Lost Returns with Water

In this section, we describe the load case "Lost returns with water", available in Oliasoft WellDesign.

Lost returns with water is a burst load case, where the unknown is the internal pressure profile of the tubing

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

This load case reflects that water is pumped from the surface down the tubing due to lost returns, and the pressure profile is given by the hydrostatic pressure from the fracture pressure at the shoe.

Printable Version

58KB

Oliasoft Technical Documentation - Load cases - Lost returns with water.pdf

pdf

Inputs

The following inputs define the lost returns with water load case

1. he 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, $\text{TVD}_{\text{hanger}}$

   2. The shoe of the tubing, $\text{TVD}_{\text{shoe}}$

   3. The mud-water interface, $\text{TVD}_{\text{MW}}$

3. The fracture pressure profile from hanger to shoe.

4. The mud weight / density, $\rho_{\text{mud}}$ .

5. The density of water, with default value $\rho_\text{water} = 998\, \text{kg/m}^3$ .

6. A fracture margin of error, added to the fracture pressure.

Scenario Illustration

Calculations

1. Calculate the fracture pressure at the shoe, $p_\text{f, shoe}$

2. Calculate the hydrostatic pressure from shoe to hanger, taking the mud-water interface into account. Explicitly, if the mud-water interface is below the shoe, i.e. $\text{TVD}_{\text{MW}}\geq \text{TVD}_{\text{shoe}}$ , then the internal pressure in the tubing, parametrised by TVD, is given by

$$p_i = p_\text{f, shoe} - \rho_\text{water}\, g\left(\text{TVD}_{\text{shoe}} - \text{TVD} \right) \;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\ (1)$$

where $g$ is the gravitational constant. If, on the other hand, the mud-water interface is between the hanger and the shoe, i.e. $\text{TVD}_{\text{hanger}} \leq \text{TVD}_{\text{MW}} < \text{TVD}_{\text{shoe}}$ , then calculate the pressure at the mud-water interface

$$p_\text{MW} = p_\text{f, shoe} - \rho_\text{mud}\, g\left(\text{TVD}_{\text{shoe}} - \text{TVD}_\text{MW} \right) \;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\ (2)$$

and the internal pressure in the tubing is

$$\begin{equation} p_i = \begin{cases} p_\text{MW} - \rho_\text{water}\, g\left(\text{TVD}_{\text{MW}} - \text{TVD} \right), \qquad \text{TVD} \leq \text{TVD}_{\text{MW}}, \\ p_\text{f, shoe} - \rho_\text{mud}\, g\left(\text{TVD}_{\text{shoe}} - \text{TVD} \right), \qquad \text{else}. \end{cases} \;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\ (3) \end{equation}$$