US3216731A - Well tools - Google Patents

Description

Nov. 9, 1965 w. w. DoLLlsoN 3,216,731

WELL TooLs Filed Feb. 12, 1962 2 sheets-sheet 1 Nov. 9, A1965 w. w. DoLLlsoN 3,216,731

WELL TOOLS Filed Feb. 12, 1962 2 sheets-sheet 2 22.5 so` @a7 183 227 202 .INVENTOR F'Q- 2 william w.oo|||son ATTORNEYS United States Patent O 3,216,731 WELL TOLS William W. Dollison, Dallas, Tex., assignor to Otis Engineering Corporation, Dallas, Tex., a corporation of Delaware Filed Feb. 12, 1962, Ser. No. 172,478 14 Claims. (Cl. 277-1) This invention relates to well tools and to methods relating to wells and more particularly to blow out preventers for preventing escape of well fluids from a well during movement of a well flow conductor into or out of the well and methods for preventing such blow outs of well uids.

An object of this invention is to provide a new and improved blow out preventer for preventing blow out or escape of well fluids from a well during the movement of a well ilow conductor into or out of the well which does not slow down the operation of pulling out or running in of a well flow conductor of a well.

Another object is to provide a blow out preventer having a plurality of resilient elements engageable with a well flow conductor being run into or pulled out of a well to prevent escape of well fluids from the well during such running or pulling operations wherein the pressure to which each of the sealing elements is subjected is relatively low and only a fraction of the pressure of the well iluids whereby excessive wear of the resilient elements is avoided.

Another object is to provide a blow out preventer having a plurality of spaced resilient elements which engage the well flow conductor to prevent escape of well fluids from the well as the well flow conductor is run into or pulled out of the well wherein the resilient sealing elements are subjected to approximately equal pressure diiierentials thereacross with the pressure across each of the resilient elements being a fraction of the pressure of the well iluids.

A further object is to provide a blow out preventer having a plurality of resilient elements for engaging a well flow conductor being run into or pulled out of a well having automatic means for maintaining the pressure dilerential across each of the sealing elements at predetermined substantially constant values.

A still further object is to provide a blow out preventer having a plurality of low pressure sealing elements or strippers for engaging a well flow conductor being run into or pulled out of the well, each of which is subjected to a predetermined low pressure diferential and which cumulatively retain the high pressure well fluids within the well and prevent their escape out of the well during such running and pulling operations.

Another object is to provide a blow out preventer having a plurality of vertically spaced resilient elements engageable with the well flow conductor and having means for maintaining substantially constant equal pressure differentials across each of the sealing elements to hold the sealing elements in sealing engagement with the well flow conductor being run into or pulled out of the well, the pressure below each of the resilient elements being higher than the pressure below the next resilient element positioned immediately thereabove.

Still another object of the invention is to provide a new and improved method for preventing blow out or escape of well fluids from a well during running in or pulling out of a well flow conductor into or out of a well by maintaining substantially constant pressure dillerentials across a plurality of longitudinally spaced sealing elements closing the annular space of the well about the well flow Conductor to hold the sealing elements in sealing engagement with the well ilow conductor with the pressure lCe below each of the sealing elements being maintained at a value substantially higher than the pressure below the sealing element spaced immediately thereabove.

Additional objects and advantages of the invention will be readily apparent from the reading of the following description of a device constructed in accordance with the invention, and reference to the accompanying drawings thereof, wherein:

FIGURE 1 is a vertical sectional schematic illustration of a blow out preventer of the invention usable to practice the method of the invention mounted on a well head of a hydraulic snubbing apparatus employed therewith for running in or pulling out a well ow conductor, such as a tubing string, into or out of the well;

FIGURE 2 is an enlarged vertical partly sectional view of the blow out preventer;

FIGURE 3 is an enlarged sectional view of a pressure regulator of the blow out preventer of FIGURE 2;

FIGURE 4 is an enlarged sectional view of a pressure relief valve of the blow out preventer;

FIGURE 5 is a schematic illustration of the uid pressure system of the blow out preventer illustrated in FIG- URES 1 and 2 which employs the pressure of the well fluids to cause the sealing elements thereof to engage the well ilow conductor;

FIGURE 6 is a schematic illustration of another iluid pressure system for the blow out preventer which employs the pressure of the well iluids for the operation thereof;

FIGURE 7 is a schematic diagrammatic illustration of a lluid pressure system for operating the blow out preventer wherein an external source of iluid under pressure is employed; and,

FIGURE 8 is a schematic illustration of still another fluid pressure system for the blow out preventer which also employs an external source of uid under pressure.

Referring now particularly to FIGURES 1 through 5 of the drawing, the blow outpreventers 10 and 11 embodying the invention are shown supported on the wellhead 12. Asnubber apparatus 15 is mounted on theupper preventer 11 for running in or pulling out a well ilow conductor, such as a tubing string T, formed ofsections 16 connected by the usual collars orcouplings 17.

The snubber apparatus may be of any suitable type such as a snubber apparatus illustrated and described in the United Sates patent application, Serial No. 103,- 351, tiled April 17, 1961 by Phillip S. Sizer. The snubber apparatus may include astationary snubber 18 having alower section 19 having slips 26 which are employed to hold the tubing string against downward movement into the well and anupper section 21 havingslips 22 which are employed to hold the tubing string against upward movement out of the well. The upper and lower sections of the stationary snubber are secured together in any suitable manner, as by thebolts 24. The slips of the stationary snubber may be moved into tubing string engaging positions by any suitable means which are not described in detail since they constitute no part of this invention.

Thesnubber apparatus 15 also includes acylinder 27 having an internalcylindrical wall 28 to form an annular chamber C in which theannular piston 29 is movable. The cylinder is secured to theupper section 21 of thestationary snubber 18 by any suitable means as by means of thebolts 30. AAcylindrical piston rod 31 extends upwardly from thepiston 29 and through a suitableannular yopening 32 in the topannular closure 33. Suitable seal means (not shown) of course are provided to seal between the piston rod and thetop closure 33.Conduits 35 and 36 communicate with the upper i andlower portions 38 and 39 of the chamber so that by selectively admitting fluid under pressure into one portion and releasing fluid for the other portion through these conduits, the piston and the piston rod may be caused to move upwardly or downwardly as desired.

