GB2201707A - Apparatus for well logging telemetry - Google Patents

Abstract

Apparatus for sending pressure pulses through drilling fluid in a drill string in a well bore includes an assembly (50) adapted to be mounted in the drill string adjacent the lower end of the drill string (54). The external dimension of the assembly is less than that of the internal diameter of the drill string to permit substantial flow of drilling fluid down the drill string, past the assembly, through a drill bit on the lower end of the drill string, and into an annular space between the drill string exterior and the well bore. The assembly includes an internal bore (201) to permit some drilling fluid to flow through the assembly. Valve means (216, 227), located nearer the lower end of the assembly than the upper end, are provided for intermittently restricting flow of drilling fluid through the assembly to send pressure pulses to the surface in response to the magnitude of a downhole condition to be measured. <IMAGE>

Description

APPARATUS FOR WELL LOGGING TELEMETRY 1. Field of the Invention This invention relates to logging wells during drilling, and more particularly to the wireless telemetry of data related to downhole conditions.

2. The Prior Art It has long been the practice to log wells by sensing various downhole conditions within a well and transmitting the acquired data to the surface through a wireline or cable-type equipment. To conduct such logging operations, drilling is stopped, and the drill string is removed from the well. Since it is costly and time-consuming to remove the drill string, the advantages of logging-while-drilling, or at least without removing the drill string from the well bore, have long been recognized. However, the lack of an acceptable telemetering system has been a major obstacle to successful logging-while-drilling.

Various systems have been suggested for loggingwhile-drilling. For example, it has been proposed to transmit data to the surface electrically through wires. Such methods have been impractical because of the need to provide the drill string sections with a special insulated conductor and appropriate connections for the conductor at the drill string joints. If a steering tool is used for directional drilling, and is controlled by wires from the surface, the wires and tool must be withdrawn from the well before continuing drilling in the rotary mode. Other proposed techniques include the transmission of acoustical signals through the drill string. Examples of such telemetering systems are shown in U.S. Pats. Nos. 3,015,801 to Kalbfell and 3,205,477 to Richards.In those systems, an acoustical signal is sent up the drill string and frequency modulated in accordance with a sensed downhole condition.

Wireless systems have also been proposed using lowfrequency electromagnetic radiation through the drill string, borehole casing, and the earth's lithosphere to the surface of the earth.

Other telemetering procedures proposed for loggingwhile-drilling use the drilling fluid within the well as a transmission medium. U.S. Pats. Nos. 2,759,143 and 2,925,251 to Arps and 3,958,217 to Spinnler disclose systems in which the flow of drilling fluid through the drill string is periodically restricted to send positive pressure pulses up the column of drilling fluid to indicate a downhole condition.

U.S. Pats. Nos. 2,887,298 to Hampton and 4,078,620 to Westlake et al disciose systems which periodically vent drilling fluid from the drill string interior to the annular space between the drill string and the well borehole to send negative pressure pulses to the surface in a coded sequence corresponding to a sensed downhole condition. A similar system is described in U.K. Patent Publication No. 2,009,473 A (Scherbatskoy).

A general problem with using pressure-pulsing equipment in a drill string to send information through the drilling fluid is that the pulse generators to date have been bulky and, therefore, impose a wasteful pressure drop in the drilling fluid flowing through the drill string.

Moreover, the previous pulse generators require a relatively large amount of electrical power, which means short operating time if batteries are used, or else require expensive downhole electrical generators. The previous pulse generators also tend to plug when the drilling fluid includes lost circulation material, and are subject to excessive wear, resulting in short service life and frequent failure under operating conditions.

In addition, some of the prior art pulse generators require specially built drill collars in the drill string to receive the generators and cannot reliably be positioned in the lower end of the drill string without removing the drill string from the well bore.

U.S. Pat. No. 4,550,392 to Mumby discloses an improved pressure pulse generator which overcomes many of the disadvantages of the prior art. However, we have found that the pressure pulse generator shown in that patent is sometimes subjected to excessive vibration, which shortens its service life.

This invention provides an improved pressure pulse generator less subject to vibration or problems with lost circulation material and, therefore, with a longer and more reliable service life.

As with the pressure pulse generator of the Mumby patent, the one of this invention can also be quickly lowered into, or removed from, a standard drill string without removing the drill string from the well bore. The pulse generator of this invention does not require a special section of drill string or drill collar to permit the generator to operate. For example, in the rotary drilling mode, the pulse generator can be landed on a TOTCO ring or baffle plate made up in the drill string at the desired location.

Under some circumstances, the pulse generator may simply be lowered in the drill string to rest on the drill bit. If drilling with a bit driven by a downhole motor (i.e., with the drill string not rotating), the pulse generator can be landed in an improved landing-restrictor of this invention, and made up in the drill string to orient the pulse generator relative to the face of the drill bit.

Another advantage of the pressure pulse generator of this invention is that when it is in operating position in the drill string, it offers a relatively low resistance to flow of drilling fluid, and is more tolerant of lost circulation material, which is sometimes added to the drilling fluid for well control.

The pulse generator of this invention can be used to measure many different downhole conditions, such as electrical resistivity, radioactivity, temperature, drilling fluid flow rate, weight-on-bit, torque, and the like. It is also well suited for directional survey work, i.e., determining the inclination and azimuth of a borehole.

Such information is important for ascertaining that the well is being accurately drilled to a selected downhole position. In one form of this invention, the pressure pulse generator can quickly and easily be lowered through the drill string to a position just above the drill bit so that the inclination and azimuth of the well bore, or any other downhole condition, can be measured and transmitted to the surface by generating pressure pulses in the drilling fluid. This saves pumping energy because the pulse generator need be in the drill string only when measurements are required and, therefore, does not impose a permanent impediment to the flow of drilling fluid through the drill string.

