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Quantifying Salt Induced Stress Anomalies to Assist in Targeting Wells Near Salt WeldsNormal access

Authors: S. Grebe and H.L.J.G. Hoetz
Event name: 76th EAGE Conference and Exhibition 2014
Session: Geomechanics and Fracture Propagation
Publication date: 16 June 2014
DOI: 10.3997/2214-4609.20141075
Organisations: EAGE
Language: English
Info: Extended abstract, PDF ( 729.38Kb )
Price: € 20

Summary:
Hydrocarbon reservoirs below salt welds are exposed to stress anomalies due to point loading from the overburden. This affects not only reservoir properties like porosity and permeability but also can lead to erroneous depth prognosis due to increased acoustic velocities in the vicinity of salt welds. An accurate prediction of the 'Salt Induced Stress Anomaly' (SISA) is required to reduce the risk of disappointing wells due to depth errors and/or diagenetically altered reservoirs. Correct SISA predictions require an understanding of the key controlling factors. The effect of the detailed geometry of a salt weld and its surrounding structures and the elastic rock properties are investigated using a numerical 2D Finite Difference model. A case where the SISA effect was observed in the Dutch North Sea is reproduced with this approach. The modelled stress anomaly at the weld (additional vertical stress) amounts to 38 MPA. This result can be compared with an independent stress anomaly estimate of 35 MPa based on sonic well data.


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