Atraveling snubber 42 is secured to the upper end of thepiston rod 31 and hasslips 43 which are engageable with the tubing string. The means for operating the slips may be of any suitable type and have not been shown since the snubber apparatus constitutes no portion of this invention.

In FIGURE 1, thetraveling snubber 42 is shown in use for forcing the tubingT string T downwardly into the well against the pressure of the well uids. It will be noted that the tubing string extends downwardly through thesnubber 42, thecylindrical wall 28 of the snubber apparatus, thestationary snubber 18 and the blow outpreventers 11 and 10 into thewell head 12 and thence into the bore of the well. During the operations wherein thesnubber 42 is in the position illustrated in FIGURE 1 and is being employed to force the tubing string downwardly into the well against the pressure exerted by the well uids, theslips 43 of thetraveling snubber 42 are caused to engage the tubing section while the piston is in its uppermost position and theslips 22 of theupper tubing section 21 are then moved to their retracted positions out of engagement with the tubing string. Fluid under pressure is then introduced into theupper portion 38 of the chamber C of thecylinder 27 through the conduit 35, while the fluid in thelower portion 39 of the chamber C is allowed to escape through theconduit 36, to cause thepiston 29 to move downwardly and thus force the tubing string downwardly into the well. When the piston reaches the lower limit of its downward travel, theslips 22 of the upperstationary snubber 21 are caused to engage the tubing string to hold the tubing string against upward movement whereupon theslips 43 are moved out of engagement with the tubing string. The piston and thetraveling snubber 42 are then moved upwardly to their initial upper positions by introducing fluid under pressure into thelower chamber 39 of the chamber C through theconduit 36 while permitting the fluid in theupper portion 38 of the chamber C to escape through the conduit 35. This cycle of operation can then be repeated so that the tubing string is moved incremently downwardly into the well.

If the upper snubber is used to support the tubing string and control its downward movement and if the weight of the tubing string is sufficiently great to cause it to move downwardly by gravity, the position of the traveling snubber is reversed so that theslips 43 will tend to grip and hold the tubing string against downward movement relative to the snubber. The uid in thelower portion 39 of the chamber is then released 4at a controlled rate, While fluid is permitted to enter into the upper portion of thechamber 38 through the conduit 35, so that the tubing string is permitted to move at a controlled rate downwardly into the well. When the piston and the traveling snubber reach the lower limits of their movement, theslips 20 of thelower section 19 of thestationary snubber 18 are caused to engage the tubing string to hold it against further downward movement. Theslips 43 are then moved out of engagement with the tubing string and fluid under pressure is introduced into thelower portion 39 of the chamber C through theconduit 36, while the fluid in theupper portion 38 is permitted to escape through the conduit 35, to move thetraveling snubber 42 back to its uppermost position whereupon theslips 43 thereof are again caused to engage the tubing string and theslips 20 are moved out of engagement with the tubing string so that this cycle of operation may again be repeated to permit another length of the tubing string to moved downwardly at a controlled rate into the well.

It will be apparent that the snubber apparatus may also be used to pull out the tubing string T or control its upward movement out of the well in the event that the pressure of the fluids in the well is suicient to expel the tubing string therefrom, in a similar way by the appropriate use of the stationary and traveling sunbbers and by the controlled flow of fluids into and out of the upper and lower portioins of the chamber C.

During movement of the tubing string T into or out of the well, the lower and upper sealing elements or strippers a and 50h of the blow outpreventers 10 and 11 prevent blow out or escape of the wall fluids from the well. The lower blow outpreventer 10 includes a tubular body orhead 51 having alongitudal bore 52 in which are disposed the resilient sealing elements 50a and 50b. The adjacent surfaces of the well head and thehead 51 are provided with aligned annular grooves 53a and 53b, respectively, in which are received lower and upper portions, respectively, of aseal ring 54 which seals therebetween. Thehead 51 is provided with a lower external liange 5S which is secured to theflange 56 of thewell head 12 by means ofbolts 57.

The lower sealing element 50a has anexternal retainer ring 59 at its upper end portion, the resilient sealing element being moulded to the retainer ring. The sealing elements are tubular in form having a central longitudinal bore orpassage 60 defined by the upper outwardly beveled or flared surface 61, a substantially cylindrical upperinternal surface 62, a downwardly and inwardlytapered surface 63, a cylindricallower surface 64 and a lower downwardly and outwardly beveled or aredsurface 65. The lowercylindrical surface 64 is of somewhat smaller diameter than the external surface of thetubing section 16 so that resilient sealing element is in an expanded or stretched condition when atubing section 16 extends therethrough. The beveled upwardly facingsurfaces 61 and 63 act as cam surfaces to help guide the tubing string downwardly through the sealing element and thecoupling 17 thereof to prevent damage to the resilient sealing element, and to cause progressive stretching or expansion of the resilient sealing elements as the tubing sections and the couplings move downwardly and approach the lowercylindrical surface 64 which delines the narrowest section of the flow passage of the sealing element. The downwardly and outwardly beveled or flaredsurface 65 at the lower end of the sealing elements similarly helps to guide the tubing sections and the couplings upwardly to thecylindrical surface 64 of the sealing element and cause progressive stretching or expansion of the sealing element as the tubing string is moved upwardly through the sealing element point. An annular downwardy extendingexternal lip 66 intermediate the ends of the sealing element is adapted to engage the internal surfaces of the head and seal thereagainst since upwardly acting uid pressure in thepassage 52 will tend to expand the lip against the head.

The retainer ring has a downwardly facingshoulder 68 adapted to engage the upwardly facing internal shoulder 69 provided in thepassage 52 by the enlargedupper portion 70 thereof. Theretainer ring 59 also has an upper downwardly and outwardly beveledshoulder 72 which is engaged by the lower annular similarlybeveled shoulder 73 of atubular adapter 75 disposed in the enlargedupper portion 70 of thebore 52.

The sealing element 50b is identical in structure to the sealing element 50a and components thereof have been provided with the same reference numerals to which the subscript b has been added as the corresponding components of thesealing element 50.

