Natural sealing of leaky wells by creep of rocksalt
conference paper
Wells drilled through salt formations can be subject to leakage if a (micro)annulus is present between the salt formation and well casing that allows significant fluid flow over large well sections. Laboratory experiments were performed to assess if natural sealing by rocksalt creep can close flow paths over such a salt-casing annulus. The experiments were performed on a scaled down well system consisting of a casing in a hollow salt sample that was placed in a triaxial deformation apparatus. The applied experimental conditions were equivalent to conditions of Zechstein salt at ~2.5 km depth in the Netherlands. Sealing of flow through the salt-casing annulus was observed. Salt seals could sustain more than 35 bar of pressure difference over the 100 mm casing length for both brine-filled and oil-filled annulus after 5-8 days of creep, up to a maximum of 148 bar after 7-10 days of creep. The timing of sealing barrier formation critically depends on temperature and difference between axial/radial stress and annulus pressure. The experimental results show that salt creep can effectively close a salt-casing annulus at conditions relevant for leaky wells drilled through salt overlying reservoirs used for hydrocarbon production or storage of CO2 or H2.
Topics
TNO Identifier
997001
Publisher
ARMA, American Rock Mechanics Association
Source title
This paper was prepared for presentation at the 58th US Rock Mechanics/Geomechanics Symposium held in Golden, Colorado, USA, 23-26 June
2024
2024
Pages
1-11
Files
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