Abstract: This invention provides a measurement-while-drilling (MWD) downhole assembly for use in drilling boreholes which utilizes gyroscopes, magnetometers and accelerometers for determining the borehole inclination and azimuth during the drilling of the borehole. The downhole assembly includes at least one gyroscope that is rotatably mounted in a tool housing to provide signals relating to the earth's rotation. A device in the tool can rotate the gyroscope and other sensors on the tool to one of a plurality of preselected positions and optionally lock the sensors. A processor in the tool combines measurements from the sensors taken at a plurality of positions at the same depth to determine the systematic bias in the sensors before further processing. Accelerometers in the MWD tool provide gravity measurements from which the toolface and inclination are determined.

Abstract: A method for simulating the drilling performance of a roller cone bit drilling an earth formation may be used to generate a visual representation of drilling, to design roller cone drill bits, and to optimize the drilling performance of a roller cone bit. The method for generating a visual representation of a roller cone bit drilling earth formations includes selecting bit design parameters, selecting drilling parameters, and selecting an earth formation to be drilled. The method further includes calculating, from the bit design parameters, drilling parameters and earth formation, parameters of a crater formed when one of a plurality of cutting elements contacts the earth formation. The method further includes calculating a bottomhole geometry, wherein the crater is removed from a bottomhole surface.

Abstract: A method and system for determining the relative strength and classification of rock strata in near real-time during drilling operations is provided for use in underground mines. Neural network technology is used to classify mine roof strata in terms of, for example, relative strength or strength index as the roof bolt hole is being drilled (i.e., in near real-time). Measurements taken while a layer of the rock strata is being drilled are used to compute the specific energy input and convert these data to suitably scaled features. A neural network is then used to classify the strength of the layer. The neural network can be trained using data of known rock strata classifications prior to using it to classify new measurements. The present system allows for detection of unsafe conditions within the rock strata being drilled, and allows appropriate warnings to be issued in near real-time so that appropriate actions can be taken.

Abstract: A method and apparatus for performing well planning and design includes performing a general-level design. The general-level design involves generating a proposed well configuration based on inputs from a user. The proposed configuration, generated by a software module, includes a well trajectory, the reservoir-wellbore interface, and completion equipment. The proposed configuration is refined by an optimizer based on a performance measure or a target constraint.

Abstract: A method for eliminating the tool mode signal from a received combined signal including both tool mode and formation mode components, uses a signal from a reference receiver that is consists primarily of the tool mode signal. A transfer function is derived relating the time reversed combined signal and the time reversed reference signal and used to predict the tool mode portion of the combined signal. Subtracting the predicted tool mode portion of the combined signal from the combined signal gives an estimate of the formation mode component.

Abstract: A method for taking into account the effects of complex conveyance method model technique results in real time in a wellbore operation, the method including, in certain aspects, calculating with a conveyance method model technique a series of data points based on wellbore data (actual and/or predicted), modeling the relationship between the series of data points and the wellbore data using a simple mathematical model technique to develop a model for predicting a wellbore operations parameter, and using the model to predict a wellbore operations parameter; and, in one aspect, a procedure for drilling a wellbore in the earth using such a method to predict, among other things, weight on bit, torque on bit and stretch of a conveyance system (coiled tubing, wireline, drill pipe string) used to move the bit in a wellbore.

Abstract: In highly deviated wells or when the relative dip angle between formation layering and wellbore axis is large, array induction measurements exhibit erratic spikes, misleading curve separations, and inaccurated resistivity values, preventing log analysts from accuratly evaluating invasion and formation resistivities. Our newly developed deviated-well software focusing (DSF) method that is derived from the Born approximation simultaneously accounts for all these dipping effects. The induction response is separated into two portions: a background response and a perturbation respones. An inhomogeneous, anisotropic background formation model is used to calculate the background response, and the perturbation response is interpreted through a software focusing technique. The combination of the two solutions is the final result.

Abstract: A system and method provide for electronic development of a bore plan for use in connection with an underground boring machine. Electronically developing a bore plan involves receiving bore path plan information representative of an intended bore path at the bore site, which may include topographical and utility related information. A pre-established bore plan is generated using the received bore path plan information. Actual bore path information is acquired indicative of an actual bore path produced by the boring machine. A modified bore plan is generated using the actual bore path information and at least some of the bore path plan information. The modified bore plan comprises data representative of a modified bore path that minimizes a deviation in alignment between the actual bore path and the intended bore path. Selected bore plan data can be displayed in both textual and graphical forms.

