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Specific type of Pressure Tests performed in cased-hole well and related to correlation between Both downhole (BHP) and surface (THP)  and flowrates in the same or remote well.


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).


The quantitative interpretation of pressure transitions is based on pressure diffusion model and is a subject of the Pressure Transient Analysis (PTA).


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


Objectives



Primary deliverablesMath SymbolConditional DeliverablesMath Symbol

Current formation pressure

p_e

Initial formation pressure assuming no or little historical interference with offset wells

p_i

Skin-factor

S

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

\sigma

Permeability assuming flowing thickness h is known

Flowing thickness assuming permeability k is known

Water-oil column assuming permeability k and flowing thickness h are both known

k

h

h_{OWC}

Minimum drainable volume around the well

V_\phi

Minimum hydrocarbon reserves around the well

Drainage area around the well assuming flowing thickness h is known

Flowing thickness assuming the drainage area A around the well is known

Boundary proximity assuming the circular boundary

V_{hc}

A_e

h

r_e

Minimum drainable area around the well

A_e

Half-size of drainage area r_e providing the shape of the drainable area is known


Boundary type


PSS, \, SS, \, BAFFLE



Effective horizontal section

L_f



Hydraulic fracture size

X_f



Dynamic fracture opening threshold

\delta P_{X_f}



Proximity r_{ext} of the remote reservoir composition

Transmissibility \sigma_{ext} of the remote reservoir composition

W_{ch}, \, D_{ch}

R_{owf}

R_{ogf}

Channel width and proximity to its nearest boundary

Proximity to oil-water front

Proximity to oil-gas front


Scanning area around the well

A_{\rm scan}

Scanning radius of the area r_{\rm scan} around the well assuming radial isobaric propagation


Interpretation




Samples




Fig. 1. Transient response in vertical well.

Pressure drop is in blue and log-derivate of Pressure drop is in red

Fig. 2. Transient response in horizontal well

Pressure drop is in blue and log-derivate of Pressure drop is in red


See Also


Petroleum Industry / Upstream / Subsurface E&P Disciplines / Well Testing / Pressure Testing

Well & Reservoir Surveillance ]

References



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