EP0208770A1 - Fluid means for data transmission. - Google Patents

Abstract

In a means for transmitting recorded data via a fluid medium, the preferred embodiment comprises a hydraulic positive displacement pump (10) connected to a constant pressure pump (12) which pumps fluid through a train of rods (13) for drilling oil wells. A variable orifice (27) is located at the bottom of the well in the drill string (13) and its diameter changes depending on the signals recorded. The injected fluid is displaced by a delivery piston (20) driven by a second piston (31), which is actuated by a hydraulic fluid under constant pressure. The injected fluid is maintained at a constant pressure, therefore a variation in the diameter of the orifice (27) will modify the volume of flow through the orifice and therefore modify the volume of flow of the hydraulic fluid. actuation. The flow rate of the latter is thus measured to record the variations in the diameter of the orifice and in return to receive the signals emitted by the variation in the diameter of the orifice.

Description

FLUID MEANS FOR DATA TRANSMISSION

- The present apparatus is directed to a means to transmit recorded data through a fluid medium and more particular to a means to transmit recorded data from an instrument located in a oil well subsurface drill string to a surface recording means, the transmission occurring through the circulation fluid medium employed to assist in drilling the well. In drilling oil wells it is desirable to log the different earth formations, well temperature, bore hole deviation, etc., as the wells are being drilled. Thus various recording instruments are placed in the drill string generally near the drill bit to log this different data. It is also desirable to transmit this data to the surface while the well is being drilled. This transmission of data to the surface during drilling is a difficult process because of numerous transmission problems that have to be overcome. The most successful means of trans- mitting these signals to the surface presently consists of magnification of the logged data by batteries or other means and employing the data to create pressure pulses in the circulating drilling fluid medium, the pulses gener- ally being created by valve means either momentarily restricting the flow of drilling fluid or momentarily dumping a part of the flow of drilling fluid. The pres¬ sure pulses in turn travel through the drilling fluid to the surface where they are received by a recording instrumen .

Numerous problems exist with the transmission of pressure pulses through the drilling fluid including the many and varied pulsations transmitted to the same fluid by the drilling fluid pump. The system of this invention employs the technique of holding the drilling fluid pres¬ sure relatively constant thus varying the flow rate of the drilling fluid and recording the various flow rates at the surface. In my technique the same type down hole logging tools and down hole signaling devices are employed, except the signaling device will in turn change the flow rate of • the drilling fluid which in turn is recorded at the surface thus eliminating the necessity to send pressure pulses through the fluid medium.

Fig. 1 is a schematic drawing .illustrating the arrangement of the different components that constitute the signal transmission means of this invention.

Fig. 2 is an end view of a drive fluid distribution valve employed in the schematic drawing of Fig. 1.

Fig. 3 is a section view taken along the lines 3-3 of Fig. 2.

Fig. 4 is a section view taken along the lines 4-4 of Fig. 3.

Attention is first directed to Fig. 1 where the numeral 10 generally identifies a hydraulic driven pump that has the capability to create and sustain a constant pressured pumped fluid system. The numeral 11 generally identifies a drilling fluid circulating system circulating drilling mud through a pumping cylinder 12, a drill string 13, a down hole logging device 14, a drill bit 15, a bore hole 15, and a mud reservoir 17.

Pumping cylinder 12 is one of generally three pumping cylinders of the pump illustrated by the numeral 10. The circulating fluid, which generally is a weighted drilling mud, is drawn from reservoir 17 through line 18 and into the pumping chamber at 19. A reciprocating piston 20 driven by rod 21 discharges fluid from a chamber 23 across unidirectional outlet valve 22 as piston 20 moves in one direction on its power stroke. At the same time fluid is drawn into a chamber 24 behind piston 20. Piston 20 next moves on its return stroke at which time the fluid is transferred from chamber 24 to chamber 23 moving across one or more unidirectional valves 25 carried in movement by piston 20. A small amount of fluid equal to the rod 21 area in volume will be drawn into chamber 23 from reser¬ voir 17 as piston 20 moves in return stroke.

Pump 10 can function with two or more cylinders 12 to provide constant pressure pumping, however the preferred embodiment employs three or more cylinders 12. Inlet line 18 is connected in parallel to all cylinders 12 and the drill string 13 is connected in parallel to the outlet of all cylinders 12. The piston 20 of all cylinders 12 are driven in sequential order and overlapping drive movement whereby the total output flow from all cylinders 12 is uniform in constant volumetric flow for a given fluid displacement. Each piston rod 21 is driven in pumping movement with a constant force which in turn creates a constant pressure in chamber 23 and in the circulating fluid passing through drill string 13. The means to drive piston rod 21 with a constant force will be discussed later.

