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Measuring-While-Drilling System
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MWDS Overview
CGDS172NB Near-bit Geosteering Drilling System is the drilling equipment that is researched and developed jointly
by Drilling Engineering Technology Research Institute of China National Petroleum Corp., Beijing Petroleum Machinery
Factory and the Logging Instrument Plant of CNPC Logging Limited Company. The geosteering drilling technology is new
advanced drilling technology publicly recognized by the international drilling industry, which is integrated with
drilling technology, logging technology and oil reservoir engineering technology and utilize near-bit geologic and
engineering parameter measurement and drilling control measures to guarantee that the actual wellbore goes through
the reservoir bed and get the best position and, according to the characteristic stratum information measured while
drilling, adjust and control the track of the well bore in a real-time manner so that the drilling bit can go along
with the path of the “oil taste”. Therefore, it has such characteristics as strong function to recognize oil and gas
strata while drilling and strong steering function.
Structure of the MWD System
CGDS172NB Near-bit Geosteering Drilling System is composed of measurement data transmission motor (CAIMS), wireless
receiving system (WLRS), positive-pulse wireless MWD (CGMWD) and ground information processing and steering
decision-making software system (CFDS),
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Functions of CGDS172NB Near-bit Geosteering Drilling System
CGDS172NB Near-bit Geosteering Drilling System has three functions: measurement, transmission and steering:
1) Measurement: In the near-bit measurement transmission spool, there is resistivity sensor, natural gamma
sensor and well inclination sensor installed; in the wireless short-distance transmission receiving spool
there is receiving coil installed. The near-bit measurement transmission spool can measure resistivity of
drilling bit, azimuth resistivity, natural gamma and near-bit well inclination and angle of tool face and
these parameters can be converted into electromagnetic wave signals and then transmitted by the wireless
short-distance transmission transmitting coil to the receiving coil in the wireless receiving spool over
the steering screw motor in a time-sharing manner.
2) Transmission: After the wireless receiving coil has received the information from below the motor, it
will be incorporated by the data connection system to the CGMWD positive pulse MWD system located above it,
then CGMWD will activate the positive pulse generator to produce the pressure pulse signals in the slurry
channel in the drilling column and transmit the measured near-bit information (partial) to the ground processing
system, while uploading the information measured by CGMWD including well inclination, azimuth, tool face
and downhole temperature and other parameters.
3) Steering: after receiving and collecting the slurry pressure pulse signals uploaded by the downhole
instrument, the ground processing system will filter the information, reduce its noise, check, identify,
decode, display and store the information and then, transmit the 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 and use the downhole steering motor (or rotary table drilling tool assembly) as the steering
tool to instruct the steering tool to drill into the destination oil and gas layer exactly or continue to
drill in the oil and gas reservoir.
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