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Research Papers: Petroleum Engineering

Dynamic Measurement of Spatial Attitude at Bottom Rotating Drillstring: Simulation, Experimental, and Field Test

[+] Author and Article Information
Qilong Xue

Key Laboratory on Deep GeoDrilling Technology
of the Ministry of Land and Resources,
School of Engineering and Technology,
China University of Geosciences,
Beijing 100083, China
e-mail: xqlfly@gmail.com

Ruihe Wang

College of Petroleum Engineering,
China University of Petroleum,
Qingdao 266580, China

Baolin Liu

Key Laboratory on Deep GeoDrilling Technology
of the Ministry of Land and Resources,
School of Engineering and Technology,
China University of Geosciences,
Beijing 100083, China

Leilei Huang

Sinopec International Petroleum
Service Corporation,
Beijing 100029, China

1Corresponding author.

Contributed by the Petroleum Division of ASME for publication in the JOURNAL OF ENERGY RESOURCES TECHNOLOGY. Manuscript received February 27, 2015; final manuscript received September 1, 2015; published online October 29, 2015. Editor: Hameed Metghalchi.

J. Energy Resour. Technol 138(2), 022903 (Oct 29, 2015) (9 pages) Paper No: JERT-15-1093; doi: 10.1115/1.4031742 History: Received February 27, 2015; Revised September 01, 2015

In the oil and gas drilling engineering, measurement-while-drilling (MWD) system is usually used to provide real-time monitoring of the position and orientation of the bottom hole. Particularly in the rotary steerable drilling technology and application, it is a challenge to measure the spatial attitude of the bottom drillstring accurately in real time while the drillstring is rotating. A set of “strap-down” measurement system was developed in this paper. The triaxial accelerometer and triaxial fluxgate were installed near the bit, and real-time inclination and azimuth can be measured while the drillstring is rotating. Furthermore, the mathematical model of the continuous measurement was established during drilling. The real-time signals of the accelerometer and the fluxgate sensors are processed and analyzed in a time window, and the movement patterns of the drilling bit will be observed, such as stationary, uniform rotation, and stick–slip. Different signal processing methods will be used for different movement patterns. Additionally, a scientific approach was put forward to improve the solver accuracy benefit from the use of stick–slip vibration phenomenon. We also developed the Kalman filter (KF) to improve the solver accuracy. The actual measurement data through drilling process verify that the algorithm proposed in this paper is reliable and effective and the dynamic measurement errors of inclination and azimuth are effectively reduced.

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Figures

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Fig. 3

Measurement signals exhibit a sine wave during rotation (where A indicates the amplitude; ω is the rotation speed; φ is the initial phase; T is the rotation period)

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Fig. 2

Sketch diagram of the structure of rotary steerable drilling system (in the measurement section, equipped with triaxial accelerometer and triaxial fluxgate on the xyz axis, respectively): (1) strap-down stabilized platform, (2) oriented actuator, (3) rotor, (4) power section, (5) measurement and control section, (6) servo section, (7) plate valve, (8) rib, and (9) bit

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Fig. 1

Schematic diagram of the trajectory control. (The actual trajectory of drilling fluctuates with the design trajectory. This phenomenon cannot be avoided because of the hysteresis of stationary surveying).

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Fig. 4

Analysis of the stick–slip vibration phenomena, asshown in (a), when the surface top drive rotary speed is 100r/min, the speed of drill bit has fluctuated between 0 and 200 r/min and the stick–slip phenomenon is very critical. From (b), the stick–slip vibration is always existent throughout the drilling process. (a) Surface RPM and bit RPM and (b) speed statistical histogram.

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Fig. 5

Dynamic measurement algorithm flowchart, when the drillstring is not rotating, real-time signals on three-axis were all used for calculation, at the same time, signals on x- and y-axis were stored in the memory block. When the drillstring is rotating, signals on z-axis and stored signals of x- and y-axis were adopted to solve the inclination and azimuth. Then, based on the trajectory model, to improve the solver accuracy, KF was developed.

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Fig. 9

The solving results of DAU method (inclination and azimuth show great fluctuations when the drilling string is rotating, whereas the fluctuations are significantly smaller when momentarily at rest)

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Fig. 10

Accelerometer and fluxgate x-axis measurement data (sampling frequency 100 Hz)

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Fig. 11

Contrast inclination and azimuth dynamic measurement results with the DAU and DAS methods: (a) is the results of inclination and (b) is the results of azimuth, algorithm of DAS with KF approach could effectively enhance measurement precision and deduce the effect of vibration on resolve results

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Fig. 7

Dynamic solution error at a different inclination and azimuth: (a) accelerometer: 20 dB and fluxgate: 30 dB, (b) accelerometer: 5 dB and fluxgate: 30 dB, and (c) accelerometer: 1 dB and fluxgate: 30 dB

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Fig. 8

Laboratory experiment: (a) is an experimental equipment, when the string continuous rotation with a constant speed and be located at a particular borehole inclination and azimuth, accelerometer (x, y, and z axes) and fluxgate (x, y, and z axes) measurement data will be obtained, (b) is the accelerometer measurement signals, and (c) is the fluxgate measurement signals

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