姬塬地区长4+5油藏成藏期次的流体包裹体证据

Oil-Gas Accumulation Phases and Fluid Inclusion Proof of Chang 4+5 Reservoir in Jiyuan Area in Ordos Basin

在对鄂尔多斯盆地姬塬地区延长组长4+5储集层砂岩成岩作用及其自生成岩矿物形成序列分析基础上,研究了成岩矿物中流体包裹体特征及其代表的成藏期次。结果表明,长4+5储集层砂岩成岩作用主要有压实作用、压溶作用、胶结作用、重结晶作用、溶解作用和裂隙作用等。成岩矿物主要为自生石英、钠长石、白云石、方解石和黏土矿物等。根据流体包裹体所在寄主矿物的形成时间序列,识别出了3期流体包裹体。研究认为,第1期流体包裹体是沉积有机质演化早期阶段形成的含有机酸流体产物,与油气成藏事件无关;第2期油气包裹体为大量无荧光沥青包体,代表了早期油气藏被破坏后的残余物,记录了早期的一次油气成藏改造事件;第3期油气包裹体特征与孔隙吸附烃特征相同,是现今油气藏形成过程的记录,其分布在钠长石、硅质和钙质等大量晚期胶结物中,说明晚期成岩作用与油气大量注入同期发生。

Based on the analysis of diagenesis and formation sequence of the authigenic diagenetic minerals of Yanchang 4＋5 sandstone reservoir in Jiyuan area in Ordos basin,the characteristic of fluid inclusions in diagenetic minerals and the representing hydrocarbon accumulation phases are studied.The results show that the main diageneses include compaction,pressolution,cementation,recrystallization,dissolution and fissuring process.The diagenetic minerals are authigenetic quartz,albites,dolomite,calcite and clay mineral,etc.Three different phases of hydrocarbon inclusions have been identified according to the formation time series of the host diagenetic minerals.The first phase of fluid inclusions is early-forming organic fluid inclusions,which have nothing to do with the event of hydrocarbon accumulation;the second phase of fluid inclusions is non-fluorescent asphalt inclusions,which represent the residues after damage of early oil-gas reser-voirs,recording one event of hydrocarbon-accumulation reconstruction;the third phase of fluid inclusions has fluorescence characteristics of hydrocarbons absorbed in pores,distributed in albites,calcareous and siliceous cements and other late-generating cements,showing that late diagenesis occurs at the same time with charging of large amount of oil and gas,which is the record of present petroleum reservoir forming process.