Hydrocarbon distribution rules in the deep and shallow parts of sedimentary basins are considerably different, particularly in the following four aspects. First, the critical porosity for hydrocarbon migration is much...Hydrocarbon distribution rules in the deep and shallow parts of sedimentary basins are considerably different, particularly in the following four aspects. First, the critical porosity for hydrocarbon migration is much lower in the deep parts of basins： at a depth of 7000 m, hydrocarbons can accumulate only in rocks with porosity less than 5%. However, in the shallow parts of basins （i.e., depths of around 1000 m）, hydrocarbon can accumulate in rocks only when porosity is over 20%. Second, hydrocarbon reservoirs tend to exhibit negative pressures after hydrocarbon accumulation at depth, with a pressure coefficient less than 0.7. However, hydrocarbon reservoirs at shallow depths tend to exhibit high pressure after hydrocarbon accumulation. Third, deep reservoirs tend to exhibit characteristics of oil （-gas）-water inversion, indicating that the oil （gas） accumulated under the water. However, the oil （gas） tends to accumulate over water in shallow reservoirs. Fourth, continuous unconventional tight hydrocarbon reservoirs are distributed widely in deep reservoirs, where the buoyancy force is not the primary dynamic force and the caprock is not involved during the process of hydrocarbon accumulation. Conversely, the majority of hydrocarbons in shallow regions accumulate in traps with complex structures. The results of this study indicate that two dynamic boundary conditions are primarily responsible for the above phenomena： a lower limit to the buoyancy force and the lower limit of hydrocarbon accumulation overall, corresponding to about 10%-12% porosity and irreducible water saturation of 100%, respectively. These two dynamic boundary conditions were used to divide sedimentary basins into three different dynamic fields of hydrocarbon accumulation： the free fluid dynamic field, limit fluid dynamic field, and restrain fluid dynamic field. The free fluid dynamic field is located between the surface and the lower limit of the buoyancy force, such that hydrocarbons in this field migrate and accumulate展开更多
Considering the existing problems of the petroleum system, this paper bringsforward the concept of natural gas accumulation system and presents the dividing principles. Thendetailed statistics on the accumulation fact...Considering the existing problems of the petroleum system, this paper bringsforward the concept of natural gas accumulation system and presents the dividing principles. Thendetailed statistics on the accumulation factors of the 32 typical natural gas accumulation systemsin China and studies on the laws controlling distribution of gas are collected. The research showsthat the petroleum accumulation system is the basic unit controlling petroleum generation, migrationand accumulation. Generating intensity, generating amount, accumulating efficiency and migrationdistance plays an important role in the distribution of natural gas. Through analysis on results ofresources evaluation, discovered reserves and residual reserves, potential areas in middle-scaledpetroliferous basins in China are forecasted in this paper. Ordos, Sichuan, Tarim and Qaidam basinsare found out to be the main basins developing and enriching gas accumulation systems.展开更多
基金supported by the National Basic Research Program of China (Grant No: 2011CB201100)
文摘Hydrocarbon distribution rules in the deep and shallow parts of sedimentary basins are considerably different, particularly in the following four aspects. First, the critical porosity for hydrocarbon migration is much lower in the deep parts of basins： at a depth of 7000 m, hydrocarbons can accumulate only in rocks with porosity less than 5%. However, in the shallow parts of basins （i.e., depths of around 1000 m）, hydrocarbon can accumulate in rocks only when porosity is over 20%. Second, hydrocarbon reservoirs tend to exhibit negative pressures after hydrocarbon accumulation at depth, with a pressure coefficient less than 0.7. However, hydrocarbon reservoirs at shallow depths tend to exhibit high pressure after hydrocarbon accumulation. Third, deep reservoirs tend to exhibit characteristics of oil （-gas）-water inversion, indicating that the oil （gas） accumulated under the water. However, the oil （gas） tends to accumulate over water in shallow reservoirs. Fourth, continuous unconventional tight hydrocarbon reservoirs are distributed widely in deep reservoirs, where the buoyancy force is not the primary dynamic force and the caprock is not involved during the process of hydrocarbon accumulation. Conversely, the majority of hydrocarbons in shallow regions accumulate in traps with complex structures. The results of this study indicate that two dynamic boundary conditions are primarily responsible for the above phenomena： a lower limit to the buoyancy force and the lower limit of hydrocarbon accumulation overall, corresponding to about 10%-12% porosity and irreducible water saturation of 100%, respectively. These two dynamic boundary conditions were used to divide sedimentary basins into three different dynamic fields of hydrocarbon accumulation： the free fluid dynamic field, limit fluid dynamic field, and restrain fluid dynamic field. The free fluid dynamic field is located between the surface and the lower limit of the buoyancy force, such that hydrocarbons in this field migrate and accumulate
文摘Considering the existing problems of the petroleum system, this paper bringsforward the concept of natural gas accumulation system and presents the dividing principles. Thendetailed statistics on the accumulation factors of the 32 typical natural gas accumulation systemsin China and studies on the laws controlling distribution of gas are collected. The research showsthat the petroleum accumulation system is the basic unit controlling petroleum generation, migrationand accumulation. Generating intensity, generating amount, accumulating efficiency and migrationdistance plays an important role in the distribution of natural gas. Through analysis on results ofresources evaluation, discovered reserves and residual reserves, potential areas in middle-scaledpetroliferous basins in China are forecasted in this paper. Ordos, Sichuan, Tarim and Qaidam basinsare found out to be the main basins developing and enriching gas accumulation systems.
