微-纳多孔介质核磁共振响应机理与探测方法研究

Micro- and nano- porous medium, such as tight oil and shale oil reservoir, has very complicated pore structure, fluid occurrence state and molecular motion, which is make difficult to find out the mechanism of NMR relaxation. It is hard to acquire effective data in down-hole, as the spin echoes decay very fast with low signal to noise ration. This project attempts to build petrophysical models of micro- and nano- porous medium (shale oil) through digital rock imaging technology with multi-scale CT of ultra-high resolution. Combined with molecular dynamics model, fast lattice Boltzmann method will be developed with parallel computing algorithm with GPU (Graphics Processing Unit). We will try to analysis the mechanism of surface relaxation while different fluid occurred in different pore system of organic and matrix with different state, the mechanism of diffusion relaxation of adsorbed fluid and free fluid in extremely limited space. Internal magnetic field gradient produced by the difference of magnetic susceptibility between solid and liquid (solid and gas) will be detected. We will try to reduce the influence of internal magnetic field, develop new pulse sequences and data acquisition methods of effective detection of short relaxation components. The high resolution inversion methods will be employed to process the data which has low signal to noise ration. The objective of this project is to develop a NMR technology of micro- and nano- porous medium, which is more effective to evaluate the reservoir parameters of density oil and shale oil quantitatively. The state key laboratory of petroleum resources and prospecting has all the necessary facilities to support this project.

以致密油和页岩油地层为代表的微-纳多孔介质中微观孔隙结构、流体赋存状态和分子运动规律复杂，导致其核磁共振弛豫机理不明确，自旋回波信号衰减快、信噪比低，在井下难以对含油气信息进行准确而有效的探测。本项目试图通过多尺度超高分辨数字岩石成像与表征技术，建立微-纳多孔介质岩石物理模型，开发基于GPU并行计算的快速格子波尔兹曼方法，结合分子动力学模型，探索有机质和基质微-纳孔隙系统中流体分子在不同赋存状态下的表面弛豫机制，研究吸附态流体和极度受限空间中游离态流体的扩散弛豫机制，探测固-液、固-气磁化率差异产生的内部非均匀磁场，发展能够有效检测超短弛豫组分的新脉冲序列和观测模式，研究高分辨率反演方法提高短弛豫组分的分辨率，形成微-纳多孔介质核磁共振探测方法。从而为致密油和页岩油储层油气定量评价提供理论基础与观测手段。申请人及其研究团队具备相应的研究经验与创新能力，依托单位具有开展相应基础研究的各项条件

针对页岩/致密油气地层微-纳多孔介质的成岩特征、矿物特征及超微孔隙结构特征，利用高精度多尺度数字岩石图像获取、表征与整合技术，建立了岩石物理模型；采用数值模拟方法，结合分子动力学模型，获得了微-纳孔隙系统中流体分子的赋存状态及扩散特征；在分析页岩/致密岩石有机质中吸附态流体、极度受限空间中游离态流体的核磁共振响应机理的基础上，改进优化了固体回波序列、ME（Magic Echo）序列和BE-CPMG序列，提出了微纳多孔介质核磁共振数据采集和数据处理方法，形成了井下核磁共振探测新技术，在新疆某油田5口井中应用，实现了对页岩地层孔隙性、渗透性、有机质含量、含油气量等的定量计算，为页岩储量评估和高效开采的机理研究及技术优选提供理论依据与方法基础，达到了预期研究目标。项目研究过程中发表论文10篇，授权发明专利10件，其中美国发明专利2件，登记软件著作权2项，研究成果参与获得省部级科学技术一等奖2两项，获中国石油和化学工业联合会优秀发明专利奖1项，项目负责人获得中国仪器仪表学会”朱良漪“青年科技奖。参与培养博士生4人，独立培养硕士研究7人。