Abstract: A method and apparatus is disclosed for removing offsets and temperature induced offset drifts of electronic devices of gamma ray spectroscopy apparatus. A flash ADC circuit is used to digitize output signals from a detector assembly. The bit stream of the least significant bit lead of the ADC circuit is first integrated to produce a D.C. level proportional to the duty cycle of the bit stream appearing on such bit lead. Such D.C. level is fed back to be summed with the D.C. level of the output lead from the detector assembly, thereby canceling offset voltages from the detector assembly and associated amplifiers.

Abstract: In drilling a well, a condition at the surface which contributes to a downhole condition is identified. A set of observed measurements is collected for the surface and downhole conditions. From this set of observations a predictor equation is derived which expresses the downhole condition as a function of the measured surface condition. After the predictor equation has been developed, it is applied to a measured surface condition to estimate the resulting downhole condition.

Abstract: A seismic processing method relating finely sampled data of earth formations, such as that obtained from borehole measurements, to substantially longer wavelength seismic data, such as that obtained from surface seismic surveys or the like, while improving the ease of manipulation and processing speed of seismic processing. In a preferred embodiment, a fine layer model having n layers is defined, with the properties of each fine layer corresponding to the properties of each of n sampling points. An equivalent model is constructed by defining m equivalent layers, where m is substantially smaller than n and the thickness of the thickest of the equivalent layers is substantially smaller than a predetermined dominant wavelength of a seismic signal. Equivalent formation properties are generated for each equivalent layer by combining the sampled formation properties of the fine layers within the respective equivalent layer, preferably in accordance with the equivalent medium theory.

Abstract: A method of locating hydrocarbon reserves comprising: selecting on the basis of a hydrocarbon hypothesis from a region of interest below the surface of the earth patches having probabilities of containing hydrocarbon reserves greater than a predetermined probability; defining from structural data a respective structural closure for each of the patches, each structural closure comprising an area capable of enclosing a hydrocarbon reserve and having a perimeter of constant depth substantially equal to the deepest point of the patch; determining a measure of the geometrical match between each patch and the respective structural closure; and selecting each patch having a measure of the geometrical match exceeding a predetermined measure. Particular geometrical matching methods include those relating to the height, area, volume and perimeter outline of the potential reserves.

Abstract: A method and apparatus is disclosed for suppressing microphonic noise in proportional counter neutron detection in borehole logging-while-drilling measurements. Noise is reduced by (1) applying the outputs of two detectors respectively to positive and negative inputs of a differential amplifier; (2) generating output pulses by applying the output of the differential amplifier to positive and negative comparators to produce first and second output pulses; (3) counting output pulses as neutron counts only if the first or second output pulses have time lengths less than a predetermined time length; and (4) rejecting the output pulses in the count of pulses as neutron counts if first and second output pulses coincide in time.

Abstract: A sensor protection system for use with an MWD tool includes a tubular body having lesser and greater diameter portions, antennas mounted in grooves in the lesser diameter portion, shield sleeves covering the antennas and being locked in place against longitudinal and rotational movement, and a wear band on the greater diameter portion to provide a standoff for the shield sleeve, the wear band also being locked against movement in the longitudinal and rotational directions. The locking mechanism also can be used to fix a sleeve-type stabilizer on the tubular body.

Abstract: A steerable rotary drilling tool includes a drill bit mounted on the lower end of a housing by a drive shaft having an articulative coupling that allows the bit's rotation axis to be inclined relative to the rotation axis of the housing, an eccentric weight in the housing that maintains the bit axis pointed in only one direction in space as the bit is turned by the housing, and a clutch system that allows such direction to be changed downhole. A measuring-while-drilling tool is included to allow the progress of the drilling to be monitored at the surface, and to allow changing the bit axis or toolface by a selected amount.

Abstract: An apparatus for sealing a first pressure environment from a second, lower pressure environment, includes a plug having a desired cross section for insertion into a barrier wall aperture shaped to receive the plug. The barrier wall has a first pressure environment on its outside surface and a second environment on its inside surface. A bearing surface on the plug bears against the wall of the aperture. A flexing member, subject to and reactive to the first pressure environment, has an outer surface providing at least a portion of the bearing surface. The flexing member, in reacting to the first pressure environment, flexes at least a portion of the bearing surface to bear more tightly against the wall of the aperture and tends to seal the first pressure environment from the second pressure environment and maintain the seal under a variety of mechanical loads. A chassis is secured within the barrier wall.

Abstract: Apparatus for determining the density of underground formations surrounding a borehole, such as a wireline logging tool or a logging-while-drilling tool, includes a high energy neutron source for irradiating the formations from within the borehole and a detector which detects gamma rays in the borehole resulting from the irradiation of the formations with high energy neutrons. The detected gamma rays are analyzed to determine the density of the formations.

Abstract: An apparatus for determining a property of earth formations surrounding a borehole is presented. In accordance with a particular embodiment, an elongated logging device movable through a borehole is provided with a transmitter array consisting of only first, third, and second transmitting antennas longitudinally spaced on the device. A pair of longitudinally spaced receiving antennas are also provided and are located between the second transmitting antenna and one of the first and third transmitting antennas. In particular, the first, third, and second transmitting antennas are spaced from the midpoint between the receiver pair by first, third, and second distances, respectively, where the first and second distances are substantially the same while being different from the third distance. This antenna arrangement is possible while still providing a borehole compensated output.

