火山岩储层中的烃碱流体作用及其地质意义

Hydrocarbon alkali fluid and its geological significance of volcanic reservoir

徐家围子断陷位于松辽盆地北部,断陷发育期火山活动强烈,早白垩世营城组火山岩分布最为广泛,是松辽盆地北部深层天然气的重要储层类型。兴城地区营城组火山岩气藏储层以酸性火山岩为主,储集空间可分为原生孔隙、次生孔隙和裂隙3种类型,其中次生溶蚀孔隙是本区主要储集类型之一。烃碱流体作用对改善储层的储渗能力具有重要意义,主要体现在次生孔隙带的形成、发育程度上。烃碱流体不仅可以使火山岩体处于开放体系,原有矿物发生交代蚀变、溶蚀,造成岩石内部结构破坏、机械强度减低、孔隙度增加,形成类似海绵体的结构,也可以充填、阻塞孔隙而降低孔渗性质,这取决于烃碱流体在储层中引起物质带入与带出的比例。

Xujiaweizi Faulted Depression is located in the north of Songliao Basin and the vocanic activity was violent during the development stages of the depression. The vocanic rocks of the early Cretaceous Yingcheng Formation are widely distributed, and they are the important reservoir type of the deep natural gas in northern Songliao Basin. The volcanic gas reservoirs are mainly acidic volcanic rocks in Yingcheng Formation of Xingcheng Region. There are 3 types of reservoir spaces. They are primary pore, secondary pore and cracks, and the secondary dissolution pore is one of the most important types of the reservoir space in this region. The activity of hydrocarbon alkali fluid is important in improving the storing capacity and the permeability, which might depend on the extent of formation and development of the secondary pores. This mainly depends on the proportion of the objects dragged in and out caused by hydrocarbon alkali-fluids. Hydrocarbon alkali fluid can not only make the vocanic rocks under the opened-system which leaded to the metasomatic alteration and corrosion of original minerals, internal structure of rocks destroyed, the mechanical strength decreased, the porosity increased and structure similar to the spongiform formed, but also can fill or block pores ,which resulted in lower porosity and permeability. This also mainly depends on the proportion of the objects dragged in and out caused by hydrocarbon alkali fluids.