鄂尔多斯盆地中生界延长组长7泥页岩岩电关系

Study on relationship between lithology and electric logging of mud shale in Cheng 7 Member of Yanchang Formation in Ordos Basin

为了新增常规油气的地质储量,对盆地内各个地区总计400多口油气井测井资料、岩心资料进行了统计分析,结合前人研究成果,运用岩心观察、岩电对比、泥页岩电性取值范围统计、电测曲线形态对比分析等方法对长7泥页岩层的展布特征、岩电关系及泥、页岩电性差异进行了细致的分析后认为:长7泥页岩层分布范围至少超过6×104km2,厚度0～120 m,整体呈现西、南深且厚,东、北浅且薄的分布特征;声波时差和自然伽马在泥页岩层响应明显,且受沉积相带控制,泥页岩层在深—半深湖区呈现大幅高值巨厚的箱型或钟形,而在浅湖区则多表现为单峰(或双峰)指尖状突起或小幅低值细薄钟形;受铀和有机质含量、岩层含气性及裂缝发育差异的影响,泥、页岩层在电性上存在着差异;研究区西、南可以依靠声波时差和自然伽马取值范围的差异对泥、页岩进行区分,而东、北部则主要依靠声波时差取值范围并结合泥、页岩层不同的曲线形态特征进行区分.

In order to search for new conventional oil/gas geologic reserves,the distribution of the mud shale,lithology-electrical property relationship and the difference in electrical property between mud stone and shale are studied by the observation of cores,the contrast of lithology with electrical property,the statistics of mud-shale electric logging data and the analysis and contrast of electrical logging curve shapes based on logging data and core data from more than 400 oil/gas wells distributed in the whole basin and combined with the previous results of other researchers.It is held that,the distribution area of the mud shale in Chang 7 is larger than 6×104 km2,the thickness of the mud shale is 0~120 m.The distribution of the mud shale is deep and thick in the west and the south of the basin and is shallow and thin in the east and the north of the basin.The logging response of AC and GR in the mud shale layer is evident,and it is controlled depositional facies.In deep to semi-deep lake area,logging curves present great-amplitude huge-thick box or bell shape,while in shallow lake area,they present single-peak(or double-peak) fingertip shape or little-amplitude thin box.There is difference in electrical property between mud and shale because of different uranium and organic matter content,gas-bearing potential and fracture development degree.The mud and shale in the west and the south of the studied area can be distinguished according to the ranges of AC and GR values,while in the east and the north,they can be distinguished by combining the range of AC value with AC curve shape.