Tubular Material Selection for HTHP Well with Example Calculation

HTHP-selection-cover

This article demonstrates how to select material that will be suitable for high pressure, high pressure and corrosive environment. The material chart is based on the Sumitomo tubular chart.

HTHP-selection-cover

Well conditions are as follows;

Reservoir: High pressure & high temperature gas reservoir

Reservoir Temperature: 420 F (216 C)

CO2 content: 2.9% mol

H2S:40 ppm

Chloride Ion Content in Produced Water: 150,000 ppm

Fluid saturation pressure: 10,000 psig Continue reading

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Piston Force on Closed-Ended Tubular (Plugged Tubular)

Piston-Force-on-Closed-Ended-Tubular

According to the previous post (piston force on open-ended tubular), applied surface pressure will reduce tensile force on surface. In this article, this is an analysis on the piston force on a plugged tubular string and the details are shown below;

Tubing Detail

  • 5” Tubing
  • ID of tubing = 3.696”
  • Packer seal bore OD = 5.25”
  • Weight per length = 17.7 lb/ft
  • Total Length = 10,000 ft
  • Plugged tubing depth = 10,000 ft
  • Fluid density = 10 ppg
  • Tubing is free to move in the packer
  • Applied surface pressure = 5,000 psi

Figure 1 shows the wellbore schematic. Applied pressure (5,000 psi) will cause a piston effect to push the tubing. Therefore, at the bottom of tubing buoyancy and piston force will act in an upwards direction (compression).

Figure 1 - Wellbore Schematic

Figure 1 – Wellbore Schematic

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Piston Force on Open-Ended Tubular

Piston-Force-on-Open-Ended-Tubular

Piston force is a load caused directly by changes in pressure acting on the exposed cross sectional area of pipe. This results in changing in length of tubular and force acting against tubular. In this article, it generally demonstrates force distribution based on a simple tubular diagram.

Piston-Force-on-Open-Ended-Tubular

Tubing Detail

  • 5” Tubing
  • ID of tubing = 3.696”
  • Weight per length = 17.7 lb/ft
  • Total Length = 10,000 ft
  • Fluid density = 10 ppg
  • Tubing is free to move in the packer
  • Applied surface pressure = 5,000 psi

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Buoyancy Effect on Weight of Tubular Submersed in Fluid

Buoyancy-Effect-on-Weight-of-Tubular

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

Weight of Tubing When Submersed in Fluid Continue reading

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Design Factor for Tubular Design

Design-Factor-for-Tubular-Design-cover

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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