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四川盆地上震旦统灯影组是世界上最老的油气储集层之一,由于其时代老、埋藏深、成岩演化历史复杂,岩层储层物性的演化总趋势是越来越致密,因此,研究灯影组储层的致密化过程是掌握其作为优质储层形成机理和发育规律的前提,也是揭示我国西部叠合盆地海相储层演化过程和特征的有效途径。指出:震旦系灯影组在四川盆地一般厚300~1 200 m,主要以藻白云岩、晶粒白云岩为主,可见马鞍状白云岩,成岩后期的改造主要以准同生白云岩化为主,次为埋藏白云岩化,另具发生深埋白云石及热液白云石的条件;主要储集类型为裂缝—孔洞型,基质孔隙度较低(1%~2%)。认为四川盆地不同地区震旦系灯影组溶孔或溶洞中的充填矿物具有相似性;溶蚀作用是形成该盆地震旦系灯影组优质储层的必要条件,发育有表生岩溶、埋藏岩溶及构造(褶皱)岩溶作用;硅化作用是使震旦系灯影组致密化的重要因素,其期次多、形态多样。着重指出:灯影组晶粒白云岩致密化过程为成岩早期压实及窗格孔内亮晶胶结(孔隙约降低40%~45%)→早期硅化/重结晶作用(孔隙度变化不大)→抬升溶蚀/填充作用(或持续深埋)→(再次埋藏)压溶/重结晶(油气充注)→深埋溶蚀作用→充填及重结晶作用→构造抬升破裂/角砾化作用(或持续埋深)→淡水淋滤/硅化/去白云石化作用(或持续埋深)→充填作用;灯影组颗粒白云岩致密化过程为淡水、海水、混合水各类成岩胶结作用(少量溶蚀作用)(孔隙约降低10%~20%)→压实变形→表生岩溶→硅化作用/重结晶作用→压溶/构造岩溶/重结晶作用/深埋溶蚀/充填(油气充注)→抬升/构造破裂作用(或持续埋深)→溶蚀/硅化/充填作用。
The Upper Sinian Dengying Formation in the Sichuan Basin is one of the oldest oil and gas reservoirs in the world. Due to its age-old, buried and diagenetic evolutionary history, the evolutionary trend of petrophysical properties of the reservoirs is becoming more and more dense. Therefore, To study the densification process of the Dengying Formation reservoir is a prerequisite for grasping its formation mechanism and development as a good reservoir and an effective way to reveal the evolution process and characteristics of marine reservoirs in the western superimposed basin. It is pointed out that the Sinian Dengying Formation is generally 300-1,200 m thick in the Sichuan Basin, mainly composed of algae dolomite and crystalline dolomite. Saddle-shaped dolomites are visible. During the late diagenesis, The main and secondary burial dolomitization, the other with the occurrence of deep dolomite and hydrothermal dolomite conditions; the main reservoir type of fracture - hole type, the matrix porosity is low (1% to 2%). It is considered that the filling minerals in the pores or karst caves of the Sinian Dengying group in different areas of Sichuan Basin are similar. The dissolution is the necessary condition for the formation of the high-quality reservoirs of Sinian Dengying Formation in this basin. There are epikarst karsts, buried karsts and structures (Fold) karstification; Silicification is an important factor in the densification of the Sinian Dengying group, with many more and more diverse forms. It is emphatically pointed out that the densification process of the Dengying Formation dolomite is the early compaction of diagenesis and the bright cementation (approximately 40% -45% reduction of pores) → early silicification / recrystallization (little change of porosity) → (Or buried deep) → (re-buried) pressure solution / recrystallization (hydrocarbon filling) → deep dissolution → filling and recrystallization → tectonic uplift / brecciation (or continuous burial) Depth) → freshwater leaching / silicification / dolomitization (or continuous burial) → filling; the densification process of the Dengying Formation dolomite dolomite is diagenetic cementation (small amount of dissolution) of freshwater, seawater and mixed water About 10% ~ 20% reduction) → compaction deformation → epikarst → silicification / recrystallization → pressure dissolution / tectonic karstification / recrystallization / deep dissolution / filling (hydrocarbon filling) → uplift / tectonic rupture (Or continuous buried depth) → dissolution / silicification / filling.