自然伽马测井约束的火山岩储集层孔隙度计算方法

火山岩岩性复杂多变，不同岩性化学成分变化大，非均质性强，其骨架参数往往变化频繁，常规采用固定骨架参数计算孔隙度方法中，骨架参数往往很难确定，导致计算误差很大。文章针对火山岩储集层孔隙度评价难度大的问题，优选了与岩石骨架密度相关性好、对岩性变化反应敏感且成本低、实际容易获取的自然伽马测井值建立随深度变化的自然伽马连续变骨架模型来计算储集层孔隙度，该方法实现了火山岩孔隙度的连续定量表征，解决了孔隙度计算精度低的难题，在中拐凸起火山岩储集层孔隙度评价中取得了很好的应用效果。

Porosity Calculation Method of Volcanic Reservoir Constrained by Natural Gamma Logging

The lithology of volcanic rocks is complex and changeable, and the chemical composition of different lithologies varies greatly, and the heterogeneity is strong. Its skeleton parameters often change frequently. In the conventional method of calculating porosity with fixed skeleton parameters, the skeleton parameters are often difficult to determine, resulting in great calculation errors. In view of the difficulty in evaluating the porosity of volcanic reservoirs, this article selects the natural gamma logging values which have good correlation with rock skeleton density, are sensitive to lithological changes, are low-cost, and are actually easy to obtain to establish natural gamma logging values that vary with depth. The gamma continuous variable framework model is used to calculate porosity of the reservoir. This method realizes continuous quantitative characterization of the porosity of volcanic rocks and solves the problem of low porosity calculation accuracy. A good application effect has been achieved in the porosity evaluation of volcanic reservoirs in Zhongguai Uplift.