Moreover, the assembly of this invention can be substantially shorter than prior equipment, thus reducing pressure drop imposed on the drilling fluid while the assembly is in the well.

Preferably, the pulse generator is retrievable from the drill string by the use of an overshot tool on a wireline operated from the surface. If the drill string sticks in the well bore, the pulse generator can be recovered, even if the lower portion of the drill string must be abandoned in the well.

SUMMARY OF THE INVENTION The pressure pulse generator of this invention includes an elongated assembly adapted to fit in a drill string near the lower end of the drill string while the drill string is in a well filled with drilling fluid circulated by a pump to flow down through the interior of the drill string, past the assembly and a drill bit on the lower end of the drill string, into the space between the drill string and the well wall, and then to the surface.

The assembly includes a valve housing and a control valve in the housing. The valve includes a valve bore having an inlet and an outlet through which a portion of the drilling fluid may flow. The bore inlet opens upstream into a high-pressure zone of the drilling fluid flowing through the drill string, and the bore outlet opens downstream into a low-pressure zone of the drilling fluid.

The assembly is constructed and arranged so that a substantial portion of the drilling fluid always flows through a space between the assembly exterior and the drill string interior when the assembly is in the drill string.

To this end, the exterior dimension of the assembly is substantially less than the interior dimension of the drill string, which, in the preferred embodiment, also facilitates the assembly sliding freely into and out of the drill string.

The assembly includes electronic means for generating a control signal responsive to a downhole condition and valve operating means responsive to the control signal to change the rate at which fluid flows through the valve bore to send a pressure pulse through the drilling fluid to a pressure pulse detector at the upper end of the well.

The valve is adjacent the lower end of the assembly and preferably below the electronic means. In the preferred form, the valve bore outlet discharges substantially coaxially into the drill string when the valve is operated to increase the flow of drilling fluid through the drill string. We have found that this arrangement substantially reduces the vibration of the assembly compared to those prior art configurations in which the valve is nearer the upper end of the assembly, or in which the valve discharges drilling fluid from the assembly at an angle to the longitudinal axis of the well bore.

Preferably, the invention includes a restrictor between the drill string interior and the valve housing exterior to develop a working pressure drop in the drilling fluid between the valve bore inlet and outlet. The pressure drop helps to power the valve to vary the flow rate of drilling fluid through the bore.

Preferably, the restrictor includes landing means for receiving and supporting the assembly at the lower end of the assembly. In a further preferred embodiment for directional drilling or surveying, the restrictor and the lower end of the assembly include improved mating means which orient the assembly in a fixed position relative to the drill string when the restrictor supports the assembly.

Preferably, latching means on the upper end of the assembly permits it to be retrieved from the drill string by a corresponding latch attached to.a wireline and operated from the surface without removing the drill string from the well bore.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: FIG. 1 is a fragmentary schematic elevation of a drilling rig and system for logging a well with a drill string in it; FIG. 2 is a sectional elevation of the preferred embodiment of a pulse generator assembly made in accordance with this invention, and mounted in operating position in a drill string; FIG. 3 is an enlarged view taken on line 3-3 of FIG. 2; FIG. 4 is an enlarged view taken on line 4-4 of FIG. 2 with the valve in the open position; FIG. 4A is an enlarged view of the area within line 4A-4A of FIG. 4, showing the detail of the valve seat with the valve almost closed; FIG. 5 is an enlarged elevation taken on line 5-5 of FIG. 2 showing the lower end of the assembly;; FIG. 6 is a sectional elevation showing an alternate form of the lower end of the assembly and means for mounting it in a drill collar sub on a baffle plate; and FIG. 7 is an enlarged view taken on line 7-7 of FIG. 6.

DESCRIPTION OF SPECIFIC EMBODIMENTS Referring to FIG. 1, a well 10 is drilled in the earth with a rotary drilling rig 12, which includes the usual derrick 14, derrick floor 16, draw works 18, hook 20, swivel 22, kelly joint 24, rotary table 26, casing 27, and a drill string 28 made up of sections of drill pipe 30 secured to the lower end of the kelly joint 24 and to the upper end of a section of drill collars 32, which carry a drill bit 34.

Drilling fluid (commonly called "drilling mud" in the field) circulates from a mud pit 36 through a mud pump 38, a desurger 40, a mud supply line 41, and into the swivel 22. The drilling mud flows down through the kelly joint, drill string and drill collars, and through nozzles (not shown) in the lower face of the drill bit. The drilling mud and formation cuttings flow back up through an annular space 42 between the outer diameter of the drill string and the well bore to the surface, where it returns to the mud pit through a mud return line 43. The usual shaker screen (not shown) separates formation cuttings from the drilling mud before it returns to the mud pit.

A transducer 44 in the mud supply line 41 detects variations in drilling mud pressure at the surface. The transducer generates electrical signals responsive to drilling mud pressure variations. These signals are transmitted by an electrical conductor 46 to a surface electronic processing system 48, such as that described in U.S. Pat. No.

4,078,620 to Westlake et al.

Thus, as described in detail below, pressure pulses may be transmitted through the drilling fluid to send information from the vicinity of the drill bit on the lower end of a drill string in a well to the surface of the earth as the well is drilled. At least one downhole condition within the well is sensed, and a signal is generated to represent the sensed condition. The signal controls the flow of drilling fluid in the drill string to cause pressure pulses at the surface in a coded sequence representing the downhole condition.

Referring to FIG. 2, an elongated, cylindrical pressure pulse generator assembly 50 is mounted substantially coaxially in a drill collar 32 so the lower end 52 of the assembly rests in an annular restrictor-lander 53 mounted inside a conventional float shoe subsection 54 made up in the lower end of the drill collars immediately above the drill bit.

