渤中19-6凝析气田太古界潜山储层裂缝特征及低渗主控因素

Fracture characteristics and low permeability main controlling factors of Archean buried hill reservoirs in BZ19-6condensate field

渤中19-6凝析气田太古界潜山裂缝性储层物性差,表现为特低孔、特低渗特征。综合成像测井、岩心、薄片等资料对渤中19-6潜山裂缝特征及低孔、低渗原因进行了研究和分析。渤中19-6潜山主要储集空间类型为裂缝,受附近主要断层影响,裂缝走向与断层方向基本一致,以NE向、近EW向为主,裂缝倾角主要分布在30°~70°,以中—高角度裂缝为主。成像测井解释成果表明,渤中19-6潜山裂缝密度主要分布在1~5条/m,宏观裂缝开度100~400μm,宏观裂缝开度仅有蓬莱9-1、锦州25-1南等中高渗潜山裂缝开度的1/5~1/2。另外,宏观裂缝多被石英、碳酸盐岩矿物以及伊利石、绿泥石等黏土矿物充填,裂缝以充填、半充填裂缝为主,极少见未充填缝。镜下微观裂缝开度10~30μm,大多数被硅质、铁白云石以及黏土矿物充填,微观裂缝整体充填程度达到85%。分析认为,裂缝开度小和充填程度高造成裂缝网络有效通道数减少、单条裂缝通道局部堵塞,是造成储层低渗特征的主要因素。

The physical properties of Archean buried hill fracture reservoirs in BZ19-6condensate field are poor,showing the characteristics of ultra-low porosity and ultra-low permeability.Combined with the data of imaging logging,core and thin section,the fracture characteristics and the main reasons for low porosity and low permeability of BZ19-6 buried hill are studied and analyzed.Fractures,as the main reservoir space of BZ19-6 buried hill,have basically the same directions with those of faults,which are mainly NE and near EW directions,and the inclination of fractures is mainly distributed in30°~70°,dominated by medium-high angles.The results of imaging logging interpretation show that the fracture density of BZ19-6 buried hill is mainly distributed in1~5 fractures per meter,and the macroscopic fracture aperture is 100~400μm,which is only1/5-1/2 of that of PL9-1,JZ25-1S and other buried hills with medium-high permeability.In addition,macroscopic fractures are mainly filled,semi-filled and rarely unfilled fractures,filled with quartz,carbonate minerals,illite,chlorite and other clay minerals.Microscopic fractures have a fracture aperture of 10-30μm,and most of them are filled by siliceous,ferrodolomite and clay minerals,with an overall filling ratio of 85%.The analysis shows that the main factors for low reservoir permeability are the decrease of effective channels of fracture network and local blockage of single fracture channel caused by small fracture aperture and high filling degree.