基于恒定梯度编码一维选层T_(2)谱的胶结砂岩层析成像方法  

Tomography Method of Cemented Sand Based on Constant Gradient Coded 1D T_(2)Spectrum

作　　者：吴土荣[1] 陈金定[1] 张群[1] 赵希春 郭敏灵 程芳桂 WU Turong;CHEN Jinding;ZHANG Qun;ZHAO Xichun;GUO Minling;CHENG Fanggui(CNOOC Energy Technology&Service Limited Zhanjiang Branch,Zhanjiang,Guangdong 524057,China;Qingdao Shida Huatong Technology CO.LTD.,Qingdao,Shandong 266400,China)

机构地区：[1]中海油能源发展股份有限公司工程技术湛江分公司,广东湛江524057 [2]青岛石大华通科技有限公司,山东青岛266400

出　　处：《测井技术》2024年第2期190-197,共8页Well Logging Technology

基　　金：广东省软科学研究计划项目“广东省海上高温高压油气藏勘探开发企业重点实验室”(2018B030323028)。

摘　　要：核磁共振成像是探究岩心尺度非均质性的先进技术,受岩石复杂性和编码技术影响,现有方法效果不佳。基于梯度场的二维/三维核磁共振技术成像容易但信噪比低,无梯度场的传统选层T_(2)谱(频率编码/相位编码)方法效率低。该研究提出恒定梯度编码一维选层T_(2)谱层析成像方法,做到了成像数据体量小、信噪比高且信号更完整。层析T_(2)谱图像及其热度分布,能够有效表征毛细管压力和成岩作用对流体非均匀分布的影响。饱和油状态时,T_(2)谱层间差异性反映成岩作用影响。高饱和油阶段,轴向热度图反映了低毛细管压力游离油的脱出规律。完全驱替后毛细管压力进入稳定状态,轴向热度图反映了微孔中吸附油赋存状态的差异。该技术在胶结砂岩气驱油实验中取得了良好效果,并对解析强非均质岩石渗流规律有重要作用。Nuclear magnetic resonance(NMR)imaging is an advanced technology for core-scale heterogeneity analysis.Affected by rock complexity and encoding technology,existing methods are not really effective.2D/3D nuclear magnetic resonance technology based on gradient fields is easy to image but has a low signal-to-noise ratio.The traditional T_(2)method(frequency coding/phase coding)without gradient field is in low efficiency.This study proposes a tomography method based on constant gradient coded 1D T_(2)spectrum,which can achieve small imaging data volume,high signal-to-noise ratio and more complete signal.Tomographic T_(2)spectrum images and their heat distribution can effectively characterize the effects of capillary force and diagenesis on the non-uniform distribution of fluids.In the oil-saturated state,the difference between T_(2)spectrum layers reflects the influence of diagenesis.The heat change of the image in the high saturation stage mainly reflects the displace pattern of low capillary force controlled free oil.After complete displacement,the capillary force enters a stable state,and the axial heat reflects the difference of micro-pore content that filled with adsorbed oil.The new technology has achieved good results in gas displacement experiments of cemented sandstone,and is expected to play an important role in the analysis of seepage laws of strong heterogeneous rocks.

关 键 词：岩心核磁共振 T_(2)谱成像 梯度编码 毛细管压力 非均质性 

分 类 号：P631.84[天文地球—地质矿产勘探]