含不规则形状裂缝低渗透储层的双侧向测井响应数值模拟研究

The irregular shape of fractures obviously affects the permeability, conductivity and Archie’s parameters in low permeability reservoirs. It will seriously affect the accuracy and effectiveness of the evaluation in low permeability reservoirs, if people continue to use the response results of dual laterolog (DLL) in the flat plate fractures. Therefore, it is urgently needed to carry out the numerical simulation research of the DLL characteristics of fracture shape in low permeability reservoirs. Firstly, the low permeability reservoir model, logging tool model and the corresponding parameters schemes are established. The parameter schemes of fracture tortuosity and unequal thickness are established in detail. The forward scheme for DLL in fractured low permeability reservoirs is established using the three dimensional finite element method (FEM), and the scheme are test, analyzed and optimized by using classical analytic method. Based on the parameters and forward schemes, the DLL responses in fractured low permeability reservoir with different parameters are simulated. The logging responses of fracture tortuosity and unequal thickness are calculated in detail. Finally, The response characteristics and the difference characteristics of deep and shallow lateralog of DLL in low permeability reservoirs are analyzed and summarized. The logging response and sensitivity characteristics of fracture tortuosity and unequal thickness are analyzed in detail. The research will reveal the logging response and sensitivity characteristics of fracture tortuosity and unequal thickness. A set of basic understanding and results for improving the accuracy of logging identification and evaluation in low permeability reservoirs with irregular shapes fractures can be obtained.

裂缝形状不规则对低渗透储层的渗透性能、导电能力和阿尔奇参数有显著影响，继续沿用平板状裂缝双侧向测井响应成果评价低渗透储层，势必会严重影响精度和效果。为此，迫切需要低渗透储层裂缝形状的双侧向测井响应特征的数值模拟研究。首先研究建立低渗透储层、仪器模型和相关参数方案，详细建立裂缝迂曲度、不等厚程度的参数方案；利用三维有限元方法建立裂缝低渗透储层双侧向测井的正演方案，利用经典解析方法检验、分析并优化该方案；基于参数和正演方案，模拟计算不同参数裂缝低渗透储层的双侧向测井响应，重点计算裂缝迂曲度、不等厚程度的测井响应；最后分析总结不同裂缝参数时，低渗透储层裂缝的双侧向测井响应特征、深浅侧向差异特征，重点分析裂缝迂曲度、不等厚程度的响应特征和敏感性。研究将揭示板状裂缝迂曲度、不等厚程度的双侧向测井响应和敏感性特征，获取一套可提高低渗透储层中形状不规则裂缝的测井识别和评价精度的基础性认识和成果。

裂缝形状不规则对低渗透储层的渗透性能、导电能力和阿尔奇参数有显著影响，继续沿用平板状裂缝双侧向测井响应成果评价低渗透储层，势必会严重影响精度和效果。为此，基于低渗储层特征，研究构建了形状不规则裂缝参数方案和双侧向测井仪器模型，详细建立了折弯板状裂缝的不同迂曲度参数方案，以及不等厚裂缝程度参数方案；进一步研究建立了不规则裂缝储层模型的测井正演方案；模拟计算了低渗储层含形状不规则裂缝时的测井响应，并分析总结了不同裂缝参数时，低渗透储层的双侧向测井响应特征和深浅侧向差异特征。其中，裂缝迂曲度直接影响着不规则形状裂缝储层的深浅侧向电阻率大小和“临界角”范围，表现在裂缝宽度相同时，裂缝迂曲度越大，深浅侧向电阻率值整体越大，且迂曲度越大导致深浅侧向“临界角”范围增大，但深浅侧向的差异越小，即“正异常”或“负异常”越不明显，且随着裂缝宽度增加，裂缝迂曲度对深浅侧向电阻率值仍有增大影响，但增大程度有限，且深浅侧向差异进一步变小；而裂缝不等厚程度影响着深浅侧向电阻率值大小和异常值分布范围，表现为在裂缝宽度相同时，不等厚程度越大深浅侧向电阻率整体值越低，裂缝附近电阻率值变小的深度范围更大，且裂缝宽度越大这些特征约明显，而当裂缝开度小于0.05mm时，这些影响越来越小，甚至在考虑井眼、侵入影响时，裂缝不等厚程度的影响可以忽略不计。项目按照原计划顺利完成预期研究目标，发表学术论文5篇，其中SCI检索4篇。