Simulation Experiments and Characteristics of Secondary Migration Driving Force of Tight Oil: A Case Study of Jurassic in Middle Sichuan

Abstract

Abstract

In traditional petroleum geology theory, the main secondary migration driving force of petroleum is buoyancy or hydrodynamic force or both of them. However, as the rapid rising of its production, tight oil is becoming an important petroleum resource, and it is uncertain that whether those two forces still be the main secondary migration driving force. There are two reasons cause the uncertainty. The first one is the extremely low porosity and permeability of tight reservoir, which causes much larger migration resistance than that in conventional reservoir. The second one is the absence of necessary geology conditions for the formation of huge buoyancy and hydrodynamic force in tight oil producing regions.

Then, how large is the migration resistance in tight reservoir? Can buoyancy or hydrodynamic force overcome this resistance? If not, which kind of force can? To solve these problems, tight oil of Jurassic in Middle Sichuan was taken as an example to investigate the driving force characteristics of tight oil secondary migration. The physical analog experiments and geological data from the oil field were utilized in the paper.

According to the physical analog experiments of secondary migration resistance, magnitude of the resistance is about 10MPa, while the maximum buoyancy is only 0.09065MPa. Meanwhile, the production data from oil field also suggests that the water content of 80% of producing wells are less than 5%, which indicates the lack of material foundation for the formation both of buoyancy and hydrodynamic force. What's more, relation between oil and groundwater is complex, indicating the lack of buoyancy effect. On the other hand, physical analog experiment of hydrocarbon generation pressurization proves that maximum overpressure caused by hydrocarbon generation can be 38MPa, large enough to break through the migration resistance in tight reservoir. Moreover, the positive correlation between single well output and formation pressure coefficient is another proof for the viewpoint that overpressure is closely connected with the accumulation of tight oil. To sum up, not buoyancy but hydrocarbon generation pressurization serves as the main secondary migration driving force of tight oil. Acquiring the source of migration driving force of tight oil is of great significance during exploration for this new resource.

AAPG Datapages/Search and Discovery Article #90260 © 2016 AAPG/SEG International Conference & Exhibition, Cancun, Mexico, September 6-9, 2016