苏北盆地溱潼凹陷古近系阜宁组二段页岩油形成条件及有利区评价

Formation conditions of shale oil and favorable targets in the second member of Paleogene Funing Formation in Qintong Sag,Subei Basin

通过对苏北盆地溱潼凹陷古近系阜宁组二段泥页岩段生烃、储集条件及含油性分析,优选了页岩油勘探有利层段;综合岩性、压力、裂缝预测资料,评价出有利区带。溱潼凹陷阜二段有机碳含量大于1.0%的泥页岩厚度为160~260 m,广泛分布;镜质体反射率R o为0.5%~1.1%,成熟范围广;有机质类型好,有机显微组分以藻类体为主,具备页岩油形成的物质基础。阜二段孔隙度平均为8.9%,储集空间主要为溶孔、黏土矿物和碳酸盐晶间孔,纹层状泥灰岩和粉砂质泥岩微裂缝较发育,裂缝控制了储层渗透性。阜二段③~⑤亚段脆性矿物含量为62%~65%,以石英、方解石和白云石为主,游离烃含量S 1为0.1~2.7 mg/g,平均为0.54 mg/g,为页岩油勘探的最有利层段。溱潼凹陷阜二段页岩油整体评价为Ⅱ类和Ⅲ类,其中时堰和储家楼深凹带是寻找粉砂质泥岩和泥灰岩油藏最有利区,东斜坡是寻找凝灰岩夹层型页岩油藏有利区。

The favorable targets of shale oil exploration were optimized based on the analyses of hydrocarbon generation,reservoir conditions and oil content of the shale sections in the second member of Paleogene Funing Formation in the Qintong Sag,Subei Basin.Some favorable zones were predicted according to the properties of lithology,pressure and fractures.The mud shale with an organic carbon content(TOC)greater than 1.0%is widespread in the second member of Funing Formation with the thickness distributed between 160-260 m.The R o values vary from 0.5%to 1.1%,indicating a wide maturity range.The organic matter type is good,and the organic microscopic maceral is dominated with algae,which provides a substantial potential for generation of shale oil.The average porosity of the second member of Funing Formation is 8.9%.Dissolved pores,clay minerals and carbonate intercrystalline pores act as main reservoir spaces.For the laminar marls and silty mudstones,micro-fractures were well developed,which controlled the permeability of the reservoir.From the third to the fifth section of the second member of Funing Formation,the content of brittle minerals distributed between 62%-65%,mainly composed with quartz,calcite and dolomite.The free hydrocarbon content(S 1)showed a range of 0.1-2.7 mg/g,with an average value of 0.54 mg/g,referring the most favorable layers for shale oil exploration of the sections mentioned above.The shale oil in the second member of Funing Formation in the study area was mainly typesⅡandⅢ.It has also been indicated that the Shiyan and Chujialou deep depressions are the most favorable areas for silty mudstone and marl reservoirs,while the eastern slope is favorable for tuff mudstone shale reservoirs.