The retainer ring 59b of the upper sealing element 50h has its downwardly facing shoulder 68h engaging the upwardly facingshoulder 78 of theadapter 75 which limits downward movement of the upper sealing element in thehead 51. The external annular lip 66b of the sealing element Stlb engages the inner wall of the enlarged upper portion 70a of the bore 52a of the adapter. The lower and upper sealing elements 50a and Sb and the adapter are held against upward movement in the bore orpassage 52 of thehead 51 above the shoulder 69 by akeeper ring 80 releasably secured to the head by asplit ring 81 whose inner and outer portions extend into aligned external and internal recesses 82 and 83 of the head and of the retainer ring, respectively. The split ring is held against movement by the screws 84 which extend through suitable apertures of the keeper ring into threaded bores of the split ring. Abevel ring 85 has a downwardly and outwardly beveled shoulder 86 which engages the upper shoulder 72b of the keeper ring 59h of the upper sealing element 5017 and an upper surface which engages the lower surface of the split ring.

Theadapter 75 is provided with a plurality of lateral apertures orports 90 which communicate with an external annular recess or groove 91 thereof. Thegroove 91 is below a sealing means, such as an O-ring 93, disposed in a suitable annular recess of the adapter which seals between the adapter and the head.

The head is provided with alateral port 96 which communicates with the externalannular recess 91 of the adapter head so that uid under pressure may be admitted into the chamber 97 within the adapter between the lower and upper sealing elements.

Flow of fluid into the chamber 97 through thelateral port 96 of the head is controlled by apressure regulator Valve 100 which includes ahousing 101 threaded into theenlarged portion 102 of thelateral port 96. Avalve seat 104 has a reduced portion 105 which extends laterally outwardly into the bore 107 of thehousing 101. The valve seat is held in position in theport 96 by the engagement of the inner annular shoulder 108 of thehousing 101 with theannular shoulder 110 of the valve seat and the engagement of its annular end surface 111 with theshoulder 112 provided by theenlarged portion 102 of theport 96. The valve seat has an external annular recess in which a sealing means, such as an O-ring 113b is disposed to seal between the head and the valve seat. The housing is provided with a similar sealing means, such as an O-ring 113:2 disposed in an external annular recess thereof which seals between the head and the housing.

Thevalve seat 104 has a bore 114 through which extends the valve stem 115 of the valve head 116 whose beveled shoulder 117 engages with the annular edge or shoulder 118 of the valve seat to close the bore 114 of the valve seat inwardly of thetransverse flow passage 120 of the valve seat. The opposite ends of the transverse How passage open outwardly into theenlarged portion 102 of theport 96 and into an annular passage about the valve head formed between seal means 113:1 and 113b. The valve head 116 is baised toward engagement with the valve seat by aspring 121 disposed about the valve stem whose opposite ends bear against the inner end surface of the reduced portion 105 of the valve seat and the washer 123 disposed about the valve stem and held against outward movement thereon by a nut 124 threaded on the valve stem. It will be apparent that the force with which thespring 121 biases the valve head toward engagement with the valve seat shoulder 118 may be adjusted by rotation of the adjusting nut 124 in one direction or another on the valve stem.

Thehead 51 of the blow out preventer is also provided with alongitudinal passage 126 whose upper end communicates with theenlarged portion 102 of theport 96 between the O-rings 113a and 113b and whose lower end intersects a lowertransverse passage 128 of the head and opens downwardly of the head inwardly of theseal ring 54. The lowertransverse passage 128 of the head opens inwardly into thebore 52 below the lower sealing element 50a.

It will be apparent -that the uid in thebore 52 below the lower sealing element A50a may ow upwardly through thelongitudinal passage 126 to theenlarged portion 102 of theport 96, thence through thepassage 120 and bore 114 of thevalve seat 104 and through the lateral 6port 96 of the head into thebore 52 between the upper and lower sealing elements, and then through the ports of the adapter into the chamber 97 under the control of thepressure regulator valve 100. It will be apparent that the pressure regulator valve will maintain the pressure in the chamber 97, when a tubing string extends through the lower blow out preventer, at a predetermined value which is lower than the pressure in thebore 52 below the lower valve head. The pressure regulator valve opens whenever the pressure diferential between the chamber 97 and thebore 52 below the lower sealing element 50b rises above Value predeter-A mined by the adjusted position of the adjusting nut 124, it being apparent that the fluid pressure acting through thelongitudinal passage 126 tends to move the valve head towards its open position and the pressure within the chamber 97 tends to 4assist thevalve spring 121 in biasing the valve head towards its closed position.

Thehead 21 is also provided with alateral port 130 which opens into the bore orpassage 52 of the head and communicates with theexternal recess 91 of the adapter head below the O-ring 93 thereof. Thehousing 132 of apressure relief valve 134 is threaded into thelateral bore 130. Thepressure relief valve 134 permits flow of fluids from the chamber 97 whenever the pressure within the chamber 97 exceeds a predetermined value. The pressure relief valve houisng has apassage 135 which is closable by avalve body 137 whoserounded seat face 138 is engageable with theannular seat 139 of the housing. The valve |body 137 has an enlargedspring retainer portion 140 provided with arecess 141 in which is disposed abiasing spring 142 one of whose ends bears against theshoulder 143 of the Valve and whose other end bears against the adjustingscrew 144 threaded into the outer end of the housing. Thevalve body 137 may be provided with thepassages 145 which communicate with the interior of the spring retainer recess to facilitate flow of uid through the housing when thevalve body 137 is moved to open position against the resistance of thespring 142. The adjusting screw has anorice 148 through which the lluid may escape to the atmosphere from the relief valve housing.

It will be apparent that the pressure relief valve is responsive to the pressure within the chamber 97 whenever such pressure exceeds a predetermined value. Rotation of theadjutsing screw 144 in one direction or the other will of course change this predetermined value as desired.

Thehead 51 is also provided with an upperlateral passage 150 whose inner end opens into and communi- Cates with thebore 52 of the head above thekeeper ring 80 and the upper sealing element 50h and whose outer end communicates with the lowertransverse passage 128 through theconnector 151 which has a T fitting 152 threaded in the enlargedouter end portion 153 of the upper transverse passage, theconduit 155 whose upper end is threaded intoVthe T connector 151, thepressure regulator valve 156 connected to the lower end of theconduit 155,T connector 157 whose fitting 158 is received in the threaded enlarged portion 159 of the lowertransverse passage 128, thepressure regulator valve 156 also being connected to theT connector 157.

