Hydrocarbon Migration – An Old Friend or Foe?
Robert G. Tscherny and Marek Kacewicz
Chevron Energy Technology Company, Houston, Texas
Forecasting of hydrocarbon volume and quality (gas-oil-ratios, oil densities, viscosities, and more) is critical in play and prospect appraisal. The forecast depends on the quality of input data and resolution. Hydrocarbon volume potentially accumulated in reservoirs is a function of generated and expelled hydrocarbons minus hydrocarbon losses along migration pathways from source to trap. The quantification of migration losses, which is key component of volumetric analysis, depends on many factors including utilized migration algorithms, meshing routines, and selected numerical solvers.
Hydrocarbon migration modeling incorporates three main aspects: selection of physics (assumptions), algorithmic implementation, and workflows utilized by different software packages. Classic approaches e.g., Darcy flow assumes three factors controlling hydrocarbon migration: gravity, viscosity and capillarity. Typically they result in more hydrocarbons left behind. Simpler physics e.g., omitting viscosity leads to methods such as invasion percolation that typically produce different (more focused) hydrocarbon migration pathways and less hydrocarbons left behind. Basin models utilizing same basin modeling framework (geometry, ages, phases, etc.) but assuming different physics (using different flow algorithms) are associated with different volumes of hydrocarbons left behind, i.e. different migration losses.
This paper discusses hydrocarbon migration problem emphasizing differences between migration methods and software implementations. Presented basin to prospect scale case studies from West Africa and Gulf of Mexico demonstrate that different migration concepts may result in significant differences in estimated migration losses which can be critical in day-to-day exploration.
AAPG Search and Discovery Article #120098©2013 AAPG Hedberg Conference Petroleum Systems: Modeling the Past, Planning the Future, Nice, France, October 1-5, 2012