Hydrocarbon Exploration Potential Along the Upper Thamama Hydrocarbon Migration Pathways of Abu Dhabi
Hydrocarbon Exploration Potential Along the Upper Thamama Hydrocarbon Migration Pathways of Abu Dhabi Tuesday 4th May, 2021 , time: 3:00 PM (GST)
By Ahmed Taher
SpeakerAhmed Taher (ADNOC - Upstream)
Historically, oil and gas discoveries were from conventional four-way dip closures or from stratigraphic traps, and directly produced from mature source rock kitchens. Inbetween conventional traps and unconventional kitchens are migration pathways. Migration pathways work not only as conduits, or as a link between source rock kitchens and conventional traps, but they also contain significant volumes of oil - possibly more than those discovered in the conventional and unconventional resources. In addition to saturated migration pathways rocks, a significant part of this oil is movable and can be discovered in a subtle trap that developed along the hydrocarbon migration pathway. Faults and heterogeneity along migration pathways act as a lateral seal and result in hydrocarbon accumulations behind these barriers. Oil accumulations in these secondary migration pathways may represent a huge potential for future exploration activities. The Upper Thamama migration pathways, in east and central Abu Dhabi for example, may represent one of the best potential areas for oil accumulation in secondary migration pathways. Some of the well-known conventional fields in these areas are in reality migration pathways fields. Also, some of the stratigraphic traps in Wasia Group formations are other examples of hydrocarbon exploration potential in migration pathways. Some studies suggest that less than 10% of the generated hydrocarbons has reached the conventional traps and more than 50% of the generated hydrocarbons are trapped in the migration pathways. The trap mechanisms along the migration routes were developed in response to the presence of segmented faults that down-step the tight rocks encountered in the porous reservoirs. Also, diagenetic traps can develop in response to the presence of an equilibrium state between the buoyancy forces trying to move the hydrocarbon through the rocks and the capillary pressures in the low permeable layer that resist these movements. The only requirement to develop such traps is for the capillary pressure to be greater than the migration buoyancy forces. Smaller pore throat sizes will greatly enhance the seal capacity, especially for the larger oil molecules that were expelled during early oil generation which plugged the small pore throat sizes and resulted in larger oil columns. The improved technologies in seismic imaging, basin modeling, horizontal drilling, fracture testing and steam injection will result in discovering commercial volumes of hydrocarbon that are accumulated in subtle traps along the migration pathways.
Ahmed Taher is a Geology Exploration Specialist with ADNOC Upstream in the Exploration Studies Division. Ahmed has been with ADNOC since 1982 and has conducted more than 45 in-house technical reports and published more than 33 technical papers. Some of these publications are considered the standard reference for the discussed topics and are frequently quoted in other articles. His main focus areas are in stratigraphic traps, tight gas potential, unconventional resources evaluation and basin modeling.