Interpretation workflow of pressure transitions in pressure test data in terms of well properties and formation properties of connected subsurface reservoirs.
It may
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 formation properties by analysing a pressure transient from one flow regime to another and which is called Pressure Transient Analysis.
Definition
Pressure Transient Analysis (PTA) is a single-well pressure dynamic survey and associated interpretation workflow in terms of wellbore and formation properties.
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refer to analysis of a stand-
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alone pressure transient or several pressure transients (MRST) and may also cover
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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
The pressure is usually recorded downhole but the surface pressure can be also informative.
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is based on pressure diffusion model.
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There are three major types of PTA:
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Below are the major types of PTA with abbreviation and indication of well flow status during the test:
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Objectives
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Primary deliverables | Math Symbol | Conditional Deliverables |
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Math Symbol |
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Current Formation |
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Initial formation pressure assuming no or little historical interference with offset wells |
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Assess formation damage
Assess formation penetration
Formation damage as permeability deterioration assuming damage penetration is known Formation damage penetration assuming damage value is known Fracture |
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-network development around the well |
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Permeability assuming flowing thickness
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Flowing thickness assuming permeability
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Water-oil column assuming permeability
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Minimum |
drainable volume around the well |
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Minimum hydrocarbon reserves around the well |
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Drainage area around the well assuming flowing thickness
Flowing thickness assuming the drainage area
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is known Boundary proximity assuming the circular boundary |
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Minimum drainable area around the well |
| Half-size of drainage area
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Boundary type |
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Effective horizontal section |
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Hydraulic fracture size |
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Dynamic fracture opening threshold |
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Proximity |
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Pick up the channel size/proximity
of the remote reservoir composition |
| Channel width and proximity to its nearest boundary Proximity to |
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oil-water front |
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Proximity to |
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oil-gas front |
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Scanning area around the well |
| Scanning radius of the area
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Interpretation
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Samples
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Fig. 1. Transient |
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response in vertical |
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well. Pressure drop is in blue and log-derivate of Pressure drop is in red | Fig. 2. Transient |
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response in horizontal well Pressure drop is in blue and log-derivate of Pressure drop is in red |
See Also
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Petroleum Industry / Upstream / Subsurface E&P Disciplines / Well Testing / Pressure Testing
[ Well & Reservoir Surveillance ] [ PTA Diagnostic Plot ]
[ Rate Transient Analysis (RTA) ]
References
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