Abstract: This invention provides a measurement-while-drilling (MWD) downhole assembly for use in drilling boreholes which utilizes gyroscopes, magnetometers and accelerometers for determining the borehole inclination and azimuth during the drilling of the borehole. The downhole assembly includes at least one gyroscope that is rotatably mounted in a tool housing to provide signals relating to the earth's rotation. A device in the tool can rotate the gyroscope and other sensors on the tool to one of a plurality of preselected positions and optionally lock the sensors. A processor in the tool combines measurements from the sensors taken at a plurality of positions at the same depth to determine the systematic bias in the sensors before further processing. Accelerometers in the MWD tool provide gravity measurements from which the toolface and inclination are determined.

Abstract: The invention uses the continuous inclination, direction and tool-face information supplied from either an MWD tool and/or a rotary steerable drilling system, and/or other downhole equipment, e.g., the at-bit inclination measurement (AIM), to give a prediction of the tendency of a rotary, steerable, or rotary steerable system. These measurements are used with a finite element mathematical model of the drilling process to continually calibrate in real-time the drilling parameters that are not obtainable from measurements, and to refine the subsequent tendency prediction in real-time. The continuous data will be used in conjunction with the accepted survey measurements (which occur less frequently than the continuous inclination and direction measurements) so that the optimum slide and rotation ratio between well sections can be selected, and drilling targets can be more accurately hit.

Abstract: A method and system for ascertaining relationships between collected geological samples and remotely sensed geological data within a region is provided. The locations of physical samples and the locations of data points associated with remotely sensed data are identified and stored. The locations within the region are determined using a position identifying system, such as the global positioning system. The collected physical samples are analyzed to obtain data values for physical and chemical properties of the collected samples. Data mining algorithms are used to generate input data for the formulation of a set of spatial relationships. The locations of the physical samples within the region are associated with the locations of the remotely sensed data to form a set of spatial relationships.

Abstract: In a drilling system for drilling a well borehole from a surface location, hydraulic calibration is performed by making a plurality of hydraulic calibration measurements, each hydraulic calibration measurement being made at a respective drill-string RPM and flow-rate within a hydraulic calibration range. A hydraulic baseline function is then determined which predicts, within a predetermined degree of accuracy, each of the plurality of hydraulic calibration measurements.

Abstract: The present invention provides a system for drilling boreholes having a downhole subassembly which contains an acoustic measurement-while-drilling system. It uses the acoustic velocity through the formations surrounding the borehole and an acoustic transmitter and a set of receivers for determining the bed boundaries surrounding the borehole formation. An acoustic isolator on the tool may be used to attenuate body waves traveling between the transmitter and the receivers. Additional attenuation of the body waves is provided by a threshold filter based upon the absolute maximum of the received signals. Semblance of the data is determined in a slowness/intercept-time domain. Coherence and semblance filtering methods are used to differentiate between reflection signals and noise. The position and orientation of the bed boundary relative to the tool are determined.

Abstract: A method and apparatus for predicting the performance of a drilling system for the drilling of a well bore in a given formation includes generating a geology characteristic of the formation per unit depth according to a prescribed geology model, obtaining specifications of proposed drilling equipment for use in the drilling of the well bore, and predicting a drilling mechanics in response to the specifications as a function of the geology characteristic per unit depth according to a prescribed drilling mechanics model. Responsive to a predicted drilling mechanics, a controller controls a parameter in the drilling of the well bore. The geology characteristic includes at least rock strength. The specifications include at least a bit specification of a recommended drill bit. Lastly, the predicted drilling mechanics include at least one of bit wear, mechanical efficiency, power, and operating parameters.

Abstract: A method is disclosed for compressing a frame of data representing parameter values, a time at which each parameter value was recorded, and an orientation of a sensor at the time each parameter value was recorded. Generally the method includes performing a two-dimensional transform on the data in the orientation domain and in a domain related to the recording time. In one embodiment, the method includes calculating a logarithm of each parameter value. In one embodiment, the 2-D transform includes generating a Fourier transform of the logarithm of the parameter values in the azimuthal domain, generating a discrete cosine transform of the transform coefficients in the time domain. This embodiment includes quantizing the coefficients of the Fourier transform and the discrete cosine transform. One embodiment of the method is adapted to transmit resistivity measurements made by an LWD instrument in pressure modulation telemetry so that while-drilling images of a wellbore can be generated.

