Classifications

• • E—FIXED CONSTRUCTIONS
  • E21—EARTH OR ROCK DRILLING; MINING
  • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
  • E21B21/00—Methods or apparatus for flushing boreholes, e.g. by use of exhaust air from motor
  • E21B21/08—Controlling or monitoring pressure or flow of drilling fluid, e.g. automatic filling of boreholes, automatic control of bottom pressure
• • E—FIXED CONSTRUCTIONS
  • E21—EARTH OR ROCK DRILLING; MINING
  • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
  • E21B7/00—Special methods or apparatus for drilling
  • E21B7/18—Drilling by liquid or gas jets, with or without entrained pellets

Definitions

• This invention relates to a pressure converter for mounting above the drill bit at the lower end of a drill pipe for deep drilling, in particular for oil and gas, for the purpose of generating an increased fluid pressure by utilizing energy in a drill fluid flow downwards through the drill pipe.
• drive means is adapted to be driven by the drill fluid flow and to move valve means controlling piston means for reciprocating movement with a pressure stroke and a return stroke
• said piston means having at one side a relatively large piston area adapted to be subjected to the drill fluid pressure in the drill pipe during the pressure stroke, and having at the other side a first, opposite piston area which both during the pressure stroke and the return stroke is subjected to the return pressure in the drill fluid flow upwards outside the drill pipe, and a second, opposite and relatively small piston area which during the pressure stroke is adapted to provide an increased pressure in a smaller proportion of the drill fluid flow, whereby a check valve provides for discharge of this smaller proportion of the flow to a header channel leading forwards to the drill bit, whereas the large piston area during the return stroke is adapted to be subjected to the return pressure outside the drill pipe and the small piston area to the pressure in the drill pipe.
• the pressure in the drill fluid flow which is employed can be about 200-300 bar, whereas the smaller flow which is converted can obtain an increased pressure of for example 1500-2000 bar.
• pressure magnitudes are in the principle relative magnitudes, i.e. pressure differences, since the static pressure determined by the depth concerned has been neglected.
• the resulting high pressure fluid is led to nozzles in the drill bit, from which it is emitted in the form of powerful jets being able to cut into the surrounding rock and thereby release stresses in underlying masses. This facilitates the drilling operation and speeds up the drilling.
• the piston member can be freely movable in its axial direction under the influence of the drill fluid and spring pressures mentioned, and besides the recipro ⁇ cating movement of the piston preferably takes place in the longitudinal direction of the drill pipe.
• the header channel for the high pressure flow is arranged to be through-going from one to the opposite end of the pressure converter, in order to make possible a coupling to similar pressure converter units at both ends, so that there is formed a common header channel for several pressure converter units constituting a group, for example consisting of 15 to 20 units. This will increase the total capacity in providing the desired high pressure fluid flow. Moreover, there is obtained a substantial advantage by phase-shift of the pressure strokes in the individual units in such a group, in order thereby to obtain a total, smooth high pressure flow.
• the pressure converter according to the invention will be able to operate exclusively under the direct influence or control through the normal fluid flow from pumps at the top of the drill string, so that it is not necessary to provide specific control systems or connections in order to regulate the generation of the desired high pressure flow of drill fluid.
• the pressure converter units By increasing the pressure, the velocity and/or the amount of drill fluid being supplied by the pumps, the pressure converter units will give a high pressure flow having a larger or smaller magnitude, and a higher or lower pressure respectively.
• Commonly employed means for controlling the drill fluid flow downwards from the top of the drill string will be useful in this connection.
• the drill fluid from the pumps which typically provide a pressure of 200 to 340 bar, thus, flows downwards within the drill string or the drill pipe, whereby a main portion is led directly to the drill bit, whereas a smaller proportion of the drill fluid flow passes through the pressure converter units for conversion to the desired higher pressure.
• Fig. 1 is a highly schematic flow diagram showing, among other things, typical pressure relationships in connection with a drill string provided with pressure converters according to the invention.
• Fig. 2 shows in partial cross-section a practical embodiment of a pressure converter according to the invention.
• Fig. 3 shows the pressure converter of Fig. 1 with internal parts, including movable parts removed,
• Fig. 4 in partial cross-section shows a cover being provided at the top of the converter unit in Fig.
• Fig. 5 shows in plane view a plate shaped valve member incorporated into the pressure converter unit in
• Fig. 2 shows a cross-section according to the line A-A in
• Fig. 2 shows an assembly of four pressure converter units according to Fig. 2, in a group provided with a top piece and a bottom piece, Figs. 8A and 8B more in detail show the top and the bottom of the group in Fig. 7 when mounted in a drill pipe.
• FIG. 1 Main features of what takes place in a drill string and accompanying typical examples of pressure relationships when using pressure converters according to the invention for conversion from fluid having a relatively low pressure of about 200 to 340 bar to a smaller amount of fluid having a high pressure of about 1500 to 2000 bar (relative magnitudes) , are shown in Fig. 1.
