Tag Archives: casing design

Buoyancy Effect on Weight of Tubular Submersed in Fluid

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When a tubular submerses into drilling fluid or completion fluid, it will affect how the force distribution works on the tubular. This article will describe how buoyancy will affect tubular weight and a location of neutral axial load (zero axial load).

Weight of Tubing in Air

When tubing is hung in the air, the string weight is equal to linear weight per foot multiplied by the total length of the string. The maximum tensile load is on surface and the zero axial load point is at the bottom.

Tubing Detail

  • 5” Tubing
  • Weight per length = 17.7 lb/ft
  • Total Length = 10,000 ft

Total weight = 17.7 x 10,000 = 177,000 lb

Weight at the bottom of tubing is 0 and weight on top is 177,000 lb in tensile.

Figure 1 demonstrates force distribution of tubing hanging in air.

Figure 1 - Weight of Tubing in Air

Figure 1 – Weight of Tubing in Air

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Design Factor for Tubular Design

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Tubular must be properly deigned to cover all anticipated load cases during the life of the well.  Engineers must select the appropriate tubular grade and weight, which will withstand the loads and be economic for the project. High grade to tubular can lead to excessive cost, which may not be economic viable. However, if the selected tubular is very close to the anticipated load, it might not be safe to operate the well. Therefore, engineers must fully understand the concept about design factors in tubular design.

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Oilfield Casing Data Sheet Free Download

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Casing information is very important part of working in the oilfield. This information is used in several calculations as expected displacement volume, cement calculation, stuck pipe calculation, burst/collapse, casing design, etc. Therefore our team collects casing data into one spreadsheet and pdf file for you to download.

casing-Data-sheet-cover

What is Information inside the Casing Data Spreadsheet?

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Casing Size Selection – How To Select Casing Size to Match the Drilling and Completion Goal

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We’ve learnt several topics in regard to casing design and this article will demonstrate you how to determine casing size in the well.

casing-size-selection-cover

Casing size selection is determined from the inside outward and it starts from the bottom hole.

The sequence of design is based on the following steps;

1. Proper sizing of tubing is determined by inflow performance analysis.

2. Completion equipment is planned to install with tubing string. Determine which part has the biggest OD. This will directly impact of production casing.

3. Bit size for drilling the production section.

4. Casing size must be smaller than bit size and its ID must be bigger than the biggest component in completion string.

5. Once you get the last casing string, the upper string is selected by repeating bit selection and casing selection similar to step #3 and #4.
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Casing Seat Selection – How To Select Casing Setting Depth

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From the previous article, you’ve learnt about overall of casing design process and in this article we are going to discuss about how to select casing setting depth. The selection of casing string and setting depth is based on formation pore pressure and fracture gradient of the well.

casing seat selection fb

For the casing setting depth determination, pore pressure and fracture gradient are normally described in PPG (Figure 1).

Figure-1---Pore-Pressure-and-Fracture-Pressure-Plot

Figure 1 – Pore Pressure and Fracture Pressure Plot

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