Mud: 2021 #4

True statements about drilling fluids include (select any that apply):
__ The majority of wells today are drilled with water-based drilling fluids.
__ The use of pneumatic drilling fluids is limited to depleted zones or areas where the formations are low pressured.
__ Polymers are used to prevent clay dispersion in freshwater or seawater-based drilling fluids.
__ Oil-based fluids typically include 10-40% water.
__ One function of a drilling fluid can be categorized as: ensure maximum logging information.
__ One function of a drilling fluid can be categorized as: support part of the drillstring and casing weight.
__ Poor fluid loss control can cause surge, swab, and circulation-pressure problems.

Click the button for the answer, along with commentary and SPE references sourced. Note that the provided SPE Reference Guide will not help at all on these types of problems. Feel free to ask questions in the comment box below.

True statements about drilling fluids include (select any that apply):
 X  The majority of wells today are drilled with water-based drilling fluids.
 X  The use of pneumatic drilling fluids is limited to depleted zones or areas where the formations are low pressured.
 X  Polymers are used to prevent clay dispersion in freshwater or seawater-based drilling fluids.
 X  Oil-based fluids typically include 10-40% water.
 X  One function of a drilling fluid can be categorized as: ensure maximum logging information.
 X  One function of a drilling fluid can be categorized as: support part of the drillstring and casing weight.
 X  Poor fluid loss control can cause surge, swab and circulation-pressure problems.

Note that this "multi-choice" format in the new EBT exam makes it extremely difficult to know if you have it fully correct. The 2021 practice problem sets have many in this format (likely more than the real exam) because it's a good way to test knowledge.

Source HS2 (P89-93).
The majority of wells are drilled with water-based drilling fluids (P91).
The use of pneumatic drilling fluids (i.e. air, gas, and foam)is limited to depleted zones or areas where the formations are low pressured (P90).
Polymers are used to provide viscosity, fluid-loss control, shale inhibition, and prevention of clay dispersion in freshwater or seawater-based drilling fluids (P91).
OBF: The oil/water ratios typically range from 90:10 to 60:40 (P93).
The function of a drilling fluid can be categorized as: ensure maximum logging information (P89).
The function of a drilling fluid can be categorized as: support part of the drillstring and casing weight (P89). Poor fluid loss can cause surge (an increase in wellbore pressure under a bit from running into the hole), swab (a decrease in wellbore pressure under a bit from running out of the hole), and circulation-pressure problems (known as ECD) (P89).