Abstract: A method is provided for generating an improved torque-drag model for at least the collar portion of the drill string in a directional oil or gas well. The technique of the present invention determine the stiffness of incremental portions of the drill string, and uses this information, the borehole clearance, and the borehole trajectory to determine the contact locations between the drill string and the sidewalls of the well. The contact force at these determined locations can be calculated, taking into consideration all significant kinematic, external, and internal forces acting on that incremental portion of the drill string. More acurate torque-drag analysis provided by the improved model of the present invention assists in well planning, prediction, and control, assists in avoiding drilling problems, and reduces total costs for the well.

Abstract: For the purposes of determining the orientation of a surveying instrument in a borehole, while compensating for the effects of perturbing magnetic fields associated with magnetized sections of the drill string both above and below the instrument, the inclination angle .theta. and the highside angle .phi. of the instrument are determined, together with two transverse components Bx and By of the local magnetic field as measured at the instrument in the borehole. Additionally either a single component of, or the magnetide of, the true earth's magnetic field at the location of the borehole is ascertained from a look-up table or directly by measurement away from the influence of the drill string. A value .PSI.a for the azimuth angle of the instrument is then determined from the inclination and highside angles, the measured component(s) of the local magnetic field, and only the single component of, or the magnitude of, the true earth's magnetic field.

Abstract: In order to support a mud-driven impeller of a down-hole turbogenerator in such a manner as to provide long bearing service life in the hostile conditions down-hole, a bearing sleeve is provided which comprises an outer shell of marine brass and an inner lining of nitrile rubber bonded to the inside surface of the shell. The lining extends axially beyond the end of the shell to form a portion positioned beyond the end of the shell and turned over the end of the shell. This portion comprises radical lands separated by radial grooves, and the radial lands define axial bearing surfaces for cooperating with an axial bearing surface of a bearing member which the bearing sleeve surrounds in use.

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 single-shot or multi-shot measurement probe incorporates a magnetic field sensor for sensing the earth's magnetic field, a processing unit for determining from the output of the sensor that the probe has moved from within a section of a drill pipe made predominantly of magnetizable material to within a collar made of substantially non-magnetizable material, and a switching unit for initiating the taking of one or more survey measurements by the probe when an output is received from the processing unit indicating that the probe has entered the collar. The probe further incorporates a gravity sensor for sensing the earth's gravitational field and a further processing unit for determining from the output of the gravity sensor that movement of the probe has stopped and for controlling the switching unit such that the taking of one or more survey measurements by the probe is not initiated until after receipt of an output from the further processing unit indicating that movement of the probe has stopped.

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: In a borehole telemetry system for acoustically transmitting data over a pipe suspended in a borehole, the level of noise in the data stream is inherently high due to the environment existing in a drilling operation and to the physical characteristics of a drill string. It has been discovered that certain discrete frequency passbands exist in a drill string which permit transmission of an acoustic signal with a minimum level of attenuation. In addition, it is now known that a fine structure exists within these frequency passbands which presents gaps or voids that attenuate the signal at a much higher rate. These gaps are on the order of 20 Hz.By generating an acoustic signal at a precise frequency spectrum within these passbands and then phase shifting the signal before its transmission, the energy spectrum of the transmitted signal is spread out over a sufficient frequency range to bridge these gaps.

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 borehole is surveyed by positioning at the mouth of the borehole a survey instrument having a casing and a three-axis rate gyroscope unit mounted within the casing, and sensing at least two components of gravity in at least two mutually transverse directions with respect to the survey instrument by means of a gravity sensor unit. The survey instrument is then moved along the borehole with the start and finish of the run being at the mouth of the borehole or at some known reference along the path of the borehole. During the run the rates of rotation about three non-coplanar axes are sensed at a series of locations along the length of the borehole by means of the rate gyroscope unit.

Abstract: A system for providing a fluid communication path between the surface and a downhole location in a borehole includes a capillary tubing which is secured to the outside of a production pipe string and which is run into the borehole on the pipe string. The tubing is sized to accommodate the downhole injection of treating chemicals into the producing fluid stream, primarily for corrosion control. In many instances it is desirable to make downhole pressure measurements in a producing well. A small solid slickline with an attached plunger is pumped down the chemical injection tubing into a chamber at the bottom of the tubing. The slickline substantially restricts the cross-sectional area of the injection tubing to accommodate accurate direct pressure measurements at the remote downhole location.

Abstract: A device for protecting and securing small diameter tubular members along a pipe string in a wellbore is disclosed. The protector is designed to fit about the joints of connecting pipe sections and comprises a sleeve assembly capable of being arranged and locked about a pipe joint. The sleeve assembly preferably comprises a plurality of symmetrical, most preferably semi-cylindrical, sleeve members having interfitting longitudinal end portions, preferably held by hinge pins in circular arrangement about a pipe joint. At least one longitudinal channel is formed, preferably with a pair of parallel, longitudinal ridges on the interior surface of the sleeve assembly to receive and hold therein a small diameter tubular member. The sleeve assembly is further characterized by shoulder members spaced sufficiently far apart to bracket the greater diameter pipe joint to prevent longitudinal displacement of the sleeve assembly with relation to the pipe string and joint.

