基于自然伽马能谱测井的岩溶型碳酸盐岩储层层位划分与对比

塔河油田奥陶系碳酸盐岩储层埋藏深，厚度变化大，非均质性强，给地层对比工作带来较大困难。为认清油气分布规律，提出以自然伽马能谱测量比值的组合交会为基础的测井特征比值参数法来研究碳酸盐岩地层的沉积特性，并建立了该区奥陶系自然伽马能谱测井的地层划分模式。研究表明，该区奥陶系碳酸盐岩储层自然伽马能谱测井的铀相对含量远大于钍／铀比，为岩溶淋滤带，应在此带内寻找岩溶储层；上奥陶统恰尔巴克组地层沉积稳定，为区域标志层；一间房组上段发育礁滩相裂缝-孔隙型储层，具有连片分布的特点，下段发育块状致密泥微晶灰岩，与中下奥陶统鹰山组相隔。连井对比发现，奥陶系顶面（T7^0）的区带存在岩溶台地，在有中、下奥陶统顶面（T7^4）的地区，岩溶地貌变化多样，反映奥陶系及中奥陶统一间房组和鹰山组上部碳酸盐储层都有油气存在的可能，表明塔河油田具有广阔的油气发展空间。经过50余口井的应用验证，采用以自然伽马能谱比值参数为基础的多参数综合评价方法来划分地层和储层是可行的，且效果明显，已推广应用于油区各新钻井的储层评价及老井的进一步分析。

Karst carbonate reservoir division and contrast based on natural gamma ray spectrometry logging in Tahe Oilfield

Carbonate reservoir in Tahe Oilfield is characterized by large burial depth,great thickness variations and strong anisotropism which result in the difficulty of making layer contrast.In order to recognize the distribution regularity of hydrocarbon,a logging-ratio characteristic parameter method based on natural gamma ray spectrometry log data ratio computing and overlapping technology was presented to study the deposition characteristics of the carbonate reservoir.By using the method,the strata division mode of natural gamma ray spectrometry logging was established in Ordovician system of the region.The results show the relative content of U,which is derived from natural gamma ray spectrometry logging,is greater than Th-U ratio.So the region develops karst leached zone,and karst reservoirs should be found in the belt.The Qarbag formation of upper Ordovician has steady deposition and is regional criteria layer.The upside of Yijianfang formation develops fracture-pore reservoirs of reef-beech facies,and is characterized by continuous distribution.The downside develops tight schollen micrite limestone,and is separated by the Yingshan formation of lower Ordovician.By contrast of well tie,it is found that the belt on top surface of Ordovician(T~0_7) has karst platform,and that of middle and lower Ordovician(T~4_7) has changeful karst ground feature.These characteristics reflect that the carbonate reservoirs in the upside of Ordovician and the Yijianfang formation and Yingshan formation of middle Ordovician probably possess hydrocarbon available.It also indicates that Tahe Oilfield has a wide development space of hydrocarbon.The application to more than fifty wells proves that the method using more parameters to determine reservoir type is effective.And the method can be applied to reservoir evaluating of new-drilled well and further analyzing of old-drilled well in oil region.