ~he drawings, a hydraulic circuit for a safety valve controller is illustrated generally at 10. It includes a comnection to the tubing line by which a surface controlled sul~surface safety valve ("SCSSV") 11 is controlled 25 and a similar tubing line to open and close a surface safety valve ("SSV") 12.
Each of the valves 11, 12 is comlected to a manual pumping circuit 13 or to a powered pumping circuit 14. Lilkewise, SCSSV 11 is connected to a dual pilot dump valve 15. Dual pilot puml~ valve 15 will be described in greater detail hereafter. The pump circuit 13 further includes a dual pressure pump assembly 1730 as will be described in greater detail.

~ 2~3S9~l A pressure sensing pilot valve 20 is connected to a flow line 21 which extends from the well-head (not illustrated). The pilot valve 20 allows the control circuit 22 to drain back to the reservoir when the flow line is above orbelow plr/1rlr, Illil.r,l pressures.

A stored fluid ~i~.,,.,.l','~ll 23 has an indicator rod 24 which visibly represents the level of fluid in the I ~-,r 23. The operation of the stored fluid ~c lml-l 23 will be expl.ained in greater detail hereinafter.
A reserve fluid sa~er valve 30 is positioned in the hydraulic circuit so as to allow the closing of the SCSSV 11 utilizing dump valve 15 while alily preventing further outflow of hydraulic fluid from ~ ".,1"~.-, 23.
The reserve oil saver valve 30 will be described in greater detail hereafter.
A pumping interlock valve 31 is positioned in the hydraulic circuit of the safety valve controller 10. The interlock 31 allows the SSV 12 to be opened only after SCSSV 11 is first opened. The pumping interlock valve 31 will be described in greater detail hereinafter.
An open pilot automatic override 32 is positioned in the control circuit of the safety valve controller 10. The override 32 prevents hydraulic fluid flow from the control circuit 22 Ihrough an open pilot 20 until the SSV 12 has been ~ uliL~d, i.e., pumped open, as will be described. The open pilot automatic override 32 will be described in greater detail hereafter.
A dual pilot dump valve 15 (Figure 1) is used to maintain the SCSSV 11 in the open position until SSV 12 is closed. A single pilot dump valve 33 is used to hold SSV 12 open until control circuit 22 is d~ u~iL~I. The dual pilot dump valve will be described in greater detail hereinafter.

~ 2~3~951 A jumper tube 34, in place as shown in Figure 1, can be removed and replaced by plugs 35. The function of jumpers 34 will be described in greater detail hereinafter.
OPERATIQN
In operation amd ~vith reference to Figure 1, it will initially be assumed that the SCSSV 11 amd SSV 12 are in the open condition below surface and above surface, lC~ ly. It will also be assumed that flowline 21 is 10 operating within pressure set pOillts and that pilot 20 is in the position illustrated;
that is, no fluid is being drained from the control circuit 22. It will further be assumed that a jumper tube 34 is installed in the control circuit; that is, bypassing check valve 39. In such position, it is intended that the SCSSV 11 will close following the closure of SSV 12 after a time delay as determined by the setting of 15 time delay 44.
In this ~...,ri~,.,ali~"~, SSV 12 will close, in a first instance, when the fusible fittings 40 melt such as would be the case, for example, when there was a fire at the well. The fusible fittings 11 will ~ / bleed off control 20 pressure from dump valve 33 in control circuit 22 which will allow the high pressure actmg to hold open SSV 12 to be dumped through closmg rate control 41.
When tubing jumper 34 is removed and replaced by plugs 35, check valve 39 prevents branch 25 of t~le control circuit from being ~ u~ d when 25 the pilot goes outside its set poinl:s. Dump valve 15 cannot open if control pressure remains m control circuit 25 and the SCSSV therefore remains open untilcircuit branch 25 is d~ l by meltmg of fusible plug ~0 or the actuation of a manual ESD valve 51, 52.
When SSV 12 is o]?en, the pressure used to hold it open is also applied to h~ 1 50 and to the righthand pilot 43 of SCSSV dump valve 15.
.