The restrictor-lander is described in detail below with reference to FIG. 4. Briefly, the restrictor-lander orients the assembly both longitudinally and rotationally in a fixed position with respect to the drill string when measuring borehole direction, or to conduct directional drilling in the steering mode. Alternatively, the assembly may rest in a conventional TOTCO ring or baffle plate 55, as shown in FIG. 6, if fixed orientation is unimportant.

A fishing head 60 secured to the upper end of the assembly includes a latch knob 62 integrally formed at the upper end of a downwardly extending shaft 64, which expands outwardly at its lower end to provide an internally threaded cylindrical skirt 65 threaded onto the upper end of a first coupling 66, which carries a first annular bumper 68 having an outside diameter slightly greater than the main body of the downwardly extending assembly, but substantially less than the inside diameter of the drill collar. The bumper can be of any suitable durable elastomer, such as highgrade polyurethane, which can withstand the abrasion and high temperatures encountered in drilling deep wells. The latch knob 62 on the upper end of the fishing head permits the assembly to be retrieved from the surface without pulling the drill string from the well bore, as described below.

The lower end of the first coupling 66 threads into the upper end of an elongated cylindrical sensor and electronics housing 70, which carries a sensor 72, and electronics (not shown) for processing sensor signals to generate control commands as described in U.S. Patent 4,216,536 to More.

The sensor can be of any suitable type for measuring downhole conditions to be monitored and reported to the surface while the drill string is in the well bore. For example, the sensor can indicate well bore inclination and azimuth.

The sensor and electronic circuitry are not shown or described in detail because they form no part of the present invention.

If the downhole condition depends on the magnetic field of the earth, then the portion of the assembly and the drill collar around the sensor are made of a conventional nonmagnetic metal alloy.

The lower end of the sensor and electronics housing 70 threads onto the upper end of a second coupling 74, which carries a second annular bumper 76, identical with. the first bumper. The lower end of the second coupling threads into the upper end of a cylindrical battery pack housing 78, which contains a battery power supply (not shown) for the electronic circuitry referred to above.

The lower end of the battery pack housing threads into the upper end of a third coupling 80, which carries a third annular bumper 82 identical with the first and second bumpers.

The lower end of the third coupling threads into the upper end of a cylindrical transfer housing 84 (see FIG.

3), the lower end of which threads into the upper end of an elongated cylindrical and upright motor housing 86. A pair of 0ring 87, each in a respective outwardly opening circumferential groove 88 around the exterior of the lower portion of the transfer housing, make a fluid-tight seal between the transfer housing and the motor housing. The couplings, battery pack housing, and sensor and electronics housing are sealed together in a similar way (not shown) to form the upper part of the assembly and provide a fluid-tight elongated chamber 90 within them at atmospheric pressure to hold the battery pack supply, electronics, and sensor or sensors.

An externally threaded main lock nut 92 threads into the upper end of the motor housing and just below the lower end of the transfer housing to bear against the upper face of an annular bulkhead seal 94, the lower face of which includes a stepped bore 95 which increases in diameter in the downward direction to form a downwardly facing annular shoulder 96 which bears against the upper end of an annular boss 97 formed integrally with the upper end of an annular bulkhead retainer 98. An upwardly facing annular shoulder 99 around the periphery of the retainer 98 squeezes an annular O-ring seal 100 up against the lower face 101 of a downwardly extending annular skirt around the periphery of the lower end of the bulkhead seal 94, so the O-ring 100 makes a fluid-tight seal against the inner surface of the motor housing 86.

The upper end of a circular bulkhead 104 bears against a downwardly facing annular shoulder 105 on the bulkhead retainer. A plurality of electrical leads 106 are each sealed in separate respective glass insulators 108, each of which are bonded in a respective longitudinal bore 110 extending through the bulkhead. The electrical leads 106 are connected to electrical conductors (not shown) to provide circuitry from the electronics and battery pack sections to a reversible stepper motor 112 mounted in the motor housing 86 below an annular spacer 114, the upper end of which is of reduced diameter and threaded into the lower end of the bulkhead retainer 98 so the upper end of the threaded portion of the spacer 114 bears against the underside of the bulkhead and holds it securely against shoulder 105.An annular O-ring 116 fits snugly in an outwardly opening annular groove 117 around the periphery of the central portion of the bulkhead, and seals the bulkhead against the bulkhead retainer. A longitudinally extending cavity 118 in the bulkhead spacer 114 contains an oil bath under the hydrostatic pressure on the exterior of the motor housing.

Screws 120 extending through vertical bores 121 in an outwardly extending annular flange 122 on the upper end of an annular adapter 123 secure the adapter to the underface of the stepper motor, which has a downwardly extending motor shaft 124 which fits snugly into a longitudinal bore 125 in a transmission shaft 126 secured to a flat spot 129 on the motor shaft by pins 127 press-fitted through horizontal bores 128 in the portion of the transmission shaft surrounding the motor shaft. An upper annular thrust bearing 130 is confined between the lower end of the adapter 123 and an upwardly facing annular shoulder 131 formed on the transmission shaft. An annular thrust bearing housing 132 has an outer diameter which makes a snug fit against the interior of the motor housing.The upper end of the bearing housing threads onto the outer periphery of the adapter and bears against the lower face of the stepper motor.

A lower annular thrust bearing 134 is confined around the transmission shaft between a downwardly facing shoulder 135 on the transmission shaft and an upwardly facing shoulder 136 on the interior of the bearing housing. The lower portion of the bearing housing fits around a needle roller bearing 138 disposed around the lower end of the transmission shaft.

The upper end of a ball screw lead shaft 140 threads into the lower end of the transmission shaft. The ball screw lead shaft is of conventional design and carries an external helical thread (not shown) in which ball bearings (not shown) ride. The ball bearings also ride in a matching helical thread (not shown) formed in the interior of an annular ball screw nut 142, the upper end of which bears against the lower face of the bearing housing.