Logging device 14 can be any number of different down hole monitoring systems, it can be a device to monitor or log the different earth formations, the down hole tempera¬ ture, bit rotation, bit inclination, etc. These devices generally employ highly sophisticated and complex means to pick up a signal, magnify the signal and then transmit the signal into movement of some type of plunger or valving device such as plunger 26 to restrict a typical orifice 27 through which the circulating fluid flows. This technique is well known by those versed in the art. In the present state of the art, this or similar means are employed to create pressure pulses in circulating fluid to transmit date to the surface.

This same logging technique can be employed in my system of transmitting data, however in the constant pressure circulating fluid system of this invention the same restricting or opening up of orifice 27 causes a change in circulating fluid flow rate. This change in flow rate then forms the means for transmitting the logged signal to the surface. For example, if orifice 27 is one square inch in flow area then a constant pressured fluid may pass a constant flow of 100 gallons per minute across the orifice. But if the orifice is increased in flow area to one and one half square inches, then the same constant pressure will pass a increased flow across the orifice. Likewise if orifice 27 is decreased in flow area, then the flow across the orifice will decrease in volume.

Thus by recording the flow rate of the pumped circu¬ lating fluid at a surface location such as 28 and corre- lating the change in flow rates with the known character¬ istics of the signal producing logging instrument, the signal produced by the logging device can be instantly interpreted at the surface location.

In the drilling of wells, the drill bit is generally rotated by some type of down hole motor located near the bit such as 29, or the complete drill string is rotated from a surface rotary table which.naturally requires a swivel of some type in the drill string above the rotary table. In the illustrated schematic of numeral 1, the rotary table and swivel are omitted for clarity purposes as their functions obviously have no bearing upon this data transmission means.

The down hole motor 29 is illustrated as located in a position above the logging instrument 14. Motor 29 could also be located at a point below instrument 14 if desired. It is generally desirable to have the logging instrument located as close as possible to the drill bit; for example if the instrument is logging a potential oil bearing formation, then i.t is desirable to have data transmitted to the surface as soon as possible after the drill bit enters the formation. Thus it is advantageous to be able to locate the logging instrument below the motor and still transmit signals.

Motor 29 is generally a motor driven by the circu¬ lating fluid. Thus with the present state of the art of transmitting signals by the creation of pressure pulses it will be obvious to one skilled in the art that difficul- ties arise due to signal interferences by the motor if the signaling device is located below the motor. In the system of this invention the transmission of signals will cause a change in speed of a down hole motor driven by the circulating fluid but there should be no appreciable interference with signal transmission whether the motor is above or below the logging device. From the above discus- sion, it will be apparent that logging device 14 can be utilized to speed up or slow down the rotation of down hole motor 29 by increasing or decreasing the flow rate of the circulating fluid passing through the motor 29. The state of the art of typical logging instrument 14 allows for the instrument to pick up its signals from many and various different sources, thus any of these various sources can be utilized to in turn control the rotation speed of motor 29 that is driven by the circulating fluid. For example, instrument 14 may be programmed to close orifice 27 upon a given temperature or pressure thus stopping motor 29; or instrument 14 may be programmed to enlarge orifice 27 thereby increasing the drilling speed of motor 29 when a particular type earth formation is encountered.

From the above discussion it will be apparent that ^'-the constant pressured circulating fluid system of trans¬ mitting signals may also provide automatic down-hole motor speed control capabilities, or the transmitting of signals from a first to a second or more down hole instruments.

Attention is further directed to Fig. 1 of the drawings where the numeral 10 generally identifies the hydraulic driven pump utilized to create the constant pressured circulating fluid system illustrated by numeral 11. Numeral 10 generally illustrates a hydraulically driven cylinder 30 having a reciprocating drive piston 31 drivingly connected on one side to piston rod 21 and hav- ing on its other side a rod 32 sealingly extended through the end of cylinder 30. Each pumping cylinder 12 is driven by a cylinder 30. Rod 32 has a larger cross section area than a rod 21 so that equal pressure upon both faces of piston 31 will move piston 31 in the direc- tion of rod 32. Rod 32 and piston 31 defines an expan- sionable drive fluid chamber 33 on one side of piston 31, and rod 21 and piston 31 defines a part of an expansion- able return fluid chamber 34 on the other side of piston 31. A fluid port at 37 is fluidally connected to chambers 34 of all other drive cylinder 30 to form an intercon- nected chamber 34 common to all cylinders 30.

The driving movement of piston 31 provides the drive means that creates the constant pressured drilling fluid system prior discussed. Constant pressured hydraulic drive fluid is connected with each drive chamber 33 in sequential and overlapping turn to move or not to move piston 31 in pressured circulating fluid displacement or non displacement - the circulating fluid displacement being dependent upon the opening size of orifice 27. In other words, if orifice 27 allows fluid to circulate then the drilling fluid will circulate with a volumetric flow rate relative to the orifice flow area. If orifice 27 allows no -flow to pass therethrough, then the circulating fluid will be in static movement with a constant applied pressure.