,~ 21'~59~1 After SSV 12 is allowed to close, the fluid stored in ~ 50 is bled off through adjustable time delay choke 44. The time required to do this ensures that SSV 12 is completely closed and that fluid motion in the tubing string will havesubsided before the righthand pil~ot 43 is fully d~LcDDulcd and dump valve 15 isS permitted to open thereby closing SCSSV 11.
The action of the '~SV 12 and the SCSSV 11 in respect of the melting of either of the fusible fillings 40 is similar to the case where either the panel normal trip 51 of the ESD (Emergency Shut Down) or station manual trip 10 52 are operated.
It will next be assllmed that it is desired to shut down only the SSV
12 when the pilot 20 is activated when the operating highlow pressure set conditions within flowline 21 are exceeded. In this case, pilot 20 will i~lulledid~cly 15 open and drain the pressure from pilot 53 in latching trip valve 54 permitting latching trip Yalve 54 to open and drain control circuit 22 and pilot valve 60 of single pilot dump valve 33 whicll in turn will dump the high pressure of SSV 12 through closing rate control 41. Thus, SSV 12 will close and open pilot automatic override 32 will ~"l,,. ~1....~lly cla,se. However, the control circuit branch 25 20 connected to pilot 42 will not bleed off due to the isolation between the twocontrol circuits 22, 25 caused by the removal of jumper 34 bridging check valve 39. C~ntrol circuit 25 will be maintained at pressure and dual pilot dump valve 15 will remain closed thereby ,..,~;.,l-;..;,.~ pressure to keep SCSSV 11 in its open ...,.r~ i".
It will next be assllmed that SCSSV 11 and SSV 12 are closed and it is desired to open the valves 11, 12 to put the well into production. If power pumping is to be used, power pumping selection valve 65 must be in the C & S
position as indicated. For powel or manual pumping, circuit selector valve 62 30 must be in the C position as indicated, latching trip valve 54 closed and latched and SSV closing valve 66 in the RUN position. Valves 51, 52 and fusible fittings 2~ 51 40 must all be in the closed condition. Hydraulic fluid can now be pumped into the corltrol circuit æ and branch 25 through pressure reducing valve 101 by operating either manual pump 13 or power pump 14. Pressure reducing valve 101 closes when pressure in the contlol circuits 22, branch 25 and ~rc-lm~ r,r 45 has 5 reached the pressure setting of plessure reducing valve 101.
Pressure m the colltrol circuit will close SSV dump valve 33 by acting on pilot 60 and, similarly, SCSSV dump valve 15 will be closed by controlpressure acting on pilot 42.
Power pumping selector valve 65 must now be turned to the DH
position as indicated. Either pump can be used to pump hydraulic fluid from its respective reservoir into the ~ " and through the control line to open SCSSV 11.
Reference is now made to the stored fluid :lrrllmlll 23 and its indicator rod 24 (Figures 1 and 3). Since hydraulic fluid under pressure is used to maintain the SCSSV 11 in its open position, it is desirable to provide for a supply of oil to maintain pressure in the line as the oil slowly bleeds off due to possible 20 leakage past the seals (not shown~ of the SCSSV 11. To that end, the stored oil 23 has a piston 70 (l~igure 3) which is driven by a source of nitrogen gas 71 to maintain the pressure a~: a p.~,l. i~ .",;,.. .I value. The side of piston 70 opposite to the side acted on by the nitrogen gas 71 is connected to piston rod 80 which is of a smaller diameter th.m piston 70. With reference to Figure 3B, oil is 25 provided to Ihe stored oil ~ .l"".~ 23 through port 72 by a source of hydraulic fluid such as portable pump assembly 74 or dual pressure pump assembly 17 The fluid will enter between the piStOII rod 80 and the cylinder 81 and will move the piston rod 80 and piston 70 leftw,~rdly as viewed in Figure 3.
Because the area ol piston rod 80 is smaller than the area of piston 70, the pressure at port 72 required to push piston rod 80 leftwardly will be 2135~51 g ol~ ldl to the area of piston 70 to the area of piston rod 80. ~ m~ f lr 23 thereby acts as a pressure intensifier. By selecting the ratio of diameters between piston 70 and piston rod 80 it is possible for the purpose of ~ the dC,~,I ' ' 23, to use the press~lre in commercially available cylinders of 5 u,...~ d nitrogen. Thus the lligher pressures, required to operate the subsurface safety valve 11, are achievable with lower pressure nitrogen gas precharge in the ~ m~ rl~,l 23.
The ~c-lml-l ~il.~,~ir.~. 23 will be mounted in a vertical position 10 with the nitrogen end being uppermost. A layer of lubricating oil is carried on the upper end of piston 70 and acts to lubricate the piston seals and cylinder walls and to also optimize the function of the piston seals to eliminate leakage of nitrogen past the piston seals. The difference in the diameters between piston 70 and piston rod 80 provides an annular ring through which an mdicator rod 24 can slide and 15 the piston actuated end of low hydraulic fluid reserve trip valve 84 can also be situated.
This annular regio]l under piston 70 is sealed off from the nitrogen gas 71 by the seals on piston 70 ,md from the high p}essure fluid in cylinder 81 by 20 piston rod packing 85 and can therefore be operated at dllllU~ iC pressure. This region is conmected to the reservoir through drain port 86.
An indicator rod 24 is kept in contact with the piston 70 by the use of springs 82. As the piston 70 moves upwardly under the influence of the entry 25 of the hydraulic fluid, as viewed in Figure 1, the indicator rod 24 along with attached plate 25 will likewise m~Dve upwardly until the cylinder 81 is fully charged with hydraulic fluid. Plate 25 is attached to a graduated scale that will appear in a transparent tube on t~le top of a enclosure (not shown). This will indicate the amount of hydraulic fluid in the stored fluid ~ Ilmlll 23.

