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Green Cement Pressure Test

In this section we describe the load case "Green Cement Pressure Test" available in Oliasoft WellDesign™.​


Green Cement Pressure Test is a burst load case, where the unknown is the pressure profile of the tubing. The internal and external pressure profiles are based on the hydrostatic pressure from mud and cement, and then a test pressure is applied on the inside of the tubing from the hanger to a float/plug. When using these pressures in axial loads calculations, the cement is treated as any other fluid, and does not restrict movement. //: # (end - introduction)

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​

Green Cement Pressure Test is a burst load case. In this scenario, the cement has not hardened, thus it is treated like a fluid in the calculations. The internal pressure is given by a test pressure from surface with a hydrostatic mud pressure from RKB to the casing shoe. If a float is installed, this pressure only applies from RKB to the float. From the float and below, the pressure at the casing shoe is given by the external pressure profile from "Mud and Cement Slurry" with tail cement from the casing shoe to the float. //: # (end - summary)


Illustrating Pressure Profile Graph​

Printable Version​

Oliasoft Technical Documentation - Green Cement Pressure Test


Inputs​

The following inputs define the Green Cement Pressure Test 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 float/plug, TVDfloat_{float}.
  3. The temperature profile of the wellbore, TT.
  4. The mud weight/density, ρmud\rho_{mud}.
  5. A complete description of the fluid columns on the inside and outside of the tubing.
  6. The test pressure, PtestP_{test} //: # (end - inputs)

Calculation​

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

Pe=’Hydrostatic pressure from external fluid column.’(1)P_e = \text{’Hydrostatic pressure from external fluid column.’} \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={Ptest+’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} P_{\text{test}} + \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.