The T connectors are provided with the usual T- shaped flow passages 151a and 157:1, respectively. The upper end of theconduit 155 is threaded into one end of theconnector 151 so that the upper end of its passage 155a communicates with the passage 151:1 of the oon.- nector. The lower end of theconduit 155 is provided with an externalannular ange 160 which is secured to the upper end of thehousing 162 by a cap 163 threaded on the upper end of the housing. A sealing means, such as an O-ring 164, is disposed between theinternal flange 165 of the cap and the upper surface of theconduit flange 160 to seal therebetween and a sealing means, such as an O-ring 166, is disposed in an internal annular recess of the cap 163 to seal between the cap and the pressure regulator valve housing below the flange.

Thepressure regulator valve 156 is identical in all other respects to thepressure relief valve 134 illustrated in FIGURE 3, thehousing 162 being threadedly connected to thelower T connector 157 so that itspassage 168 is in communication with the T-shaped passage 157a of the T connector. The ow of fluid through thepressure regulator valve 156 is controlled by thevalve lbody 170 having an arcuate -surface 171 of its lower end engageable with anannular valve seat 172 to close theow passage 168. The valve body is biased toward closed position by the biasingspring 175 whose lower portion is disposed in the recess 176 of the spring retainer portion 177 of the valve body with its lower end bearing against the upwardly facingshoulder 178 and its upper end bearing against the adjustingscrew 180 threaded into the housing. It will be apparent therefore that thepressure regulator valve 156 will open to permit uid to flow from thebore 52 of thehead 10 bel-ow the lower sealing element 50a into thebore 52 above the keeper ring whenever the pressure differential between the upper and lower portions of tht bore 52 above and below the sealing elements exceeds a value predetermined by the position of the adjusting -screw 180.

Apressure relief valve 183, identical in all respects with thepressure relief valve 134 is connected to theconnector head 151 to permit flow of fluid from its passage 151a. Thepressure relief valve 183 opens to permit escape of iluid from thebore 52 of the head above the upper sealing element 50h whenever the pressure at this point exceeds a predetermined value.

The upper blow outpreventer 11 is substantially identical in all respects to the lower blow out preventer having abody 200 secured to thehead 51 of the lower blow out preventer by means of thebolts 201 which extend through suitable apertures in the lowerexternal flange 202 of thehead 200 into suitable threaded bores in the upper external flange of the lower head. Aseal ring 204 whose lower and upper portions are received in the aligned annular recesses orgrooves 205 and 206 of the adjacent upper and lower surfaces of the two heads seal therebetween. Theupper flange 210 of thehead 200 of the upper blow out preventer is secured to thelower section 19 of thestationary snubber 18 by means ofbolts 211. A suitable sealing ring orgasket 212 has upper and lower portions which are received in the alignedgrooves 213 and 214 of the head and of thesnubber 19, respectively, to seal therebetween.

The upper blow outpreventer 11 has upper and lower sealing elements a and 50b which are held in spaced relationship by anadapter 75. The assembly of the two sealing elements and the adapter is disposed between theannular shoulder 216 of the head and the retainer ring secured to the head by screws 84 in the same manner as are secured the sealing elements of the lower blow out preventer.

Thehead 200 has a lowertransverse passage 220 similar to the lowertransverse passage 128 of thehead 51 whose inner end does not communicate with the bore orpassage 222 of thehead 200 since its inner end is closed, in any suitable manner, as by aweld 223. Thelongitudinal passage 224 of thehead 200 which corresponds to thelongitudinal passage 126 of thehead 51, which intersects and communicates with the lowertransverse passage 220, is closed by aweld 225. One conduit 227, has one end threaded in the outer enlarged end portion of thetransverse passage 220 and has its other end threaded in a suitable bore of an upper connector 228. The connector 228 has an L-shapedpassage 229 which communicates with the bore 230 of the conduit 227 and thebore 232 of aconduit 233 whose upper end is threaded in a suitable bore of the upper connector 228 and whose lower end is threaded into a bore of alower connector 234. The

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connector 234 has an L-shapedpassage 235 which is in communication with thebore 232 of theconduit 233 and also with thebore 237 of a fitting 236 connected thereto. The tting 236 is threaded in a bore of theT connector 157 and itsbore 235 is in communication with the passage 157a of the T connector and thus with thepassage 128.

Flow of fluid from thebore 52 of the lower blow out preventer into thechamber 240 between the upper and lower sealing elements of the upper blow out preventer is controlled by apressure regulator valve 242 identical in all respects with thepressure regulator 100. Thepressure regulator valve 242 is identical in structure with thepressure regulator valve 100 and, accordingly, the various components of thepressure regulator valve 242 have been provided with the same reference characters as the corresponding elements of thepressure regulator valve 100.

Thehousing 101 of thepressure regulator valve 242 is threaded in theenlarged portion 244 of a lateral port of thehead 200. The lateral port communicates with thechamber 240 and also with the upper end of thelongitudinal passage 224 of the head. Thespring 121 of course holds the valve head 116 in closed position preventing flow from thelongitudinal passage 224 into the valve of the head until the pressure differential therebetween exceeds a predetermined value.

Thehead 200 of the upper blow out preventer is also provided with alateral port 250 which communicates with thechamber 240 through the ports of theadapter 75 and in whose threaded portion is secured apressure relief valve 252 whose structure is identical to that of thepressure relief valve 134. The components of thevalve 252 are therefore provided with the same reference characters as the corresponding components of thepressure relief valve 134. Thepressure relief valve 252, of course, prevents the pressure within thechamber 240 of the head from exceeding a predetermined Value. Thehead 200 has an uppertransverse passage 254 which however is plugged or closed by theplug 255 in such installations as that illustrated in FIGURE l wherein only two blow out preventers are employed.

In use, when the blow out preventers of the invention are employed to prevent the escape of well fluids from the well during movement of the well flow conductor, such as tubing string T, into or out of the well, and if, for example, the pressure of the well fluids is ten thousand pounds per square inch, the pressure regulator valve is adjusted by rotation of its nut 124 so that it will open whenever the pressure differential between thebore 52 of the lower blow out preventer below the lower sealing element 50a and the chamber 97 between the two sealing elements thereof exceeds two thousand tive hundred pounds per square inch. As a result whenever the pressure within the chamber 97 drops below seven thousand five hundred pounds per square inch, thepressure regulator valve 100 will open to permit the flow of well uids into the chamber 97 until the pressure in the chamber 97 is again raised to seven thousand ve hundred pounds per square inch. Therelief valve 134 is adjusted to open whenever the pressure in the chamber 97 rises a predetermined degree above seven thousand tive hundred pounds per square inch, say to seven thousand ve hundred fifty pounds per square inch, so that the pressure within the chamber 97 will not fall below seven thousand tive hundred pounds per square inch and will not rise above seven thousand five hundred fifty pounds per square inch. As a result, the pressure differential across the lower sealing element never exceeds a predetermined value, in this case approximately two thousand tive hundred pounds per square inch.

