ECS测井在火山岩岩性识别中的应用

火山岩岩性定名与识别是岩相划分、储层综合评价与预测、井网部署、开发方案编制的基础。火山岩岩性与岩石成分、结构、构造和成因有关,岩石类型多,定名和识别难度大。ECS利用快中子与地层中的原子核发生非弹性散射碰撞及热中子被俘获的原理,通过解谱和氧化物闭合模型得到地层中主要造岩元素的相对百分含量,并应用聚类分析、因子分析等方法定量求解地层的矿物含量,从岩石成分的角度较好地解决了火山岩岩性识别的问题。研究区火山岩以SiO2为主,Al2O3、K2O Na2O及Fe2O3次之,CaO和MgO则不发育,Si、Al、Fe、Gd是研究区岩性识别的主要指示元素。研究结果表明从基性玄武岩到酸性流纹岩,Si元素产额和K40含量增大、Al和Fe元素产额则减小;熔结凝灰岩的Gd元素产额比熔岩高;常规测井的GR与ECS测井的Si元素产额正相关,地层密度与Fe元素产额正相关,能谱测井的Th含量则与Fe元素产额负相关。ECS以崭新的测井概念、先进的测井技术,具有广泛的应用前景,但各种误差和价格昂贵的问题则使其推广应用受到一定的限制;常规测井信息丰富,从多个方面提供了识别火山岩岩性的资料和手段;将ECS与常规测井、成像测井相结合,是解决火山岩岩性识别难的有效途径。

APPLICATION OF ESC WELL LOGGING IN VOLCANIC LITHOLOGIC DISCRIMINATION

Volcanic lithology naming and discrimination are the foundation of lithofacies division, overall reservoir evaluation and prediction, well net disposition and development project making up. Volcanic lithology is related with rock component, arrangement, structure and cause of formation. It is hard to name and identify the volcanic lithology because it has many types. ECS uses the principle that fast neutrons and nucleus in the formation collide to occur inelastic scattering and the thermal neutrons are captured. Relative percentage composition of the main rock elements is obtained through spectrum unscrambling and oxide colse model. Mineral contents of the formation are measured quantitively by using cluster analysis and factor analysis. Volcanic lithological discrimination is solved from the rock component.