• a fluid flow A comes from a pump system resulting in a pressure of about 200 bar and a maximum of 340 bar, and an amount of about 2000 to 4000 litres per minute, depending upon the lenght of the drill string and the capacity of the system.
• the drilling fluid enters a pressure converter group having four units, where it passes by a turbine B for valve operation. There is estimated to be a pressure drop of about 50 bar through the drill string and by passing through the turbine.
• the drilling fluid is subdivided into two flows.
• One of about 400 to 600 litres per minute goes through the pressure converters, whereas the remaining part goes through the system to the drill bit where, because of jet nozzles, there is a pressure drop of about 180 to 270 bar.
• the fluid flow C will perform its work by increasing the pressure in a smaller proportion of the drilling fluid, and thereby the pressure in this flow drops from about 200 to 290 bar to about 20 bar.
• the flow passes through a tube D and out into the return flow H, which runs at the outside of the drill string or pipe inside the usual casing and at pressure of about 20 to 40 bar.
• the embodiment shown in Fig. 2 in the first place comprises a generally sylindrical housing 10 adapted to receive a piston 6 which has three operative piston areas, namely an upper, relatively large piston area 11, a first, opposite piston area 13 and a second opposite and relatively small piston area 12 at the lower end of piston means 6.
• This is adapted to be freely movable axially under the influence of varying drilling fluid pressures on the respective piston areas, as well as under the influence of a compression spring 14 engaging the piston area 13.
• volume 31 in front of piston area 11 can be denoted low pressure space
• volume 32 in front of piston area 12 correspondingly can be denoted high pressure space.
• a check valve 15 this latter space is connected to a header channel 16 for the resulting drilling fluid flow at an increased pressure.
• the channel 16 runs through the housing 10 in the whole longitudinal direction thereof for the purpose of interconnecting several such pressure converter units to a group. Such a group arrangement shall be discussed more closely below with reference to Figs. 7 and 8.
• a widened wall part having a bore for a through- going drive axle 21 which at its ends has means intended for coupling to corresponding pressure converters at both ends.
• the drive axle has a small gear 25 which via a second (not shown) small gear on an axle 24, serves to rotate a valve member in the form of a round plate 27 having teeth around its circumference as shown more clearly in Fig. 5.
• the valve plate 27 is adapted to rotate continuously about the longitudinal axis of the pressure converter unit, which axis normally will coincide with the axis of the drill pipe in which the pressure converter is mounted.
• valve plate 27 constitutes an essential component in valve means serving to direct a portion of the drilling fluid flow into and out of the space 31 above the piston area 11.
• This valve moreover, at the top of housing 10 comprises a cover 22 which has two channels positioned substantially oppositely to each other, i.e., an inlet channel 34 and and outlet channel 35, both of which continue through the piston housing wall, as seen at 34 in Fig. 2.
• the cover 22 is also shown more in detail in Fig. 4. See also Fig. 3 as far as the extension of channels 34 and 35 through the piston housing wall is concerned. Further radially out from channel 35 the outlet continues through a short tube (not shown) to the annulus for the return flow between the drill string or tube and the casing.
• the inlet channel 34 in cover 22 leads inwards to an arcuate slit 22A, whereas the outlet channel 35 in a corresponding manner communicates with an arcuate slit 22B. Both slits are open downwards in order to cooperate with a through-opening 27B in valve plate 27 during rotation thereof.
• valve plate 26 having similar slits as in the cover, between valve plate 27 and cover 22.
• a similar bearing plate or sealing plate 28 is mounted underneath valve plate 27 and has corresponding arcuate slits as in plate 26 and cover 22.
• the complete valve means with cover 22 on top and sealing plate 28 at the bottom, is maintained in its place first by an upper locking ring 23 and second by a lower locking or sealing ring 29.
• a central bolt at 30, which among other things constitutes the axle for the rotation of valve plate 27, whereas the other plates in the valve means are stationary.
• the various plates incorporated in the valve design can be made of different materials, but in order to withstand the tough environment which is represented by the circulating drilling fluid, it may be an advantage to employ high quality materials, possibly in the form of surface coatings, for example cherami ⁇ materials, which in particular can be of interest for the two bearing plates 26 and 28 mentioned.
• Figs. 2 and 3 there are further shown (three of a total of four) short tubes or connections 37A, 37B and 37C for putting the space in front of the first, opposite piston area 13 in fluid communication with the return passage-way for the upwardly running drilling fluid in the annulus between the drill tube or string and the well casing.
• short tubes or connections 37A, 37B and 37C for putting the space in front of the first, opposite piston area 13 in fluid communication with the return passage-way for the upwardly running drilling fluid in the annulus between the drill tube or string and the well casing.
