3. Subject: Basic Drill Floor Measurements

01. Identify all and describe the following gauges used by the driller’s console:

a) Rotary Speed (RPM)    b) Surface Weight on Bit (WOB) (string weight)

c) Pump stroke (SPM)   d) Pump Pressure (PP)    e) Surface Torque

f) Depth (Depth Encoder or Geolograph)

 

Ans. a) Rotary Speed (RPM):

It is rotational speed of the drillstring with the help of either Top drive or the rotary table in case of Kelly System.

It is displayed on a gauge in the driller’s console expressed in revolutions per minute (RPM).

 

b) Surface Weight on Bit (WOB) (string weight):

The amount of downward force placed on the bit by the weight of the drill collar. It is displayed by a gauge, which shows the string weight and the applied weight on the bits (Units: Klbs/Tons).

 

c) Pump stroke (SPM):

Pump stroke is measured by the Pump stroke counter, which is installed on the Pump frame.

The display of the SPM can be seen at the driller’s console.

 

 

 

d) Pump Pressure (PP):

It is the Standpipe pressure, which is measured using the SPT. It is measured in kPa or PSI.

 

 

e) Surface Torque:

It is the amount of torque the drilling string requires to rotate, while rotary mode drilling. It is measured in ft-lb.

 

f) Depth (Depth Encoder or Geolograph):

It is the distance of the bit from the surface. It can be measured with the help of either Depth Encoder or Geolograph. It is measured in meters (m).

 

02. Describe how the gauges in the driller’s console are calibrated.

Ans. The sensors are based on a two-point straight-line calibration. By measuring a low point and a high point of the desired system the tool can be calibrated.  The drilling company electrician typically calibrates the rig systems.

 

03. State the typical range for each of the above measurements in English (SI) & metric units.

Ans. Rotary speed (RPM):  0-200 rpm.

 

Surface Weight on Bit (WOB) (String Weight):

The deeper we go the higher the pressure. We must apply more pressure than bottom hole pressure 200 – 40000 lb.

            

Pump stroke (PS): Depends on the number of pumps if there is one could be 0-120 strokes, if more then less strokes depending on how many pumps.

 

Pump pressure (PP): Can be between 2-2000 PSI.

 

Surface Torque: 0 – 25000 ft-lb

 

Depth: Can go from 0 to 12000 m (no real limit).

 

 

 

 

 

4. Describe the measurement of ROP and list several sources of ROP data.

a) Describe the applications of ROP data.

b) List the factors, which affect ROP and describe their effect.

Ans (a).  The applications of ROP are as follows:

v ROP is a very important parameter in correlation.

v A change in ROP is a good indicator of formation change.

v It may be also an indicator for the bit condition.

v It is an indicator of the drilling performance.

 

Ans (b).  Factors, which affect ROP, are as follows:

 

Lithology

ROP is directly proportional to the hardness of the drilled formation.

Hard lithology  = Slow ROP

Soft lithology   = High ROP

 

Differential pressure

ROP increases with the increase in the differential pressure, as it makes the formation more drillable.

 

Surface & Down Hole Weight on bit

With roller cone bits ROP is directly proportional to the WOB, while PDC & Diamond bits are more efficient with less weight.

 

RPM

ROP is directly proportional to RPM.

 

Bit condition

The ROP decreases as the bit starts wearing

 

Bit type

Some bits give high ROP with certain formations (depends on bit specification).