Abstract: The invention relates to a method of real time control of fluid influxes into an oil well from an underground formation during drilling.The injection pressure p.sub.i and return pressure p.sub.r and the flow rate Q of the drilling mud circulating in the well are measured. From the pressure and flow rate values, the value of the mass of gas M.sub.g in the annulus is determined, and the changes in this value monitored in order to determine either a fresh gas entry into the annulus or a drilling mud loss into the formation being drilled.

Abstract: A system for eliminating the need for one or more mud loggers on a drilling rig keeps track of the travel of drilling mud injected into the bottom of the well as it moves to the surface of the well with entrapped drill cuttings and gas so that for mud reaching the surface of the well, the system knows at what depth in the well the mud was injected. The system indicates to drill rig personnel when mud from preselected well depths reach the surface of the well and when to collect samples of drill cuttings strained from the mud in order to have the required samples representative of the preselected well depths. The system monitors the performance of well personnel in collecting samples by monitoring the time it takes to collect a sample after the indication that the sample should be collected.

Abstract: A borehole tool employs a drill string having a plurality of sections of drill pipe connected together for traversing a wellbore. Drilling fluid is circulated down the drill string and up the annulus between the drill string and the wellbore to transport entrained drill cuttings out of the wellbore. At least one section of double wall drill pipe with its outer wall perforated, is included in the drill string. Drilling fluid flow down the string into the section of double wall drill pipe is controlled to effect a desired degree of drilling fluid flow rate through the perforations in the outer wall of the double wall drill pipe section so as to provide a stirring action to the drill cuttings in the wellbore annulus and thereby improve the transport of entrained drill cuttings out of the wellbore in the circulating drilling fluid.

Abstract: A system is provided for the optimization of particle separation in a shaker system of a well drilling system. A well bore is drilled with a rotary drilling system. A stream of drilling fluid is circulated through the rotary drilling system to carry rock particles away from the bottom of the well bore as the well bore is formed. This stream of drilling fluid with the rock particles being carried therein is passed through a shaker system for separating the rock particles from the drilling fluid. A value of at least one, and preferably a plurality of operating parameters of the rotary drilling system are monitored, which parameters correlate to an average size of the rock particles being generated. The shaker system is adjusted in response to these monitored values, and more particularly in response to control signals computed based upon these monitored values, to increase separation of the rock particles by the shaker system.

Abstract: An apparatus and method for measuring differential pressure of mud internal a drill string and mud in a borehole annulus is disclosed.

Abstract: A down-hole signal generator for a mud-pulse telemetry system comprises a flow constrictor defining a throttle orifice for the mud passing along a drill string, a throttling member displaceable with respect to the throttle orifice to modulate the mud pressure for the purpose of transmitting measurement data up the drill string, and a turbogenerator. The turbogenerator incorporates an annular impeller surrounding a casing and arranged to be driven by the mud passing along the drill string, and a rotatable magnet assembly disposed in a mud-free environment within the casing.

Abstract: A mud pulse telemetry system for imparting data pulses to drilling fluids circulating in a drill string including an improved valve arrangement for modulating the pressure of the circulating drilling fluid is disclosed. A shear-type valve is arranged in a through conduit configuration so that the seat face of the valve is covered when the valve is in an open position, thus preventing impingement of abrasive fluid particles on the valve seat face during the open flow position of the valve. The activation means is connected to the valve gate through a floating connection which prevents lateral stress forces operating on the valve from being imparted to the solenoid. The floating connection also permits convenient removal of the valve seat and gate from an access opening on the exterior of the drill string housing to facilitate the replacement of critical valve parts without removing the valve subassembly from the drill string.

Abstract: A dynamic filtration unit for drilling and completion fluids employs an adjustable size annulus, high filtration pressures and temperatures, automatic filtration collection and measurement, and natural or artificial filters.

Abstract: A choker valve assembly for a drill string is provided for transmitting information measured in an underground bore hole by sensing devices, to the surface by modulating the pressure of the flushing fluid. The valve assembly includes a housing that is non-rotatably connected within the flushing fluid flow passage by cross-pieces extending between the housing and a portion of the inner pipe wall. A drag body valve element is mounted by the housing and is axially displaceable with respect to a tapered restriction portion of the inner pipe. Drive means for displacing the valve element is located outside the housing and extends between the valve element and the pipe wall through the cross-pieces. A cap is provided on each end of the valve element.

