Simulation of Mushroom Caps on Salt in Barents Sea, Norway

• Published in: Energy Exploration & Exploitation
• Main Authors: Yu, Z., Lerche, I.
• Format: Article in Journal/Newspaper
• Language: English
• Published: SAGE Publications 1991
• Subjects: Barents Sea; Norway
• Online Access: http://dx.doi.org/10.1177/014459879100900301; https://journals.sagepub.com/doi/pdf/10.1177/014459879100900301

Various shapes of moving salt were simulated in response to gravity contrast and tectonic movement, and the deformations and fractures of the surrounding sediments examined. The varying parameters in the model include the burial depth of the salt base, the overhang depth of the salt cap, the salt body's size, the salt speed of motion, and the sediment depositional rate. Variation of the surrounding rock properties with depth, such as Lame constants, shearing strength, internal friction were also considered. Mohr's criterion (Mohr, 1900) for failure was applied, allowing an indication of where fractures occur and their orientations. Including the thermal effects of salt in the models yields features favorable to hydrocarbon accumulation: (1) Fractures generated near the vertical salt body and below the mushroom cap salt provide a continuous pathway for hydrocarbon migration due to the enhancement of permeability; (2) The overhanging cap salt sheet provides a good trapping mechanism by formation of seals; (3) The thermal effect of salt enhances the maturity of the source rocks; (4) The observed faulting behaviour around the salt body is accounted for by primary and secondary fracture development as exhibited through the simulations. Application of modelling to the study of a salt diapir in Barents Sea, Norway, shows that the salt would most likely start to rise during the Early-Mid Triassic and Jurassic when the sediment cover was about 1700–2400 m. Depositional faulting was associated with salt diapir motion. The modelling also indicates that at least 1000 m of the salt cap was eroded, based on the dip angles of sedimentary strata against the salt stock.