The timing and duration of quartz cementation in sandstones have been mainly inferred from diagenetic texture, relationship between pore filling minerals, fluid inclusions and isotopic data. Fluid inclusion temperatures from North Sea reservoir sandstones indicate that most of the quartz cement forms at temperature exceeding 90℃ and is continually proceeding after oil emplacement, based on the fluid inclusion temperatures in quartz overgrowth which is approaching the bottom-hole temperatures. The duration of quartz cement after oil emplacement depends upon the saturation of porewater and the distribution of pore water film and the property of water-wet or oil-wet of the reactants. The leaching of K-feldspar by meteoric water requires pore water flow to move the released potassium and sodium and silica out the solution, which suggests the mechanism does not appear to be a major source of silica for quartz cementation. The quartz cementation coincidence with the compaction and pressure solution suggests the major source of silica. The alteration of feldspar by illitization of kaolinite may serve as another important source of silica at deep burial depth. External sources are not need to call on for illustrating the quartz cementation, because there is no evidences for large scale convection of pore water flow occurred in the burial history of reservoir sandstones of middle Jurassic in the North Sea. The timing and duration of quartz cementation in sandstones have been mainly inferred from diagenetic texture, relationship between pore filling minerals, fluid inclusions and isotopic data. Fluid inclusions from North Sea reservoir sandstones indicate that most of the quartz cement forms at temperature exceeding 90 ° C and is continually proceeding after oil emplacement, based on the fluid inclusion temperatures in quartz overgrowth which is approaching the bottom-hole temperatures. The duration of quartz cement after oil emplacement depends upon the saturation of porewater and the distribution of pore water film and the property of water-wet or oil-wet of the reactants. The leaching of K-feldspar by meteoric water requires pore water flow to move the released potassium and sodium and silica out the solution, which suggests the mechanism does not appear to be a major source of silica for quartz cementation. The quartz cementation coincidence with the compaction and press ure alte suggests the major source of silica. The alteration of feldspar by illitization of kaolinite may serve as another important source of silica at deep burial depth. External sources are not to call on for the quartz cementation, because there is no evidences for large scale convection of pore water flow occurred in the burial history of reservoir sandstones of middle Jurassic in the North Sea.