Screws 144 extending through vertical bores 145 in an outwardly extending annular flange on the upper end of an annular converter 146 secure the converter to the lower face of a matching outwardly extending flange 148 formed integrally on the lower end of the ball screw nut. The lower portion of the converter has a hexagonal external shape, which makes a close sliding fit through a vertical hexagonal bore 158, which opens out of the lower end of an annular bushing 160 which has an upper section 161 with outer diameter that makes a close fit against the inside diameter of the motor housing. The upper end of the bushing 160 threads onto the lower end of the bearing housing.

Thus, as the stepper motor shaft rotates, the rotary motion of the shaft is converted by the ball screw lead shaft, the ball screw nut, the converter 146, and the bushing 160 with the hexagonal hole into linear motion which slides the converter up or down, depending on the direction of rotation of the reversible stepper motor.

The upper end of an annular floating piston housing 162 threads into the lower end of the motor housing 86 and bears against a downwardly facing shoulder 164 on the lower end of the bushing 160. An O-ring seal 166 in an outwardly opening annular groove 168 around the piston housing 162 makes a fluid-tight seal against the interior surface of the motor housing, the lower end of which bears against an upwardly facing shoulder 170 on the piston housing. The lower end of the converter 146 extends into a central bore 171, which extends through the piston housing. The upper end 172 of a charging stem 173 threads into the lower end of the converter 146. An outwardly and upwardly extending shoulder 174 on the charging stem bears against the lower end of the converter. A longitudinal bore 176 extends through the charging stem and is collinear with a longitudinal bore 178, which extends through the converter.

An annular floating piston 179 makes a close sliding fit around its outer periphery against the interior surface of the piston housing. The interior surface of the annular floating piston makes a close sliding fit around the cylindrical charging stem 173. A first annular T-seal 182 in an outwardly opening annular groove 183 around the outer periphery of the annular floating piston makes a fluid-tight sliding seal against the interior surface of the floating piston housing. A second annular T-seal 184 in an inwardly opening annular groove 186 in the floating piston makes a sliding seal against the cylindrical exterior of the charging stem.

An oil plug 190 threads into the lower end of the charging stem. An 0-ring 192 in an outwardly opening annular groove 193 around the oil plug makes a fluid-tight seal against the interior of bore 176 in the charging stem.

Thus, all of the components lying between the bulkhead 104 and the upper face of the floating piston 180 are immersed in an oil bath. Oil is added to the space between the bulkhead and the floating piston when the assembly is dis- assembled by removing the oil plug, evacuating the space connected to bore 176 in the charging stem, and then filling that space by adding oil through bore 176. Oil plug 190 is then replaced, as shown in FIG. 3, so that the oil bath is confined between the bulkhead and the floating piston. The space below the floating piston is open to drilling fluid, the hydrostatic head of which is imposed against the floating piston, and transferred to the oil bath. Thus, the stepper motor, the ball screw lead shaft and nut, and associated bearings are lubricated and protected from the adverse environment of the drilling fluid.

The lower end of the floating piston housing threads onto the upper end of a cylindrical valve housing 200, which has a central longitudinal stepped bore 201 extending entirely through it, as shown in FIG. 4. (The bumpers 68, 76, and 82 shown in FIG. 2 are not shown around the exterior of the assembly in FIGS. 3 and 4). When the assembly is assembled as shown in FIG. 2, an annular o-ring 202 (FIG.

4) in an outwardly opening annular groove 204 around the upper end of the valve housing makes a fluid-tight seal against the interior surface of the lower end of the floating piston housing.

The lower end of the charging stem 173 threads into the upper end of a cylindrical thread adapter 206, which has a longitudinal bore 208 extending entirely through it.

Lateral bores 209 extend through the wall of the thread adapter adjacent its upper end, and connect the interior of bore 208 to the exterior surface of the cylindrical thread adapter, which is spaced from the inside surface of the valve housing.

The lower end of the thread adapter threads onto the upper end of a longitudinally extending valve lock bolt 210, which has an outwardly extending head 212 on its lower end. The bolt makes a close sliding fit within an annular valve stem 214, which includes an outwardly extending valve plug 216 at its lower end. The upper portion of the valve stem is cylindrical and makes a close sliding fit within cylindrical bore 217 of the upper portion of the valve housing. An annular T-seal 218 in an outwardly opening annular groove 219 in the valve stem makes a sliding seal against the interior surface of the valve housing.

The lower end of the thread adapter 206 bears against an O-ring cushion 220 disposed on an annular upwardly facing shoulder 222 within the upper end of the valve stem 214.

The outside diameter of the lower end of the cylindrical thread adapter makes a close, but free-sliding, fit within the upper end of a stepped bore 223 which extends through the valve stem 214.

The valve lock bolt 210 includes a longitudinal pressurebalancing port 224 extending entirely through it and opening into bore 208 of the thread adapter. The upper annular surface of the lock bolt head 212 bears against a downwardly facing annular surface 225 in stepped bore 223.

Referring to FIG. 4A, the lower face of the valve plug 216 includes a downwardly and inwardly sloping inner annular surface 226 inclined at an angle of about 60 to the longitudinal axis of the valve body. The outer edge of the inner annular surface 226 joins the inner edge of an outer annular downwardly and inwardly sloping surface 226A inclined at an angle of about 30* to the longitudinal axis of the valve body. A downwardly and inwardly sloping annular surface 227 is on the upper end of an adjustable annular valve seat 228 threaded into an internally threaded section 229 of the valve housing.The sloping surface 227 on the valve seat is inclined at an angle of about 45 to the longitudinal axis of the valve body so that the intersection of the inner and outer annular surfaces 226 and 226A on the valve plug make a circular line contact against the sloping surface 227 on the valve seat 228. Thus, the valve plug has an effective working diameter of the dimension indicated by the arrow A (FIGS. 4 and 4A), which is slightly greater than the effective working diameter of T-seal 218, the dimension of which is indicated by arrow B. As explained more fully below, this causes the valve to be bi-stable, i.e., stay in the open or closed position, once moved to either of those positions.

