Kick tolerance is the maximum gas volume for a given degree of underbalance which the circulation can be performed without exceeding the weakest formation in the wellbore. This article is the extended version of Kick Tolerance Calculation which will explain more on this topic. It is very critical that drilling personnel understand its importance to well design and drilling operation.
There are two important factors used for determining the kick tolerance
• Kick Intensity – It is the different between the maximum anticipated formation pressure and planned mud weight. For example, the planned mud weight is 13.0 ppg and the possible kick pressure is 13.5 ppg. Therefore, the kick intensity is 0.5 ppg (13.5 – 13.0).
A zero kick intensity (swabbed kick scenario) should be used for a know area where you have less uncertainty about an overpressure zone.
• Kick Volume – It is a gas influx entering into the wellbore from the formation. Gas kick is always used for well control calculation because it is the worst case scenario. The kick volume should be realistic figure which personal can detect the influx on the rig. In a larger hole, it allows bigger influx volume than a small hole.
As you know, Kick Tolerance is the maximum gas kick volume for required Kick Intensity at a certain depth that you are able to successfully shut-in and circulate gas kick out of a well without breaking down formation at shoe.
There are several factors affecting kick tolerance as listed below:
This post will teach you how to calculate kick tolerance. This concept is very important to well design and will give you an idea how much kick you can take at particular parameters.
Firstly, I would like to be clear about the following terms;
Kick tolerance is the maximum gas influx volumes (bbl) for a designed kick intensity that can be successfully shut the well in and circulated out without breaking formation pressure at the casing shoe.
Kick intensity is the different between the maximum anticipated formation pressure and planned mud weight.
Secondly, learn how to determin kick tolerance by following steps below:
You know about kick tolerance factor from previous section and you can use it to determine the maximum formation pressure which can be controlled when the well is shut in.
This equation below demonstrates you how to calculate it.
You have learned about the kick tolerance factor from the previous blog posting and this article will demonstrate you how to use the kick tolerance factor to determine the maximum surface pressure from it.
The formula is listed below;
Maximum surface pressure = kick tolerance factor x 0.052 x TVD of well
Maximum surface pressure in psi
kick tolerance factor in ppg
TVD of well in ft
Determine the maximum surface pressure with this following data:
Kick tolerance factor = 1.8 ppg
Hole depth = 10,000’MD/9500’TVD
Based on these data, you can calculate the maximum surface pressure like this;
Maximum surface pressure = 1.8 x 0.052 x 9500 = 889 psi
Please find the Excel sheet for this calculation Maximum surface pressure from kick tolerance factor
Ref book: Formulas and Calculations for Drilling, Production and Workover, Second Edition