Abstract: A method is provided for generating an indicator of potential bit abrasion in a particular wellbore. Forensic wellbore data is obtained from at least one previously drilled wellbore which is determined to be comparable to the particular target wellbore. Typically, the comparable wellbore comprises an “offset” wellbore which is proximate the target wellbore, and which has similar geologic features. An inference engine computer program is provided which consists of executable program instructions. It is adapted to utilize a plurality of wellbore parameters, including the forensic wellbore data. The inference engine includes at least one rule matrix which defines a plurality of fuzzy sets. These fuzzy sets establish correspondence between the plurality of wellbore parameters and the indictor of potential bit abrasion. The inference engine computer program is loaded onto a data processing system. At least the forensic wellbore data is supplied as an input to the inference engine computer program.

Abstract: A system, method, and computer-readable media provide for electronic development of a bore plan for use in connection with an underground boring machine. Electronically developing a bore plan involves receiving topographical information representative of topography of the bore site, receiving utility information representative of one or more utilities situated at the bore site, and receiving bore path information representative of an intended bore path at the bore site. A bore plan data is generated using the received topographic, utility, and bore path information. The bore plan data includes data representative of an intended bore defined along the intended bore path and with respect to the representative topography at the bore site. The topographical en information representative of the bore site topography may be received as two-dimensional data or three-dimensional data. A user-interface permits user alteration of one or more of topographic data, utility data, bore path data, and other bore plan data.

Abstract: A method of assaying work of an earth boring bit of a given size and design comprises the steps of drilling a hole with the bit from an initial point to a terminal point. A plurality of electrical incremental actual force signals are generated, each corresponding to a force of the bit over a respective increment of the distance between the initial and terminal points. A plurality of electrical incremental distance signals are also generated, each corresponding to the length of the increment for a respective one of the incremental actual force signals. The incremental actual force signals and the incremental distance signals are processed to produce a value corresponding to the total work done by the bit in drilling from the initial point to the terminal point. Using such a basic work assay, a number of other downhole occurrences and/or conditions can be assayed.

Abstract: A multi-pass algorithm identifies duplicative information and correlates higher confidence and/or selected primary information in distributed databases. One embodiment determines a bounded area based at least in part on location information and/or location tolerances for a location-dependent attribute and comparing the bounded areas to previously indexed location information using a multi-pass algorithm to identify duplicative information. The algorithm may also use textual tolerances, confidence levels, and other factors to determine what information is to be correlated with the option of elevating the correlated information to a higher level database.

Abstract: A method and apparatus are provided for generating an indicator of potential for abrupt changes in rock strength in a particular wellbore. Forensic wellbore data is obtained from at least one previously drilled wellbore which is determined to be comparable to the target wellbore. An interfacial severity computer program is provided. The program consists of executable program instructions. It is adapted to utilize a plurality of wellbore parameters, including at least one forensic wellbore data element. The interfacial severity computer program is loaded onto a data processing system. At least the forensic wellbore data, and possibly other wellbore parameter data elements, are supplied as an input to the interfacial severity computer program. The data processing system is utilized to execute program instructions of the interfacial severity computer program.

Abstract: A real-time method is disclosed for maintaining subterranean formation stability through monitoring the interaction between the formation and fluids introduced into (or produced from ) a wellbore penetrating the formation. The method employs real-time wellbore (in)stability logging methodology. The method is exemplified by a Pore Pressure Transmission (PPT) test. In such test, test fluids are exposed to Pierre II shales (20% w/w NaCI solution and sodium silicate fluid with 20% w/w NaCl, for example) in a PPT apparatus. Membrane efficiency of the two fluids when exposed to the outcrop shale is calculated, and based on the simultaneous acquisition of acoustic data, estimation of a dynamic rock property is made.

Abstract: A method is provided for determining the rotational stiffness of a drill string for drilling of a borehole in an earth formation, the drill string having a bottom hole assembly (BHA) and an upper end driven by a rotational drive system. The method comprises the steps of determining the time derivative of the drill string torque during drilling of the borehole at a selected time when stick-slip of the BHA occurs, determining the nominal rotational speed of the drill string at an upper part thereof and at said selected time, and determining the rotational stiffness of the drill string from a selected relationship between said time derivative of the drill string torque and said nominal rotational speed at the upper part of the drill string.

