In many practical cases the reservoir fluid flow created by well is getting aligned with a radial direction towards or away from well.
This type of reservoir fluid flow is called radial fluid flow and corresponding pressure diffusion models provide a diagnostic basis for pressure-rate base reservoir flow analysis.
The radial flow can be infinite acting or boundary dominated or transiting from one to another.
Although the actual reservoir fluid flow may not have an axial symmetry around the well-reservoir contact or around reservoir inhomogeneities (like boundary and faults and composite areas) but still in many practical cases the reservoir flow tends to become radial after some time which makes a Radial Flow Pressure Diffusion @model (in its general form or in particular BVP solution) a popular diagnostic tool.
Inputs | Outputs | ||
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total sandface rate | reservoir pressure | ||
initial formation pressure | well bottomhole pressure | ||
skin-factor | |||
wellbore radius | |||
drainage radius (could be infinite) |
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Radial fluid flow | Homogenous reservoir | Infinite boundary | Zero wellbore radius | Slightly compressible fluid flow | Constant rate | Constant skin |
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There is no universal analytical solution to the above problem – but it can be always presented as below:
where is a single-argument function describing the peculiarities of the diffusion model (well geometry, penetration geometry, formation inhomogeneities, hydraulic fractures, boundary conditions, etc.). The fact that solution of equations – can be presented as – finds a lot of practical applications in Well Testing. |
Equations and show how the basic diffusion model parameters impact the pressure response while other diffusion parameters are encoded in function and play important methodological role as they are used in many algorithms and express-methods of Pressure Testing.
In case of infinite homogeneous reservoir, produced by a infinitely small vertical well with no skin and no wellbore storage the function has an exact analytical formula, given by exponential integral (see Line Source Solution (LSS) @model). |
PTA – Pressure Transient Analysis
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The instantaneous Total Sandface Productivity Index for low-compressibility fluid and low-compressibility rocks does not depend on formation pressure, bottomhole pressure and the flowrate and can be expressed as:
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Isobar equation for a constant-rate production:
This leads to estimation of isobar velocity:
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Physics / Mechanics / Continuum mechanics / Fluid Mechanics / Fluid Dynamics / Radial fluid flow / Pressure diffusion / Pressure Diffusion @model
Petroleum Industry / Upstream / Subsurface E&P Disciplines / Well Testing / Pressure Testing
[ Well & Reservoir Surveillance ]
[ Line Source Solution (LSS) @model ] [ Linear Flow Pressure Diffusion @model ]
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