Interpretation workflow of pressure transitions in pressure test data in terms of well properties and formation properties of connected subsurface reservoirs.

It may refer to analysis of a stand-alone pressure transient or several pressure transients (MRST) and may also cover transitions in off-set wells (PIT).

Both downhole (BHP) and surface (THP) pressure records can be a source data to PTA.

The quantitative interpretation of pressure transitions is based on pressure diffusion model.

Formation pressure $\begin{array}{l}{p_i}\end{array}$ , skin-factor $\begin{array}{l}S\end{array}$ , transmissibility $\begin{array}{l}\sigma\end{array}$ and pressure diffusivity $\begin{array}{l}\chi\end{array}$ are called basic diffusion model parameters as they are essential components of all diffusion models.

Below are the major types of PTA with abbreviation and indication of well flow status during the test:

Drawdown Test	Injection Test	Build-up Test	Fall off Test	Multirate Step Test	Pressure Interference Test
DD	INS	BUS	FOS	MRST	PIT
Producer	Injector	Producer	Injector	Producer / Injector	Producer / Injector → Producer / Injector
FLOWING	FLOWING	SHUT-IN	SHUT-IN	FLOWING	FLOWING → SHUT-IN

Objectives

Primary deliverables	Math Symbol	Conditional Deliverables	Math Symbol
Current Formation pressure	$\begin{array}{l}p_e\end{array}$	Initial formation pressure assuming no or little historical interference with offset wells	$\begin{array}{l}p_i\end{array}$
Skin-factor	$\begin{array}{l}S\end{array}$	Formation damage as permeability deterioration assuming damage penetration is known Formation damage penetration assuming damage value is known Fracture-network development around the well
Formation transmissibility	$\begin{array}{l}\sigma\end{array}$	Permeability assuming flowing thickness $\begin{array}{l}h\end{array}$ is known Flowing thickness assuming permeability $\begin{array}{l}k\end{array}$ is known Water-oil column assuming permeability $\begin{array}{l}k\end{array}$ and flowing thickness $\begin{array}{l}h\end{array}$ are both known	$\begin{array}{l}k\end{array}$ $\begin{array}{l}h\end{array}$ $\begin{array}{l}h_{OWC}\end{array}$
Minimum drainable volume around the well	$\begin{array}{l}V_\phi\end{array}$	Minimum hydrocarbon reserves around the well Drainage area around the well assuming flowing thickness $\begin{array}{l}h\end{array}$ is known Flowing thickness assuming the drainage area $\begin{array}{l}A\end{array}$ around the well is known Boundary proximity assuming the circular boundary	$\begin{array}{l}V_{hc}\end{array}$ $\begin{array}{l}A_e\end{array}$ $\begin{array}{l}h\end{array}$ $\begin{array}{l}r_e\end{array}$
Minimum drainable area around the well	$\begin{array}{l}A_e\end{array}$	Half-size of drainage area $\begin{array}{l}r_e\end{array}$ providing the shape of the drainable area is known
Boundary type	$\begin{array}{l}PSS, \, SS, \, BAFFLE\end{array}$
Effective horizontal section	$\begin{array}{l}L_f\end{array}$
Hydraulic fracture size	$\begin{array}{l}X_f\end{array}$
Dynamic fracture opening threshold	$\begin{array}{l}\delta P_{X_f}\end{array}$
Proximity $\begin{array}{l}r_{ext}\end{array}$ of the remote reservoir composition Transmissibility $\begin{array}{l}\sigma_{ext}\end{array}$ of the remote reservoir composition	$\begin{array}{l}W_{ch}, \, D_{ch}\end{array}$ $\begin{array}{l}R_{owf}\end{array}$ $\begin{array}{l}R_{ogf}\end{array}$	Channel width and proximity to its nearest boundary Proximity to oil-water front Proximity to oil-gas front
Scanning area around the well	$\begin{array}{l}A_{\rm scan}\end{array}$	Scanning radius of the area $\begin{array}{l}r_{\rm scan}\end{array}$ around the well assuming radial isobaric propagation