Abstract: Disclosed is a method and system for tuning a hydraulic model to be used for estimating down hole dynamic pressure as a function of flow rate includes: a) selecting a non-tuned hydraulic model estimating the relative magnitude of the pressure losses in various annulus sections of the well bore; b) applying the non-tuned hydraulic model to give a first order estimate of the pressure gradients and the shear stresses at the drill string; c) applying the same non-tuned model to estimate the flow lift area for two different flow rates, where the first flow rate is zero or much lower than the second flow rate being substantially equal to a typical flow rate obtained during drilling; and d) performing a model tuning test where the string is rotated off bottom while said two different flow rates are used to obtain corresponding string weights.

Abstract: A method for drilling a borehole includes selecting a lower pressure limit and an upper pressure limit for a drilling fluid at a drilling location in the borehole. In addition, the method includes activating a pump to circulate the drilling fluid down a drill string and up an annulus disposed about the drill string. Further, the method includes operating the pump to maintain the drilling fluid at the drilling location at a pressure between the upper and the lower pressure limits. Still further, the method includes deactivating the pump to stop circulating the drilling fluid up the annulus. The method also includes sealing the drilling fluid in the annulus at a selected time after deactivating the pump and maintaining the pressure of the drilling fluid at the drilling location between the lower and the upper pressure limits.

Abstract: A method for estimating downhole speed and force variables at an arbitrary location of a moving drill string based on surface measurements of the same variables. The method includes a) using properties of said drill string to calculate transfer functions describing frequency-dependent amplitude and phase relations between cross combinations of said speed and force variables at the surface and downhole; b) selecting a base time period; c) measuring surface speed and force variables, conditioning the measured data by applying anti-aliasing and/or decimation filters, and storing the conditioned data, and d) calculating the downhole variables in the frequency domain by applying an integral transform, such as Fourier transform, of the surface variables, multiplying the results with said transfer functions, applying the inverse integral transform to sums of coherent terms and picking points in said base time periods to get time-delayed estimates of the dynamic speed and force variables.

Abstract: A method for estimating downhole speed and force variables at an arbitrary location of a moving drill string based on surface measurements of the same variables. The method includes a) using properties of said drill string to calculate transfer functions describing frequency-dependent amplitude and phase relations between cross combinations of said speed and force variables at the surface and downhole; b) selecting a base time period; c) measuring surface speed and force variables, conditioning the measured data by applying anti-aliasing and/or decimation filters, and storing the conditioned data, and d) calculating the downhole variables in the frequency domain by applying an integral transform, such as Fourier transform, of the surface variables, multiplying the results with said transfer functions, applying the inverse integral transform to sums of coherent terms and picking points in said base time periods to get time-delayed estimates of the dynamic speed and force variables.

Abstract: There are described methods for controlling the direction of a wellbore trajectory during directional sliding drilling by means of a drill string having a drill bit rotatable, by means of a mud motor, around a drill bit rotation axis at its lower end, the direction of the drill bit rotation axis defining a tool face, wherein one of the methods comprises the following steps: a2) obtaining data indicative of the torque of the mud motor; and b2) calculating a reactive twist angle of the drill string by multiplying the obtained torque from step a2) by the torsional drill string compliance, wherein the method further comprises the step of: c2) rotating the drill string, by means of a drill string rotation means, an angle substantially equal to but in the opposite direction of the calculated reactive twist angle. There are also described systems for executing the methods as well as computer program products comprising instructions for causing a processor to perform the methods as described herein.

Abstract: A method for detecting and localizing a valve leak in a piston machine having a shaft includes: attaching one or more vibration sensor to a valve block of the piston machine; measuring the vibrations from at least one of the vibration sensors; attaching a sensor to the piston machine where the sensor is designed to produce, directly or indirectly, an angular shaft position signal for the shaft; determining, directly or indirectly, an angular shaft position signal for the shaft; transforming vibration signals from the one or more vibration sensors into one envelope signal representing an instant vibration level; using the angular position signal for constructing window functions that pick the envelope signal in selected angular shaft sectors; using the window functions to find sector based averages of the vibration level; and comparing said averages with a critical ambient vibration level to detect and localize leaks in one or two valves.

Abstract: Methods and apparatuses for active heave compensation, the method, in certain aspects, including the steps of: (a) measuring with a measurement device (44) the heave of a vessel (10) and outputting a heave signal representative thereof; (b) using said heave signal to compensate for said heave by moving a connection device (20) relative to said vessel (10) as a function of said heave signal, whereby movement due to said heave of a load attached to said vessel via the connection device is reduced; said heave signal comprising errors induced by said measurement device (44) whereby accuracy of said compensation is reduced; (c) processing said heave signal so as to reduce said errors and outputting an adjusted heave signal; and (d) using said adjusted heave signal to move said connection device (20) to compensate for said heave.

Abstract: A method for reducing cogging torque effects of an electrical permanent magnet machine includes running an “a” test and a “b” test with different cogging compensation signals. A first value is calculated by multiplying a complex cogging amplitude of the compensation signal applied for the “a” test with a complex amplitude of a vibration signal resulting from cogging torque of the “b” test. A second value is calculated by multiplying a complex cogging amplitude of the compensation signal applied for the “b” test with a complex amplitude of the vibration signal resulting from cogging torque of the “a” test. A desired complex cogging compensation amplitude is calculated by dividing the difference between the first and second values by a difference between the complex amplitudes of the vibration signals resulting from the “b” test and the “a” test. A cogging compensation torque is applied to the machine based on the desired complex cogging compensation amplitude.

Abstract: A drawworks (10) comprising a permanent magnet motor (60) mounted inside a drum(40), said permanent magnet motor arranged to drive said drum via a gear system(50), characterised in that said gear system is located at least partially within said drum.

Abstract: Methods and apparatuses for active heave compensation, the method, in certain aspects, including the steps of: (a) measuring with a measurement device (44) the heave of a vessel (10) and outputting a heave signal representative thereof; (b) using said heave signal to compensate for said heave by moving a connection device (20) relative to said vessel (10) as a function of said heave signal, whereby movement due to said heave of a load attached to said vessel via the connection device is reduced; said heave signal comprising errors induced by said measurement device (44) whereby accuracy of said compensation is reduced; (c) processing said heave signal so as to reduce said errors and outputting an adjusted heave signal; and (d) using said adjusted heave signal to move said connection device (20) to compensate for said heave.