Thepressure regulator valve 156 is adjusted to open whenever the pressure differential between thebore 52 of the lower head below the lower sealing element 50a and thechamber 260 formed by the two heads of the two blow out preventers and between the sealing element 50b of the lower blow out preventer and the sealing element 50a of the upper blow out preventer exceeds fve thousand pounds per square inch. Thepressure relief valve 183 is adjusted to open at a value slightly higher than five thousand pounds per square inch, say ve thousand fty pounds per square inch, so that the pressure within theintermediate chamber 260 is held within the range of five thousand pounds per square inch to live thousand fifty pounds per square inch. It will thus be apparent that the upper sealing element 50h of the lower blow out preventer is subjected to a pressure differential of approximately two thousand five hundred pounds since the pressure in the chamber 97 of the lower blow out preventer is maintained at approximately seven thousand five hundred pounds per square inch.

Thepressure regulator valve 242 is similarly adjusted to open whenever the pressure differential between thebore 52 of the lower blow out preventer below the lower sealing element 50a thereof and thechamber 240 of the upper blow out preventer exceeds seven thousand five hundred pounds per square inch so that the pressure regulator valve 242 -will open whenever the pressure within thechamber 240 drops below two thousand five hundred pounds per square inch. Thepressure relief valve 252 is adjusted to open at a value slightly higher than two thousand five hundred pounds per square inch, say two thousand five hundred fifty pounds per square inch, so that the pressure within the chamber 249 is held within the range of two thousand five hundred pounds per square inch and two thousand five hundred fifty pounds per square inch.

It will now be seen that each or" the sealing elements of the lower and upper blow out preventers and 11 is held in sealing engagement with the tubing string which extends therethrough by a pressure differential of approximately two thousand five hundred pounds per square inch so that the full pressure of ten thousand pounds per square inch of the well fluids is in eflect staged across the sealing elements of the blow out preventers and no sealing element is subjected to pressure differentials greater than approximately t-wo thousand five hundred pounds per square inch as the tubing string is moved either downwardly or upwardly through the blow out preventers by a suitable snubber apparatus, such as the snubber apparatus illustrated in FIGURE l.

The pressure Within each of thechambers 240, 250 and 97 tends to rise sharply each time acoupling 17 moves thereinto because the movement of a coupling into a chamber reduces the volume of the chamber. The pressure within each chamber however remains substantially constant since thepressure relief valves 252, 183 and 134 allow the escape of fluid from each chamber as the couplings pass thereinto to prevent the pressure therein from exceeding the predetermined value. As the couplings move out of the chambers, the pressure within the chambers tends to drop since the volumes of the chambers now increase. However, as the pressure in each chamber drops below the predetermined value, the pressure differential between such chamber and thebore 52 of thehead 51 increases since the pressure of the well fluids remains substantially constant and the appropriatepressure regulator valve 100, 156 or 242 opens to permit ilow of the well fluids into such chamber until the pressure within such chamber again attains the desired predetermined value.

It will now be seen that a new and improved blow out preventer for preventing escape of well fluids from a well during the movement of a well flow conductor into or out of the well has been illustrated and described which includes a tubular member or head connectible to the well head and having its bore in longitudinal alignment with the bore of the well, the tubular member being provided with `a plurality of resilient sealing elements which seal between the well llow conductor and such tubular member or head, the blow out preventer having means for regulating the pressure differential across each of the sealing elements so that the fluid pressure below each sealing element is greater than the pressure immediately thereabove and so that each sealing element is subjected to a pressure differential which is much smaller than the pressure differential bet-Ween the atmosphere and the well fluids and bears only a portion of the force exerted by the pressure of the well fluids tending to llow between the well flow conductor and the tubular member.

It will further be seen that the means for subjecting the sealing elements of the blow out preventer to a predetermined pressure diferential includes pressure regulator valves for admitting fluid under pressure into the tubular member between adjacent spaced sealing elements of the blow out preventer to maintain the pressure differential across such sealing elements at predetermined values and with relief valves for preventing the pressure between adjacent ends of adjacent sealing elements from exceeding predetermined Values.

It will be apparent that the well flow conductor, such as a tubing string having externally extending couplings orcollars 17, may be moved continuously through the sealing elements of the blow out preventers without the necessity of stopping movement of the tubing string each time a coupling is moved through the blow out preventer as is necessary where conventional ram type blow out preventers are used.

It will further be seen that the blow out preventer includes a head having a pair of resilient sealing elements 50a and 50h which are held in longitudinally spaced positions byadapter 75 to provide a chamber between the sealing elements, that fluid under pressure is admitted into the chamber through a pressure regulator valve and that lluid is allowed to escape from the chamber through a pressure relief valve so that the pressure .within such chamber is maintained at a substantially constant predetermined value.

It will further be seen that the pressure relief Valves permit escape of fluid from the chamber as the volume of the chamber is decreased by the passage of a tubing string thereinto to prevent the pressure therein from increasing above predetermined value and that the pressure regulator valves permit flow of fluids into such chamber as the volume of the chamber is increased upon the movement of a coupling orcollar 17 out of the chamber to prevent the pressure therein 4from falling below a predetermined value,

It will now be seen that the method of the invention for preventing blow out or escape of well fluids from a well during movement therethrough of a well flow conductor which may or may not have spaced external annular flanges, such as couplings, includes disposing a plurality of longitudinally spaced sealing elements about the -well flow conductor to engage the well flow conductor to close the annular space thereabout and to form chambers between adjacent yends of adjacent sealing elements and about the well flow conductor, introducing fluid pressure into the chambers to create a predetermined pressure diflerential across each of the sealing elements tending to hold the sealing element in sealing engagement with the well flow conductor, and maintaining the pressure within each chamber at a predetermined value which is lower than the pressure to which is subjected the lower end of the sealing element defining the lower end of the chamber.

The method also includes the step of permitting lluid to escape from each chamber as an external flange of the well flow conductor enters into such chamber and decreases the volume of the chamber to prevent the pressure within the chamber from exceeding a predetermined value and the step of permitting fluid under pressure to enter each chamber as an external flange leaves the chamber to prevent the pressure within the chamber from falling below a predetermined value.

