Oil and gas migration: chemical and physical constraints
Primary migration of oil in aqueous solution is not possible because the composition of dissolved hydrocarbons is vastly different from that of crude oils. Migration oil solubilized in surfactant micelles is also rejected. Migration by oil-droplet expulsion also is not feasible. It is proposed that oil and gas are generated in, and flow from, source rock in a three-dimensional organic-matter (kerogen) network. Oil or gas flowing in this hydrophobic network would not be subject to interfacial forces until it entered the much larger water-filled pores in the reservoir rock. Secondary migration of separate-phase oil and gas should occur by buoyancy, when their saturations attain 20 to 30% along the upper or lower surfaces of the reservoir rock. Oil or gas entering at the lower surface would intermittently cross the rock when the buoyancy head became sufficient. In contrast, secondary migration of gas or oil in solution would be very inefficient and require large volumes of water. Unless all pores in the reservoir rock attained 20 to 30% gas or oil saturation, separate-phase flow could not occur, and oil and gas would remain locked in the pores and would not form reservoirs in trap positions. Residual gas and oil in cores taken along suspected secondary-migration pathways should show this residual gas or oil saturation, and recovered water should always contain equilibrium concentration of dissolved hydrocarbons, but this has seldom been observed. The proposed mechanisms of primary migration of oil and gas through a kerogen network, and secondary migration by separate-phase buoyant flow do not require the flow of water. Water flow probably disperses water-soluble constituents instead of concentrating them in reservoir traps. 4 figures, 8 tables.
- Research Organization:
- Chevron Oil Field Research Co., La Habra, CA
- OSTI ID:
- 5580802
- Journal Information:
- Am. Assoc. Pet. Geol. Bull.; (United States), Journal Name: Am. Assoc. Pet. Geol. Bull.; (United States) Vol. 63:5; ISSN AAPGB
- Country of Publication:
- United States
- Language:
- English
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020200* -- Petroleum-- Reserves
Geology
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03 NATURAL GAS
030200 -- Natural Gas-- Reserves
Geology
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BITUMINOUS MATERIALS
CARBONACEOUS MATERIALS
CHEMICAL PROPERTIES
ENERGY SOURCES
FLUIDS
FOSSIL FUELS
FUEL GAS
FUELS
GAS FUELS
GASES
HYDROCARBONS
KEROGEN
MIGRATION
NATURAL GAS
ORGANIC COMPOUNDS
PETROLEUM
PHYSICAL PROPERTIES
RESERVOIR ROCK
ROCKS