Geothermal wells with water hammer during injection fall-off test: Numerical pressure transient analysis

• Published in: Geothermics Vol. 87; p. 101838
• Main Authors: Adiputro, Azhari S., Zarrouk, Sadiq J., Clarke, Richard J., Harcouët-Menou, Virginie, Bos, Stijn
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-09-2020; Elsevier Science Ltd
• Subjects: Belgium; Deep geothermal well; Fractional dimension; Fractured reservoir; Geothermal power; Injection fall-off test; Numerical PTA; Oscillations; Permeability; Pressure; Reservoirs; Transient analysis; Water hammer; Water wells; Wave equations; Injection fall-off test; Deep geothermal well; Fractured reservoir; Water hammer; Belgium; Fractional dimension; Numerical PTA
• ISSN: 0375-6505; 1879-3576
• DOI: 10.1016/j.geothermics.2020.101838

•Geothermal well test data with oscillations can not be interpreted using analytical methods.•Water hammer effects resulting from valve shutting off observed immediately after valve closure.•Numerical PTA framework with fractional dimension grid gave low permeability and small fractures.•Water hammer effect investigated using the wave equation provided estimates of reservoir extent.
Extended pressure fall-off test data of low permeability wells can display oscillations that cannot be easily interpreted by using the existing analytical pressure transient analysis (PTA) methods. Additionally, water hammer effects resulting from wellhead valve shutting off are observed immediately after valve closure.
Numerical PTA applied to well MOL-GT-03, Belgium, using 1-D radial model with fractional dimension grid gave a good match with field data clearly indicating low reservoir permeability and the fractured nature of the reservoir. In addition, the water hammer effect was investigated by solving the wave equation to help identifying the extent of the well reach providing an estimate to the reservoir boundary.