Abstract: A method for use with equipment located downhole in a subterranean well includes providing a model describing behavior of the equipment and measuring a state of the equipment downhole. An indication is received of the state at a surface of the well, and the model is modified based on the indication. The system includes a communication link, a circuit and a machine. The communication link is adapted to furnish an indication of a state of the equipment to the surface of the well. The circuit is located downhole and is adapted to detect the state and produce the indication. The machine is adapted to provide a model describing behavior of the equipment and modify the model based on the indication.

Abstract: An apparatus for communication with a downhole tool includes uphole and downhole equipment. The uphole equipment includes a signal source (or array) coupled to a programmable triggering system and a precision clock. Optionally, the uphole equipment may include receivers for capturing reference signals near the source and may include telemetry equipment for receiving MWD signals from the downhole equipment. The downhole equipment includes one or more receivers, signal processing equipment, memory, and a precision clock. Optionally, the downhole equipment also includes MWD telemetry equipment for transmitting data to the surface. The methods of the invention include, but are not limited to, synchronizing the recordation of signals detected downhole with the firing of the signal source and processing the recorded signals to eliminate useless information.

Abstract: A method of controlling rock drilling wherein the cut length changes from a predetermined cut length, the drilling length is changed by transferring the position of the pattern in the longitudinal direction of the tunnel so that the positions of the end points of the holes remain essentially the same with respect to one another, and a collaring surface is crosswise of the tunnel and different from the actual rock surface.

Abstract: The present invention provides a measurement-while-drilling (MWD) system having a downhole computer and multiple downhole sensors. Relatively large amounts of basic or “raw” data are measured by downhole sensors, and these data are processed within a downhole computer to be reduced to parameters of interest, which may be utilized to control the drilling operation by downhole devices, stored downhole, telemetered to the surface, or both. The measurements may be correlated downhole with stored reference data thereby providing additional information pertaining to the drilling operation. Downhole depth correlation between downhole measured parameters may be made by utilizing surface determined or downhole determined borehole depth.

Abstract: A method of processing logs to enhance vertical resolution is disclosed. In one embodiment the method includes: (a) obtaining a measurement signal from a sensor tool moving through a borehole; (b) determining a Walsh deconvolution filter; and (c) integrating a product of the Walsh deconvolution filter and the measurement signal to obtain an enhanced measurement signal.

Abstract: A method of determining characteristics of a rotary drag-type drill bit comprises the steps of: creating a computerized representation of the cutters on the drill bit, and then, with each cutter in turn, projecting the shape of the cutter onto a fixed plane having an array of cells, and assigning a first marker to those cells of the array which overlie the projection of the selected cutter. The representations of the other cutters are then rotated about the bit axis until they have all passed through the plane at least once, the cutters also being moved axially while being rotated so as to represent the axial movement of the bit during drilling. The shapes of the other cutters are projected onto the plane, as they pass through it, and a second marker is assigned to those cells of the array which overlie both the projection of the selected cutter and the projections of any of the other cutters.

Abstract: The present invention provides a closed-loop drilling system for drilling oilfield boreholes. The system includes a drilling assembly with a drill bit, a plurality of sensors for providing signals relating to parameters relating to the drilling assembly, borehole, and formations around the drilling assembly. Processors in the drilling system process sensors signal and compute drilling parameters based on models and programmed instructions provided to the drilling system that will yield further drilling at enhanced drilling rates and with extended drilling assembly life. The drilling system then automatically adjusts the drilling parameters for continued drilling. The system continually or periodically repeats this process during the drilling operations. The drilling system also provides severity of certain dysfunctions to the operator and a means for simulating the drilling assembly behavior prior to effecting changes in the drilling parameters.

Abstract: A processor uses signals from at least two GPS receivers and a 3-component accelerometer located on a stable non-magnetic platform to determine the roll, yaw and pitch angles of the platform, thus providing a measurement of geographic north. The processor also uses signals from a 3-component magnetometer on the platform to determine the magnetic north and thence the magnetic declination. A proton magnetometer is used to provide a check on the measurements of the 3-component magnetometer. Additionally, three single component magnetometers provide a measure of the local magnetic field gradient and serve to monitor artificially induced magnetic fields. An alternate embodiment of the invention uses at least three GPS receivers and may dispense with the 3-component of accelerometer to determine geographic north. Temporal local variations of the earth's magnetic field are tracked and used to correct conventional magnetic well surveys.

