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Cementing

In this section we describe the load case "Cementing" available in Oliasoft WellDesign™.​


Cementing is a collapse load case, where the unknown is the pressure profile of the tubing, both external and internal.

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.


Summary​

Cementing is an internal collapse load case, for the cementing operation. Usually, the cement is installed with a float inside the casing. The internal pressure profile is then given by hydrostatic pressure from the displacement fluid from RKB to the float. Below the float, the initial pressure at the casing shoe is given by the external pressure at shoe from the load case: "Mud and cement slurry”. From the casing shoe up to the float, the pressure profile is given by the fluid density below float which normally is equal to the tail cement density.


Illustrating Pressure Profile Graph​

Graph 1: Illustrates a case without a float presented in the casing. The internal pressure profile is then only a function of the mud column.


Graph 2: Illustrates a case with float installed in the casing. The internal pressure at the casing shoe is then dependant on the external pressure profile "Mud and cement slurry" which is diisplayed on the right hand side.


Graph 3: Illustrates the external pressure profile from "Mud and cement slurry"


Printable Version​

Oliasoft Technical Documentation - Cementing


Inputs​

The following inputs define the Cementing 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, TVDhanger_{hanger}.
    2. The shoe of the tubing, TVDshoe_{shoe}.
  3. The temperature profile of the wellbore, TT.
  4. A complete description of the fluid columns on the inside and outside of the tubing. //: # (end - inputs)

Calculation​

The external pressure profile is just the hydrostatic pressure profile from the external fluid column,

Pe=’External profile from Mud and cement slurry .’(1)P_e = \text{’External profile from Mud and cement slurry .’} \qquad \qquad \qquad \qquad \qquad \qquad \qquad \qquad \qquad \qquad (1)

The internal pressure profile is divided in two, from hanger to float, and from float to shoe,

Pi={’Hydrostatic pressure from internal fluid column.’,TVD  ∈ [TVDhanger , TVDfloat]Pe,shoe−’Hydrostatic pressure from internal fluid column.’,TVD  ∈ [TVDfloat , TVDshoe]  (2)P_i = \begin{cases} \text{'Hydrostatic pressure from internal fluid column.'}, \quad &\text{TVD}\; \in\, [\text{TVD}_{\text{hanger}}\, , \,\text{TVD}_{\text{float}} ] \\ P_{e,\text{shoe}} - \text{'Hydrostatic pressure from internal fluid column.'}, \quad &\text{TVD}\; \in\, [\text{TVD}_{\text{float}}\, , \,\text{TVD}_{\text{shoe}} ] \end{cases} \;(2)

where Pe,shoeP_{e,\text{shoe}} is the external pressure at the shoe from the external profile "Mud and Cement slurry.