Number of strokes required to displace cement calculation/ Petrosmartt

    Calculating the number of strokes required to displace cement during a cementing job involves determining the volume of fluid that needs to be displaced and the volume delivered per stroke by the pump. Here’s a step-by-step method to perform this calculation:

Steps to Calculate the Number of Strokes Required to Displace Cement

1. Determine the Total Cement Volume (V)

• This is the volume of cement that needs to be displaced into the annulus. It can be calculated using the total cement slurry volume required for the job.

$$V = \text{Total Cement Volume (bbl)}$$

2. Determine the Pump Displacement per Stroke (D)

• This is the volume of fluid that the pump displaces with each stroke. It is typically provided by the pump manufacturer and is usually expressed in barrels per stroke (bbl/stroke) or liters per stroke (L/stroke).

$$D = \text{Pump Displacement per Stroke (bbl/stroke)}$$

3. Calculate the Number of Strokes Required (N)

• Use the total cement volume and the pump displacement per stroke to calculate the total number of strokes needed to displace the cement.

$$N = \frac{V}{D}$$

Where:

• N = Number of strokes required
• V = Total cement volume (bbl)
• D = Pump displacement per stroke (bbl/stroke)

ASME B31.3 QUIZ & Answers

Example Calculation

Suppose you have the following data:

• Total Cement Volume (V): 200 bbl
• Pump Displacement per Stroke (D): 0.05 bbl/stroke

Step 1: Determine the Total Cement Volume

$$V = 200 \text{ bbl}$$

Step 2: Determine the Pump Displacement per Stroke

$$D = 0.05 \text{ bbl/stroke}$$

Step 3: Calculate the Number of Strokes Required

$$N = \frac{200 \text{ bbl}}{0.05 \text{ bbl/stroke}} = 4000 \text{ strokes}$$

So, you would need 4,000 strokes to displace 200 bbl of cement using a pump with a displacement of 0.05 bbl per stroke.

Notes

• Pump Efficiency: Ensure the pump is operating efficiently and at the correct stroke rate to maintain consistent cement displacement.
• Fluid Properties: Take into account the properties of the cement slurry and the displacement fluid, as they may affect the actual displacement volume.
• Pump Type: Verify that the pump specifications match the required displacement volume per stroke and adjust calculations if using multiple pumps or different pump configurations.

Conclusion

Accurate calculation of the number of strokes required to displace cement ensures that the correct amount of cement slurry is pumped into the wellbore, achieving proper zonal isolation and well integrity.