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

Maximum pit gain from gas kick in water based mud In water based mud, you can not only estimate the maximum surface casing pressure, but you are also be able to determine the maximum pit gain due to g...
How To Determine Hole Size By Fluid Caliper This article will demonstrate you how to determine hole size by fluid caliper. First of all, you need to know what is the fluid caliper is. The fluid ...
Basic Understanding about Well Control with Pipe o... Well control with pipe off the bottom is one of the most serious well control situations because kick below a drillstring can create very complicated ...
Lag Time for Drilling Business and How to Calculat... I got an email from Sanan asking me about how to calculate lag time. First of all, you need to know what the lag time is. Lag time is traveling t...
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.