21~59~1 In operation, withl SCSSV 11 in the open position, a certain amount of leakage of hydraulic fluid may occur past the seals of the SCSSV 11. This fluid will be replaced by fluid irl the stored fluid ' 23 which slowly passes mto the line of SCSSV 11 through rese}ve fluid saver valve 30. As the S fluid leaves the stored fluid 23, the indicator rod 24 will move do..l-~vdldly thereby indicatrng to IllAi~llr~lAIII r personnel the amount of fluid remaining and the need for fluid ll.~ll~rl,,r,,l Fluid reserve trip valve 84 is a poppet type valve held closed by a spring and pushed open by the downward movement of piston 70 as it nears the bottom extent of its stroke. Port 87 is connected to the control circuit and when 84 is opened, control circuit 22 is drarned and a closing sequence of SSV 12 is initiated. The hydraulic fluid drained from the control circuit into the region under piston 70 is utilized to saturate an absorbent ring on the lower end of piston 70 to lubricate the cylinder walls below piston 70. The excess is drained to thereservoir through port 86.
The fluid reserve saver valve 30 is illustrated more clearly in Figure 2. A check valve 84 has a bias by springs 90 which are mounted in a spring poppet 91. An O-ring 92 is molmted about the upward facing nose of poppet 91.
Port 93 is connected to the control line of SCSSV 11 while port 94 is connected to the line from dual pressure puml~ assembly 17 and port DH of power pumping selector valve 65. Port 95 is co1mected to drain valve 97 while port 96 is connected to stored oil ~ "..I ~ " 23.
rn operation, whell either of pumps 17, 74 provides fluid pressure to SCSSV 11, poppet 17 will be driven downwardly into the position illustrated in Figure 2. Fluid will pass through check valve 84 to the A~`~`lln~ ' 23. As fluidis used by SCSSV 11 due to lea~.age past the seals, it is replaced by fluid bleeding past the ~ lrtl~;llct of poppet 91 from ~ ." 23.

