数字井筒构建与声电物理属性模拟研究

In recent years, digital core technology has made many useful results in the logging field. However, the scale of the digital core is still at centimeter-level or smaller. So it can't effectively study the law and mechanism of the impact of macroscopical factors on petrophysical properties and it can't effectively explain sonic, resistivity characteristics of tight reservoir. Meanwhile, the ideal model for the simulation based on physical field theory is simple and can't effectively reveal the sonic, resistivity characteristics of tight reservoir. Combining the past six years research in the digital core, the applicant proposes a method to construct 3D digital borehole which is consist of a complete set of strata in the vertical direction and borehole, invaded zone, original formation in the radial direction. First, building a high precision 3D digital core as the trainning image. Then, getting the rock structure, particle size, pore distribution, fracture and other two-dimensional information offered by electrical imaging and NMR logging.Finally, using multi-scale and multi-point statistics (MPS) method to establish the digital borehole. Finally, the finite element method and lattice Boltzmann method are used to simulate sonic, electro-physical properties of the digital borehole and also compared with the results of physical field theory. Based on these research, explaining the acoustic, resistivity characteristics of tight reservoir even the unconventional reservoir and proposing a new interpretation model via study the impact of various factors on the petrophysical properties, and adapt to the arrival of the three-dimensional digital rock physics and three-dimensional digital logging era.

近年来，数字岩心技术在测井领域取得了诸多有益成果，但数字岩心研究的尺度均为厘米级或以下，不能有效地研究宏观因素对致密储层声波、电阻率等岩石物理属性影响的规律和机理，而由于传统的物理场论模拟所采用的模型比较理想，也不能有效揭示致密储层声波、电阻率特征。为此申请人结合近六年在数字岩心方面的研究成果，首先选取有代表性的地层构建起高精度的三维数字岩心，然后利用电成像与核磁测井提供的岩石结构、粒度、孔隙分布、裂缝等二维信息，通过多尺度融合和多点统计学等手段建立起纵向由一套完整的地层相序，径向由井眼、侵入带和原状地层组成的三维数字井筒。采用有限元、格子玻尔兹曼等数值模拟方法开展数字井筒的声、电物理属性模拟，并与传统物理场模拟结果对比，在此基础上研究各种因素对岩石物理属性的影响规律,为解释致密储层乃至非常规储层声波、电阻率特征及提出新的解释模型奠定基础，主动适应三维数字岩石物理和三维数字测井时代的到来。

近些年来数字岩心技术在国内外取得了长足的进步，常规的数字岩心分析手段已经较为成熟。但是岩心分辨率与岩心大小的矛盾关系限制了数字岩心技术的应用范围。本项目在常规数字岩心技术研究的基础上，将数字岩心模型从单一尺度扩展到多尺度，构建了多尺度数字岩心，通过建立数字井筒模型，可以将从数字岩心模拟结果升尺度到井筒尺度，与测井解释相结合，同时可以基于数字井筒开展宏观的物理属性模拟。主要研究内容和成果如下：.1）构建厘米级的数字岩心。本项目实现了几种数字岩心尺度融合的方法构建可达到厘米级的多尺度数字岩心模型。通过岩心多分辨率CT成像、图像配准、跨尺度标定分割的方法构建柱塞岩心的多尺度数字岩心模型；通过融合跨尺度孔隙网络模型构建与实际孔隙结构相吻合的多尺度孔隙网络模型；通过多点地质统计学由粗尺度数字岩心构建对应细尺度数字岩心；通过利用压汞、核磁和孔隙网络模型技术，添加丢失掉的微孔隙，建立高分辨率数字岩心。.2）构建数字井筒。本项目实现了利用全直径岩心CT图像和电成像图像构建三维数字井筒模型。通过多点地质统计算法，对电成像图像的空白条带进行填充；通过浅侧向电阻率刻度电阻率，根据阿尔奇公式求解孔隙度，将电成像图像转换为孔隙度图像；通过柱塞岩心对全直径岩心刻度实现孔隙度转换；基于多点地质统计算法结合电成像和全直径岩心的孔隙度数据构建数字井筒模型；.3）基于数字岩心、数字井筒的数值模拟研究。完成了基于井筒的泥浆侵入数值模拟；完成了基于井筒的阵列方位侧向测井正演模拟；研究了不同参数条件下的数字岩心和井筒储层物理属性变化规律。