A plurality of valve inlet ports 230 (FIGS. 2 and 4), radially spaced at equal intervals, open downwardly and inwardly through the sidewall of the cylindrical valve housing around the valve plug so that drilling fluid from the annular space surrounding the valve housing can flow into the valve housing, past the valve plug and valve seat, and down through the main bore 201 of the valve housing.

That flow is prevented when the valve plug is moved down against the valve seat by operation of the stepper motor, as described in detail below.

As shown best in FIG. 2, the valve ports 230 are longitudinally elongated so each port is at least several times longer than it is wide so that the ports serve as a screen to prevent larger solid particles in the drilling. fluid from entering the valve housing.

An annular O-ring 232 in an annular groove 234 around the adjustable valve seat exterior makes a fluid-tight seal between the valve seat and the adjacent interior surface of the valve housing.

A annular jam nut 236 threaded into the threaded section 229 of the valve housing interior locks the valve seat in the required position for proper control of drilling fluid through the valve housing.

The lower end of the valve housing threads onto the upper end of an elongated, cylindrical lander-stinger 240, which has a uniform bore 241 extending entirely through it to be collinear with the stepped bore 201 extending through the valve housing. An 0-ring 242 in an outwardly opening annular groove 243 around the upper portion of the landerstinger makes a fluid-tight seal against the interior surface of the lower portion of the valve housing.

The lower portion of the lander-stinger is of smaller exterior diameter than its upper portion, and the lower end of the lander-stinger is cut off at an angle of about 3O from the vertical to provide a relatively sharp point 244 to facilitate entry of the lower end of the lander-stinger into a central vertical stepped bore 246 extending entirely through the cylindrical restrictor-lander 53, the lower outer surface of which rests on an upwardly facing annular shoulder 250 in the drill collar or float shoe subsection 54. The outer surface of the lander-stinger point 244 includes a downwardly and inwardly extending section 251 inclined at an angle of about 159 to the central axis of the assembly to facility travel of the assembly down the drill string and past any minor interior obstructions the lander-singer may encounter on the drill string wall.

An outer annular 0-ring 254 in an outwardly opening annular groove 256 in the exterior of the restrictor-lander makes a fluid-tight seal against the interior surface of the drill collar or float shoe subsection. An inner annular 0ring 258 in an inwardly opening annular groove 260 in the inner surface of the lander-restrictor makes a fluid-tight seal against the outer surface of the lander-stinger, which includes an annular upwardly and outwardly sloping shoulder 262 on its exterior adapted to rest on an annular upwardly and outwardly extending surface 264 on the upper face of an annular protector cap 266 disposed on annular Bellville springs 268 supported on an upwardly facing annular shoulder 270 in the restrictor-lander central stepped bore 246.A C-shaped retainer snap ring 272 at the upper end of the protector cap fits into an inwardly opening annular groove 274 in the restrictor-lander to confine the protector cap Bellville springs.

Eight jet-bit nozzles 280 are each disposed in the lower end of a separate respective stepped bore 282 extending vertically through the restrictor-lander at equally-spaced radial intervals, i.e., so that the centers of adjacent bores 282 are 45 apart. A separate annular O-ring 284 in a respective inwardly opening annular groove 286 in each bore 282 makes a fluid-tight seal against the exterior of a respective jet-bit nozzle 280. The upper end of each jetbit nozzle bears against an annular downwardly facing shoulder 288 in bore 282. Each jet-bit nozzle is held in place by a separate respective C-shaped snap ring 290 bearing against the lower face of a respective nozzle. Each ring 290 fits in a respective inwardly opening annular groove 292 in a respective bore 282.

A bore 291 extends through each jet-bit nozzle. Each nozzle bore 291 includes a straight upper section 291A which merges at its lower portion into the upper portion of a downwardly and inwardly extending frustoconical section 291B which merges at its lower end into the upper portion of a lower straight section 291C, which terminates in a plane substantially perpendicular to the longitudinal axis of the drill collars.

As shown in FIG. 2, the outside diameter of the motor housing 86 and valve housing 200 are each slightly larger than that of the parts of the assembly above it, and make a fairly close fit in the lower end of the drill collar just above the restrictor 53. This confines the lateral movement of the lower end of the lander-stinger to be within the diameter of the upper end of the stepped central bore 246 through the restrictor and ensures proper landing as the assembly is lowered into the restrictor.

The upper end of the restrictor-lander includes an inwardly and downwardly sloping frustoconical surface 294 to guide the lower end of the lander-stinger into central bore 246 of the restrictor lander. The lower section 296 of the lander-stinger is of slightly smaller exterior diameter than the interior diameter of the lower end of stepped central bore 246 of the restrictor-lander to leave an annular space 298 between the lander-stinger and restrictor-lander to facilitate complete entry of the lander-stinger into the central bore of the restrictor-lander. The outside diameter of a section 299 of the lander-stinger immediately below spring cap 266 is of slightly greater diameter than lower section 296, and it makes a close sliding fit in central bore 246 of the restrictor.

As shown in FIG. 4, the restrictor-lander is locked against rotation within the drill collar or float shoe subsection by a horizontal orienting pin 300, which extends through a horizontal bore 302 through the sidewall of the drill collar or float shoe subsection, and extends into an outwardly opening recess 304 in the exterior wall of the restrictor-lander. An annular O-ring 306 in an annular groove 308 around the orienting pin makes a fluid-tight seal against the wall of bore 302. The outer end of orienting pin 300 threads into an intermediate portion of bore 302. A C shaped retaining snap ring 310 at the outer end of orienting pin 300 fits into an inwardly opening annular groove 312 in the outer end of bore 302 to prevent inadvertent removal of the orienting pin.

