摘要
通过实例介绍一种特殊的碳酸盐岩储层类型——白垩储层的特征。叙利亚Tishrine油田上白垩统-始新统油藏具微孔隙-裂缝,其典型特征是孔隙度高、渗透率特低,岩心孔隙度高达35%,多数样品渗透率却小于1×10-3μm2;地层电阻率较低(1～5Ω.m),束缚水饱和度可高达70%～95%。分析认为:Tishrine油田上白垩统-始新统是陆棚和外陆棚沉积的白垩储层或类白垩储层,含大量颗石藻(球),颗粒半径小,直径几个微米,发育大量粒间微孔,喉道半径在0.5～1.0μm,加之高矿化度(海水的3～7倍),造成该碳酸盐岩地层电阻率极低。沉积环境、泥质含量及方解石胶结作用、重结晶作用和压实作用是影响白垩型储层发育的主要因素。对于该区而言,无大气水暴露、高水位期、无陆源碎屑供应条件下有利于形成有效储层。晚期造缝事件对储层渗透性影响至关重要,裂缝多与晚期走滑断裂作用或构造反转有关,同时裂缝也控制了油藏的几何形态和非均质性。如何预测裂缝的分布、识别油层及确定储量计算参数是该类储层研究的难点。
Taking the Tishrine oilfield in Syria as an example,this paper discusses a characterization of a special type of carbonate reservoir—chalk reservoir.The Upper Cretaceous-Eocene reservoirs in this oilfield are rich in micro-pores and fractures,and typically have high porosity and ultra-low permeability.Lab analysis shows that their core plug porosity can be as high as 35%,permeability is less than 1×10-3 μm2 for most samples,formation resistivity is rather low（0.1-5 Ω·m）,and the irreducible water saturation can be as high as 70-95%.The study suggests that the Upper Cretaceous-Eocene are chalk or chalkoid（chalk-like）reservoirs deposited in shelf and off-shelf environments,which contain a large number of tiny coccolithophores of a few microns in diameter and well developed intergranular micropores.Their pore throat radius is in the range from 0.5 to 1 μm.Coupled with high salinity（3-7 times higher than that of sea water）,these reservoirs have very low formation resistivity.Factors such as sedimentary environment,shale content,calcite cementation,recrystallization and compaction are considered as the key forces controlling the development of the reservoirs.As far as the study area is concerned,such conditions as no exposure to atmospheric water,highstand deposition and no clastic input were favorable for forming high-quality reservoirs.The late fracturing event played a very important role in the forming of present permeability of these reservoirs.The fractures are mostly associated with late strike-slip faulting or tectonic inversion and also control the geometry and heterogeneity of the reservoirs.The challenges we are going to facing in the study of this special reservoir include the prediction of fracture distribution,identification of oil-bearing intervals,and determination of reserves estimating parameters
出处
《石油与天然气地质》
EI
CAS
CSCD
北大核心
2012年第5期720-729,共10页
Oil & Gas Geology
基金
国家科技重大专项(2008ZX05005-002-01)
