Specific interpretation workflow of pressure transitions in terms of well properties and formation properties of connected subsurface reservoirs.
Despite the explicit name It does not necessarily refer to analysis of a stand-alone pressure transient and also cover the complex pressure histories with numerous pressure transitions.
Both downhole and surface pressure records can be a source of information recoverable through PTA.
The quantitative interpretation of pressure transitions is based on pressure diffusion model.
Below are the major types of PTA:
Objectives
| Primary deliverables | Math Symbol | Conditional Deliverables | Math Symbol | |
|---|---|---|---|---|
Assess current formation pressure | p_e | Assess initial formation pressure assuming no or little historical interference with offset wells | p_i | |
Assess skin-factor | S | Assess formation damage Assess formation penetration Identify fracture-network development around the well | ||
Assess formation transmissibility | \sigma | Assess permeability assuming flowing thickness h is known Assess flowing thickness assuming permeability k is known Assess water-oil column assuming permeability k and flowing thickness h are both known | k h h_{OWC} | |
Assess minimum drainable volume around the well | V_\phi | Assess minimum hydrocarbon reserves around the well Assess drainage area around the well assuming flowing thickness h is known Assess flowing thickness assuming the drainage area A around the well is known Assess boundary proximity assuming the circular boundary | V_{hc} A_e h r_e | |
| Assess minimum drainable area around the well | A_e | |||
Identify boundary type | PSS, \, SS, \, BAFFLE | |||
Identify fracture presence and assess its size | X_f | |||
Assess the fracture opening threshold | \delta P_{X_f} | |||
Assess the presence r_{ext} of remote reservoir composition areas and its transmissibility \sigma_{ext} | Pick up the channel size/proximity Pick up the oil-water front and its proximity Pick up the oil-gas front and its proximity |
Interpretation
Samples
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| Fig. 1. Transient responses in vertical producer | Fig. 2. Transient responses in horizontal producer |
