Loading history dependence of stress field around salt diapirs due to path dependence of visco-elasto-plastic rheology

<p>One of the most unstable and unpredictable process in sedimentary basin is salt diapir movement. It changes the structure of strata and can break its integrity and make trap structures for hydrocarbons. The movement of salt diapir through geologic timescale can be described in viscous terms, elastic terms were used to predict the geomechanical response of sediment surroundings.</p><p>This work describes the workflow of visco-elastic flow modeling of salt diapirism process. Salt has different geomechanical property such as much lower viscosity comparing to typical sediments. Mixed rheology make different geomechanical response such as stress, which cannot be solved in the same timescale.  To solve the problem of different timescales of viscous and elastic flow there was used a pseudo-transient method of solving the system of equations. Used equations calculate full stress tensors and pressure over time which can help in understanding of stress evolution around salt diapir. Maximizing time step during each calculation was accomplished with density scaling, which assumes that inertial forces are negligible.</p><p>The used approach allows taking into account the loading history and easily can be supplemented with sedimentation mechanisms.</p>

Dynamic Response Interaction of Vibrating Offshore Pipeline on Moving Seabed

The dynamic response interaction of a vibrating offshore pipeline on a moving seabed is herein investigated where the pipeline is idealized as a beam vibrating on an elastic foundation. This problem is of relevance in offshore exploration where pipelines are laid either on or buried in the seabed. When such pipes carry oil and gas, the undulating topography of the sea floor and the internal motion of the fluid subject the entire structure to vibration due to bending forces and form the subject of our study. Our analysis revealed that in general, the seabed acts either as a damper or as a spring and in particular when we have sedimentation, the seabed geology permits the geomechanical property of the sediment cover to act only as a damper. As expected, external excitation will increase the response of these pipes for which an amplification factor has been derived. For soft beds, high transverse vibrations were dampened by increasing the internal fluid velocity whereas they became amplified for hard beds. These results are of contemporary interest in the oil/gas industry where deep sea exploration is now receiving significant attention.