西湖凹陷花港组绿泥石成因及其对储层物性的影响

在西湖凹陷花港组储层整体低渗的背景下，优质储层的发育往往伴随绿泥石的富集。通过薄片观察、X衍射分析和扫描电镜及能谱分析等研究，认为研究区绿泥石呈黏土包膜、孔隙衬里和孔隙充填3种产出状态。黏土包膜为同沉积期铁镁物质絮凝吸附形成，成分复杂。孔隙衬里是绿泥石最主要的产出状态：Ⅰ类孔隙衬里绿泥石在早压实期前后由黏土包膜重结晶形成，单晶呈半自形片状，铁镁质量分数较低，排列杂乱；Ⅱ类孔隙衬里绿泥石在早压实期后由孔隙流体在洁净的颗粒表面结晶而成，单晶呈相对自形六方片状，铁镁质量分数较高，多垂直颗粒表面有序排列。孔隙充填绿泥石可细分为分散片状、书页状和绒球状，与溶蚀作用密切相关，单晶自形程度和铁镁质量分数均最高。黏土包膜绿泥石对储层物性的影响较小，但有助于衬里绿泥石的形成；孔隙衬里绿泥石难以缓解压实作用，但能够在一定程度上抑制压溶作用和有效地抑制早期石英加大，其中Ⅰ类孔隙衬里绿泥石由于连续性较好、排列杂乱、结晶较差和晶间孔复杂，对硅质胶结抑制作用明显，而Ⅱ类孔隙衬里绿泥石则相反，对硅质胶结的抑制作用有限；孔隙充填绿泥石仅充填较大原生粒间孔和粒间溶孔，对渗透率影响较小，仅在一定程度上减小了孔隙度。现今储层物性更多受控于储层砂岩的原始沉积组构以及相应的压实和溶蚀强度的改造过程，绿泥石的富集对优质储层具指示作用。

Origin Mechanism of Chlorite and Its Impact on Reservoir Properties in Huagang Formation,Xihu Depression

In the context of low-permeability reservoirs in the Huagang Formation in the Xihu depression, high quality reservoirs are often associated with the enrichment of chlorite. There are three different types of chlorites: Clay coating chlorite, pore-lining chlorite, and pore-filling chlorite. The clay coating chlorites with complex composition were formed in the syn-sedimentary stage through flocculation and adsorption of Fe and Mg. The pore-lining chlorites are the most common type:Among them,type I pore-lining chlorites were formed by recrystallization of clay coating chlorites during early compaction period, and the monocrystals are subhedral platelets with low Fe and Mg content and disorderly arrangement; Type Ⅱ pore-lining chlorites were formed by crystallization of pore fluid on clean grain surface, and the monocrystals are euhedral hexagonal platelets with higher Fe and Mg content and mainly arranged orderly on the surface of vertical particles. The pore-filling chlorites are in dispersive flake, booklet, and pompon aggregation, which are closely related to dissolution with the highest euhedral crystals and highest Fe and Mg content. The clay coating chlorites have little effect on reservoir physical properties, but can help the formation of pore-lining chlorites; The pore-lining chlorites are difficult to alleviate compaction, but can inhibit pressure solution and early quartz overgrowth to a certain extent. Type I-pore-lining chlorites are characterized by good continuity, disorderly arrangement, poor crystallization, and complex intergranular pores, and have obvious inhibition on quartz cementation, but type Ⅱ-pore-lining chlorites have limited inhibition on quartz cementation; The pore-filling chlorites only fill larger primary intergranular pores and intergranular dissolved pores, which have little effect on permeability and only reduce porosity to a certain extent. The physical properties of reservoirs are mainly controlled by the original sedimentary structure of reservoir sandstone and the transformation process of corresponding compaction and dissolution strength; And the chlorite enrichment plays an indicative role in high-quality reservoirs.