When, however, S~,CSSV 11 closes due to the hydraulic fluid in its control pressure line being dumped through valve 15, poppet 91 will be propelledupwardly by the sudden surge of fluid until O-ring 92 contacts the poppet gland 98. No further fluid from the ~ mlll 23 may pass through the valve 30 thereby conserving the fluid in ~ cnmlll )r 23.
Open pilot automatic override valve 32 is shown in detail in Figure 4. Port 100 is connected to the line from pressure reducing valve 101. Port 102 is connected to the line from latchmg trip valve 54. Port 103 is connected to the line to SSV 12.
When the override valve is in the closed position, plunger 63 is biased towards port 103 by sprin,~ 105 thus holding pin 104 in the position shown.
Ball 102 is held against seat O-rimg 106 by spring 107 thereby preventing fluid in port 100 from flowing to the latching trip valve and beyond through pilot 20 and/or low fluid reserve trip valve 84.
Fluid pressure is t}lereby held in control circuit 22 by override valve 32 although pilot 20 or low fluid reserve trip valve 34 may be open.
When SSV 12 is pumped open, the pressure in the SSV line will maintain the plunger 63 in the u~wards posi~ion as viewed in Figure 4. In this position, ball valve 102 will be held open by pin 104 and fluid will freely pass to the latching trip valve 54 from the pressure reducing valve 101. When, however, SSV 12 closes due to the dumping of the fluid in the line of SSV 12, plunger 63 will move downwardly and ball ~alve 102 will close thereby preventing fluid fromflowing to the latching trip valve 54 in ~l~alaLi~)~l for the next valve openingoperation.
The function of pumping interlock valve 31 is to prevent opening of SSV 12 until SCSSV 11 has been pumped open. The two different diameters of ~ 213~9~1 stepped plunger 110 are slidably positioned in the upper and lower seals housed in body 123. Port 111 is positione~l between the two seals and connected to the tubing line to SCSSV 11. Thus pressure to SCSSV 11 acts on the difference m areas of the two diameters of plunger 110. Plunger 110 is biased rightwardly by S adjustable spring 116. Pin 121 is an extension of plunger 110 and holds ball 112 off its seat thereby allowing fluidl from ports 113 and 114 to flow back to reservoir 122 through port llS.
When sufficient pressure has been built up by pumping into the SCSSV 11 and stored fluid ;~rmlrmll 23 to open SCSSV 11, this pressure acting through port 111 will force plunger 110 leftwards against spring 116. Ball 112 will be pressed against its valve ~:eat by spring 117 closing access of ports 113 and 114 to reservoir port 115. Wher~ this occurs, pumping to SCSSV 11 circuit can be.l;~..,,l;,,,l~l and pumping switched to open SSV 12.
The dual pressure pump assembly 17 is illustrated more clearly in Figure 6. It has two plungers 124, 125, plunger 124 being the smallest plunger which is connected to the line of SCSSV 11 requiring the highest pumping pressure and plunger 125 being used to provide a lower pressure to the line of SSV 12. A suction port 135 common to each plunger is provided, the suction port 135 being connected to a reservoir 130 (Figure 1). Outlet ports 131, 132, each fitted with check valves, provide fluid to either or both of the lines to SCSSV 11 and SSV 12. A pair of valve stems 133, 134 are provided to open and close p~ W~ly~ bypassing the suction ball valves of each of the plungers 124, 125.
When 133 or 134 are closed, the hydraulic fluid displaced by the axial movement of their associated plungers will l~e forced through their comnected outlet check valve.
By opening or closing the bypass valves 133, 134, the effort of manual pumping can be directed to the desired circuit. In particular, when SCSSV11 has been pumped open, bypass valve 134 will be opened and fluid displaced by 2~3~9Sl plunger 124 will be bypassed arclund its associated suction valve. Thus the force required to operate the manual pl~mp will be limited to the pressure in the circuit selected times the area of the plunger whose bypass valve is closed.
The dual pilot durllp valve 15 is illustrated in detail in Figure 7.
Exhaust port 140 corlnects to the reservoir 141. ~ plunger 143 is under the influence of the high pressure line of SSV 12. The plunger 42 is under the influence of low pressure or control circuit branch 25 entering port 142. Port 143 is the inlet pressure port connect~d to the line of SCSSV 11.
In operation, so lo~1g as the pressure in the line to SSV 12 is sufficient to hold SSV 12 open, plunger 43 will contact plunger 42 and needle valve 144 will preYent fluid flow between ports 143, 140. If there is no pressure in the line of SSV 12 but there is pressure in the control circuit 257 ,,""",.,~ n between the two ports 143, 140 i~, lilcewise prevented. However7 if there is no pressure in both the ports 1427 1507 needle 144 will be unseated7 thereby allowing direct ~;~l.,.".", -~;.7.l between po:rts 1437 140. Thus, SCSSV 11 will close only if both SSV 12 is closed and the control circuit 25 has been bled.
The single pilot dump valve 33 is illustrated in detail in Figure 8.
The inlet pressure port 151 connected to the line of SSV 12 is prevented from exhausting to reservoir 152 (Figuue 1) via port 153 by the action of needle valve 154 under the influence of plunger 160 which is acted on by the pressure in control circuit 22. When the control circuit 22 is bled, valve 33 will dump the fluid from the line of SSV 12 thrclugh the closing rate control screw 161 thereby allowing SSV 12 to close.
Both dump valves 15, 33 act to relieve excess pressure from the lines connected to their respective inlet ports 143, 151. Each dump valve plunger 42, 160 contains a spring that is ~ llr~ when the needle contacts its seat as the plunger is pushed against the bottom of the cavity in which it operates. The , . .. .. . ... .. . . ...