Abstract: Information is conveyed from a downhole location within a well, by varying the rate of flow of drilling fluid at the downhole location in accordance with changes in a predetermined condition at that location, and then sensing variations in the rate of flow of the drilling fluid at the surface of the earth as an indication of the downhole information being transmitted. A readout unit can be actuated in accordance with the information sensed at the surface of the earth to give a visual indication or other output representative of or dependent upon the downhole information.

Abstract: A control apparatus preferably for concurrently protecting a downhole fluid pressure operated device from excessive fluid pressures and indicating at the surface when any such excessive fluid pressure level has been reached. The pressured fluid is directed through a bore of a sleeve, and a flow plug is normally located in an axially remote position relative to the sleeve bore. The flow plug is moved upon the occurrence of a predetermined fluid pressure across the downhole device to move into the bore of the sleeve and produce a flow constriction which will result in an detectable fluid pressure signal at the surface. Concurrently, a bypass flow path is established around the fluid pressure operated device to immediately reduce the fluid pressure being applied to such device.

Abstract: A drill bit having cutting cones is provided with a plenum chamber communicating with orifices for supplying lubricants to the bearings of the cutting cones and orifices communicating with the plenum for supplying cutting liquid and gaseous fluid to jet nozzles on the periphery of the drill bit for supplying a low volume of said cutting liquid and gaseous fluid to the area below the drill bit cutting cones thus reducing the velocity of the cuttings and orifice communicating with the plenum chamber and a meter for measuring the volume of cutting liquid and gaseous fluid being supplied to the drill bit.

Abstract: The infusion of fluid from the formation being drilled into a borehole is detected in an MWD system by modulating the drilling fluid stream in the drill pipe and detecting pressure variations commensurate with the modulation at the surface in the annulus between the drill pipe and wall of the well. Modulation to generate the pressure variations in the annulus is accomplished by the same pressure generating element used to generate pressure signals in the mud column for MWD measurements. The detected pressure variations are compared in phase and/or amplitude with their own near term past history or with the drilling fluid pressure variations in the drill pipe resulting from the modulation. Variations in phase or amplitude which can not be attributed to changes in the drilling operation will be indicative of fluid infusion.

Abstract: The infusion of fluid from the formation being drilled into a borehole is detected by modulating the drilling fluid stream in the drill pipe and detecting pressure variations commensurate with the modulation at the surface in the annulus between the drill pipe and wall of the well. The detected pressure variations are compared in phase and/or amplitude with their own near term past history or with the drilling fluid pressure variations in the drill pipe resulting from the modulation. Variations in phase or amplitude which can not be attributed to changes in the drilling operation will be indicative of fluid infusion.

Abstract: Information is conveyed from a downhole location within a wellbore being drilled by producing pressure and velocity of flow variations from the steady state drilling fluid pressure and velocity of flow so as to set up transient acoustic waves that propagate to the surface through the drilling fluid within the drill string. The acoustic waves are detected at the surface to obtain the propagated information. According to this invention, a simple and reliable method of recovering the propagated information is to monitor the pressure of the gas filled side of the accumulator or desurger device that is coupled to the drilling fluid line adjacent the pump.

Abstract: A bundle type gauge carrier including a support assembly which may be loaded with a plurality of downhole gauges, the support assembly being quickly insertable in a case assembly incorporated in the pipe string used for a formation test. The gauges are grouped in the support assembly about an unobstructed central flow path, whereby each gauge is exposed to the pressure and temperature of the flowing oil and gas during a drill stem test.

Abstract: Lag-determining method and apparatus which provides for determination of and an indication of when borehole cuttings from preselected depths arrive at the surface of the earth is disclosed and includes devices for inputting the value of the lag strokes and the predetermined drilling depth increments. A signal representative of the actual drilling depth is provided to a computer circuitry. Counter circuitry accumulates a count of the strokes of the positive displacement mud pump. Adder circuitry sums the lag strokes and the accumulated count of the mud pump. Comparator circuitry provides an output when the compared values of the accumulated number of strokes of the positive displacement mud pump equals the sum of the lag strokes and the strokes of the positive displacement mud pump at a predetermined depth plus the depth increment. Visual and audio indications provide notification of the arrival of borehole cuttings from preselected depths.

