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But historically it was given a specific focus popularity due to computational simplifications from using the Superposition Time concept, particularly when the following conditions hold true:
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periods reach radial flow regime: , |
| Condition 2 | |
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IN does not reach the boundary |
In this case the pressure diffusion during the SHUT-IN period can be simulated as:
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| anchor | Horner_pwf |
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| alignment | left |
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p_{wf}(\Delta t) = p_e - \frac{q_t}{4 \pi \sigma} \, \ln \left( 1 + \frac{T}{\Delta t} \right) |
The equation
| LaTeX Math Block Reference |
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shows that pressure during
the shut-in segment of Horner Test this period of time is not dependent on skin-factor
and pressure diffusivity
.Even if pressure during the FLOWING survey (Drawdown / Injection) period of time is not available (which is the most popular case in practise) one can still interpret the SHUT-IN survey(Build-up / Fall-off) and get reliable estimation of formation but provide an easy linear way to assess formation pressure
and formation transmissibility
(but not a skin-factor ).
The benefits of this survey interpretation method is that:
- it provides the robust straightforward estimation of formation pressure and formation transmissibility
- it does not require the knowledge of pressure diffusivity (unlike the case of a drawdown test)
- it does not depend on diffusion model specifics as soon as IARF is developed during the test and the outer boundary did not affect the pressure
It should be mentioned that in modern Pressure Transient Analysis the above Condition 1 and Condition 2 are not required and one can use the powerful arsenal of modern softwares to fit the pressure readings with pressure diffusion models.
See Also
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Petroleum Industry / Upstream / Subsurface E&P Disciplines / Well Testing / Pressure Testing / Pressure Transient Analysis (PTA)
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