~ 2t 3~Sl ~;UIll~ ;VII force is transmiaed to needles 144, 154 through the threaded r~ between the needle and vhe nut abutting the lower end of the Culll~ul-,~-,d spring.
S The tbreaded ~ c, ,llr ll of the needle with the nut is utilized to adjust the protrusion of the n~ edle past the end of the plunger and thus the force exerted by the spring to hold the needle in leak tight contact with the seat. When the pressure in the inlet port ~lcting on the exposed area of the needle in the seat exceeds the spring force, the meedle will be lifted to bleed off excessive pressure.
A further embodiment of the invention ~l...lrl"~ rc two surface valves which would operate ill a IJIr-~ rd sequence and im association with a surface controlled subsurface safety valve. It is cl l l ' that one surface safety valve would be located in the master valve position and a second would be15 located in the wing valve or filowline position. The uvllll,;.laLiull would be a,u~)lu~liat~ in certdin ~I.l,li. -l i- .,-~ where two surface safety valves in proper ,. .. ,riL. .., l i- -" would be d~lvll .
While specific rlllbOdilllrllL~ of the invention have been described, 20 such description should be taken as illustrative of the invention only and not as limiting its scope as defined ill accordance with the â~ulu~ally ~ claims.

Claims (14)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An accumulator/intensifier used with a safety controller, said being charged with hydraulic fluid on one side of a piston and a gas operable on the opposite side of said piston, said gas being operable to maintain pressure on said hydraulic fluid, said hydraulic fluid being operable to maintain opening pressure on a surface controlled subsurface safety valve.

2. An accumulator/intensifier as in claim 1 wherein said gas is nitrogen.

3. An accumulator/intensifier as in claim 2 and further comprising an indicator to indicate the amount of hydraulic fluid remaining in said accumulator.

4. An accumulator/intensifier as in claim 3 and further including a first control circuit and a first dump valve, said first dump valve closing a surface safety valve when said hydraulic fluid reaches a predetermined quantity.

5. An accumulator/intensifier as in claim 4 and further comprising a fluid reserve saver valve operably inserted between said surface controlled subsurface safety valve and said accumulator, said fluid reserve saver valve operably preventing oil from passing to said subsurface safety valve when pressure in the tubing line controlling such subsurface safety valve is suddenly reduced when said subsurface safety valve is being closed.

6. An accumulator/intensifier as in claim 1 wherein the area of said one side of said piston acted on by said hydraulic fluid is of a predetermined proportion to the area of said opposite side of said piston acted on by said gas.

7. A dual pressure pump assembly operably connected between first and second hydraulic circuits, said first hydraulic circuit being charged by a first movable plunger and said second circuit being charged by a second stationary plunger, said first and second plungers being concentric.

8. An adjustable time delay choke connected with a control circuit of a surface controlled subsurface safety valve dump valve, said choke being operable to delay the pressure loss from said control circuit thereby to defer closing of said subsurface safety valve.

9. A safety valve controller for opening and closing a subsurface safety valve and a surface safety valve comprising a hydraulic circuit connected between said surface and subsurface safety valves, said circuit allowing the closing of said surface safety valve without closing said subsurface safety valve.

10. A safety valve controller as in claim 9 wherein said hydraulic circuit further allows the subsurface safety valve to close only after closure of said surface safety valve.

11. A safety valve controller as in claim 9 wherein said hydraulic circuit includes a dump valve, said dump valve including a high and low pressure operated pilot, said dump valve allowing said subsurface safety valve to close only upon the release of pressure from both said high and said low pressure operated pilots.

12. An interlock valve operable within the hydraulic circuit of a safety valve controller, said interlock valve acting to allow the opening of a surface safety valve only after the opening of a surface controlled subsurface safety valve.

13. A method of opening a closed surface controlled subsurface safety valve and closed surface safety valve used in controller safety valves for oil and gas wells, said method comprising first opening said surface controlled subsurface safety valve and, thereafter, opening said surface safety valve in a predetermined sequence and at a predetermined time following said opening of said subsurface safety valve.

14. A method of closing surface controlled subsurface safety valve and a surface safety valve used in a controller for safety valves of oil and gas wells in a predetermined sequence, said method comprising initially closing said surface safety valve and, thereafter, closing said surface controlled subsurface safety valve after an adjustable predetermined and adjustable period of time following said closure of said surface safety valve.