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Thursday, December 22, 2011

Kick Tolerance Calculation

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:

1. Determine kick intensity

2. Determine maximum allowable shut in casing pressure (MASICP)

3. Determine influx height with this following equation

4. Calculate influx volume at BHA based on the influx height
Influx volume at BHA, bbl = Kick Height, ft x Annular Capacity of BHA and Hole, bbl/ft

5. Calculate influx volume at shoe base on the influx height
Influx volume at shoe, bbl = Kick Height, ft x Annular Capacity of DP and Hole, bbl/ft

6. Calculate influx volume at the bottom based on the influx volume at the shoe by applying Boyle's Law

Influx volume at bottom, bbl = (Influx volume at shoe x Leak off test pressure at shoe) ÷ (Formation pressure, psi)

Formation pressure can be calculated from well TVD and maximum anticipated formation pressure.

7. Compare both figures. The smaller figure is the Kick Tolerance.

For more understanding, please determine kick tolerance with following data;

Possible maximum formation pressure = 12.5 ppg
Planned TD mud weight = 12.0 ppg
Casing shoe = 6,500'MD/5,500' TVD
Leak off test at casing shoe = 14.7 ppg
Hole depth = 10,100'MD/9,500'TVD
Bit = 12-1/4"
BHA = 850 ft
Average OD of BHA = 6.5"
Drill pipe size = 5"
Influx gradient (gas) = 0.12 psi/ft

1. Kick intensity = 12.5 – 12.0 = 0.5 ppg

2. Maximum Allowable Shut In Casing Pressure (MASICP) ** some people may call maximum allowable initial shut in casing pressure**.
= (14.7 – 12.0) x 0.052 x 5,500 = 772 psi

3. Influx height:

4. Calculate influx volume at BHA based on the influx height
Annular capacity between hole and BHA =
Influx volume at BHA, bbl = 0.1047 x 1021= 106.9 bbl
5. Calculate influx volume at shoe base on the influx height
Annular capacity between hole and drill pipe =
Influx volume at shoe, bbl = 0.1215 x 1021 = 124.1 bbl

6. This volume is a reference at shoe; therefore, you need to convert it to the bottom hole condition.

Boyle's gas law is utilized in order to get the figure at the bottom hole.
P1 x V1 = P2 x V2

For this case, you need to use the maximum pressure at shoe which is the Leak Off Test pressure because it is the maximum value before you will break the wellbore.
Rearranging the equation, you will get like this.

Influx volume at bottom, bbl = Influx volume at shoe x Leak off test pressure at shoe ÷ Formation pressure, psi

Influx volume at shoe = 124.1 bbl
Leak off test pressure = 0.052 x 14.7 x 5,500 = 4,204 psi
Formation pressure = 0.052 x 12.5 x 9,500 = 6,175 psi

Influx volume at bottom, bbl = (124.1 x 4, 204) ÷ (6175) = 84.5 bbl

7. We need to compare 2 cases and the smaller figure is the kick tolerance of the well.
1 st case: 106.9 bbl
2 nd case: 84.5 bbl
Therefore, the kick tolerance is 84.5 bbl.

Conclusion: With the following information, the maximum kick that the well can take and personnel can circulate it out of hole without breaking formation is 84.5 bbl.

1 comment:

  1. The safety of deep sea drilling is one of the most important areas.
    In addition to monitoring the flow rate of the mud and the pressure measurements can analyze the characteristics of the mud. New electronic methods allow even the smallest changes in the speed of sound through the dissolved gases (a few percent saturation) and due to lower inflows of hydrocarbons are sure to measure and to warn.
    This also works with oil based mud.

    The digital measurement technology can measure foot securely changes the speed of 0.1 ft/m.

    Further details of the measurement technique, see below:



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