【作者】 刘航军；

【导师】 柳益群；

【作者基本信息】 西北大学 ， 矿产普查与勘探， 2013， 博士

【摘要】 在鄂尔多斯盆地一些地区的延长组中发育高自然伽马砂岩储层,该类储层平面上主要分布于宁夏盐池、陕西定边、安塞、吴起、靖边、甘肃华池等主要产油区,在纵向上主要存在于延长组长4+5、长6、长7、长2、长3等主力产油层位。高伽马储层的地质研究与测井评价,不仅对延长组储层的储集性能评价和测井解释有着重要的实际意义,而且对于确定砂岩中高自然伽马成因机理有着重要的理论意义。延长组高伽马储层岩石学、地球化学特征表明,该类储层与常规储层相比,具有以下特点：①钾长石、绿泥石、铁泥质粘土杂基含量明显上升,岩屑含量较高,且岩屑假杂基化较为普遍,石英含量明显减少,长石高岭石化强烈。②Th、U、K放射性元素含量较高,其中Th元素含量上升最为显著,主要存在于独居石、金红石、铁泥质粘土、钾长石及部分锆石、磷灰石、黑云母、岩屑中；U元素主要存在于大多数的锆石、部分磷灰石、黑云母及含镁方解石中；K元素主要存在于钾长石、黑云母、金红石、铁泥质粘土、部分钠长石及岩屑中。③高伽马储层总孔隙度比邻近常规储层高1.3%,次生孔隙相对比较发育,原生残余粒问孔隙要小一些,中小孔、微孔相对比较发育,而且这些小孔、微孔连通性好。延长组高伽马储层分布及沉积特征表明,该类储层连通性较差,在横向上或尖灭于常规储层之中,或与泥岩呈指状交叉。高伽马储层的形成不受沉积相控制,可以在三角洲环境下形成,也可以在水下的浊积扇中形成,甚至在辫状河道砂岩中也可见及。延长组高伽马储层与凝灰岩、物源关系的研究表明,火山凝灰岩与高伽马储层的形成无必然联系,高伽马储层与来自于盆地东北方向的物源有一定的亲缘性,综合分析表明,热液活动对该类储层的形成有着重要影响。与邻近常规储层测井曲线的对比表明,高伽马储层整体表现为自然伽马异常高、补偿中子、光电吸收截面指数上升明显,电阻率下降明显,声波时差略有上升,密度值略有增大,这些测井参数的变化给用测井资料准确计算出该类储层的孔隙度、渗透率、泥质含量、含油饱和度带来了一定的困难,使油、水层的识别变得复杂。在利用测井资料识别油、水层时,建议将高伽马储层与常规储层区分开,分区域、分储层类别建立新的测井解释图版,应用新的解释图版可进一步提高测井解释符合率。尽管高伽马储层有着较好的孔隙性和渗透性,是有利于油气聚集的储层,但该类储层可以是水层、油层、油水层、差油层、含油水层,甚至可以是物性很差的干层。在富含油区域,高伽马储层以油层、油水层居多,在含油区域边部区块,高伽马储层多以含油水层、水层出现,高伽马储层与油水关系的研究表明,延长组高伽马储层仅仅是一类比较特殊的储层,其含油情况受多种因素控制。本论文在高伽马储层、邻近常规储层物性分析数据、声波时差、密度测井数据基础之上,建立了高伽马储层孔隙度、渗透率计算公式。提出利用邻近常规储层泥质含量及自然伽马数值；自然电位测井数值；密度、声波时差测井数值；核磁测井数据计算高伽马储层泥质含量的4种方法。对比分析了高伽马储层与邻近常规储层岩心含油饱和度变化,结果表明两者含油饱和度相差不明显,但受高伽马储层电阻率及孔隙度变化影响,测井计算的含油饱和度两者差异较大,计算出来的高伽马储层含油饱和度往往偏低,经对比分析,提出了较为准确的计算高伽马储层含油饱和度的公式。更多还原