Abstract: Information is conveyed from downhole location within a well, by varying the rate of flow of drilling fluid at the downhole location in accordance with changes in a predetermined condition at that location, and then sensing variations in the rate of flow of the drilling fluid at the surface of the earth as an indication of the downhole information being transmitted. A readout unit can be actuated in accordance with the information sensed at the surface of the earth to give a visual indication or other output representative of or dependent upon the downhole information.

Abstract: A system for use in providing measurements from within a borehole to the earth's surface during drilling operations in which a drill pipe extends from the earth's surface having a drilling means, such as a drill bit, at the lower end and a fluid circulation system forming a column of drilling fluid within the drill string, a direct radiator telemetering system including a housing positioned within the drill string providing for the flow of drilling fluid therepast, the housing being in the form of a tubular member having within it an electrically driven pressure pulse radiating means responsive to electrical signals representing the magnitude of a downhole parameter for producing a sequence of pressure pulses indicative of the magnitude, the tubular housing being of a relatively long length being of approximately a substantial fraction of the equivalent wavelength of the pulses produced by the pulse producing means, and instruments at the earth's surface for maintaining superatmospheric mud pressure in the to

Abstract: A control system for use on fluid conducting pipe strings in earth boreholes to permit cycling of fluid flow between preselected flow rates to change conditions downhole as a result of surface exercise of fluid flow controls. A resulting change of state downhole is indicated by a change in fluid flow related pressure detectable at the surface.

Abstract: A normally straight drill string component for use just above a downhole drilling motor, or directional jet, that can be caused to be alternately straight or bent by cycling the drilling fluid flow rate between selected flow rate limits by use of controls at the earth surface.

Abstract: A method for circulating and maintaining a drilling mud in a wellbore drilled into a subterranean formation at a desired pressure during drilling operations, said method consisting essentially of;(a) circulating drilling mud through a drill pipe in the wellbore into the wellbore, maintaining a desired pressure in said wellbore and recovering drilling mud from the wellbore at a controlled rate using a mud pump and mud pit arrangement; and,(b) maintaining a second supply of drilling mud in fluid communication with the drill pipe at a suitable pressure so that when the mud pump fails to maintain pressure in the drill pipe, drilling mud is supplied from the second supply of drilling mud to maintain pressure in the wellbore.

Abstract: A down-hole signal generator for a mud-pulse telemetry system comprises a flow constrictor defining a throttle orifice for the mud passing along a drill string, a throttling member displaceable with respect to a casing to modulate the mud pressure for the purpose of transmitting measurement data up the drill string, and a turbogenerator incorporating an electrical generator within the casing. The flow constrictor and casing form an integrated unit which is installed within a drill collar and is retrievable by drawing it up the inside of the drill string. The throttling member is displaced by a pump according to the torque required to drive the rotor of the generator which is dependent on the electrical load of the generator. The pump incorporates a rotary valve member which supplies the output of the pump to one or other side of a double-acting ram according as to whether the valve member is rotating with a first phase of rotation or a second phase of rotation.

Abstract: An oil well drilling rig (10) recirculates drilling mud which is analyzed continuously by pumping it through a gas separation unit (72) where the gases in the mud become separated and mixed with a carrier gas and are conveyed to gas analyzing devices (196) where the concentration of the different hydrocarbon components of the gases in the mud are continuously measured and the signals representative of these measurements are processed together with mud flow rate, and the carrier gas flow rate or the sample gas flow rate signals in a signal processor (64) to provide a continuous log of gas component concentration during drilling.

Abstract: A column of drill collars have holes or jets extending radially from the collar bore through the collar wall. A wash pipe extends full length through the bore of the perforated collars, so sized as to leave an annular flow space between the wash pipe and the collar bore wall. A remote control selector valve is situated such as to receive drilling fluid from the upwardly continuing drill string and direct the fluid through the wash pipe to the drill bit for regular drilling, or on cue from the earth surface, direct fluid to the annulus to be expelled through the drill collar perforations to help free stuck pipe or to prevent such sticking.

