摘要
近年来,柴达木盆地英西地区深层E_3~2油气勘探获得了重要发现。基于岩心观察、系统的微观岩石学、结构构造分析以及地球化学分析,研究柴达木盆地英西地区白云岩储集层特征及发育的主控因素。泥晶白云岩为英西地区E_3~2的主要有效储集岩,具有"低孔—特低渗"的物性特征,储集空间类型以白云石晶间孔为主,含部分微裂缝,这类孔径较小而数量极多的晶间孔储油是英西地区油藏稳产的重要控制因素。储层地球化学特征研究结果显示,白云岩储层为成化条件下的准同生交代成因类型,主要证据包括:①微观孔隙结构特征;②高Ca/Mg摩尔比值的非理想状态的成分组成;③"低锰"的元素地球化学特征;④"碳偏负氧偏正"的同位素地球化学特征及其反映的低温成因;⑤成核结晶速度较快的不稳定环境造成的低有序度结构特征。这类特殊成化环境下因晶格内部离子交换造成体积变化形成的收缩晶间孔,其孔径大小受控于当时的Mg^(2+)丰度,进而决定着储集层的物性,且这类晶间孔具有较强的抗压实能力,在深层、超深层依然能保存完好。准同生交代成因模式决定了白云岩在平面上分布广泛,因此这一研究成果在平面展布上和纵向深度上均拓展了柴西地区湖相白云岩勘探新领域。
In recent years, importan petroleum from deep reservoirs of t breakthrough progress and discovery has been made in exploration of E3^2 in western Qaidam Basin.Based on core observation, petrographic and structural microscopic characteristics analysis, and geochemical analysis, the characteristics and major fac- tors controlling the development of dolomite reservoirs in the Yingxi area in Qaidam Basin are studied.Do- lomicrite was the main effective reservoir rock of E3^2 in the Yingxi region,whose physical characteristics are ＂low porosity-extra low permeability＂.The reservoir spaces of the dolomite are mainly intergranular pore, but including some micro-cracks.Oil and gas can be produced stably in the Yingxi Oilfield because most oil and gas are preserved in these ＂small size-large quantity＂ pores.Research results of the geochemical characteristics of reservoir show that the dolomite is penecontemporaneous metasomatic type which formed in the salty conditions. Main evidence includes：（1）micro pore structure characteristics, （2）high Ca/Mg molar ratio of no ideal components, （3） low content of ＂Mn＂ element geochemical characteristics, （4） ＂carbon negative-oxygen positive＂ isotope geochemistry and the low temperature characteristics reflected by it, （5）low degree of order structure which is caused by the rapid nucleation and crystallization unstable environment. The shrinkage intergranular pores were formed by ion exchange in the crystal lattice in the special salty environment,and its pore size is controlled by the abundance of Mg2＋ at that time. Therefore, the physical property of the reservoir is indirectly controlled by the paleo salinity. These intergranular pores have a strong ability to resist compaction and they can still be preserved in the deep,ultra deep strata.The origin model of dolomite determines its wide distribution in the plane.So the research findings expanded a new exploration field about lacustrine dolomite in western Qaidam whether in the plane distribution or in depth.
出处
《天然气地球科学》
EI
CAS
CSCD
北大核心
2017年第2期219-231,共13页
Natural Gas Geoscience
基金
国家科技重大专项"柴达木盆地复杂构造区油气成藏
关键勘探技术与新领域目标优选"项目(编号:2016ZX05003-006)资助
关键词
柴达木盆地
成化湖盆
E3^2准同生交代
白云岩储集层
晶间孔
Qaidam Basin
Saline lacustrine basin
E3^2
Penecontemporaneous metasomatism
Dolomite reser- voirs
Intercrystalline pores
