Category Archives: Applied Drilling Calculations

Estimated mud weight required to safely drill the well

By | | , ,
10 Comments

I have an interesting question to share with you about how to estimate minimum mud weight required to safely TD the well.

The question is shown below.

7” casing shoe was set at 6,500’MD/5,000’ TVD. The geologist team in town expects 2 hydrocarbon reservoirs and information is listed below;

Formation sand A: Expected depth 5,500’ TVD, pressure gradient is 0.48 psi/ft.

Formation sand B: Expected depth 8,800’ TVD, pressure gradient is 0.49 psi/ft.

The planned TD is 9200’MD/9000’TVD and the drilling team requires 250 psi overbalance while drilling.

What is the mud weight required to drill the well with 250 psi overbalance?

First of all, let’s draw a simple diagram like this.

Continue reading →

Effect of Frictional Pressure on ECD while Reverse circulation

By | | , , ,
Leave a comment

A reverse circulation is another way to circulate by circulating into annulus up to a bit and drill string. The fluid outlet is on surface. For drilling operation, we most of the time use forward circulation; however, in completion operation, the reverse circulation is utilized more often. For more understanding, we would like to show an image below (Figure 1) which demonstrates a flow path of the reverse circulation.

Figure 1 – Reverse Circulation

Continue reading →

Effect of Frictional Pressure on ECD while Forward Circulation

By | | , , ,
14 Comments

In this article, we will describe the effect of friction pressure on bottom hole pressure and equivalent circulating density while performing forward circulation.

What is forward circulation?

It is the typical circulating path which is from a mud pump into drill pipe. Mud is pumped down into drill string / BHA and come out of a bit.  Then, the mud is flown up the annulus and return back to surface as you can see in the diagram below (Figure 1).

Figure 1 – Forward Circulation Path

Continue reading →

Bottom hole pressure change while performing well control operation with driller’s method

By | | , ,
4 Comments

In the first circulation of driller’s method, driller circulates gas kick with 25 spm and the initial circulating pressure (ICP) is 1600 psi. The initial shut in drill pipe pressure is 450 psi. After shift change, another driller accidentally changes pump rate to 30 spm but he still holds drill pipe pressure constant.

What will happen to bottom hole pressure?

Continue reading →

Kick Tolerance Calculation

By | | , , ,
15 Comments

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:

Continue reading →