Basrah University for Oil and Gas
College of Petroleum and Gas Engineering
Department of Petroleum and Gas Engineering
Subject: Well Control
Class:
4th year 2nd semester
Examiner: Najah Saeed Abd.
Answer All Questions
Group – A
No.1 to No 16
Exam: Midterm
Date: 29.06.2021
Time: 120 Mints
Q1:A: Discuss how Swab/Surge pressures lead to wellbore instability ?
Q1:B: Due to formation considerations, you have been told that pressure at
depth cannot exceed 5,500 psi. You are currently pumping 12.6 lb/gal
drilling fluid at 2,000 psi as you approach a depth of 5,300 feet. Is it safe
to continue without reducing the pump pressure?
* Ignore any possible frictional losses in the system.
* Include a brief explanation of your answer.
Q2: A: Explain in your words BHP and write the Equation of BHP under the cases below:
a. BHP While Drilling?
b. BHP While Tripping Out (POOH)?
c. BHP While Tripping In (Running in the Hole)?
Q2: B:
1. Find the hydrostatic pressure at 4,429 ft of a fluid mixture with 65% 8.5 lb/gal water
and 35% 7.25 lb/gal oil based mud (OBM).
2. Mud weight =13 ppg influx gradient = 0.1 psi/ft After 30 Mints both pressure have
risen by 150 psi due to gas migration. Calculate the speed of gas migration in feet per
hour?
Q3: A: Given the following Data:
Find:
Hole Data
⁄ Inch Casing (ID 8.751inch) set at 11,500 feet
7inch Liner (ID 6.276 inch) set at 13,000 feet
Liner Top set 500 feet inside 9 5/8 inch casing
6 inch Open hole drilled to 15,500 feet
Drill String data
4 ½ inch Drill Collars (ID 2.25 inch) Length 500 feet
3 ½ inch Drill pipe (ID 2.625 inch) Length 7000 feet
5 inch Drill pipe (ID 4.375 inch)
1. Draw the Profile of the Well?
2. Annular Volume (bbl)?
3. Total Volume (bbl)?
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Q3: B: You have taken a kick and shut the well in. The active tank while drilling contained
250 bbls. And the mud return line to the pits contains 25 bbls. The tank now contains 300
bbls. How many barrels of mud has been displaced from the well?
(Include a brief explanation of your answer)
Q4: A: A deviated borehole has a measured depth of 12,320 ft. (TVD 10429 ft). 9 5/8”, 47
lb/ft. Casing in set at a measured depth of 9750 ft. (9200 ft. TVD) 11.4 ppg mud is in use
when the well kicks and is closed in.
 Shut in Drill Pipe Pressure is 750 psi
 Shut in Casing Pressure is 1050 psi and kick volume is 15 bbls.
Pre- recorded information is as follows:


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Fracture mud weight = 14.4 ppg
Capacity of 19.5 lbs. Drill pipe = 0.01776 bbl/ft.
Capacity of 9 5/8” J55 casing = 0.0732 bbl/ft.
Slow Circulating Rate Pressure = 850 psi
Determine:
1. The maximum allowable annular surface pressure .
2. The kill mud weight required to balance the formation pressure.
3. The kill mud weight with a Safety Margin of 100 psi.
Q4: B:
In a 10 000’ well, the target ECD being kept while drilling is 15ppg, if the mud density used is
15ppg and annular friction losses are 100psi, determine:
a. If it is necessary to apply backpressure while drilling, and, if the answer is yes,
determine its value?
b. If it is necessary to apply backpressure during connections (static periods), and,
if the answer is yes, determine its value?
Good Luck
Examiner:
Najah Saeed Abdulridha
Head of Department
Dr. Nabeel K.
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