.pounds per square inch.

If desired, as indicated in broken lines in FIGURE 5,accumulators 266, 267 and 263 may be connected to the blow out preventers in such manner that they are placed in communication with thechambers 240, 260 and 37, respectively, in order to minimize the llow of iluids through the pressure regulator valves and the pressure relief valves. Each. accumulator may be in the form of a closed container, a portion at least of which is lllled with a compressible gas so that fluid lfrom each of the chambers of the blow out preventers will tend to flow into its associated accumulator thus further compressing the gas in the accumulator as a coupling enters into such chamber and reduces its volume and will flow therefrom and into its associated chamber as the collar of the well flow conductor moves out of such chamber and thus increases its volume. In this manner the llow of fluid through the pressure regulator and pressure relief valves is minimized which may be desirable where the well lluids contain sand, mud or other abrasives which tend to damage the seating surfaces of such valves.

It will be apparent that when thepressure regulator valves 100, 156 and 242, as shown in FIGURES 1, 2 and 5, are connected in parallel with thebore 52 of thehead 51 of the lower blow outpreventer 10 below the lower sealing element 50a thereof, thepressure regulator valve 242 must regulate the flow of fluids when subjected to a higher pressure differential than the other two pressure regulator valves and that thepressure regulator valve 100 must regulate the flow of fluids when it is subjected to a predetermined but lower pressure differential than the other two pressure regulator valves. If desired, the pressure regulator valves may be connected in series, as illustrated schematically in FIGURE 6, to the source of fluid pressure in order that each of the pressure regulator valves may be subjected to the same pressure differential. It will be noted that thepressure regulator valve 100 is connected between thebore 52 of thelower head 51 below the lower sealing element 50a of the lower blow out preventer and the chamber 97 thereof between its upper and lower sealing elements so that the pressure on the upstream side of thepressure regulator 100 in the given case is ten thousand pounds per square inch and the pressure on the downstream side is approximately seven thousand five hundred pounds per square inch. Thepressure regulator valve 100 is then subjected to a pressure differential of approximately two thousand five hundred Thepressure regulator valve 156 has its inlet end in communication with the downstream or outlet end of thepressure regulator valve 100 while its downstream or outlet end is connected to thechamber 260 between the lower and upper sealing ele- `ments of the upper and lower blow out preventers and per square inch. Thepressure regulator valve 242 has its upstream or inlet end connected to the downstream or outlet end of thepressure regulator valve 156 and its downstream or outlet end connected to thechamber 240 of the upper blow outpreventer 11 so that its upstream end is subjected to a pressure of lve thousand pounds per square inch and its downstream end is subjected to a pressure of two thousand tive hundred pounds per square inch. This pressure regulator valve, like the other two pressure regulator valves, is thus subjected to a pressure differential of approximately two thousand five hundred pounds per square inch. It will thus be seen that the pressure regulator valves when connected in series as illustrated in FIGURE 6 are each subjected to equal pressure differentials. Therelief valves 134, 183 and 252 are of course adjusted to open at some value slightly higher than seven thousand five hundred pounds per square inch,

ve thousand pounds per square inch, and two thousand five hundred pounds per square inch, respectively.

In the event that the well iluids contain excessive amounts of sand, mud or other abrasives or are highly corrosive, thechambers 97, 260 and 240 between the sealing elements of the blow outpreventers 10 and 11 may be provided with clean fluids under pressure from anexternal source 275 which may be another well producing relatively clean fluids or which may be a hydraulic pump. In this event, the lowertransverse passage 128 of thehead 51 of the lower blow out preventer would be provided with anexternal plug 276, similar to theplug 255 illustrated in FIGURE 2, to close the outer end of the lowertransverse passage 128 while the inner end of thetransverse passage 128 is closed in the sa-me manner as the lowertransverse passage 220 of the upper blow outpreventer 11 is closed by theweld 223. The lower end of thelongitudinal passage 126 of thehead 51 of the lower blow out preventer is also closed at its lower end in the same manner that thelongitudinal passage 224 of thehead 200 of the upper blow outpreventer 11 is closed by theweld 225. As shown in FIGURE 7, the external source of fluid under pressure is connected to the chambers between adjacent sealing elements of the blow out preventers with the pressure regulator valves thereof connected in series.

It will be apaprent of course that the pressure .regulator valves could be connected in parallel between the chambers and the external source of lluid under pressure as is shown in FIGURE 8 wherein thehydraulic pump 300 is employed as the source of fluid under pressure. Thedrive shaft 301 of thepump 300 is driven by any suitable prime mover such as an electric motor (not shown). Theinlet duct 303 of the pump extends and opens into areservoir tank 304 of the liquid which is to be delivered to thechambers 97, 260 and 240 formed by the two blow out preventers through the regulator valves and 156 and 242, respectively. Theoutlet conduit 305 of thepump 300, which has acheck valve 307 connected therein to prevent reverse flow of iluid therethrough is connected to theconduit 308 whoseparallel branches 311, 312 and 313 are connected to the inlet ends of thepressure regulator valves 100, 156 and 242. Apressure accumulator 315 may be connected in communication with theconduit 305 between the pressure regulator valves and thecheck valve 307. The pressure accumulator has at least a portion thereof lllled with compressible gas. Anoverload dump valve 318 may be connected by means of theconduits 319 and 320 across the outlet andinlet conduits 305 and 303, respectively, of thepump 300. The overload dump valve is provided with a biasingspring 322 which biases theoverload dump valve 318 towards closed position. Theconduit 323 transmits the pressure of the fluid in theoutlet line 305 to the overload dump valve to cause it to open whenever the pressure in the outlet line exceeds a predetermined value.

In operation, thexed displacement pump 300, when initially placed in Operation, pumps the liquid from thetank 304 and the regulator Valves will permit tlow of the liquid into the chambers of the blow out preventers until the pressure differential across each of the pressure regulator valves attains a predetermined Value and the pressure accumulator is filled with liquid to a predetermined degree and held under a predetermined pressure by the thus compressed gas of the accumulator. When the pressure within thepressure accumulator 315 attains a predetermined value, the overload dump valve 31S opens since such pressure is transmitted thereto by theconduit 323. Thepump 300 may therefore continue to operate even though no further fluid is permitted to tlow past thecheck valve 307 and merely recirculates the fluid between its inlet andoutlet conduits 303 and 305. Should the pressure within one of thechambers 97, 260 or 240 now drop to increase the pressure differential across one of the pressure regulator valves, such valve opens and permits Huid to flow into such chamber causing ythe pressure within theconduit 305 to drop. VThis drop in pressure causes the pressureoverload dump valve 318 to close and the pump will now cause iluid under pressure to ow through thecheck valve 307 to the pressure accumulator and to such chambers of the blow out preventer through the regulator valves.