To orient the position of the assembly with respect to the drill collar (which is required, for example, when the assembly is used to do well survey work or directional drilling), the lower end of the lander-stinger includes an outwardly opening and longitudinally extending groove 320 diametrically opposed from point 244 at the lower end of the lander-stinger. Thus, as the lander-stinger is lowered into the central bore 246 of the restrictor-lander, the sloping surface on the lower end of the lander-stinger engages the uppermost of three inwardly extending, horizontal, and vertically aligned locating pins 322, each of which is press-fitted through a respective horizontal bore 324 extending through the lower end of the restrictor-lander.

The locating pins cause the lander-stinger to rotate as it is lowered until the vertical groove 320 is aligned with the three vertically aligned locating pins 322.

When the pulser assembly is inserted (either by dropping it in the drill string or lowering it in the drill string on a wireline and a releasable latch (not shown) secured to the latch knob 62 on the upper end of the fishing head) into the restrictor-lander as shown in FIGS. 2 and 4, the restrictor creates a differential pressure across valve seat 228 when the drilling fluid flows through the eight jet-bit nozzles.

To send information to the surface in response to signals from the sensor, the stepper motor 112 rotates in a direction to drive sealing surface 226 (FIGS. 4 and 4A) of the valve plug 216 down against the sloping surface 227 of the valve seat 228.

Since the effective working diameter (A) of the valve plug is slightly larger than the effective working diameter (B), T-seal 218, the net force caused by the differential pressure across the valve seat holds the valve plug against the seat because of the relatively low pressure downstream from the valve plug transferred through pressure-balancing port 224 in the valve lock bolt 210 and out lateral ports 209 in the thread adapter 206.

Closing the valve increases mud pressure at the surface, which is detected by transducer 44 on mud supply line 41 (FIG. 1). To create a pressure drop, a signal from sensor 72 causes the stepper motor to reverse direction, pulling valve plug 216 off the valve seat surface i27. As the valve plug is pulled off, the drilling fluid flowing through the increasing space between the valve plug and the valve seat further decreases the pressure inside the valve stem 214. This lower pressure is transferred above T-seal 218.

With the high pressure below the T-seal, and the lower pressure above it, the valve plug moves rapidly to the full open position and is held up off the valve seat hydraulically until the next signal to close it. In this manner, the valve plug is bi-stable, i.e., it remains either closed or open without the application of continuous power to the stepper motor.

As the valve opens and closes, the pressure in the drilling mud at the surface decreases, and transducer 44 detects that pressure change. By coding the sequence of the pressure pulses transmitted to the surface, information corresponding to the value of the downhole property being measured can be determined without having to remove the drill string from the well.

The O-ring cushion 220 at the lower end of the thread adapter 206 acts as a compression spring and absorbs the shock on the stepper motor shaft and the intermediate linking elements as the valve plug contacts sealing surface 227 on the valve seat 228, thus extending the life of the equipment.

The stepper motor is of conventional type, i.e., it rotates the motor shaft a precise distance for each pulse of electrical energy supplied to it. Thus, the stepper motor can be turned quickly and precisely to cause the valve plug to move longitudinally exactly the required amount. The adjustable valve seat 228 permits precise adjustment of the contact the valve plug makes with the seat.

The Bellville compression springs 268 in the restrictorlander absorb the shock of dropping the assembly into the position shown in FIG. 4, and the shock imposed on the assembly as the valve opens and closes, thus extending the life of the equipment.

FIGS. 6 and 7 show an alternate embodiment of the invention. The same reference numerals used in FIGS. 1-5 have been used in FIGS. 6 and 7 to indicate corresponding elements. In the embodiment shown in FIGS. 6 and 7, the lower end of the assembly 50 includes an elongated solid lander 400 with a downwardly and inwardly extending nose 402, which rests in a central bore 404 of the conventional TOTCO circular baffle plate 55, which rests on the upper end of a subpin 408 in the drill string 28. The upper end of the subpin threads into the lower end of a conventional drill collar sub 410, which has a central bore 412 extending longitudinally through it. The upper end of the drill collar sub threads onto the lower end (not shown in FIG. 7) of a drill collar, which may be of conventional design.

Referring to FIG. 7, the upper end of the lander 400 extends into the lower end of a stepped bore 414, which extends longitudinally through a shock absorber housing 416, the upper end of which threads onto the lower end of a cylindrical bypass housing 418.

An annular T-seal 420 in an outwardly opening annular groove 422 makes a sliding fit against the lower end of stepped bore 414 extending through the shock absorber housing.

Longitudinally extending splines 424 on the exterior of the lander make a sliding fit in longitudinally and inwardly extending grooves 426 opening out of the lower end of the shock absorber housing 416.

A first annular Bellville compression spring 428 is confined between an annular and upwardly facing shoulder 429 on the lander and an annular downwardly facing shoulder 430 in the stepped bore 414 of the shock absorber housing 416. A second annular Bellville spring 432 is confined between an annular upwardly facing shoulder 434 in the stepped bore 414 and the bottom surface of a washer 436 mounted around the upper end of the lander and held in place by a lock washer 438 and nut 440 threaded onto the upper end of the lander.

A floating piston 442 in an oil bath chamber 444 carries a pair of annular O-rings 445, each in a respective outwardly opening annular groove 446 around the exterior of the piston so that the O-rings make a sliding seal against the interior wall of stepped bore 414. An oil plug 448 threads into a central threaded bore 450, which extends entirely through the floating piston. An 0-ring 452 in an annular groove 454 around the oil plug makes a fluid-tight seal against the upper end of bore 450. The space between the O-rings 445 and annular T-seal 420 is filled with oil by removing the oil plug 448 when the equipment is disassembled above the shock absorber housing, evacuating the space below the floating piston, and filling it with oil.The plug is then replaced so that an oil bath in chamber 444 is maintained around the splined lander and Bellville springs, which act as shock absorbers as the assembly is landed, and the valve is operated as described above for the apparatus of FIGS.

