Calculate Influx Height

Once you know how much pit gain you got, you are able to determine influx height. Please take a look at the figure below for more understanding.

 

 

The influx height can be calculated by this following equation.

Influx height = Pit gain ÷ annular capacity

Where: influx height in ft,

Pit gain in bbl

Annular capacity in bbl/ft

 

The annular capacity can change depending on how big of your pipe and your hole.

Note: if you would like to get more understanding regarding annular capacity, please check this link, Annular Capacity Calculation.

Let’s get more understanding about it via this example.

 

Pit gain = 25 bbl

Hole size = 8.5 inch

BHA OD = 6 inch

BHA length = 420 ft

Drill pipe size = 5 inch

 

Firstly, you need to know annular capacity between BHA and hole.

Annular capacity, bbl/ft = (8.52 – 62) ÷ 1029.4 = 0.0325 bbl/ft

 

You can calculate how much annular volume between hole and drill collar via this following equation.

Annular Volume, bbl = BHA length x annular capacity

Annular Volume, bbl = 420 x 0.0325 = 14.8 bbl

 

Because you gain a total of 25 bbl, there will be some influx above the BHA.

Influx above the BHA, bbl = Total pit gain – Annular volume between hole and drill collar

Influx above the BHA, bbl = 25 – 14.8 = 10.2 bbl

 

Secondly, after knowing that 10.2 bbl of influx above the BHA, you need to convert this volume into height so as to determine height of the influx.

 

Determine annular capacity between drill pipe an hole.

 

Annular capacity, bbl/ft = (8.52 – 52) ÷ 1029.4 = 0.0459 bbl/ft

 

Determine height of 10.2 bbl influx across 5” DP.

Height, ft = Volume, bbl ÷ Annular Capacity, bbl/ft

Height, ft = 10.2 ÷ 0.0459 = 222 ft

 

It means that there is 222 ft of influx across DP so you can determine the total influx height:

 

Height of influx = 222 + 420 = 642 ft

Ref book: Drilling Formula Book Formulas and Calculations for Drilling, Production and Workover, Second Edition

Related Post

Mixing Fluids of Different Densities with Pit Spac... You many have different drilling fluid densities in your mud pits so you can have option to mix different fluid densities together in order to get you...
IWCF Well Control Quizzes My friend just sent me the very useful well control stuff again. This time is the IWCF well control quizzes by Transocean which use to train their peo...
Adjusted maximum allowable shut-in casing pressure You calculate the maximum initial shut-in casing pressure (MISICP) based on the original mud weight before you start drilling ahead. Once you drill de...
Well Flowing After Disconnecting The Wireline Lubr... Please watch the footage below. It was a flow back after breaking out the lubricator on the rig floor. We don’t know full details what was happened...
Share the joy
  • 10
  •  
  •  
  •  
  •  
  •  
  •  
  •  
  •  
    10
    Shares
Tagged . Bookmark the permalink.

About DrillingFormulas.Com

Working in the oil field and loving to share knowledge.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.