Stimulation Surface Leak

In this section we describe the load case "Stimulation Surface Leak" available in Oliasoft WellDesign™.

---

Stimulation surface leak is a burst load case, where the unknown is the internal pressure profile of the tubing. It models a tubing leak near the wellhead during injection.

NOTE!
Note: In this documentation we denote any tubular as tubing. All calculations however encompass any tubular, such as tubings, casings, liners, tie-backs etc. //: # (end - note)

Summary

Stimulation surface leak is a burst load case. It models a tubing leak near the wellhead between tubing and tubing annulus during injection. The pressure profile is given by an initial surface pressure from RKB, an injection fluid gradient from RKB to the hanger and packer fluid from the hanger to the packer. From the packer to the casing shoe, the pressure profile is determined by the hydrostatic injection fluid.

Illustrating Pressure Profile Graph

Printable Version

Oliasoft Technical Documentation - Stimulation Surface Leak

Inputs

The following inputs define the Stimulation Surface Leak 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 and inclination.
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 packer depth, TVD$_{packer}$.
3. The temperature profile of the wellbore, $T$.
4. The packer fluid density, $\rho_{pfl}$.
5. The injection pressure, $P_{inj}$
6. The injection fluid density, $\rho_{inj}$.
7. The gravitation constant, $g$.

Calculation

The hanger pressure is given by

$P_{\text{hanger}} = P_{\text{inj}} + g\, \rho_{\text{inj}} \, \text{TVD}_{\text{hanger}}.\qquad \qquad \qquad \qquad \qquad \qquad \qquad \qquad \qquad \qquad \qquad \qquad \qquad \qquad (1)$

Then, from hanger to the minimum of the shoe and packer, the internal pressure is given by

$P_i = P_{\text{hanger}} + g\, \rho_{\text{pfl}} \, \left(\text{TVD} - \text{TVD}_{\text{hanger}}\right), \quad \text{TVD}\, \in\, [\text{TVD}_{\text{hanger}}\,,\, \text{min}(\text{TVD}_{\text{shoe}}, \text{TVD}_{\text{packer}})]. \qquad (2)$

If the shoe is deeper than the packer, then the internal pressure from packer to shoe is given by

$P_i = P_{\text{inj}} + g\, \rho_{\text{inj}}\, \text{TVD}, \quad \text{TVD}\, \in\, [\text{TVD}_{\text{packer}}\,, \text{TVD}_{\text{shoe}}]. \qquad \qquad \qquad \qquad \qquad \qquad \qquad \qquad \qquad (3)$