1-5.

The lower end of the bypass housing 418 threaded into the upper end of the shock absorber housing closes the upper end of the stepped bore 414 in the shock absorber housing. The space in the stepped bore 414 of the shock absorber housing 416 is connected by a lateral port 460 to the annular space between the shock absorber housing exterior and the drill collar sub interior. Thus, the floating piston is free to move back and forth as the lander reciprocates in the shock absorber housing during landing and operation of the pulser assembly.

Upwardly and inwardly extending ports 462 in the end of the bypass housing connect an annular space 463 between the assembly and the drill collar sub to a central longitudinally extending bore 464, which opens out the upper end of the bypass housing, which threads into the lower end of a cylindrical valve housing 466. An annular O-ring 468 in an outwardly opening annular groove 470 around the exterior of the upper end of the bypass housing 418 makes a fluid-tight seal against the interior surface of the lower end of the valve housing 466.

An annular wear sleeve 472 makes a snug fit around an intermediate portion of the valve bypass housing, and is confined between an annular upwardly facing shoulder 474 on the bypass housing exterior and the lower end 476 of the valve housing. An annular restrictor 480 is disposed around and spaced from the wear sleeve and makes a snug fit in the upper end of the drill collar sub. An outwardly extending annular flange 482 formed integrally on the upper end of the restrictor rests on the upper surface of an annular seal 484 disposed in the lower endof a threaded box joint 486 at the upper end of the drill collar sub. The lower end of a drill collar (not shown) threads into the threads of the box joint and clamps the restrictor against the seal in the position shown in FIG. 7.

A valve plug 216, identical with the valve plug 216 of FIG. 4, is mounted in the valve housing 466 with associated structure identical with that described for the valve housing of FIG. 4, and, therefore, that description is not repeated here. Valve inlet ports 230 extending downwardly and inwardly through the wall of the valve housing are identical with those of FIGS. 2 and 4 and likewise are not described here.

Like parts in FIG. 7 are given reference numerals corresponding with those of FIG. 4.

The operation of the valve in the pulser assembly shown in FIG. 7 is similar to that of the valve shown in FIG. 4, except that as the valve opens and closes, drilling fluid bypasses around the restrictor by flowing downwardly and outwardly through outlet ports 362 (?) and against the interior surface of the drill collar sub 410.

The embodiment of FIG. 7 is of more simple construction than that of PIG. 4, but the embodiment of FIG. 7 has the disadvantage of directing drilling fluid laterally from the assembly with respect to the longitudinal axis of the well and thus is subject to slightly more vibration than the arrangement shown in FIG. 1, where the discharge from the valve is coaxial with the well bore. However, since the valve outlet is located relatively close to the lower end of the assembly, and where the assembly is supported by the baffle plate 55, the vibration problem is much less severe than prior art arrangements in which the valve outlet was located at the upper end of the assembly and spaced a relatively long distance from the support at the lower end.

An important advantage of both embodiments shown in FIGS.

2 and 6 is that by having the restrictor and valve located near the lower end of the assembly, the assembly need be no longer than that required to accommodate the equipment required for its operation, which permits a substantial reduction in the overall length of the assembly. For example, in the embodiment shown in FIG. 5 of U.S. Patent 4,550,392 to Mumby, the valve is adjacent the upper end of the pulse generator assembly, and the restrictor is mounted in a joint between two drill collar sections. The lower end of the assembly is supported in a special fitting, which must be provided in a special drill collar section, or else mounted in the next adjacent drill collar joint, which is normally about thirty feet away. In the latter case, the assembly had to be about thirty feet long, irrespective of the need for that length. With the apparatus shown in FIG.

1, the restrictor can be mounted in a float shoe sub to support the assembly at its lower end, and the assembly need be only as long as required to accommodate the equipment needed for its operation. In practice, this means the assembly can be reduced from a length of about thirty feet to about eighteen feet, which substantially reduces its tendency to vibrate, and also reduces the pressure drop imposed on the drilling fluid when the assembly is in the drill string.

Another advantage of the valving arrangement shown in the pulse generator of FIGS. 4 and 7, is that it does not require small openings for pilot valve operation, and thus is more tolerant of lost circulation material in the drilling mud than are the pilot valves shown in the embodiments of U.S. Patent 4,550,392 to Mumby.

Claims (30)

CLAIMS:

1. Apparatus for sending information to a surface pressure pulse detector through drilling fluid in a borehole drilled in the earth with a drill bit on the lower end of a drill string in the borehole and through which the drilling fluid is circulated to flow through the interior of the drill string, past the drill bit, and into an annulus between the drill string and the borehole wall, the apparatus comprising:: an elongated retrievable assembly adapted to fit in the drill string near the drill bit, the assembly having a bore with an inlet and an outlet through which a portion of the drilling fluid which flows through the drill string and past the drill bit may flow, the assembly being constructed and arranged so a first portion of the drilling fluid which flows through the drill string and past the drill bit may flow through the bore and a second portion of drilling fluid may flow between the assembly exterior and the drill string when the assembly is in the drill string; means in the drill string and in the vicinity of the drill bit for supporting the assembly near its lower end so the assembly extends in the same general direction as the drill string; electronic means in the assembly for generating a control signal responsive to a downhole condition; and valve means in the assembly and responsive to the control signal to change the rate at which drilling fluid flows through the bore to send a pressure pulse through the drilling fluid to the surface pressure pulse detector, the valve means being located closer to the lower end of the elongated assembly than to the upper end.

2. Apparatus as claimed in claim 1, in which the assembly is adapted to slide into and out of the drill string from the upper end of the drill string to a location near the drill bit.