While theoutlet conduit 305 of the pump has been shown as connected to theconduit 308 whose parallel branches are connected to the regulator valves, it will be apparent that theoutlet conduit 305 of thepump 300 could be connected to the upstream or inlet end of thepressure regulator valve 100 of the circuit as illustrated in FIGURE 7 wherein the pressure regulator valves are connected in series. It will now be seen that thepump 300 may be employed as the external source of fluid pressure for the blow out preventers.

The pressure of the well fluids may be of such value that only two sealing elements are necessary. For example, if each sealing element operates satisfactorily under a pressure dilerential thereacross of two thousand ive hundred pounds per square inch and the pressure of the well fluids does not exceed five thousand pounds per square inch, only the lower blow outpreventer 10 would be employed. In this case, the lower and uppertransverse passages 128 and 150 of thehead 51 would be closed to the outside by suitable plugs, such as theplug 255. Thepressure regulator valve 100 would be adjusted to open when the pressure diierential thereacross increased above two thousand ive hundred pounds per square inch. Thepressure regulator valve 134 would be set to open at a somewhat higher pressure, say two thousand five hundred twenty-live pounds per square inch. As la. result, the pressure differential across the lower sealing element 50a would be maintained at approximately two thousand live hundred pounds per square inch since the pressure immediately therebelow would be ve thousand pounds per square inch and the pressure immediately thereabove in the chamber 97 would be approximately,

two thousand tive hundred pounds per square inch. Similarly, the upper sealing element 50a would be subjected to a pressure diierential of approximately two thousand live hundred pounds per square inch since the pressure in the chamber 97 is maintained at approximately two thousand five hundred pounds per square inch and the upper end thereof is now exposed to the atmosphere since the upper blow outpreventer 11 is not present.

It will be apparent that as many of the blow out preventers, connected serially one to another in longitudinal alignment, may be employed as desired depending upon the pressure of the well fluids and the pressure differential to which the individual sealing elements may be subjected without causing undue wear or deterioration of the sealing elements.

It will now be seen that a new and improved blow out preventer has been illustrated and described which employs any desired number of longitudinally aligned and spaced sealing elements in a tubular member which is placed in longitudinal alignment and in communication with the well, so that a well ow conductor may be moved through the sealing elements with the sealing elements sealing between the tubular member and the well flow conductor and that the tubular member may be composed of any number of the heads or sections.

It will further be seen that each of the sealing elements is subjected only to a fraction of the total pressure differential between the atmosphere and the well bore so that a plurality of sealing elements, each one of which is capable of satisfactorily resisting only a small pressure differential thereacross, may be employed to prevent blow out of the well fluids.

It will further be seen that the low conductor may be moved continuously through the sealing elements without the necessity of arresting its movement each time an enlarged portion of the well ow conductor, such as the labor when the blow out preventers embodying the invention are employed.

The foregoing description of the invention is explanatory only, and changes in the details of the construction illustrated may be made by those skilled in the art, within the scope of the appended claims, without departing from the spirit of the invention.

What is claimed and desired to be secured by Letters Patent is:

1. A well tool including: a tubular member having a bore; a plurality of tubular sealing elements disposed in said tubular member in longitudinally spaced relation, said sealing elements being engageable with an elongate member movable through said tubular member and sealing therebetween to provide a plurality of longitudinally spaced chambers between each adjacent pair of sealing elements; and means providing for flow of fluid from the bore of the tubular member at a point upstream of one end sealing element exteriorly of the sealing elements and back into the tubular member into the chambers between said sealing means, said last mentioned means including pressure regulator means for maintaining the pressure in each successive chamber at a pressure reduced by a predetermined amount below the pressure in the chamber next upstream therefrom.

2. A well tool of the character set forth in claim 1 wherein, said pressure regulator means includes pressure regulator valve means controlling admission of fluid pressure to each of said chambers for preventing the pressure in each of said chambers between said sealing elements from decreasing below a predetermined value; and fluid pressure responsive release means for preventing the pressure in each of said chambers between said sealing elements from exceeding said predetermined value.

3. A well tool for preventing escape of well uids from a well during movement of an elongate member into or out of the well including: a tubular member installable on the well and having a longitudinal passage in longitudinal alignment with the well bore; a plurality of tubular sealing elements disposed in said tubular member in longitudinally spaced alignment, said sealing elements being enga geable with an elongate member movable through the tubular member for sealing therebetween, said tubular member, said elongate member and said sealing elements providing annular chambers between adjacent ends of adjacent: sealing elements; tluid pressure responsive regulating means for conducting fluid under pressure at predetermined reduced values from upstream of each of said sealing elements into the chamber between said sealing element and the next downstream sealing element; and fluid pressure responsive means communicating with the chamber between adjacent pairs of said .sealing elements for releasing uid pressure from said chamber when the pressure within the chamber exceeds a predetermined value, whereby a predetermined pressure reduction is maintained across each sealing element of the plurality of sealing elements decreasing in value from the most upstream sealing element to the most downstream sealing element.

4. A well tool for preventing escape of well lluids from a well during movement of an elongate member into or out of the well including: a tubular member installable on the well and having a longitudinal passage in longitudinal alignment with the well bore; a plurality of tubular sealing elements disposed in said tubular member in longitudinally spaced alignment, said sealing elements being engageable with an elongate member movable through the tubular member for sealing therebetween, said tubular member, said elongate member and said sealing elements providing annular chambers between adjacent ends of adjacent sealing elements; fluid pressure responsive regulating means for introducing fluid under pressure from upstream of each of said sealing elements into the chamber between said sealing element and the sealing element next downstream thereof at a predetermined reduced lower pressure, whereby the pressure in the chambers between each of said sealing elements is introduced at a predetermined reduced value from the upstream to the downstream side of such lsealing elements in each of said chambers; and pressure responsive means for releasing fluid from each of said chamber when the pressure within the chamber exceeds a predetermined value. 5. A well tool for preventing escape of Well fluids from a Well during movement of an elongate member into or out of the well including: a tubular member installable on the well and having a longitudinal passage in longitudinal alignment with the well bore; a plurality of tubular sealing elements disposed in said tubular member in longitudinally spaced alignment, said sealing elements being engageable with an elongate member movable through the tubular member for sealing therebetween, said tubular member, said elongate member and said sealing elements providing annular chambers between adjacent pairs of sealing elements; and means connectable to a source of fluid under pressure for introducing fluid under pressure into said chambers at a predetemined value in each of said chambers whenever the pressure within said chambers falls below said predetermined values, including means for maintaining the pressure in each of said chambers at a predetermined lower value than the pressure in the chamber next upstream, whereby the pressure across each of said sealing elements is reduced by a predetermined amount from upstream to downstream thereof.

