Modelling and Computation for Petroleum Systems in Basins with Complex Structural Geometries
Researcher: Jane Lee- Academic Supervisors: Robert Van Gorder, Kathryn Gillow, Jonathan Whiteley
- Industrial Supervisors: Remco Groenenberg, William Senior, Konstantinos Leventis
Background
Hydrocarbons are found in rocks within sedimentary basin below the Earth’s surface. Whilst they remain a primary energy source, many hydrocarbon fields are nearing depletion, and new, more advanced exploration and recovery techniques are required to find new reserves and sustain production. One such technique aims at predicting the evolution of pressure and temperature profiles within basins from past to present, to determine whether in the past there was potential for hydrocarbon generation in a certain location. Furthermore, this technique is used for predicting pore pressures in the subsurface at present day to reduce drilling risk.
In this project, we identify and mathematically model the primary geological processes within a sedimentary basin. We develop a fundamental model which describes the compaction of sediment within a basin as a function of burial, and its influence on the porosity, pressure, and temperature profiles. This results in a highly co-dependent system of equations. We use the finite-element method to develop a solver which can tackle our full model in multiple dimensions. Building from the fundamental solver, we aim to develop and employ further numerical techniques which can account for real and physical boundary conditions, as well as complex geological structures within the basin. Such structures include sills, faults, and salt domes.
Progress
We derived a new mathematical model which improves on the current one used in industry. It is able to incorporate both mechanical and chemical compaction and is developed in such a way that complex geological structures such as faults (lines along which sedimentary layers break and separate from their original geometry), salt domes, and sills (horizontal magmatic intrusion) can be easily incorporated. A sedimentary basin (in Utah) which contains a sill and faults is shown in Figure 1 (below).
Figure 1: A sedimentary basin in Utah with a sill and faults.
Currently, we have an initial solver that can evaluate the variable profiles in a compacting basin. We use the finite element method for our entire system and use the open source deal.ii library. For the sake of efficiency, we build the solver to allow for multiple solution methods (direct, CG, for example) as well as adaptive meshing. The latter is particularly useful when introducing discontinuities, such as sills, that result in large jumps in variables (such as temperature) over a relatively small spatial range. An example of the resulting mesh with a sill in the middle of the basin is pictured in Figure 2 (below).
Figure 2: An adaptively-refined mesh resulting from a scenario with a sill in the middle of the basin.
Future Work
We are interested in developing an efficient solver which is flexible enough to account for all the geological phenomena mentioned above in a single run. This will allow us to calculate the main geological processes in the most realistic physical setting possible, and thereby predict pressure and temperature profiles and potential hydrocarbon presence more accurately.