Abstract: A method and apparatus for establishing the rate at which fluid is transferred between an offshore well 16 and the formations 20 surrounding the well 16 in the course of drilling the well 16 from a floating drilling rig 14. A drilling fluid handling system 31 is used to inject drilling fluid into the well 16. A marine riser 22 extending from the sea bottom 18 to the rig 14 is provided to return the drilling fluid to the rig 14. The riser 22 is provided with a slip joint 26 to accommodate wave induced heave of the rig 14. Inflow and outflow flowmeters 42,44 are provided to monitor the rates at which drilling fluid is injected into the well 16 and returned to the rig 14. The return flow rate signal is filtered to mitigate the cyclical variations resulting from extension and contraction of the slip joint 26. A signal processing system 46 is provided to maintain the time constant applied in the filtering process at an optimum level as the rate and magnitude of rig heave varies with time.

Abstract: A method and system for detecting and identifying abnormal drilling conditions. It determines the normal pump speed-pressure ratio over the range of usual working conditions. It measures the output pressure from the pump. And it measures the speed of the pump. Then it detects a change from the normal pump speed-pressure ratio which indicates abnormal conditions. Identification of the abnormal condition depends upon whether the pump speed increased above normal or the output pressure decreased below normal. If the former, the volume of drilling fluid returning is observed in order to identify one of three conditions. If the latter, the number of decreases greater than a predetermined extent are counted over a predetermined interval of time which may indicate malfunctioning pump valve or valves.

Abstract: An external gauge carrier for use in tubing-conveyed drill stem testing comprises a protective housing for locating and securing the pressure measuring and recording system. The gauge carrier may be manufactured from drill collar bar stock but provides a 1--1 interface with ordinary drill pipe, other measurement subs, perforating guns and the like; i.e., to the complete system it "looks" like a drill collar. The gauge measures and records drill stem bore pressure while providing "full bore" testing capabilities, i.e., the gauge carrier allows unimpeded wireline operation therethrough and causes essentially no pressure drop throughout its length. Special machining and gauge placement is required in order to provide the above capabilities and features while still maintaining sufficient wall thickness to ensure structural integrity. A unique system for protecting the relatively delicate gauges from damage due to shocks from pressure surges is also disclosed.

Abstract: A down hole blow out preventer which can be installed at the lower end of a drill string as close as possible to the drill bit and which can isolate an unexpected producing zone in a bore hole from the rest of the hole by closing off the drill string at its lower end and closing off the annulus between the drill string and the wall of the bore hole by means of an inflatable packer. The packer can be operated when a predetermined pressure difference exists between the annulus and the mud column inside the tool.

Abstract: Method and apparatus are provided for determining the formation pressure. The magnitude of formation pressure may be derived as a function of changes in bottomhole pressure following swabbing the borehole to draw formation fluids into the borehole, monitoring the borehole for influx of formation fluids, determining the reduced pressure due to swabbing, repeating the swabbing and monitoring steps until an influx of formation fluids is detected thereby determining the pressure of the formation.

Abstract: The present invention is directed to a method for optimizing the tripping velocity of a drill string. The method of the present invention comprises determining the hydraulic fluid pressure in the borehole in a plurality of intervals as the drill string is pulled out of or run into the borehole. These actual pressures are compared against a predetermined acceptable pressure range for each interval. The limits for this acceptable pressure range are set by the maximum acceptable surge pressures and the minimum acceptable swab pressures established for the interval. The velocity of the drill string in each such interval is then adjusted in order to maximize the tripping velocity while maintaining the hydraulic fluid pressure within the acceptable range for each interval.

Abstract: A fluidic pulsing device is disclosed which comprises at least one fluid lifier and several vortex valve restrictors. One or more amplifiers direct fluid flow to the several vortex valves, which are arranged in parallel fashion. Such an arrangement allows for optimization of design geometries, and therefore, optimization of performance, despite the fact that the physical dimensions of the apparatus may be severely restricted.

Abstract: In accordance with an illustrative embodiment of the present invention, a drill stem testing apparatus includes a housing leaving a full-opening bore, and a main test valve for opening and closing the bore in order to flow and shut-in the formation interval being tested. The apparatus further includes a first port means for communicating the pressure of fluids in the bore below the test valve to a first pressure transducer, a second port means for communicating the pressure of fluids in the bore above the test valve to a second pressure transducer, and a third port means for communicating the pressure of fluids in the well annulus externally of the housing to a third pressure transducer. The outputs of the respective transducers are fed to a recording gauge so that a pressure record is obtained of the changes in fluid pressure that occur in the bore of the housing above and below the test valve as well as in the annulus externally of the housing.

