摘要
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300～1200m，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一孔洞型，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 Dengying Formation of the Upper Sinian Series is one of the oldest reservoir rocks in the world. It is such an old age, deep burial and complex diagenesis that the reservoir is more and more tight. The study of the densification process of the formation is the precondition to probe into the formation mechanism of good reservoirs in the formation, and is an effective approach to explore the evolution process and characteristics of the marine carbonate reservoirs in the superimposed sedimentary basins in west China. In general, the thickness of the Dengying Formation is 300～1 200 m. It mainly consists of algal dolomite and crystalline dolomite, and occasionally saddle dolomite. The main dolomitization in the formation is penecontemporaneous and burial dolomitization. There are also conditions for the occurence of hypergene dolomitization and hydrothermal dolomitization in the formation. The fracture-cavity is the main storage space, and the matrix porosity is low （1%～2%）. There are some similarities of the infillings in pores and cavities in the formation in different regions of the Sichuan Basin. DiSsolution is the necessary condition for the formation of good reservoirs, including the hypergene karstification, burial dissolution and structure （folding） karstification. Silicatization is an important factor, which makes the Dengying Formation tight. The silicatization took place many times with many types. The densification process of the crystalline dolomite is as follows： the compaction during early diagenesis and the sparry cementation in fenestra （reducing about 40%～45% porosity）→early silicatization/recrystallization （little or no change of porosity）→the uplifted dissolution/infilling （or standing burial）→（reburial） presolution/recrystallization （hydrocarbon infilling）→the dissolution during deep burial？ infilling and recrystallization--→the fracturing of tectonic uplift/brecciation （or standing burial）→ the leaching of freshwater/silicatization/dedolomitization （or standing burial）→infilling. The densification process of the grain dolomite is as follows： the cementation （minor dissolution） of freshwater, seawater and the mixing water of freshwater and seawater （reducing 10%～20% porosity）→compaction → Hypergene karstification →silicatization/recrystallization →presolution/tectonic karstification/recrystallization/dissolution during deep burial/infilling （hydrocarbon infilling）; uplift/ tectonic fracture （or standing burial） dissolution/silicatization/infilling.
出处
《天然气地球科学》
EI
CAS
CSCD
2007年第4期485-496,共12页
Natural Gas Geoscience
基金
国家重点基础研究发展计划"973"项目(编号:2005CB422106)资助
关键词
储集层
致密化过程
灯影组
上震旦统
四川盆地
Reservoir rock
Densification process
Dengying Formation
Upper Sinian Series
Sichuan basin.