6. A well tool for preventing escape of well fluids from a well during movement of an elongate member into or out of the well including: a tubular member installable on the well and having a longitudinal passage in longitudinal alignement with the well bore; a plurality of tubular sealing elements disposed in said tubular member in longitudinally spaced alignment, said sealing elements being engageable with an elongate member movable through the tubular member for sealing therebetween; said tubular member, said elongate member and said sealing elements providing annular chambers between adjacent ends of adjacent sealing elem-ents; and means connectable to a source of luid under pressure for introducing fluid under pressure into each of said chambers at a value reduced by a predetermined amount below the pressure in the chamber next upstream therebelow when the pressure within each of said chambers falls below said predetermined values, said predetermined pressure in each of said chambers being maintained at a lower value than the pressure in the next lower chamber; and fluid pressure responsive means for releasing fluid from each of said chambers when the pressure within the chamber exceeds a predetermined value.

7. The method of preventing escape of fluids from a well during movement of an elongate member into or out of the wall including: disposing a tubular member having a longitudinal passage with a pair of longitudinally spaced tubular sealing elements therein in longitudinal alignment with the well, moving the elongate member through the longitudinal passage, and introducing lluid pressure from the well bore upstream of the lowermost chamber successively; into each annular chamber thereabove between adjacent sealing elements defined by said sealing elements, the tubular member and the elongate member to maintain a successively lower predetermined pressure differential across successive sealing elements tending to hold the sealing elements in sealing engagement with the elongate member and the tubular member; and maintaining the pressure within each chamber at a predetermined value which is lower than the value of the pressure in the chamber next below.

8. The method of preventing escape of iluids from a We duri-Hg movmell of an elongate member into or out of the well including: disposing a tubular member having a longitudinal passage with a pair of longitudinally spaced tubular sealing elements therein in longitudinal alignment with the well, moving the elongate member through the longitudinal passage, and introducing fluid pressure into an annular chamber between adjacent sealing elements defined by said sealing elements, the tubular member and the elongate member to maintain a predetermined successively lower pressure differential across the 4sealing elements from the lowermost to the uppermost of said elements tending to hold the sealing elements in sealing engagement with the elongate member and the tubular member; permitting fluid to escape from the chamber whenever the volume of the chamber decreases and an enlarged portion of the elongate member moves into the chamber to prevent the pressure differential across of the lower sealing element from decreasing below a predetermined value, and permitting fluid to flow into the chamber as the volume of the chamber increases as an enlarged portion of the elongate members moves out of the chamber to prevent the pressure differential across the lower sealing element from increasing above a predetermined value.

9. The well tool of claim 5, wherein said means for maintaining fluid under pressure of predetermined value in each of said chambers includes pressure regulator valves, each of said pressure regulator valves regulating introduction of iluid into an associated chamber.

10. The well tool of claim 9, wherein said pressure regulator valves are connected in series to said source of fluid under pressure.

11. The well tool of claim 9, wherein said pressure regulator valves are connected in parallel to said source of fluid under pressure.

12. The well tool of claim 5, and pressure accumulator means connected to each of said chambers for minimizing flow of iluid into said chamber.

13. The well tool of claim 6, and pressure accumulator means connected to each of said chambers for minimizing flow of fluid into and out of said chambers.

14. A well tool for preventing the escape of well fluids from a well during movement of an elongate member into and out of the well including: a tubular member installable on the well and having a longitudinal passage in longitudinal alignment with the well bore; a plurality of tubular sealing elements disposed in said tubular member in longitudinally spaced alignment therein, said sealing elements being engageable with an elongate member movable through the tubular member for sealing therebetween, said tubular member, said elongate member and said sealing elements providing a plurality of longitudinally spaced annular chambers in said tubular member between adjacent ends of adjacent sealing elements, the volume of the chamber between adjacent sealing elements varying as portions of said elongate member of different external diameter are moved therethrough; and fluid pressure responsive means for controlling the pressure of fluid introduced into the chambers between said elements and maintaining said pressures in said chambers at predetermined fixed successively lower values from the lowermost chamber to the uppermost chamber.

References Cited by the Examiner UNITED STATES PATENTS 528,773 11/94 Ellis 277-3 728,124 5/03 Mitchell 277-3 2,080,715 5/37 Hinderliter 277-6 2,155,837 4/39 Penick et al. 277-6 2,908,515 10/59 Schellens 277-3 3,145,995 8/ 64 Adamson et al. 277-28 EDWARD V. BENHAM, Examiner.

LEWIS I. LENNY, Primary Examiner,

Claims (1)

1. A WELL TOOL INCLUDING: A TUBULAR MEMBER HAVING A BORE; A PLURALITY OF TUBULAR SEALING ELEMENTS DISPOSED ON SAID TUBULAR MEMBER IN LONGITUDINALLY SPACED RELATION, SAID SEALING ELEMENTS BEING ENGAGEABLE WITH AN ELONGATE MEMBER MOVABLE THROUGH SAID TUBULAR MEMBER AND SEALING THEREBETWEEN TO PROVIDE A PLURALITY OF LONGITUDINALLY SPACED CHAMBERS BETWEEN EACH ADJACENT PAIR OF SEALING ELEMENTS; AND MEANS PROVIDING FOR FLOW OF FLUID FROM THE BORE OF THE TUBULAR MEMBER AT A POINT UPSTREAM OF ONE END SEALING ELEMENT EXTERIORLY OF THE SEALING ELEMENTS AND BACK INTO THE TUBULAR MEMBER INTO THE CHAMBERS BETWEEN SAID SEALING MEANS, SAID LAST MENTIONED MEANS IN-

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