It is noted at this point that a leak in the constant pressured circulating system can be detected any time orifice 27 is closed by monitoring the flow rate at typical plane 28, any flow of fluid across this plane indicates a correspondingly sized leak. This fact can be especially useful in checking leakage of the threads of the different joints of drill pipe employed in the drill string. Also this can be employed to check each tool joint thread as the drill string is being lowered into the hole by having orifice 27 in a closed position and check¬ ing each joint after the joint is added to the drill string. A typical orifice 27 could be programmed to per¬ manently release after the drill bit reaches bottom and then continue other transmission. Also the constant pressured circulating fluid can be utilized to check for leakage of added tool joint threads during drilling operations by the technique of noting the flow rate of fluid crossing plane 28 immediately prior to lowering circulating pressure for adding the next tool joint. After the joint is added and pressure is resumed, then an increase in the noted flow rate would indicate a leakage of the threads just added - assuming orifice 27 does not change in size.

Referring again to numeral 10 of Fig. 1, as chambers 33 of drive cylinder 30 are in turn connected with a constant hydraulic drive fluid pressure to thereby main¬ tain the constant pressure upon the circulating fluid, each chamber 33 not connected with the hydraulic drive fluid is connected with chamber 34 and with a low pres¬ sured hydraulic fluid supply system to a hydraulic drive pump 35 that supplies the constant pressured hydraulic drive fluid. The sequential and in turn connection be- tween chambers 34 and each chamber 33 is accomplished by a valving means 36 that will be explained later, this connection provides the same low pressured fluid upon both faces of piston 31 thus due to the difference in piston 31 face areas because of rod 32 and rod 21 then piston 31 is moved in the return direction of movement.

The primary source of piston 31 return movement is supplied by one or more drive pistons 31 moving in the drive direction which displaces fluid from one or more chambers 34 through interconnected ports 37. One or more pistons 31 moving in drive movement will in turn drive other pistons 31 in return movement through interconnected fluid chambers 34.

A secondary source of return piston movement is supplied by a system charge pump 38 connecting with chambers 34 and the inlet of hydraulic pump 35 to keep chambers 34 and the inlet line to pump 35 in a precharged pressured state.

A relief valve 39 also connects with chambers 34 and the inlet line to pump 35. Valve 39 exhausts excess fluid to a hydraulic reservoir 40. The.relief valve 39 is adjusted to bypass fluid to reservoir 40 whenever the fluid in chambers 34 reach a pressure slightly higher than the pressure required to drive piston 31 in the return direction. This setting cannot be exactly calculated and should be determined after assembly of cylinder 12 and 30. Each assembly of cylinders 12 and 30 will require slightly different chamber 34 piston 31 return pressure due primar- ily to difference in frictional drag, thus valve 39 must be set to relieve fluid at a pressure higher than the piston 31 return pressure of all cylinders 12 and 30 assemblies.

In operation, the combined total volume of chambers 34 continually expands and contracts. The volume will expand as long as any piston 31 is free to move unre¬ stricted in the return direction. The volume will con¬ tract when all returning pistons reach the end of their stroke and a driving piston 31 raises the pressure in chamber 34 to the relief valve 39 setting to exhaust excess fluid. This exhausting process normally occurs upon each piston 31 return stroke, except when the stroke length of piston 31 is shortened. When the stroke length of piston 31 is shortened during pumping operation, then all pistons 31 will move toward the return direction in shortened stroke length. The dumping of excess fluid does not occur during this movement as all chambers 34 are in the process of expansion. All pistons 31 will thus reciprocate infinitely close to the fully returned end of cylinder 30 as the pistons are driven in infinite short stroke length and all chambers 34 become infinite close to maximum filled capacity. During experimentation it was verified that the expansion of chambers 34 was the only practical means to accomplish piston 31 stroke length change without inter¬ ruption of the constant pumping action to provide the constant pressure status of the pumped circulating fluid. For example, if chambers 34 are held at a given filled volume capacity that is required to support pistons 31 reciprocating at full stroke, as has heretofore been disclosed by United States Patent No. #3,295,451 to Smith for a different but similar type pump; then as the pistons 31 reciprocate in shortened stroke each piston 31 will assume a reciprocating position relative to that piston's overall drive movement resistance. One piston 31 may ^'assume a position of reciprocation near the drive end stroke of cylinder 30, a second piston 31 may assume a position of reciprocation near the return end of cylinder 30, and third piston 31 may be reciprocating at a point anywhere along the length of cylinder 30. Since this occurs it means that once the pistons have assumed skew positions of relative reciprocation it is impossible to again increase the stroke length without at least one drive piston 31 hitting the end of its stroke too soon, thereby interrupting the continuity of the constant drive action of pistons 31. In the device disclosed in Smith, skewed piston position would lock up the disclosed system because the disclosed valve movement is timed with and dependent upon piston movement.

Further, the device disclosed in Smith may be char¬ acterized by prohibitive and destructive pressure surges in both the hydraulic drive fluid and the pumped circulat¬ ing fluid upon a piston 31 reaching the end of its stroke too soon. Additionally, the above described skewed piston positions will normally prohibit starting of stopped pistons 31 without encountering the same premature stoppage of pistons 31. Thus from the above discussion it will be apparent that the continued expansion of chambers 34 is necessary to achieve an uninterrupted constant pressured pumping action.