• FIG. 6 shows more in detail the high pressure space 32 which in addition to an outlet through the check valve 15 to header channel 16 for high pressure fluid, has two inlets with respective associated check valves 39A and 39B which makes possible inflow of drilling fluid from the main flow thereof inside the drill pipe.
• the return stroke is initiated when the opening in the valve plate through the outlet channel 35 puts the space 31 in communication with the annulus between the drill tube and the casing, i.e., with the mentioned much lower pressure in the return flow of drilling fluid. Then in the first place the pressure on piston areas 11 and 13 will be equal, and the compression spring 14 provides for initiating the upward movement of the piston means. At this phase there will still exist a relatively high pressure in space 32 in front of the small piston area 12, typically a pressure somewhat below 1500 bar, which also contributes to the upward piston movement. Valve 15 will close for the established high drilling fluid pressure in header channel 16. As the piston moves upwards space 32 will expand and inlet valves 39A and 39B (Fig.
• Fig. 7 shows four pressure converter units 41, 42, 43 and 44 being coupled together end to end in the longitudinal direction, with a top piece 3 mounted on unit 41, whereas a bottom piece 5 is mounted on unit 44.
• converter unit 41 there are indicated short tubes 37A and 37B as in Figs. 2 and 3, as well as the drive axle 21 which is rotationally coupled to the drive axle of the remaining units, i.e., axles 21A, 2IB and 21C respectively.
• the top piece 3 carries drive means in the form of a turbine 20 adapted to be driven by the drilling fluid flow, whereby a gear transmission conveys the power from the turbine axle to the assembled drive axles for rotating these in common and thereby provide for the intended control of the valve means in the converter units. It is an advantage to have these phase shifted, i.e., with mutual angular displacement, so that the pressure strokes and thereby the high pressure output from each of the units to the common header channel are smoothed to a more constant high pressure flow than will result from each individual pressure con- verter.
• the header channel is extended into the bottom piece 5 which has a central outlet for further fluid flow to the region at the drill bit (not shown) .
• the assembled group of pressure converters is mounted free-standing in the drill pipe supported by the bottom plate.
• Fig. 8 shows some details in this connection, at the top and the bottom of the group respectively.
• Converter units 41 and 44 are shown completely, whereas units 42 and 43 are shown only in part.
• the surrounding drill pipe 1 forms an annular fluid passageway 40 outside and surrounding the pressure converter units in the group, so as to make possible a normal movement of the main portion of the drilling fluid flow down to the drill bit.
• the total drilling fluid flow from above is indicated with arrow 19 in Fig. 8A.
• each individual pressure converter alone can have a tc-> small capacity with respect to its discharge of high pressure fluid, in relation to the actual require ⁇ ment, the assembly into groups as discussed above will make it possible to obtain a sufficiently large combined yield.
• Each individual pressure converter unit will have a capacity (litres per minute) which also depends upon the stroke rate of the piston means.
• a factor in this connection, and of significance for the operation as a whole, is that the turbine 2 with its impeller 20 is not requited to have any particularly high power output, since the purpose thereof only is to move the valve means which controls the drilling fluid flows into and out of the piston means, which is the part of the structure which must have comparatively high power capacity.
• An assembled group of for example 15 to 20 converter units in practice can have a total length of about 6 meters and can be mounted free-standing on a bottom piece within a section of drill pipe or drill string having a corresponding length, possibly with strut elements between the inside of the drill pipe or string and the pressure converter units. For additional increase of capacity, several such sections or lengths of about 6 meters can be interconnected.
• Adjustment of permanently mounted nozzles in the drill bit for determining the pressure drop depending on the drilling fluid flow to pass by.
• Variable parameters which have influence on the pressure conversion process are the flow velocity and volume as well as the pressure.
• the return pressure may also be a parameter which it is desirable to vary in order to control the process in the converter units. Theoretically one should be able to determine the pressure increase and the volume in the fluid converter by proceeding as follows:
• the turbine for valve operation will have an increased rate of rotation, and the same applies to the rate of alter ⁇ nations in the valve system. This will increase until reaching a maximum for input or output respectively of fluid in the individual units and piston movement.
• By increasing or reducing the pressure from the pumps the pressure drop across the drill bit will increase or decrease respectively, and thereby the resulting pressure in the high pressure fluid supplied, will increase or decrease respectively.
• the pressure converter described is primarily intended for supplying high pressure fluid to jet nozzles for cutting in rock, there are also possibilities of different applications of such drilling fluid under an increased pressure, for example for driving particular drilling devices.
• the cooperating openings and slits in the valve member, bearing plates and cover can be arranged "inversely" in relation to the example shown, i.e. with a small angular extension of the slits in the cover and the bearing plates, whereas the opening in the valve member can have a more extended slit shape with a larger angular extension about the central axis.

