Analysis of pressure transition dynamics and associated interpretation workflow in terms of wellbore and formation properties.
Despite the explicit name It does not necessarily refer to analysis of a stand-alone pressure transient and also cover the complex pressure histories.
Both downhole and surface pressure records can be a source of information recoverable through PTA.
The pressure is usually recorded downhole but the surface pressure can be also informative.
Motivation
Changing production (or injection) rate is leading to pressure response which depends on the properties of connected beddings.
This gives an idea of assessing well and formation properties by analysing a pressure transition from one flow regime to another
The quantitative interpretation of PTA is based on pressure diffusion model.
There are three major types of PTA:
Objectives
| Primary deliverables | Conditional Deliverables | |||
|---|---|---|---|---|
| 1 | Assess current formation pressure | p_e | ||
| 3 | Assess skin-factor | S | Assess formation damage Assess formation penetration Identify fracture-network development around the well | |
| 4 | Assess formation transmissibility | \sigma | Assess permeability k assuming flowing thickness h is known Assess flowing thickness h assuming permeability k is known Assess water-oil column assuming permeability k and flowing thickness h are both known | |
| 5 | Assess minimum drainable volume around the well | V_\phi | Assess minimum hydrocarbon reserves around the well Assess drainage area A around the well assuming flowing thickness h is known Assess flowing thickness h assuming the drainage area A around the well is known | |
| 6 | Identify boundary type PSS, \, SS, \, BAFFLE and assess its proximity r_e | |||
| 7 | Identify fracture presence and assess its size X_f | |||
| 8 | Assess the fracture opening threshold \delta P_{X_f} | |||
| 9 | 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
|
|
| Fig. 1. Transient responses in vertical producer | Fig. 2. Transient responses in horizontal producer |