【Abstract】 Some area in Ordos Basin exist high natural gamma reservoir in Yanchang Formation. The distribution of high natural gamma reservoir is mainly in oil production area in Yanchi of Ningxia and Dingbian, Ansai, Wuqi, Jingbian of Shaanxi and Huachi of Gansu. The high natural gamma reservoir is found in the Chang4+5, Chang6, Chang7, Chang2, and Chang3that accumulated rich oil in vertical profile. The geology research and well logging evaluation of high natural gamma reservoir are not only important to the evaluation of storage capability and well logging interpretation in Yanchang Formation,but also to the determination of genesis of high natural gamma in the sandstone.The petrology and geochemistry characteristics of high natural gamma reservoir show that high natural gamma reservoir has more feature compare with conventional reservoir:①High natural gamma reservoir have more K-feldspar, chlorite and iron muddy clay matrix. Some high nature gamma reservoir has higher level of debris, and complex glycosylation are common. The content of quartz is significantly reduced. Feldspar in some high gamma reservoir is seriously Kaolinitilized.②Content of Th, U, K in high natural gamma reservoir is increased compared with conventional reservoir, in which the content of Th are significantly increased that mainly exist in the Monazite, rutile, iron muddy clay, feldspar, some of the zircon, apatite, Biotite and and debris. The radioactive element of U mainly exists in most of zircon, some of apatite, biotite and magnesium calcite. The radioactive element of K is mainly in K-feldspar, biotite, rutile, iron muddy clay, and some of albite and debris.③The total porosity of high gamma reservoir is larger1.3%than conventional reservoir,and relatively developed secondary pores. The residual primary intergranular pores are small, and medium and small pore is relatively developed, and connectivity of the pore is better.The distribution and sedimentary characteristics of high gamma reservoir show that connectivity of high gamma reservoir is poor.The high gamma reservoir usually disappear in the conventional reservoir, or intersect with mudstone on lateral. The sedimentary facies is not control the high gamma sandstone formation. It can form in the delta environment, and also can form in the turbidite fan environment, or in the braided channel. The study of the relation of volcanic tuff, material source and high nature gamma reservoir show it is not inevitable connection for the volcanic tuff and formation of high gamma reservoir.To a certain degree, high gamma reservoir is indigenous to material source from northeast basin. On the whole, the hydrothermal activity maybe is important to the forming of high gamma reservoir.Comparing with conventional reservoir, the high gamma reservoir show that the value of gamma, compensated neutron, pe increase obviously. Resistivity decrease obviously. Acoustic velocity decrease a little. Density increase a little.All this change bring the difficuly for exactly computing the porosity,permeability, clay content,oil saturation,and make the oil water distinguishing more complex. When distinguishing Oil-water layer by well logging data,we suggest establish well logging interpretation diagram on the basis of reservoir classification. By using new diagram can improve the identification accuracy.In spite of the better porosity and permeability in the high gamma reservoir, and it is the favorite reservior for oil accumlation, but it can be water layer, oil layer, oil-water layer, poor oil layer, water with oil layer, even can be dry layer with poor porosity and permeability.In the area of rich oil, the high gamma reservoir usually is oil layer, oil-water layer.In the margin of rich oil area,it is often water layer, water with oil layer. The research of the relation of oil-water and high gamma reservoir show that it is only a special reservoir.The condition of oil bearing is controlled by many factors.On the base of porosity,permeability, acoustic velocity, density of high gamma and adjacent conventional reservoir, this paper establishes the formula of computing porosity, permeability, and also comes up with clay content computing formula by using clay content and nature gamma value of adjacent conventional reservoir, by using spontaneous-potential data, by using acoustic velocity, by using density data; by using nuclear magnetic resonance data. This paper discusses the drilling core oil saturation difference of high gamma and adjacent conventional reservoir. The result of analysis show the difference between high gamma and adjacent conventional reservoir is very small. But influenced by resistivity and porosity change, oil saturation value from the well logging computing is very different. The oil saturation is usually lower from well logging computing. This paper establishes more exact oil saturation formula by comparative analysis.更多还原