Abstract: A system, or apparatus combination, and apparatus components, for the measurement of fluid flow. Such system, or apparatus can be used, e.g., for measuring the amount or flow of drilling fluid, or mud, introduced into a well bore, the amount or flow of mud returned from the well bore, and differences in flow rate and density between the mud introduced into the well bore and the mud returned from the well bore. The system measures or calculates, inter alia, flow rates, viscosity, temperature, density and gas content and compensates for variations; and in marine installations the system additionally measures vessel motion and compensates for wave and tide motions.

Abstract: A down-hole signal transmitter for a mud pulse telemetry system comprises a flow constrictor defining a throttle orifice for the mud flow, a throttling member displaceable to vary the throughflow cross-section of the throttle orifice, and a pump for displacing the throttling member against the mud flow in order to modulate the mud flow. The displacement of the throttling member is controlled by a hydraulic amplifier, comprising a main pressure relief valve and a subsidiary control valve, and a solenoid to which the output signal of a measuring instrument is supplied. When the main valve is close, the pump displaces a ram, coupled to the throttling member, upwardly.

Abstract: A latch device for controlling a valve in a mud pulse telemetry system for imparting data pulses to drilling fluids circulating in a drill string is disclosed. A latch device and valve arrangement including an improved shear type, solenoid operated valve for modulating the pressure of the circulating drilling fluid is disclosed. A latching solenoid armature is connected to the valve gate through separate open and close solenoids having their armatures operatively connected to act as a single unit. The single unit armature is normally restrained from movement by the solenoid deactivated latch device. The latch device is arranged so that the vibrational and impact loads on the drill string serve to further maintain the modulating valve in a closed position.

Abstract: A drilling mud flow rate detector, including a sub adapted for being positioned in the drill string, having a sonic signal generator located near the center of the sub in both the incoming mud flow path and the return mud flow path. A set of sonic signal receivers is located at both ends of the sub in both the mud input flow path and the mud return flow path and corresponding sets of sonic signal transmitters are located near the center of the sub. The distance between the transmitting transducers at the center of the sub and the receiving transducers located at each end of the sub are equal so that under a condition of no mud flow, the sonic signals arrive at each end of the sub simultaneously. During mud flow, "doppler effect" will produce phase shifts in the sonic signals which are proportional to the direction and the rate of mud flow. Signals received by the receiving transducers are processed to produce an input mud flow rate signal and an output mud flow rate signal which are then compared.

Abstract: An apparatus for the remote transmission of information from a borehole (1) to the surface of the earth is disposed in a drilling pipe string (4) of a drilling device. The drilling device further comprises a rotary drill bit (3) and a pump (5) which pumps the flushing liquid (6) downwards in the flow passage (11) of the drilling pipe string, through the rotary drill bit (3) and upwards in an annular space (7) surrounding the pipe string. The apparatus has devices for ascertaining information data (8), for converting the information data into electrical control signals (9) and for producing pressure pulses (10) in the downwardly directed flow of the flushing liquid (6). The devices are disposed in a chamber (13) which is bounded internally by the flow passage (11) and externally by an outer tube (12).

Abstract: A rotary cutter head for a coal mining machine comprises sensor means for sensing a preselected state, as for example, the methane concentration in the vicinity of the cutter head and for deriving a signal indicative of the sensed preselected state.

Abstract: In the preferred and illustrated embodiment of the present apparatus, a drilling orientation tool is disclosed utilizing a mud pressure charging system where the pressure charge is converted into hydraulic oil pressure. The hydraulic oil flow is supplied to a four-way, three-position, solenoid operated valve having a closed center position, the valve forming a control signal delivered to an adjustable constriction in the mud flow path through the tool. Variables are encoded dependent on opening and closing of the constriction. Consecutive variables are transmitted in the form of fine and coarse measures. The electrically operated solenoid valve thus encodes two or more variables for transmission to the surface by detecting mud pressure variations in the mud flow line at the surface.

Abstract: Methods and means are disclosed for the monitoring of conditions in a mud circulation system as used in the drilling of oil and gas wells, and to quickly detect and indicate pressure failures that may occur in that system to thereby allow for the maximum time and opportunity for remedial action.