Abstract: A method and system for engineering a drilling bit program linked to rock removal at a cutting element/formation interface and specific to drilling of one or more wells in a given geographic area is disclosed. The system includes a first arrangement for planning the drilling of a particular well based upon a cascaded planning input and providing an engineered output which is a function of the cascaded planning input, wherein a level of the engineered output being dependent upon a level of the cascaded planning input. A second arrangement is provided for implementing the engineered output in the drilling of the particular well is also provided. Lastly, a third arrangement is provided for evaluating the implementation of the engineered output for the drilling of the particular well and providing an evaluation output. The evaluation output can be used by the planning arrangement as additional planning input for planning the drilling of a subsequent well in the geographic area.

Abstract: A method for ascertaining a characteristic of a geological formation surrounding a wellbore. The method comprises first generating a set of data including azimuthal and radial information. A set of parameters indicative of fluid behavior in the formation is determined for each one of at least two azimuths from the generated data. A tool-specific invasion factor is then determined. The characteristic is then determined from the parameters, the azimuthal information, and the invasion factor.

Abstract: An apparatus and method for obtaining samples of pristine formation or formation fluid, using a work string designed for performing other downhole work such as drilling, workover operations, or re-entry operations. An extendable element extends against the formation wall to obtain the pristine formation or fluid sample. While the test tool is in a standby condition, the extendable element is withdrawn within the work string, protected by other structure from damage during operation of the work string. The test apparatus is mounted on a sliding, non-rotating, sleeve on the work string.

Abstract: A method of and system for optimizing bit rate of penetration while drilling substantially continuously determine an optimum weight on bit necessary to achieve an optimum bit rate of penetration based upon measured conditions and maintains weight on bit at the optimum weight on bit. As measured conditions change while drilling, the method updates the determination of optimum weight on bit.

Abstract: A power spectrum density processor is located near the drill bit while drilling. The power spectral density processor computes the power spectral density of the vibrations generated by the drill bit while drilling. The power spectral density information is telemetered to the surface where it is used to enhance drill bit seismic techniques.

Abstract: A method and apparatus for predicting the performance of a drilling system for the drilling of a well bore in a given formation includes generating a geology characteristic of the formation per unit depth according to a prescribed geology model, obtaining specifications of proposed drilling equipment for use in the drilling of the well bore, and predicting a drilling mechanics in response to the specifications as a function of the geology characteristic per unit depth according to a prescribed drilling mechanics model. The geology characteristic includes at least rock strength. The specifications includes at least a bit specification of a recommended drill bit. Lastly, the predicted drilling mechanics include at least one of bit wear, mechanical efficiency, power, and operating parameters. A display is provided for generating a display of the geology characteristic and predicted drilling mechanics per unit depth, including either a display monitor or a printer.

Abstract: A numerical control unit and method is provided for determining a change in a positional setting in a downhole tool used to drill a wellbore, the numerical control unit comprising a plurality of rules in an IF . . . THEN format based on the current position of the wellbore and a preferred position of the wellbore.

Abstract: The present invention provides a system, apparatus and method for transmitting logging data from a primary location to a remote location in near real time. The logs can be viewed almost simultaneously at the primary and remote locations, as data is being acquired.

Abstract: An adaptive system applicable to non-ideal measurement operations wherein the reference signal includes information attempting to be extracted from the primary signal and wherein digital non-linear manipulation is applied to the signal to noise ratio in the reference signal.

Abstract: Directional drilling techniques allow for the drilling of boreholes within the earth along any three dimensional path. This invention provides a method for determining the path a wellbore needs to take in order to stay within a defined three dimensional target. This is done by using the petrophysical and spacial information received from the portion of the wellbore as drilled. First, a three dimensional model of the target is constructed using seismic data. Then, the seismic data is used to create a depth model which is continually refined during the drilling operation. This will provide the needed information to steer the wellbore to any point within a three dimensional representation of the real target.

Abstract: An apparatus and method are disclosed for obtaining samples of pristine formation or formation fluid, using a work string designed for performing other downhole work such as drilling, workover operations, or re-entry operations. An extendable element extends against the formation wall to obtain the pristine formation or fluid sample. While the test tool is in standby condition, the extendable element is withdrawn within the work string, protected by other structure from damage during operation of the work string. The apparatus is used to sense or sample downhole conditions while using a work string, and the measurements or samples taken can be used to adjust working fluid properties without withdrawing the work string from the bore hole. When the extendable element is a packer, the apparatus can be used to prevent a kick from reaching the surface, adjust the density of the drilling fluid, and thereafter continuing use of the work string.

