Geology Reference
In-Depth Information
10.3.1.3 Functions of DRGDS.
DRGDS has three major functions: measurement, transmission and
steering. These are briefly summarized next.
Measurement. Resistivity, natural gamma ray and well inclination sensors
are installed in NBMTS, and a receiving coil is installed in WLRS. The NBMTS
measures bit resistivity, azimuthal resistivity, azimuthal natural gamma, near-bit
well inclination angle and GTF angle; these parameters can be converted into
electromagnetic wave signals and then sent by the transmission coil in NBMTS
to the receiving coil in WRLS over the screw motor in a time-sharing manner.
Transmission. After the wireless receiving coil has received information
from below the motor, it is incorporated in the DRMWD by the Uploading Data
Connection Assembly; then DRMWD will activate the positive pulse generator
to produce the pressure pulse signals in the drilling column and transmit the
measured near-bit information to the ground processing system while uploading
the information measured by DRMWD, which includes well inclination,
azimuth, tool face and downhole temperature and other parameters.
Steering. After receiving and collecting the mud pressure pulse signals
uploaded by the downhole instrument (DRMWD-MD), the surface processing
system filters the information, reduces noise, checks, identifies, decodes,
displays and stores the information and then, transmits decoded data to the
driller display for the engineer to read. At the same time, the CFDS steering and
decision-making system will judge it and make a decision regarding use of the
downhole motor as the steering tool - it instructs the steering tool to drill into
the oil and gas layer or to continue to drilling as before.
Figures 10.3.1-14a to 10.3.1-14d show scenes captured at product launch.
Figures 10.3.1-15a and 10.3.1-15b importantly display wellbore trajectory
differences between “conventional geosteering” versus “near-bit geosteering.”
The former is not unlike “driving from the rear seat” - without immediate,
close-up information, the driver is likely to steer away from the target. Course
corrections can be expensive and time-consuming. The simple need to follow
the payzone as closely as possible drives the design of modern near-bit sensors
and high-data-rate MWD telemetry systems.
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