The pistons 31, on their return strokes will always return at a velocity greater than the velocity with which they are displaced on their drive strokes because of the charge pump 38. By returning the pistons at a greater velocity it is impossible for the drive piston movement and the return piston movement to be in the same timed movement as has been heretofore disclosed by Smith. The normal movement of drive piston 31 is in sequential turn and overlapping constant displacement movement to supply the same ^'movement to pumping piston 20. This mandates that the normal movement of return pistons 31 will be a sequentially interrupted overall movement, if there is an overlap in the return pistons movement it will be for all practical purposes of a non-existent magnitude. Thus, for all practical purposes, the return movement of pumping pistons 20 are non overlapping in overall movement.

Referring to pumping cylinder 12, note that the unidirectional valves 25 carried in movement by pumping pistons 20 provide an arrangement whereby the majority of the pumped circulating fluid is drawn to cylinder 12 during the movement of the displacement stroke of piston 20. As discussed above, the displacement movement is overlapping and overall constant as pistons 20 recipro¬ cate; thus by employing the moveable valve 25, means is disclosed for cylinder 12 to both receive a substantial constant flow of incoming fluid and to discharge a con¬ stant flow of pumped fluid. To illustrate the signi- ficance of this arrangement, consider what would happen if fluid were drawn to cylinder 12 as piston 20 moves in its return stroke as is the normal arrangement for fluid pumps, such as that disclosed in Smith; in this case the incoming suction flow would be stopped upon each return stroke movement as the return strokes have essentially zero overlap. Thus this repetitive stopping of incoming flow would create excessive incoming flow pulsation. Experiments using return piston suctions arrangements showed these incoming flow pulsations to be prevalent even at low flow rates and to be practically unacceptable at flow rates of 150 gallons per minute or more, when employed with free floating pistons.

Attention is again directed to Fig. 1 where the numeral 10 illustrates a closed loop hydraulic system combined with an independently sequenced valving system to drive cylinder 30 as prior discussed.

Variable volume hydraulic pump 35 is driven by a motor 41 to supply pressured hydraulic fluid through line 42 to distribution valve 36. Valve 36 is driven by a motor 43 to distribute pressured hydraulic fluid through lines 45 in a continuous uninterrupted fashion in sequen- tial turn and overlapping manner to chambers 33 of drive cylinders 31. Valve 36 also returns spent pressured fluid in sequential turn from chambers 33 to lower pressured return line 44 connecting with chambers 34 and the inlet to pump 35. The pressured fluid is distributed by valve 36 to a single chamber 33 for a substantial part of piston 31 drive movement; and then, near the end of piston 31 stroke, the fluid is switched to start another piston 31 in overlapping drive movement. The return portion of valve 36 simultaneously connects all chambers 33 that are not receiving drive fluid with the return line 44 for return piston 31 movement. Charge pump 38, driven by motor 41, keeps the closed loop pre-charged with pres¬ surized fluid through check valves 46 or 47.

In operation, the pumped circulating fluid within drill string 13 is maintained in constant pressure status by maintaining a constant drive fluid pressure against drive pistons 31. This is accomplished by a relief valve 48, a check valve 49, a small orifice 50, and a lock valve 51. Relief valve 48 serves several different functions. The main function is to limit the maximum pressure upon line 42, which is an essential function since hydraulic pump 35 is a positive displacement type pump. Pressure is relieved from line 42 to a line 52 then across check valve 49 to low pressure line 44. Valve 48 can be any type of relief valve but it is preferred that it be a type that can be remotely controlled from a pressure line 53 whereby valve 48 relieves flow to line 52 at the pressure that is held upon pilot line 53. This type of hydraulic relief valve is well known in the art thus a complete discussion • of its operation.is not necessary. This type of valve can also generally be controlled by a maximum pressure man¬ ually set and controlled anywhere below this maximum setting by the pressure held upon pilot 53.

Pump 35 is preferably a piston type pump employing a moveable swash plate that is controlled by two swash plate pistons. A typical pump 35 thus would have zero pumping displacement when the swash plate is held in a vertical plane relative to piston movement, with the swash plate being moved from the vertical plane for pumping displace¬ ment by two swash plate pistons. A remote control lever of some type generally commands the swash plate pistons to position the swash plate for pumping action anywhere from zero to maximum displacement. A typical pump of this type is a pump employed as the pump part of a typical hydraulic hydrostatic drive unit. These pumps are well known in the art and thus complete explanation of their operation is not necessary.

Referring still to Fig. 1, a line 54 connects one swash plate piston of pump 35 with line 52 through a lock valve 51. The other swash plate piston is connected by a line 55 to reservoir 40 through lock valve 51. The swash plate piston that is connected to line 55 must be the piston that is pressured to hold the swash plate in pumping displacement.

