黄骅坳陷沧东凹陷孔二段泥页岩裂缝发育特征及主控因素分析

摘要

黄骅坳陷沧东凹陷孔二段泥页岩沉积厚度大，有机质丰度高、类型好，是泥页岩致密油气勘探开发的重点层位之一。在岩心精细观察与描述基础上，利用偏光显微镜、荧光显微镜、激光共聚焦显微镜观察以及 X 射线衍射分析、岩石热解分析等技术手段，对沧东凹陷孔二段泥页岩的岩石学特征、裂缝类型及发育特征（长度、开度、角度、充填物等）进行研究，并分析了裂缝发育的主控因素。沧东凹陷孔二段泥页岩主要由长英质矿物、碳酸盐矿物及黏土矿物组成，主要岩性包括云质泥岩、砂质泥岩、泥质云岩、砂质云岩及白云岩等，沉积构造类型包括块状构造、层状构造、纹层状构造及透镜状构造等。孔二段泥页岩主要发育构造缝、层理缝、差异压实缝及异常高压缝等4种裂缝，其中构造缝最发育，其次为层理缝和差异压实缝，异常高压缝发育较少，裂缝中充填物主要包括黄铁矿、方沸石、方解石及沥青等。研究表明，构造作用、岩性与矿物组成、沉积构造、成岩作用及有机质丰度是控制沧东凹陷孔二段泥页岩裂缝发育的主要因素。%The shale in the second member of Kongdian Formation(Ek2 )in Cangdong Sag with large thickness, high values and excellent types of organic abundance,is one of the important intervals for dense petroleum ex-ploration.Based on the detail observation and description of cores,this paper studied lithologic characteristics, fracture types and development characteristics (including length,opening,angle and filling)of shales in Ek2 in Cangdong Sag of Huanghua Depression by the observation of polarizing microscope and fluorescence micro-scope and laser scanning confocal microscope together with analysis of X-ray diffraction and rock pyrolysis.Fur-thermore,it analyzed the main controlling factors of fracture development.The shales of Ek2 in Cangdong Sag are mainly composed of felsic,carbonate and clay minerals;the main lithologies are dolomitic shale,silty mud-stone,argillaceous dolostone,sandy dolomite and dolomite,etc;the main types of sedimentary structures in-clude massive structure,lamellar structure,laminated structure and lenticular structure,etc.Four sorts of frac-tures develop in Ek2 ,i.e.structural fracture,interlayer lamellation crack,vertical-difference load fracture and overpressure-breaking fracture,among which the structural fracture is the most,followed by the interlayer lamel-lation crack and vertical-difference load fracture,and the overpressure-breaking fracture is the least.The main fillings in fractures are pyrite,analcime,calcite and asphalt.The results show that tectonism,lithology,miner-al composition,sedimentary structure,diagenesis and organic matter abundance(TOC)are the main controlling factors for the development of fractures in shales of Ek2 in Cangdong Sag.