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Above/Below Packer

In this section we describe the load case "Above/below packer" available in Oliasoft WellDesign™.​


Above/below packer is a collapse load case, where the unknown is the internal pressure profile of the tubing. It describes various pressure profiles that may occur under different production scenarios.

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​

Above/below packer is an internal collapse load case. The load case looks at two different scenarios: with and without mud drop. For the scenario without mud drop, the pressure profile from RKB to the packer is given by the hydrostatic mud fluid above packer. Below packer the pressure profile is given by the hydrostatic pressure from the fluid below packer. For the scenario with mud drop, the pressure profile below packer is the same as for the scenario without mud drop. From the packer to the hanger, the pressure profile is given by the pore pressure at the casing shoe with the hydrostatic fluid above packer from the shoe to the hanger. //: # (end - summary)


Illustrating Pressure Profile Graph​

Graph 1: Illustrates a case with fluid drop resulting in an internal pressure equal to zero from RKB to the fluid level.


Graph 2: Illustrates a case without fluid drop resulting in zero pressure at RKB and incresing internal pressure from RKB to packer.


Printable Version​

Oliasoft Technical Documentation - Above/Below Packer



Inputs​

The following inputs define the above/below packer 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, TVDhanger_{hanger}
    2. The shoe of the tubing, TVDshoe_{shoe}
    3. The packer depth, TVDpacker_{packer}
    4. The perforation depth, TVDperf_{perf}
  3. The atmospheric pressure, Patm_{atm}, and pore pressure at perforation depth, Pperf_{perf}
  4. The packer fluid density above packer, ρa,fl\rho_{a,fl}
  5. The fluid density below the packer, ρb,fl\rho_{b,fl}. Default value is 0
  6. Whether or not Fluid drop above packer is possible or not //: # (end - inputs)

Calculation​

The internal pressure profile is divided into two, one above the packer and one below (assuming the casing shoe is below the packer). If Fluid drop above packer is enabled, the fluid level is given by

TVDFL=TVDperf−Pperfgρa,fl                                         (1)TVD_{FL} = TVD_{perf} - \frac{P_{perf}}{g\rho_{a,fl}}\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\ (1)

where gg is the gravitational constant, and the internal pressure profile from hanger to packer is given by

Pi=max(Patm,Patm+Pperf−gρa,fl(TVDperf−TVD))                                         (2)P_i = max(P_{atm},P_{atm}+P_{perf}-g\rho_{a,fl}(TVD_{perf}-TVD))\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\ (2)

If Fluid drop above packer is disabled, then the pressure profile from hanger to packer is simply given by

Pi=gρa,flTVD                                         (3)P_i = g\rho_{a,fl}TVD\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\ (3)

If the casing shoe is below the packer, then the pressure profile below the packer is

Pi={Patm, if ρb,fl=0gρb,flTVD, otherwise                                          (4)P_{i}= \begin{cases}P_{\mathrm{atm}}, \quad \text { if } & \rho_{\mathrm{b}, \mathrm{fl}}=0 \\ g \rho_{\mathrm{b}, \mathrm{fl}} \mathrm{TVD}, & \text { otherwise }\end{cases}\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\ (4)