The drive fluid line 42 is held in constant drive pressure in the following manner: valve 48 is set to relieve fluid at the selected constant drive pressure, pump 35 is ordered to pump maximum flow; thus when the selected pressure is reached, a bypass flow crosses valve 48 and enters line 52. Check valve 49 has a spring tension to maintain a pressure differential of generally about 50 PSI upon line 52 or as required to move the swash plate piston of pump 35. This pressured fluid within line 52 flows through lock valve 51 and then through line 54 and to the swash plate piston to reduce the pumping displacement of pump 35. As pressure is applied to line 54 to destroke pump 35 this pressure is also utilized by lock valve 51 to allow dumping of fluid from line 55 connected with the second swash plate piston of pump 35 whereby both pistons generally must be allowed to move to destroke pump 35. Orifice 50 is a small orifice that allows a small drainage of pressure fluid from line 52. Thus pump 35 is ordered to override its original displace¬ ment pumping and to pump at a displacement that causes a very small flow of fluid to cross valve 48, this allows the pressured flow entering valve 36 to be at constant selected pressure and the flow to be anywhere from zero to maximum pump 35 displacement while the efficiency of the system approaches 100% for all flow ranges. It will be noted that the components designated, which control the automatic displacement of pump 35 are only typical. There are numerous methods of performing this technique known to those experienced in the art, however most methods employs a relief valve means such as 48 to start and maintain the destroking procedure.

A flow meter 56 located on the suction side of pump 35 measures the flow of hydraulic oil pumped through pump 35. This flow meter can also be used to gauge the flow of pumped, constantly pressured and circulating fluid which passes through pumping cylinders 12 since the flow of pumped circulating fluid is directly proportional to the flow of hydraulic drive fluid passing through pump 35.

Referring again to pumping cylinder 12, note that if for some reason unidirectional valve 25 of one or more cylinders 12 becomes stuck in the open position, then.as this cylinder sequences during the pumping cycle it would suddenly cause the drive fluid pressure within drive chamber 33 to approach zero. Thus this open pumping valve 25 would cause undesirable surging in the pumped fluid also within the hydraulic drive fluid system, with the pressure cyclic surging from maximum to near zero.

To effectively eliminate the above potentially damaging conditions, a unique system is employed in hydraulic flow control, consisting of a compressible gas filled accumulator 57, a variable volume orifice 58, and a check valve 59. In operation, orifice 58 is set to admit a small flow to accumulator 57 from line 42. The line connecting accumulator 57, orifice 58, and check valve 59 is connected to the remote control line 53 of valve 48. Check valve 59 is positioned to block flow to accumulator 57, but to rapidly exhaust flow from accumulator 57. Thus as drive fluid pressure in line 42 is raised, a correspon- dingly slower rise in pressure will occur in accumulator 57 so that if a rapid surge of pressure occurs in line 42, valve 48 will^" be allowed to bypass fluid due to the remote connection 53 connected to the lower pressured accumulator 57 - accumulator 57 having not risen in pressure as rapidly as line 42 due to the orifice 58. This bypass flow across valve 48 will in turn destroke pump 35 as prior discussed. Check valve 59 allows pressure trapped in accumulator 57 to rapidly exhaust and equalize with line 42 pressure thus allowing for repetitive surges.

Reducing the size of orifice 58 lessens the magnitude of the maximum surge. If there are no large surges upon line 42, then accumulator 57 will build in pressure and valve 48 can function with a normal top pressure setting as prior discussed.

With the control illustrated by 57, 58, and 59 the pump 35 will be automatically destroked to pump a dis¬ placement that gives a maximum pressure surge as prese- lected. The maximum surge being preselected by adjustment of valve 58. This control will be automatic and will come into play only when line 42 experiences a pressure surge or drop in pressure equal to the preselected magnitude. Another useful application of this control is when fluid is being pumped by chamber 12 that carries solids in suspension whereby the solids tend to hold valves 25 in the open position.

Attention is next directed to Figs. 2, 3, and 4 of the drawings where specifics of independently driven valve 36 are shown. Specific attention is directed to Fig. 3 where a rotary spool 60 is rotatably and sealingly encased within a housing 61. Housing 61 has inlet port 62 that leads inward to grove 63 around the circumference of spool 60. Grove 63 connects through ports 64 to a crossport 65 leading through spool 60. Crossport 65 is formed to mate in rotational movement and in successive overlapping turn with multiple ports 66 formed around the circumference of housing 61. Leading from each port 66 is a connecting port 67 that connects in successive turn with a second crossport 68 leading therethrough spool 60. Crossport 68 is located at 90 degrees spacing from crossport 65 and sized so that crossport 68 and crossport 65 never overlap for direct fluid flow therebetween. Crossport 68 connects to an outlet port 69 through a port 90.