Abstract: The present invention provides a closed-loop system for drilling boreholes. The system includes a drill string having a drill bit, a plurality of sensors for providing signals relating to the drill string and formation parameters, a downhole device which processes various downhole sensors signals and computes dysfunctions relating to the drilling operations and transmits such dysfunctions to a surface control unit. The surface control unit determines the relative severity of such dysfunctions and the corrective action required to alleviate such dysfunctions based on programmed instruction and then displays the nature and extent of such dysfunctions and the required corrective action as a display for use by the operator. The programmed instructions may contain models, algorithms and information from prior drilled boreholes, geological information about subsurface formations and the borehole drill path.

Abstract: The present invention relates to a system and to a method for automatic detection of the precession of an element of a drill string, in particular of the bottomhole assembly of a drill string. The method comprises a stage of surface acquisition of signals linked with the vibration of the end of the drillpipes, automatic processing on at least one signal in order to detect a jump in average and a significant line in the spectrum of the signal. A precession criterion is calculated and an alarm is set off. The invention further relates to a system for detecting the precession of an element of a drill string.

Abstract: A pore pressure prediction method includes the steps of: (a) designing a normal compaction trend velocity model; (b) testing the normal compaction trend velocity model; (c) designing 3-D spatial adjustment parameters to compensate for water depth; and (d) processing a 3-D velocity field using the interpreted normal compaction trend velocity model and the 3-D spatial adjustment parameters.

Abstract: A novel method of determining the probability that a planned drilling path will collide with an existing wellbore is disclosed. The method utilizes available uncertainty information to determine a probability for each of a plurality of segments of the planned drilling path that a projection of the segment onto a plane will intersect a projection of a corresponding segment of the existing wellbore onto the plane. The method of this invention then determines the net probability for each segment of the planned drilling path that the segment will intersect the corresponding segment of the existing wellbore by taking into account the effect of constraints imposed on each segment, by adjacent segments. The probability that the planned drilling path will intersect the existing wellbore is determined by adding together all of the net probabilities.

Abstract: Method for the continuous up-dating of a bidimensional and tridimensional seismic image in depth in real time during the drilling of a well by using seismic velocity information comprising the initial definition of a velocity model and the subsequent re-iterative modification of this initial velocity model by integrating the geophysical data taken on the surface with the geological domain of the subsurface data obtained directly during the drilling of the well.

Abstract: The present invention provides a system, apparatus and method for transmitting logging data from a primary location to a remote location in near real time. The logs can be viewed almost simultaneously at the primary and remote locations, as data is being acquired.

Abstract: A method for producing synthetic tool responses for a well logging tool for an earth formation, the method including, in one aspect, generating wellbore logging data for a particular part of an earth formation with a wellbore logging system with a wellbore logging tool, the earth formation having at least one layer, producing an input earth model of the particular part of the earth formation based on the wellbore logging data, inputting the input earth model to a trained artificial neural network, e.g. resident in a computer, the computer with the trained artificial neural network processing the input earth model and producing synthetic tool responses for the wellbore logging tool for one point or for a plurality of points in the earth formation.

Abstract: The method according to the invention permits adapting for any fluid, a known model representative of the circulation of a fluid in an annular space around a motionless pipe, centered or eccentric uniformly over the total length thereof, to more complex cases which are encountered in practice and notably in drilling. The invention comprises the application, to the pressure loss values obtained with the known model, of a first correction factor accounting for the eccentricity variations which the pipe may undergo notably because of the variations in the axial load applied or of straightness defects of the conduit, and of a second correction factor representative of the effects due to the rotation of the pipe. The method identifies the prominent pressure loss variations which are observed in narrow annular spaces. The method can be applied to narrow hole petroleum drilling (of the slim hole type).

Abstract: The present invention provides a closed-loop drilling system for drilling oilfield boreholes. The system includes a drilling assembly with a drill bit, a plurality of sensors for providing signals relating to parameters relating to the drilling assembly, borehole, and formations around the drilling assembly. Processors in the drilling system process sensors signal and compute drilling parameters based on models and programmed instructions provided to the drilling system that will yield further drilling at enhanced drilling rates and with extended drilling assembly life. The drilling system then automatically adjusts the drilling parameters for continued drilling. The system continually or periodically repeats this process during the drilling operations. The drilling system also provides severity of certain dysfunctions to the operator and a means for simulating the drilling assembly behavior prior to effecting changes in the drilling parameters.