元素俘获谱测井在火山岩储层孔隙度计算中的应用

火山岩地层孔隙度的准确计算是储层综合评价与预测、储量计算、产能评估和开发方案编制的基础,但是由于火山岩岩石类型多,矿物组分复杂多变以及裂缝、气孔等微孔隙的发育。基于常规三孔隙度曲线的计算方法在求取火山岩储层孔隙度的时候受到很大的限制,成为火山岩储层评价技术走向成熟的最大瓶颈。元素俘获谱测井(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各种氧化物含量,而氧化物含量与火山岩岩石骨架密度紧密相关,据此建立能表征动态变化的火山岩骨架密度参数的计算模型,并结合密度测井计算火山岩孔隙度。方法在国内××油田火山岩储层的孔隙度计算中取得了很好的应用效果,为火山岩储层的精细评价提供了技术支撑。

APPLICATION OF ELEMENTAL CAPTURE SPECTRUM (ECS) LOGGING IN POROSITY CALCULATION OF A VOLCANIC RESERVOIR

Accurate porosity calculation of volcanic formation is the foundation of reservoir evaluation and pretliction, calculation of reserves,produc- tive capacity evaluation and development plan.But there are many kinds of volcanic rocks,and mineral constituents are complex and vari- able,and micropore such as fractures and pore,etc.develop well.The method based on the conventional three-porosity curve is limited in getting volcanic reservoir porosity,which becomes the largest bottle neck in volcanic reservoir evaluation technology.Element capture spec- tra logging (ECS)uses the principle that the thermal neutrnns are captured after fast neutrons collide with nuclei in the formation to occur inelastic scattering.Then the relative percentage composition of the main petrogenetic element in the formation is obtained through spec- trum unscrambling and oxide close model.Cluster analysis and factor analysis methods are used to solve different kinds of oxide contents in the formation quantitively which has close correlation with volcanic matrix density.Therefore a computational model for the volcanic matrix density parameters is established to characterize the dynamic variation and volcanic porosity can be calculated with density logging.This method has gained good result in porosity calculation of volcanic reservoir in domestic XX oilfield.It provides technical support for delicate evaluation of volcanic reservoirs.