Abstract: This invention discloses a method and system for continuously measuring the amount of solid cuttings picked up by a drilling mud being circulated in a well being drilled into subterranean formations and the amount of drilling mud carried over with the cuttings when the cuttings are separated from the drilling mud by a shale shaker. The cuttings and carryover mud discharged from the shale shaker are introduced into a vessel wherein the weight and volume of the solid cuttings and carryover mud are continuously measured and the volume fraction of solid cuttings .phi..sub.c is determined in accordance with the following equation: ##EQU1## wherein W is the weight of a fixed volume of solid cuttings and carryover mud discharged from the shale shaker, V is the volume of solid cuttings and carryover mud discharged from the shale shaker, P.sub.m is the density of the drilling mud, and P.sub.c is the density of the solid cuttings. The volume fraction of the carryover mud .phi..sub.

Abstract: A monostable, solenoid-operated valve in a passage which bypasses the drilling fluid pressure drop across a drill bit at the lower end of a drill string in a well opens and closes in response to downhole conditions to create pressure pulses in the drilling fluid. The valve is urged toward a closed position by drilling fluid pumped through the drill string. A larger force is required to open the valve than to hold it open. Current supplied to the solenoid to open the valve is thereafter reduced to a value sufficient to hold the valve open. The solenoid is de-energized to close the valve.

Abstract: A drop device, method and article of manufacture used in measuring lagtime in the drilling of a well. A unique container with calcium carbide is inserted upwardly by its guide end into the open end of a pin connection prior to its threaded assembly into a lower box connection on drill pipe. The container is handled by a resilient member during placement into the pin connection and secured in place by a loop on the resilient member. The container is formed in a right cone of thin sheet material and its tapered sides are waterproof, and a disc seals the bottom or floor of the cone. The container is held in the pin connection with the floor adjacent its lower end. The pin and box connections are assembled and resumed drilling fluid flow fragments and disperses the sheet material whereby the calcium carbide converts to acetylene that is readily detected in the outflowing drilling from the well.

Abstract: An excavation controlling method for hydraulic shield tunnelling wherein decisions are made during advances of tunnel excavation on whether respective excavated soil amounts per macroscopic unit distance belong to the same statistic population and, with respect to excavated amounts per microscopic unit distance divided out of the macroscopic unit distance, whether excavated amounts per microscopic unit distance of the same dividing order belong to the same statistic population.

Abstract: A method of removing fluids entering into a well bore from a well formation while the well is being drilled, such as gas, in which the gas bubble is chopped into small bubbles by mixing the gas with drilling mud and pumping the mixed gas and drilling mud upwardly through the drill string-bore hole annulus and removing it from the well.

Abstract: A method of and apparatus for removing fluids entering into a well bore from a well formation while the well is being drilled, such as gas, in which the gas bubble is chopped into small bubbles by mixing the gas with drilling mud and pumping the mixed gas and drilling mud upwardly through the drill string-bore hole annulus and removing it from the well.

Abstract: A drilling fluid monitoring system and method includes a pump stroke counter providing an electrical signal representing the volume of drilling fluid pumped into a well, a flow sensing device providing an electrical signal representing the volume of drilling fluid flowing out of the well, fluid level an electrical measuring device providing an electrical signal representing the fluid level changes within a tank, and a device receiving the electrical signals emitted by the pump stroke counter, flow sensor and measuring device to indicate changes in the circulation of the well drilling fluid.

Abstract: A method and apparatus is disclosed for determining the flow rate of drilling fluid flowing from a subaqueous well. The invention may also be used to determine the presence of an abnormal drilling condition during heaving motion of an offshore vessel from which the drilling operation is conducted. The invention measures the volume of fluid passing predetermined locations in the drilling system at particular points in time so as to eliminate the influence that the expansion and contraction of a telescoping section has on the total volume of drilling fluid within the system.

Abstract: Down-hole information from rotary well drilling operations is transmitted to a surface or remote location by the venting of drilling fluid from the interior of the drill stem into the bore hole annulus in a binary coded decimal format. A valve is caused to operate by the digital output of one or more down-hole transducers thus releasing and restoring the drilling fluid pressure in the desired sequence. A "sub" contains the necessary electronics, power supply and a motorized valve assembly. Commands from the surface to transmit information from any one of the transducers are transmitted by means of sequential pulses in a binary coded decimal format, in the drilling fluid pressure are provided by the operator by deliberately decreasing and then increasing the surface pump pressure in a sequence to which the applicable down-hole actuating means is responsive.