Drilling rig sensors for drilling engineeringpdf

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1. Drilling Data
Sensors

2. Drilling Surface Data Sensors
•By analyzing cuttings,
drilling mud, and drilling
parameters for
hydrocarbon-associated
phenomena, we can
develop a great deal of
information and
understanding concerning
the physical properties of
a well from the surface to
final depth.
•A critical function in data
analysis is familiarity with
the different sensors used
for gathering surface data.

3. Depth-tracking Sensors
•Current depth-tracking sensors digitally count the amount of rotational
movement as the draw-works drum turns when the drilling line moves up or
down.
•Each count represents a fixed amount of distance traveled, which can be
related directly to depth movement (increasing or decreasing depth).
•Moreover, the amount of movement also can be tied into a time-based
counter, which will give either an instantaneous or an average rate of
penetration (ROP).
•Some companies still use a pressurized depth-tracking/ROP sensor.
•The pressurized ROP system works on the principle of the change in
hydrostatic pressure in a column of water as the height of that column is
varied.
•This change can then be indirectly related to a depth measurement.
•Again, a time-based counter is used to calculate an instantaneous or average
ROP.

4. Depth-tracking Sensors
•Accurate depth measurement on
offshore rigs such as semisubmersibles,
submersibles, and drill ships is affected
by both lateral (tidal movement) and
axial (the up-and-down motion of the rig,
also called “rig heave”) effects.
•To properly compensate for this, most of
these rigs have a rig-compensator
system installed on their traveling block.
•As the rig moves up, the compensator
opens, thereby allowing the bit to stay on
bottom.
•Similarly, as the rig moves down, the
compensator must shut to keep the
same relative bit position and weight on
the bit.

5. Flow-in tracking sensors
•Flow-tracking sensors are used to monitor fluid-flow rate being applied downhole as
well as the pump strokes required to achieve this flow rate. Data gathered from these
sensors are essential inputs to calculating drilling-fluid hydraulics, well control, and
cuttings lag. Monitoring changes in trends may also indicate potential downhole
problems such as kicks or loss of circulation.
•Two commonly used types are proximity and/or whisker switches. A proximity switch,
activated either by an electromagnet (coil) or a permanent magnet, acts as a digital
relay switch when it incorporates electrical continuity.
•A whisker switch is a micro-switch that is activated only when an external rod (a
whisker) forces a piston to raise a ball bearing to initiate contact against it.

6. Pressure-tracking Sensors
•Pressure-tracking sensors are used mainly to monitor surface pressure being applied
downhole. Data gathered from these sensors are used either to validate calculated
values or to confirm potential downhole problems such as washouts, kicks, or loss of
circulation.
•Two types of sensors are available, and both monitor pressure from a high-pressure
diaphragm unit (knock-on head) located on either the standpipe or the pump manifold.
•The first sensor type derives its physical input from mud pressure expanding a rubber
diaphragm within the knock-on head.
•This expansion proportionally increases the pressure in the hydraulic-oil-filled system
and, in doing so, relays the mud pressure to the appropriate transducer.
•The second sensor type makes a direct connection with the standpipe manifold itself
(i.e., the transducer face is in contact with the mud).

7. Flow-out Tracking Sensor
•Commonly called a “flow paddle,” this sensor measures flow rate coming out
of the annulus using a strain-gauge analog transducer.
•Changes in resistance values are directly related to either an increase or a
decrease in mud-flow rate.
•This sensor provides an early warning of either a kick condition (sudden
increase in flow rate) or a loss of circulation (sudden decrease in flow rate).

8. Drill-monitor Sensors
•Drill-monitor sensors monitor surface revolutions-per-minute (RPM) values,
rotary torque, and hook load.
•The torque sensor is a clamp that sits around the main power cable to the
top-drive system (TDS).
•It works on the principle of the deformation of Hall-effect chips by the
magnetic field produced around the cable owing to the current being drawn
through it (i.e., the greater the torque being produced as the pipe rotates, the
greater the current drawn by the TDS and therefore the greater the Hall
effect).
•Torque changes can then be related to either formation lithology or downhole
drilling problems such as pipe stick/slip or motor stalling.

9. Mud Pit Monitor Sensor
•Most pit-monitor sensors use ultrasonic
transit time to measure mud level.
•The sensor is mounted over the pit
above the maximum mud level, and
sends a sonic wave that is reflected
back to the receiver.
•The transit-time measurement is then
directly transformed to a volume
measurement.
•This critical measurement is actively
used to monitor potential kicks (rapid
increase in pit volume) or loss of
circulation (rapid decrease in pit
volume).

10. Gas-detection Sensors
•The gas-detection sensors consist mainly of a gas trap, a pneumatic line
linking the gas trap to the gas-detection equipment (which is found inside a
mud-logging unit), and the gas-detection instruments (chromatograph and
total-gas detectors).
•The gas trap is basically a floating chamber with a rotating “agitator” inside.
•It works on the principle that mud flowing through the gas trap is agitated,
thereby releasing the vast majority of any gases contained within the mud.
This gas is then extracted from the trap through the unit sample line to be
analyzed in the unit.

11. Gas-detection Sensors
•The principle behind gas chromatography is simple. The gas from an oil well consists
of several hydrocarbon components, ranging from light gases (methane) to oil.
•A gas chromatograph then takes a sample of gas and separates out some of these
components for individual analysis. Typically, methane (C
1) through pentane (C
5) are
the gases of interest. These can be plotted individually, or they may be used in gas-
ratio analysis for reservoir characterization.
•Most logging companies currently use a flame ionization detector (FID) gas
chromatograph and total-gas detector.
•The FID responds primarily to hydrocarbons and has the widest linear range of any
detector in common use. The output signal is linear for a given component when
concentrations vary from less than one part per million (ppm) to percent levels, and
with care, resolution can be obtained in the low part-per-billion (ppb) range.