Drill Ahead Collapse

In this section we describe the load case "Drill ahead Collapse" available in Oliasoft WellDesign™.

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Drill ahead is a burst/collapse load case, where the unknown is the internal pressure profile of the tubing This load case represents the hydrostatic pressure from mud and Equivalent Circulating Density (ECD) for drilling a new section. //: # (end - introduction)

NOTE!
Note: In this documentation we denote any tubular as casing or tubing. All calculations however encompass any tubular, such as tubings, casings, liners, tie-backs etc.

Summary

Drill ahead is a burst/collapse load case, where the unknown is the internal pressure profile of the tubing. This load case represents the hydrostatic pressure from mud and Equivalent Circulating Density (ECD) for drilling a new section. //: # (end - summary)

Illustrating Pressure Profile Graph

Printable Version

Oliasoft Technical Documentation - Drill Ahead //: # (end - printable_version)

Inputs

The following inputs define the drill ahead load case:

1. The true vertical depth (TVD) along the wellbore as a function of measured depth. Alternatively, the wellbore described by a set of survey stations, with complete information about measured depth, inclination, and azimuth.
2. The true vertical depth / TVD of
   1. The hanger of the tubing, TVD$_{hanger}$
   2. The shoe of the tubing, TVD$_{shoe}$
3. The mud weight/density, $\rho_m$, for drilling the next section.
4. Equivalent Circulating Density, $\rho_{ECD}$ //: # (end - inputs)

Calculation

The internal pressure profile from hanger to shoe, parametrized by TVD, of the tubing is then given by

$p_{i}=\left(\rho_{m}+\rho_{\mathrm{ECD}}\right) g \mathrm{TVD},\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\ (1)$

where $g$ is the gravitational constant.