关键词: 古近系, 地层压力, 流体, 储集性, 协同演化, 差异成藏, 东营凹陷

Abstract: Hydrocarbon accumulation is attributed to the formation pressure, fluid, reservoir property and their co-evolutionary effect. The dynamic reservoiring process and the original state of oil and gas reservoirs in Dongying depression are relatively complete. Based on investigating the current characteristics and evolution process of pressure field, fluid field and reservoir properties of Paleogene, the paper establishes the formation pressure-fluid-reservoir property co-evolutionary model of Dongying depression and makes clear its controlling effect on reservoir accumulation. Under the control of tectonic activity and sedimentation, the formation pressure in Dongying depression has undergone an evolutionary process of "rise-fall-rise". The properties of diagenetic fluid are characterized by acid-alkali alternation. The effective reservoirs of different genetic types have been developed under the control of depositional fabric and diagenetic fluid action. Under the control of fault basin, the development of steep slope belt, depression belt, and gentle slope belt in Dongying depression demonstrate the co-evolutionary mode of "normal pressure/weak overpressure, alkali/acid, and medium/low porosity (less occurrence of high porosity) ", "overpressure, acid, and medium/low porosity", and "normal pressure, weak alkali/acid, and medium-/high-porosity pores", respectively. The co-evolutionary mode of formation pressure, fluid and reservoir property has a good correspondence with the structure of fault basin, types of oil and gas reservoirs and ordered distribution of properties in terms of genesis, and controls the differential enrichment of different types of oil and gas reservoirs. Lithologic gas reservoirs and condensate oil and gas reservoirs with high hydrocarbon-filling degree in the deep layer of steep slope belt, and reservoirs with medium-high hydrocarbon-filling degree in the transition area from depression belt to steep slope belt indicate a favorable pre-exploration direction; lithological structural and stratigraphic reservoirs on the hydrocarbon migration pathway in the gentle slope belt can provide a favorable direction for the evaluation of increasing reserves. The co-evolutionary mode of formation pressure, fluid and reservoir property and its corresponding accumulation mode are an effective supplement to the basic principles of oil and gas accumulation in fault basins, and both the basis for and the key to studying the ordered distribution and differential enrichment of oil and gas reservoirs, which take on significance in exploring the deep mechanism of oil and gas accumulation in continental fault basins, studying the distributions laws of reservoirs, and guiding exploration practice.

Key words: Paleogene, formation pressure, fluid, reservoir property, co-evolution, differential accumulation, Dongying depression