3. Apparatus as claimed in claim 1 or claim 2, in which the valve is adjacent the lower end of the assembly.

4. Apparatus as claimed in claim 1 or claim 2, in which the valve is below the electronic means in the assembly.

5. Apparatus as claimed in claim 1 or claim 2, and which includes a restrictor between the exterior assembly and the drill string interior and between the bore inlet and outlet to create a pressure drop in the drilling fluid flowing past the restrictor.

6. Apparatus as claimed in claim 1 or claim 2, in which the bore outlet discharges a fluid in a direction substantially parallel to the longitudinal axis of the drill string.

7. Apparatus as claimed in claim 1 or claim 2, in which the bore outlet discharges fluid substantially collinear with the longitudinal axis of the drill string.

8. Apparatus as claimed in claim 1 or claim 2, in which the bore inlet includes a plurality of openings disposed around the assembly and being elongated in the direction of the longitudinal axis of the drill string.

9. Apparatus as claimed in claim 1 or claim 2, which includes a valve seat disposed in the bore, a valve plug adapted to move into and out of contact with the valve seat in response to the control signal, and means for adjusting the position of the valve seat longitudinally with respect to the longitudinal axis of the assembly.

10. Apparatus as claimed in claim 1 or claim 2, which includes a valve seat in the bore between the inlet and outlet, a valve plug mounted to move longitudinally within the assembly into and out of contact with the valve seat, a stepper motor having a rotatable drive shaft substantially parallel to the longitudinal axis of the assembly, and means coupling the stepper motor drive shaft to the valve plug to convert the rotary motion of the stepper motor drive shaft into a linear motion which causes the valve plug to move longitudinally toward and away from the valve seat in response to the control signal.

11. Apparatus as claimed in claim 5, which includes means for mounting the restrictor in the drill string, and means on the restrictor for receiving and supporting the assembly.

12. Apparatus as claimed in claim 11, which includes means for locking the position of the restrictor with respect to the drill string.

13. Apparatus as claimed in claim 12, which includes orienting means on the assembly and the restrictor for guiding the assembly to, and holding the assembly in, a fixed position with respect to the restrictor.

14. Apparatus as claimed in claim 11, which includes a plurality of nozzles in the periphery of the restrict and around the assembly, each nozzle having a downwardly and inwardly converging section, and the outlet of each nozzle directing fluid in a direction substantially parallel to the longitudinal axis of the assembly.

15. Apparatus as claimed in claim 14, in which the outlets of the nozzles lie in a substantially common plane.

16. Apparatus as claimed in claim 15, in which the plane is substantially perpendicular to the longitudinal axis of the drill string.

17. Apparatus as claimed in claim 11, which includes shock absorber means between the assembly and the restrictor.

18. Apparatus as claimed in claim 17, in which the shock absorber means includes a compression spring mounted on the restrictor to engage the assembly.

19. Apparatus as claimed in claim 17, in which the shock absorber means includes a compression spring mounted on the assembly to engage the restrictor.

20. Apparatus as claimed in claim 11, in which the lower end of the assembly includes a downwardly and inwardly tapering point offset laterally from the longitudinal axis of the assembly, and the restrictor having a bore for receiving the lower end of the assembly.

21. Apparatus as claimed in claim 11, in which the restrictor is annular and includes a central opening with a downwardly and inwardly sloping inlet.

22. Apparatus as claimed in claim 21, in which the external diameter of the assembly and the internal diameter of the drill string above the restrictor are constructed and arranged to prevent the lower end of the assembly from moving laterally beyond the limits of the upper end of the inlet of the central opening extending through the restrictor.

23. Apparatus as claimed in claim 20, in which the offset point on the lower end of the restrictor is bevelled at its outer surface to extend downwardly and inwardly when the assembly is in the drill string.

24. Apparatus as claimed in claim 5, which includes a removable wear sleeve disposed around the assembly adjacent the restrictor.

25. Apparatus as claimed in claim 1 or claim 2, which includes an annular baffle plate mounted in the drill string to receive and hold the lower end of the assembly.

26. Apparatus as claimed in claim 25, in which the baffle plate includes an outwardly extending flange around its periphery adapted to rest on the upper surface of one section of the drill string, the upper surface of the flange being adapted to receive the lower end of another section of the drill string so the baffle plate is clamped firmly in position in the drill string, an intermediate portion of the baffle plate having openings to permit drilling fluid to flow past it.

27. Apparatus for sending information to a surface pressure pulse detector through drilling fluid in a borehole drilled in the earth with a drill bit on the lower end of a drill string in the borehole and through which the drilling fluid is circulated to flow through the interior of the drill string, past the drill bit, and into an annulus between the drill string and the borehole wall, the apparatus comprising:: an elongated assembly adapted to fit in the drill string near the drill bit, the assembly having a bore with an inlet and an outlet through which a portion of the drilling fluid which flows through the drill string and past the drill bit may flow, the assembly being constructed and arranged so a first portion of the drilling fluid which flows through the drill string and past the drill bit may flow through the bore and a second portion of the drilling fluid may flow between the assembly exterior and the drill string when the assembly is in the drill string; a support in the drill string and in the vicinity of the drill bit for supporting the assembly near its lower end so the assembly extends in the same general direction as the drill string; electronic means in the assembly for generating a control signal responsive to a downhole condition; ; valve means in the assembly and responsive to the control signal to change the rate at which drilling fluid flows through the bore to send a pressure pulse through the drilling fluid to the surface pressure pulse detector; and shock absorber means between the assembly and the support for absorbing shock imposed on the assembly as the valve operates.

28. Apparatus as claimed in claim 27, in which the shock absorber means includes a compression spring mounted on the support to engage the assembly.

29. Apparatus as claimed in claim 27, in which the shock absorber means includes a compression spring mounted on the assembly to engage the support.

30. Apparatus for sending information to a surface pressure pulse detector substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.