Chapter 6 Underbalanced and Horizontal Drilling

Question 1

Define Underbalanced Drilling:

Answer 1

When the hydrostatic head of a drilling fluid is intentionally designed to be lower than the formation being drilled, the operation will be considered to be underbalanced drilling.

Question 2

When drilling an Underbalanced or Managed Pressure Drilling well, how many barriers to pressure should there be on the inside to the drill string

Answer 2

Two non-return valves (Float Valves)

Question 3

While drilling UBD and MPD wells, what percentage of the hole volume of kill fluid must be on location at all times and readily accessible to pump during drilling operations by opening/closing no more than two valves?

Answer 3

100%

Question 4

True or False: Underbalanced drilling utilized surface equipment to replace HP

Answer 4

True

Question 5

Why does gas migrate faster in deviated wells than in comparable vertical wells?

Answer 5

This occurs due to segregation developing in the bore hole, with the lighter fluid tending to rise on the high side of the hole whereas heavier mud moves down the low side of the hole.

Question 6

Steam chambers grow and changes over time. How do you avoid drilling into unexpected pressures when drilling in close proximity of an existing or mature SAGD operation?

Answer 6

Accurate modeling of these steam chambers must be assured prior to drilling.

Question 7

When drilling a horizontal well, what is an extra precaution that should be considered in terms of well control?

Answer 7

The MACP in multilateral wells should be calculated based on the weakest formations of all wellbores.