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• Engineering & Computer Science (AREA)
• Life Sciences & Earth Sciences (AREA)
• Geology (AREA)
• Mining & Mineral Resources (AREA)
• Physics & Mathematics (AREA)
• Environmental & Geological Engineering (AREA)
• Fluid Mechanics (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Geochemistry & Mineralogy (AREA)
• Mechanical Engineering (AREA)
• Earth Drilling (AREA)
• Audible-Bandwidth Dynamoelectric Transducers Other Than Pickups (AREA)
• Diaphragms For Electromechanical Transducers (AREA)
• Apparatus For Radiation Diagnosis (AREA)
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• Details Of Television Scanning (AREA)
• Television Signal Processing For Recording (AREA)
• Two-Way Televisions, Distribution Of Moving Picture Or The Like (AREA)
• Details Of Valves (AREA)
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ID=19892556

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Citations (3)

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• 1989
  • 1989-11-08 NO NO894436A patent/NO169088C/no not_active IP Right Cessation
• 1990
  • 1990-10-31 RU SU905052345A patent/RU2078904C1/ru active
  • 1990-10-31 ES ES90916187T patent/ES2055451T3/es not_active Expired - Lifetime
  • 1990-10-31 WO PCT/NO1990/000164 patent/WO1991007566A1/en active IP Right Grant
  • 1990-10-31 DE DE69010008T patent/DE69010008T2/de not_active Expired - Fee Related
  • 1990-10-31 BR BR909007818A patent/BR9007818A/pt not_active IP Right Cessation
  • 1990-10-31 DK DK90916187.9T patent/DK0500609T3/da active
  • 1990-10-31 US US07/849,376 patent/US5246080A/en not_active Expired - Fee Related
  • 1990-10-31 EP EP90916187A patent/EP0500609B1/en not_active Expired - Lifetime
  • 1990-10-31 AT AT90916187T patent/ATE107393T1/de not_active IP Right Cessation
  • 1990-10-31 JP JP2514903A patent/JP2892156B2/ja not_active Expired - Lifetime
  • 1990-10-31 CA CA002073017A patent/CA2073017A1/en not_active Abandoned
  • 1990-10-31 AU AU66196/90A patent/AU638767B2/en not_active Ceased
• 1992
  • 1992-05-05 FI FI922012A patent/FI95408C/fi active
  • 1992-05-05 NO NO921762A patent/NO921762D0/no unknown

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