Abstract: In situations where it is necessary to directionally drill boreholes from the surface in a substantially horizontal attitude, such as for pipeline river crossings, the precise directional parameters of drilling become critical. A system of tools for efficiently accommodating the precise directional steering of the drilling includes a continuous electrical communications path within a drill string, which path provides steering data at the surface for controlling the drilling operation. A side entry sub is positioned in the tool string at its upper end. A cable system is employed in each pipe section placed in the string and includes provisions for breaking and making connections with the cable without withdrawing the cable from the pipe string. A steering tool is fixedly positioned in the drill pipe near the drill bit and is not normally withdrawn from the hole except with the drill bit.

Abstract: A surface activated multishot survey tool utilizes a dampened magnetic compass movably positioned within a probe to determine the direction of a borehole. Lamps in the probe are operable to light the face of the compass. A lens projects the image of the compass onto a movable film strip. An electrical cable is connected to the probe and is used to pass a current to the lamps and provide selective operation of the tool from the surface of the borehole. Electrical connectors are provided at each end of the probe so that the probe may be inverted within the borehole to accommodate surveys in which the angle of the borehole is greater than that at which the compass will operate without error. Because connectors are located at both ends of the probe, electrical current passes around the magnetic compass, thus creating a magnetic field about the compass.

Abstract: Data is transmitted through a drill string by means of acoustical energy by transmitting an acoustical signal for a first predetermined interval and ceasing transmission of the signal for a second predetermined interval to represent a first binary state; ceasing transmission of the signal for a third predetermined interval to represent a second binary state; and combining transmission and cessation of transmission of the signal in binary sequences representative of borehole data.

Abstract: In a borehole telemetry system for acoustically transmitting data over a pipe suspended in a borehole, the level of noise in the data stream is inherently high, making the use of discrete frequencies advantageous to provide useful data. Any drift in electrical circuits which might affect or be affected by the use of precise frequencies is undesirable. A clock synchronization or bit rate clock circuit in a data signal processing system is operated by a local crystal oscillator which is operated at substantially the same precise frequency as a crystal oscillator that is used to generate and transmit the data signal. The synchronization of the bit rate clock is arranged to make only small corrections in order to keep the frequencies fully synchronized at all times thus false signals will not shift the clocks out of synchronization.

Abstract: In a borehole telemetry system for acoustically transmitting data over a pipe suspended in a borehole, the level of noise in the data stream is inherently high, making the use of discrete frequencies advantageous to provide useful data. Any drift in electrical circuits which might affect or be affected by the use of precise frequencies is undesirable. A synchronous detector facilitates the removal of noise components from the data stream by comparing in a commutative filter the phase difference between a switching signal taken from the incoming data signal path, after the second stage of commutative filtering, with the data signal emerging from the last stage of filtering. The synchronous detector also compares a data signal having two stages of filtering with another data signal having six stages of filtering with the additional filtering, causing a phase shift in frequencies outside the precise frequency window, which the synchronous detector also rejects.

Abstract: In a borehole acoustic telemetry system for acoustically transmitting data over a pipe suspended in a borehole, the level of noise in the data stream is inherently high, making the use of precise frequencies advantageous to provide useful data. A first transmitter in the system operates at a precise frequency to transmit a signal over the pipe where it is received by a receive and retransmit circuit path. Components in the receive and retransmit section filter and amplify a data component of the signal and retransmit the data signal at a precise frequency. Crystal controlled oscillator clocks are operated in the system at a same frequency in the transmitter and receiver-retransmitter to insure precise frequency control of the system.

Abstract: A telemetry system for transmitting data between a downhole location in a wellbore and the surface of a well utilizing an acoustic signal which operates within naturally occurring passbands on a string of pipe have substantially fixed frequency ranges which are related to pipe length and condition.

Abstract: In a borehole telemetry system for acoustically transmitting data over a pipe suspended in a borehole, the level of noise encountered requires the use of specific frequencies to transmit data. Any drift in electrical circuits which might affect or be affected by such use of precise frequencies is undesirable. An automatic gain control (AGC) circuit is provided which obtains its feedback from a signal which has undergone some noise filtering so that the AGC circuit is controlled by a signal having a high signal-to-noise ratio. The circuit is arranged so that the wide temperature variations occurring in a downhole environment as well as component deterioration or change do not affect the frequency of the data signal or operation of the system in dealing with a precise frequency.

Abstract: Apparatus is provided for permitting a communication wireline to be suspended in a borehole along the outside of a drill stem for subsequent side entry therein and connection to a steering tool for the relaying of information from the steering tool to the surface of the borehole. The apparatus includes an apertured section of drill pipe having a self-contained sealing structure including a wireline clamp housed therein for securing and sealingly engaging the wireline therethrough and maintaining the sealed integrity of the drill stem. In this manner mud may be pumped under pressure through the drill stem to drive a drilling head while the wireline interconnects the steering tool and the borehole surface along the outside of the drill stem.