Referring to the circuit illustrated by numeral 10 of Fig. 1, pressured drive fluid from line 42 enters valve 36 at inlet port 62. From there it flows through groove 63, ports 64 and then is delivered in sequential and over- lapping turn to lines 45 through ports 66 to drive piston 31 displaced in its drive stroke. Simultaneously, cross¬ port 68 connects in sequential.-turn all ports 66 not receiving drive fluid to exhaust spent drive fluid to lower pressured return line 44 and to chambers 34, thereby driving other pistons in return movement.

Spool 60 is sealingly and rotatably retained within housing 61 by end plates 70 and 71. End plate 70 is attached to housing 61 by bolts 72 and has a seal at 73 and supports a thrust bearing 74 that limits end movement of spool 60 in one direction. End plate 71 is attached to housing 61 by bolts 95 and supports a seal at 76 and a thrust bearing 77 that limits end movement of spool 60 in the other direction. End plate 71 has a central opening 78 through which a drive shaft 79 of spool 60 extends.

Drive shaft 79 is sealed in static and rotational movement by seal 80. Spool 60 is finely ground to sealingly mate in static and rotational movement with the inner bore of housing 61, additionally circumferential seals are located at 81 on each end of spool 60. It will be noted that the constant pressure pumping system can be created only when typical orifice 27 is small enough in flow area to cause the maximum flow rate of pump 35 to set up a pressure in line 42 that is equal to the relief valve 48 setting. When orifice 27 is larger than this, the hydraulicly driven pump illustrated by numeral 10 will operate as a constant displacement pump wherein a reduction is orifice 27 size will cause a rise in pumped circulating fluid pressure. These features provide the means whereby signals can be transmitted from instrument 14 by two separate and distinct channels or by numerous combinations of the separate channels. The two separate channels operating through pressure pulses and by changes in circulating fluid flow rate.

Again referring to the hydraulic circuit of Fig. 1, a remote positioned relief valve 75 can be connected with relief valve 48 vent line 53, whereby the pressured fluid bypass setting of valve 48 can be remotely changed by changing the maximum relief setting of valve 75. This is well known to those skilled in the art so little explana¬ tion is necessary. Valve 75 is generally located in some type of control panel and can provide a means to easily adjust the drive circuit 42 pressure whereby the hydraulic driven circulating fluid pump can selectively function for constant pressure or constant flow pumped output.

The constant flow or constant pressure pumping modes may also be automatically selected by the down hole logging instrument 14. For example, two or more orifices 27 may be employed whereby the combined areas of all orifices give a total flow area large enough so that the maximum flow rate of pump 35 will not set up the bypass pressure requirement of valve 48. Therefore the hydraulic driven pump will pump fluid in the constant flow mode whereby signals can be transmitted by pressure pulses. However, instrument 14 can be programmed to close some of the orifices 27 upon receipt of a given signal whereby the orifices closed then the overall area of orifice 27 is small enough so that the hydraulic driven pump will automatically operate in the constant pressure pumping mode. From the above, it's obvious that the many differ¬ ent pumping and signaling arrangements are too numerous to individually explain in a complete manner.

This invention is intended to cover all changes and modifications of the example of the invention herein chosen for the purpose of the disclosure, ^"which do not constitute departures from the spirit and scope of this invention.

Claims

CLAIMS :

1. A method of measuring change in the volume of entrapped flowing fluid comprising the steps of:

entrapping a fluid within a closed container having an escape outlet which restricts the flow of escaping fluid;

applying a constant pressure to the entrapped fluid;

adding a volume of fluid to the entrapped fluid at a rate equal to the rate of fluid that is allowed to escape said container through said escape outlet; and

measuring any change in said volumetric flow rate of said fluid added to said entrapped fluid, thereby measuring said change in said volume of said entrapped fluid.

2. The method according to claim 1, including the step of receiving a signal by measuring a change in said volumetric flow rate of said added fluid, whereby the signal is transmitted by varying the size of said escape outlet of said closed container.

3. The method according to claim 1, including the step of applying said constant pressure to said entrapped fluid by multiple pumping pistons driven by a constantly pres¬ sured drive fluid; the volumetric flow rate of said drive fluid being directly proportional to the volumetric flow rate of said fluid added to said entrapped fluid.

4. The method according to claim 3, including the step of measuring change in said volume of said entrapped fluid by measuring change in said volumetric flow rate of said drive fluid.

5. The method according to claim 3, including the step of receiving a signal by measuring change in the volu¬ metric flow rate of said drive fluid, wherein said signal is transmitted by varying said size of said escape outlet of said closed container.

6. The method according to claim 3, including the step of supplying said added fluid by multiple pumping pistons which are driven by a constantly pressured drive fluid; the volumetric flow rate of said drive fluid being directly'proportional to the volumetric flow rate of said fluid added to said entrapped fluid.

7. The method according to claim 6, including the step of changing the volumetric flow rate of said fluid added to said entrapped fluid in response to signals transmitted by varying said size of said escape outlet of said closed container.