Abstract: A method for improving the signal to noise ratio from a pair of detectors such as geophones which each detect a noisy signal comprising a signal of interest (S) and a noise signal (N), wherein the signal of interest (S) has a different moveout across the pair of detectors from that of the noise signal (N), and the noise signal (N) from a given source is detected at the first detector at a time .DELTA.t before the corresponding noise signal is detected at the second detector, the method comprising delaying the noisy signal (S+N) detected at the first detector by an amount .tau. being greater than the moveout of the signal of interest but not more than .DELTA.t and subtracting the delayed signal from that detected at the second detector by means of an adaptive filter so as to minimize the power in the resultant signal. The signal detected at the first detection and optionally the resultant signal can also be delayed by an amount .tau..sub.

Abstract: A method of determining the rate of penetration .DELTA.d of a drill bit at the end of a drill string while drilling a well, comprising:(a) measuring the vertical displacement S of the drill string at the surface,(b) determining a state space description of S comprising a state space measurement equation: ##EQU1## and a state evolution equation: ##EQU2## wherein S and .DELTA.d are as previously defined, .DELTA. is the difference operator for time .tau. between adjacent samples k and k+1, .LAMBDA. is the drill string compliance, .rho. is the noise term associated with the surface displacement measurement, r is the noise term associated with fluctuations in the state, and h is the hookload, and(c) applying a Kalman filter to said equations to obtain an estimate of the state parameters including .DELTA.d.

Abstract: There is provided a rheometer, comprising a cup for a fluid to be measured, a concentric rotor and stator arrangement, and a circuit for circulating the fluid which includes a pump for providing in pulsatile, non-laminar flow in the cup. By using the pump to provide both a turbulent and pulsating flow, particulate matter can be maintained in suspension and flow induced through the measuring system while any rheology effect the pumping system has on the fluid is introduced independently of rheology effects caused by the measuring system itself. Thus the pumping can be continued while the measurement is being made.

Abstract: An articulated directional drilling tool assembly for use in drilling a borehole having a short radius of curvature includes a mud motor whose housing is pivotally connected to a lower housing having upper and lower sections that are joined together in a manner to define a bend angle. The drill bit box carries a stabilizer that centers it in the borehole. The upper housing section carries pads which are forced against the low side of the borehole by a hydraulic piston to increase the side loading on the bit and cause it to drill a sharply curving borehole. The motor housing is connected to the lower housing by an articulative, torque transmitting coupling, and the motor housing is connected to an orientation measuring sub thereabove in the same manner.

Abstract: The present invention provides a bottom hole assembly (BHA) for connection to a drillstring for use in directing the path of a drill bit while rotary drilling, the BHA comprising an apparatus for providing a modified cutting action of the bit in a predetermined portion of the hole, a stabilizer, and a flexible member interposed between the bit and the stabilizer. By "flexible" member is meant a member made from a material having a lower Young's modulus than steel and/or a member with a smaller wall thickness than the remainder of the BHA. In the case where the BHA is formed from steel pipe, a flexible member might be provided by an aluminum drill collar or a composite material drill collar. Alternatively or additionally, the wall thickness of the material from which the collar is formed can be made less than the remainder of the BHA.

Abstract: A steerable rotary drilling tool includes a drill bit mounted on the lower end of a housing by a drive shaft having an articulative coupling that allows the bit's rotation axis to be inclined relative to the rotation axis of the housing, an eccentric weight in the housing that maintains the bit axis pointed in only one direction in space as the bit is turned by the housing, and a clutch system that allows such direction to be changed downhole. A measuring-while-drilling tool is included to allow the progress of the drilling to be monitored at the surface, and to allow changing the bit axis or toolface by a selected amount.

Abstract: An articulated directional drilling tool assembly for use in drilling a borehole having a short radius of curvature includes a mud motor whose housing is pivotally connected to a lower housing having upper and lower sections that are joined together in a manner to define a bend angle. The lower housing section carries a full gage stabilizer that centers its lower end in the borehole. The upper housing section carries pads which are forced against the low side of the borehole by a hydraulic piston to increase the side loading on the bit below the lower housing section and cause it to drill a sharply curving borehole. The motor housing is connected to the lower housing by an articulative, torque transmitting coupling, and the motor housing is connected to an orientation measuring sub thereabove in the same manner.

Abstract: A method of analyzing a drilling fluid comprising subjecting a sample of the fluid to an XRF analysis technique and comparing the results obtained with a calibration model to determine the amount of one or more components of the fluid present in the sample. The method is particularly useful for determining solids in the fluid such as barite and can be combined with an FTIR technique which is sensitive to other components of the fluid. A PLS algorithm is used to construct the model from the spectra.

Abstract: Methods for providing an image at the surface of a formation surrounding a borehole in real-time include associating resistivity measurements with a predetermined number of preselected toolface positions. The resistivity measurements are subjected to data compression and transmitted uphole by MWD telemetry. At the surface, the compressed resistivity measurements are associated with the preselected toolface positions and with a calculated translational distance value. The resistivity measurements are decompressed and/or converted to pixel information. The pixel information is arranged according to toolface position and translational distance to create a high resolution of the formation. These processes are repeated over time so that the image created represents the formation over a selected distance.

Abstract: An integrated modulator and turbine-generator includes a turbine impeller which is directly coupled by a drive shaft to a modulator rotor downstream from the impeller. The modulator rotor is further coupled by a drive shaft and a gear train to a three phase alternator downstream of the modulator rotor. The modulator stator blades are arranged downstream of and adjacent to the modulator rotor and the alternator is provided with a Hall effect tachometer. The turbine impeller directly drives the modulator rotor and the alternator generates power. The speed of rotation of the modulator rotor is adjusted by reference to the speed of rotation of the alternator as indicated by the tachometer and to a reference frequency.