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A specific implementation of Well Testing based on recording and interpretation of borehole (downhole or THP) pressure response to the pre-designed sequence of increasing and decreasing flow rate variations (also called "cycles" or "pulses" ) at one or more disturbing wells wells (called "generators" or "pulsers") inducing pressure pulse propagation across the field.
The usual practise practice is to create 3 5 – 5 10 pulses.The pressure response can be recorded in
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It splits into two categories:
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| Pressure Pulse Interference Test (PIT) | |
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The pressure response to rate variation are both recorded in the same well | The pressure response to rate variation is recorded in the offset wells |
Workflow
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| 1 | Designing flowrate variation pulse sequence for disturbing wells (also called generators) based on the field primary data |
| 2 | Field operations on suspending the downhole gauges (if PDG is not available) |
| 3 | Performing flowrate variations according to the PCT design |
| 4 | Retrieving the downhole gauges |
| 5 | Downloading the data from the downhole and surface gauges |
| 6 | Primary data processing (gauge syncronization and filtering) |
| 7 | Implementing pressure pulse-code decomposition (PCD) |
| 8 | Recognising |
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the PTA type-library |
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diffusion models for decomposed DTR/CTR |
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and type-curve fitting them with analytical and/or |
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numerical pressure diffusion |
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Data Processing
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In case of harmonic pressure pulsations and sufficiently long pressure-rate delay and a simple diffusion model (single-bed homogeneous reservoir without boundary) the pressure response can be approximated by analytical model. In this case the pressure data at receiving wells are being detrended and then matched to analytical model.
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In this case the actual pressure responses should be decoded from pressure data records at receiving well using specialised pressure pulse-code decomposition algorithms and then decomposed DTR/CTR is recongised PTA type-library diffusion models and matched by diffusion modelmodels.
This type of tests is called Pressure Pulse-Code Test but this approach is equally applicable to simple periodic pulsations.
Interpretation
References
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| group | arax |
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See Also
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Petroleum Industry / Upstream / Subsurface E&P Disciplines / Well Testing / Pressure Testing / Cased-Hole Pressure Transient Test / Pressure Interference Test (PIT)
[ Well & Reservoir Surveillance ] [ Unit-rate transient response (UTR) ] [ Pressure Pulse Propagation ]
References
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| title | heap |
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С некоторыми из вышеприведенных недостатков можно побороться с помощью метода фильтрационных волн давления (ФВД), которые являются модификацией классического метода ступенчатого гидропрослушивания. В этом случае, на возмущающей скважине меняют режим работы периодически (как правило, чередуя пуск и останов скважины), задавая порядка 3 – 5 циклов и используют приближенные аналитические оценки скин-фактора, гидропроводности и пьезопроводности. Разработаны аналитические методы, которые интерпретируют циклы с несимметричными плечами (время работы и время остановки скважины не одинаковы).
Однако на практике очень редко когда удается выдержать циклирование с высокой точностью и в итоге аналитические методы не дают аккуратных оценок и требуется переход на численные методы интерпретации ФВД.
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