8. A method of transmitting signals through a flowing fluid comprising the steps of:

entrapping fluid within a closed container having a restricted flow outlet;

applying a constant pressure to said entrapped fluid whereby a first signal, inducing a change in the size of said flow outlet causes a change in the volumetric flow rate of said fluid escaping said container; and

adding fluid to said container in a rate equal to the rate of said fluid escaping from said container, whereby change in said flow rate of said fluid escaping from said container and said fluid added to said container provides the means for transmitting said signal.

9. The method according to claim 8, including the step of receiving a first signal by measuring change in the flow rate of said fluid added to said container.

10. The method according to claim- 9, including the step of utilizing a length of drill pipe as said container wherein said restricted flow outlet is positioned in a down-hole location, with said change in flow rate of said fluid added to said container being measured at a surface location.

11. The method according to claim 8, including the step of transmitting said first signal from a first instrument to a second instrument by a change in the volumetric flow rate of the moving fluid respective to an induced signal.

12. A method of transmitting signals through a moving fluid by imposing a constant pressure upon said moving fluid whereby said constant pressure produces a change in the volumetric flow rate of said moving fluid respective to an induced signal.

13. The method according to claim 12, including the step of receiving said induced signal by measuring the change in flow rate of said moving fluid responsive to the induced signal.

14. The method according to claim 12, including the step of employing multiple pumping cylinders to impose said constant pressure and to provide said moving fluid.

15. A hydraulic drive motor, adapted for use in a fluid pump, comprising:

a plurality of fluidly driven pistons each within a separate cylinder, each said piston and each said cylinder having a first end and a second end;

a control valve capable of distributing in over¬ lapping time intervals a continuous flow of pressurized fluid to convert said fluid flow into substantially uninterrupted linear piston displacement in a first drive direction within each said cylinder, each said piston being displaced by said fluid flow, in said first direction within its respective cylinder, at a first linear velocity;

wherein each said piston also capable of reciprocal displacement in a return direction within each said cylinder when a second pressurized fluid acts upon each said second end of each said piston; and a separate connecting rod attached to each said piston and extending out one of said first or second ends of each said cylinder, for trans¬ ferring said reciprocal displacement to a pumping member.

16. The motor according to claim 15 wherein said drive motor is comprised of:

at least two cylinders each having a first end and a second end;

a separate piston positioned within each said cyl- inder, said piston defining a first and a second compartment within each said cylinder, each said piston being slidably and sealingly capable of reciprocal displacement within each said cylinder;

a control valve for controlling the flow of a first pressurized fluid supplied to at least one of each of said first compartments of each said cylinder independent of said piston position within said cylinders or piston movement, said first pressurized fluid being applied sequen¬ tially to each said cylinder, and for con¬ trolling the flow of said first fluid from other of said first compartments of said cylinders to sequentially exhaust said first fluid from said other first compartments;

wherein said control valve controls the flow of said first fluid supplied to, and exhausted from, each said first compartments of each said cylinder to displace said pistons in a first direction sequentially;

first conduits connecting each said first compartment of each said cylinder with said control valve;

second conduits connecting each said second compart¬ ment of each said cylinder together, thereby creating an expansionary fluid circuit;

a second pressurized fluid within each said second compartment of each said cylinder to displace at least one of said pistons in a second return direction within its respective cylinder when said first fluid displaces at least one of said other pistons in said first direction;

means to supply and remove said second pressurized fluid within said expansionary fluid circuit; and

wherein said second pressurized fluid is added to said expansionary fluid circuit to displace said pistons in said second return direction at a greater velocity than which said pistons are displaced in said first direction, said second pressurized fluid is removed from said expan¬ sionary fluid circuit when at least one of said pistons are displaced by said first pressurized fluid in said first direction and said second fluid is pressurized to a specific pressure.

17. The motor according to claim 16 including means to drive said control valve, independent of piston position and movement, to vary the distance each of said pistons is reciprocatingly displaced, thereby varying the volume of fluid in said expansionary fluid circuit and wherein said means to supply and remove said second pressurized fluid in said expansionary fluid circuit automatically compen¬ sates for the change in said second fluid volume in said expansionary fluid circuit.

18. The motor according to claim 16 including a fluid pump to supply a continuous flow of said first pressurized fluid to said control valve from a first fluid reservoir, and wherein a third conduit connects said control valve to said first fluid reservoir to transfer said first fluid exhausted from said first compartments of said cylinders to said first fluid reservoir.

19. The motor according to claim 18 including means to vary said continuous flow of said first pressurized fluid to thereby vary the said linear velocity of each said piston in said first direction.

20. The motor according to claim 19 whereby each said piston within each said cylinder is connected, via a separate said connecting rod, to a reciprocating positive displacement pumping means.

21. The motor according to claim 19 including means to vary the flow of said second pressurized fluid supplied to each said second compartment of each said cylinder to thereby vary the said linear velocity of each said piston displaced in the said second return direction.

