Specific schematic of Pressure Test consisting of long-term shut-in, followed by FLOWING test survey (Drawdown / Injection) then followed by   SHUT-IN survey(Build-up / Fall-off) (see Fig. 1).

...

The interpretation of Horner Test can be performed by conventional pressure diffusion models fitting.

But historically it was given a specific focus due to simplifications from using the Superposition Time concept, particularly when the following conditions hold true:

• both production 

  LaTeX Math Inline
  body T

   and shut-in 

  LaTeX Math Inline
  body \Delta t

   period reach radial flow regime: 

  LaTeX Math Inline
  body T > t_{IARF}

  , 

  LaTeX Math Inline
  body \Delta t > t_{IARF}

  
  
  
• total duration of production and shut-in do not reach the boundary

  LaTeX Math Inline
  body T+\Delta t < t_e

In this case one the pressure diffusion can be simulated as:

p_{wf}(\Delta t) = p_e - \frac{q_t}{4 \pi \sigma} \, \ln \left( 1 + \frac{T}{\Delta t} \right)

The main features of Horner model are:

...

equation

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

...

pressure

The benefits of this survey is that:

• it does not require the knowledge of pressure

...

• diffusivity

  LaTeX Math Inline
  body \chi

   (unlike the case of a drawdown test)
• it does not depend on diffusion model specifics as soon

...

• as IARF

...

• is developed during the test

...

it does not provide skin-factor estimation

The formula 

The formation pressure 

\left \{ p_{wf} \right \}  = p_e - b  \, \left \{ \ln \left( 1 + \frac{T}{\Delta t} \right) \right \} 

\sigma =  \frac{q_t}{4 \pi b}

...

...

See Also

...

Petroleum Industry / Upstream / Subsurface E&P Disciplines / Well Testing / Pressure Testing / Pressure Transient Analysis (PTA)

...