Modelling facility for field-average formation pressure at any time moment as response to production flowrates history:
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where
Cumulative oil production by the time moment | |||
initial oil+gas pay drainage volume (excluding the aquifer and gas cap) | Cumulative gas production by the time moment | ||
pore compressibility | Cumulative water production by the time moment | ||
initial water saturation | Cumulative water injection by the time moment | ||
initial gas saturation | Cumulative gas injection by the time moment | ||
initial oil saturation: | Cumulative water influx from Aquifer Expansion by the time moment | ||
Oil formation volume factor as functions of reservoir pressure | Cumulative gas influx from Gas Cap expansion by the time moment | ||
Gas formation volume factor as functions of reservoir pressure | |||
Water formation volume factor as functions of reservoir pressure | |||
Solution GOR and Vaporized Oil Ratio as functions of reservoir pressure |
The MatBal equation is often complemented by constant PI model of Bottom-Hole Pressure ( for producers and for injectors):
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where | where | ||||
cumulative offtakes from -th producer by the time moment | cumulative intakes to -th injector by the time moment | ||||
productivity index of -th producer | injectivity Index of -th injector |
In practice there is no way to measure the external influx and so that one need to model them and calibrate model parameters to fit available data on production flowrates history and formation pressure data records.
There is a list of various analytical Aquifer Drive and Gas Cap Drive models which are normally related to pressure dynamics :
Gas Cap Drive @model | Aquifer Drive @model | ||
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which closes equation for the pressure .
In some specific cases equation can be explicitly integrated:
Low pressure dry gas | |||
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where
drainage volume |
This allows using simple graphical methods for estimating drainage volume .
Petroleum Industry / Upstream / Production / Subsurface Production / Field Study & Modelling / Production Analysis / Material Balance Analysis (MatBal)
[ Material Balance Pressure Plot ][ FMB Pressure @model]
[ Derivation of Material Balance Pressure @model ]