22. A reciprocating hydraulic motor, adapted for use in driving a reciprocating hydraulic pump, comprising:

a plurality of cylinders each having a first end and a second end;

a separate pistons positioned within each said cylinder, each said piston being capable of reciprocal displacement within its respective cylinder, each said piston defining a first compartment and a second compartment within its respective cylinder;

a first pressurized fluid source having a pressurized fluid inlet and a pressurized fluid outlet;

a control valve to control the flow of said first pressurized fluid from said outlet .of said fluid source to each said first compartment of each said cylinder, said control valve being operated independently of piston position and movement, said control valve also controlling the flow of said first fluid from each said first compart¬ ment to said fluid inlet of said fluid source as said first fluid is exhausted from said first compartments by said pistons displaced in said second return direction;

first conduits connecting each said first compartment to said control valve;

a second conduit connecting said control valve with said pressurized fluid outlet of said first pressurized fluid source; a third conduit connecting said control valve with said pressurized fluid inlet of said first pressurized fluid source to transfer said exhausted first fluid to said fluid inlet;

fourth conduits connecting said pressurized fluid inlet with each said second compartment of each said cylinder, thereby creating an expansionary fluid circuit common to said fluid inlet and each said second compartment;

a second pressurized fluid contained within the said second compartments of each said cylinder thereby creating an expansionary fluid circuit, wherein each said piston is sequentially dis¬ placed in a second return direction by said second pressurized fluid entrapped within said expansionary fluid circuit, displacement of one or more of said pistons in said first direction thereby displacing said second pressurized fluid from respective second compartments through said fourth conduits into other of said second compartments thereby displacing other said pistons in said second return direction;

means to continually add and remove said second pressurized fluid in said expansionary fluid circuit so that the volume of said second pressurized fluid circuit varies when each piston is displaced in a cycle, said cycle being defined by one piston displaced in both a first and second direction;

wherein said second pressurized fluid is removed from said expansionary fluid circuit when at least one of said pistons is displaced in said first direction by said first pressurized fluid thereby increasing the pressure of said second pressurized fluid entrapped within said expan¬ sionary fluid circuit to a given pressure;

wherein said second pressurized fluid is added to said expansionary fluid, circuit when said control valve allows said first pressurized fluid to exhaust from at least one of said first compartments of said cylinders; and

wherein said additional second pressurized fluid in said expansionary fluid circuit causes momentary simultaneous restriction of movement of all said pistons displaced in said second return direc¬ tion, thereby causing said increase in pressure of said second pressurized fluid.

23. The motor according to claim 22 including means to vary the volume of said first pressurized fluid supplied to said control valve to thereby vary the distance each said piston is displaced within its respective cylinder in said first direction.

24. The motor according to claim 22 including means to vary the operational speed of said control valve to vary the distance each said piston is displaced in said first direction and including means to add or remove said second pressurized fluid in said expansionary fluid circuit to compensate for said change in said second fluid volume caused by said variance in displacement distance.

25. The motor according to claim 22 wherein said expan¬ sionary fluid circuit is connected to said third conduit transferring said exhausted first fluid from said control valve.

26. The motor according to claim.22 wherein fluid is added to said expansionary fluid circuit by said first pressurized fluid source.

27. The motor according to claim 22 wherein each said piston is connected to a reciprocating positive displace¬ ment fluid pumping means, via a separate connecting rod having a first end and a second end, said first end of each said rod being connected to a separate said piston, said second end of said connecting rod being connected to said pumping means; and including means to drive said control valve independently of piston position and movement.

28. The motor according to claim 27 wherein said fluid pumping means includes unidirectional valves and recipro- eating pump piston means whereby said pumping means displaces fluid and receives fluid as said pistons of said motor are displaced in said first direction to thereby create a substantially uninterrupted pumping action of fluid through said pumping means.

29. The motor according to claim 28 wherein said recipro¬ cating pump piston means is slidably and sealingly encased within a pumping chamber by a replaceable liner.

30. Apparatus for transmitting reciprocal motion to a driven member, comprising at least two cylinders each having a piston located therein for movement longitudi¬ nally thereof in one direction on its power stroke and in the other direction on its return stroke, each piston having a rod connected thereto and extending out one end of the cylinder for transmitting the movement of the piston to a driven member, conduit means connecting the cylinders in a closed loop for fluid in the conduit means to act on one side of the pistons to move one or more pistons on their return stroke as fluid is displaced from one or more cylinders as the pistons therein move on their power stroke, means for sequentially supplying fluid under pressure to the cylinders during overlapping time inter- vals so at least two pistons are moving on their power stroke simultaneously for a portion of their stroke and means for continually supplying makeup fluid to the closed loop at a rate sufficient to move the pistons on their return stroke faster than the pistons on the power stroke move to ensure that all pistons compete their total allowed cylinder return movement and stop before moving again on their power stroke, and means to release fluid from said closed loop to maintain the pressure below a preselected amount.

31. The combination of claim 30 wherein said apparatus for transmitting reciprocal motion to a driven member comprises at least three cylinders.