陇东油田长8致密砂岩储层流体性质识别方法研究

Research on fluid property identification method of Chang 8 tight sandstone reservoir in Longdong oilfield

长8储层属于低孔低渗储层,储层非均质性强,孔隙结构复杂,油水层分异较小,流体性质识别难度大。本文为了解决陇东油田长8致密砂岩储层流体性质识别难题,通过大量文献调研,将低孔低渗储层流体性质识别难点和常用流体性质识别技术方法进行了梳理。低孔低渗储层流体性质识别难点与常规储层流体性质识别难点有所不同,研究表明低孔低渗储层流体性质识别难点既与岩性、泥质含量及胶结物、砂泥岩薄互层等宏观因素有关,又与复杂孔隙结构和地层水及泥浆滤液等微观因素有关。常用低孔低渗储层的流体性质识别方法有电阻率特征判别法、曲线重叠法、参数交会图法、无侵线法、核磁共振测井法、模糊识别法和机器学习法等,本文通过使用几种常用流体性质识别方法和基于GBDT决策树的流体性质识别方法对研究区陇东油田长8致密砂岩储层的流体性质进行识别,通过对比寻找出低孔低渗储层流体性质的有效识别方法。研究表明常用流体性质识别方法在应用到低孔低渗储层时效果不佳,而使用基于GBDT决策树的流体性质识别方法应用到研究区时效果较好,识别精度较高。

The Chang 8 reservoir is a low-porosity,low-permeability reservoir with strong reservoir heterogeneity,complex pore structure,small oil-water layer differentiation,and difficult fluid properties identification.In this paper,in order to solve the Longdong oilfield Chang 8 dense sandstone reservoir fluid properties identification problems,through a large number of literature research,the low pore low permeability reservoir fluid properties identification difficulties and common fluid properties identification technology methods have been sorted out.The difficulty of fluid properties identification in low-porous and low-permeable reservoirs is different from that in conventional reservoirs.The study shows that the difficulty of fluid properties identification in low-porous and low-permeable reservoirs is related to macro factors such as lithology,mud content and cement,thin interlayer of sand and mudstone,and micro factors such as complex pore structure and formation water and mud filtrate.The commonly used methods to identify the fluid properties of low-porosity and low-permeability reservoirs include resistivity feature discrimination method,curve overlap method,parameter intersection diagram method,non-intrusive line method,NMR logging method,fuzzy identification method and machine learning method,etc.In this paper,by using several commonly used fluid properties identification methods and GBDT decision tree based fluid properties identification method to identify the fluids properties of Chang 8 dense sandstone reservoirs in Longdong oilfield in the study area,find out the effective identification method of low porosity and low permeability reservoir fluid properties through comparison.The study shows that the commonly used fluid properties identification methods are not effective when applied to low pore and low permeability reservoirs,while the GBDT decision tree based fluid properties identification method is more effective and has higher identification accuracy when applied to the study area.