对于东营凹陷古近系沙四段近岸水下扇沉积砂体，由于其直接沉积在水下，早期

For the nearshore subaqueous fan sedimentary sand body of the fourth member of the Shahejie Formation of the Paleogene in Dongying Sag, because it was directly deposited underwater, the pore-forming effect of the leaching of atmospheric fresh water in the early stage was relatively weak, and it only experienced the subsequent middle-deep burial and the thermal evolution of organic matter. Acidic fluid and hydrocarbon thermal evolution are reformed by acid fluid to form secondary pores and accompanied by the precipitation of authigenic clay and quartz. The secondary pores are effectively superimposed, forming the present deep feldspar dissolved pore-dominated oil and gas reservoir. During the burial process of petroliferous basins, the infiltration of atmospheric fresh water and the upward conduction of deep hydrothermal fluids controlled by deep and large fault systems can also produce strong dissolution, but these dissolution and pore formation usually occur near the fault system. Limitations are not discussed here.

For the sedimentary sand body of the nearshore subaqueous fan in the fourth member of Shahejie formation of Paleogene in Dongying depression, because it is directly deposited underwater, the leaching and pore forming effect of atmospheric fresh water in the early stage is relatively weak, and it has only experienced the subsequent medium deep burial, the transformation of organic matter thermal evolution acid fluid and hydrocarbon thermal evolution acid fluid, forming secondary pores, accompanied by the precipitation of authigenic clay and quartz, and the secondary pores are effectively superimposed, Formed the current deep feldspar dissolved pore dominated oil and gas reservoir. During the burial process of petroliferous basins, the infiltration of atmospheric fresh water and the upward conduction of deep hydrothermal fluid controlled by deep and large fault system can also produce strong dissolution, but these dissolution and pore forming processes usually occur near the fault system, which are relatively limited and will not be discussed here.

As for the sedimentary sand bodies of nearshore subaqueous fan in the 4th member of Paleogene Shahejie Formation in Dongying Sag, because they are directly deposited underwater, the early atmospheric fresh water leaching pore-forming function is relatively weak, and only the subsequent middle-deep burial has undergone the transformation of acid fluid undergoing the thermal evolution of organic matter and acid fluid undergoing the thermal evolution of hydrocarbons, forming secondary pores with the precipitation of authigenic clay and Shi Ying, and the secondary pores are effectively superimposed, thus forming the oil and gas reservoir dominated by the dissolution of deep feldspar. During the burial process of oil-bearing basins, the infiltration of atmospheric fresh water and the upward conduction of deep hydrothermal solution controlled by deep and large fault systems can also produce strong dissolution, but these dissolution pore-forming processes usually occur near fault systems, which are relatively limited and will not be discussed here.