基于同步辐射CT的非常规油气储集层微纳孔隙三维多尺度结构研究

As the new highlight of oil and gas resources, the exploration and development techniques of unconventional oil and gas become important directions of international energy strategy. Unconventional oil and gas are widely distributed in great reserves in China, which have broad prospects of exploration and development. The reservoir rocks have complicated and various pore structures, which haven't been fully understood. The investigation of characterizing pore structures is one of the fundamental problems in reservoir researches, which is very important to the study of the reservoir occurrence state, migration mode and percolation mechanism. However, the researches are in the exploratory stage. Present pore characterization methods are extremely difficult to get three-dimensional pore structures with multi scales. The project is based on the advantages of synchrotron radiation light source with high flux and high monochromatic, using multi-energy synchrotron X-ray micro-CT and data-constrained modelling (DCM) method to achieve the resolution that single energy CT can't realize, aiming to quantitatively characterize the three-dimensional pore structures of reservoir rock such as shale and tight rock with multi-scale from nano to micro meters. The main task of this project is to optimize CT technology, build the specific DCM model, characterize the multi-scale three-dimensional pore structures, establish its connection model, analyze the dependence of recoverable reserves on its connectivity, and aperture size and make our method an effective approach of pore structure studies. Implementation of this project is a significant importance to unconventional oil and gas exploration and development technology researches.

非常规油气资源作为油气勘探的热点，已成为国际能源战略的重要方向。我国非常规油气资源丰富，具有广阔的勘探开发前景。非常规油气储集层孔隙结构复杂多样，特征不清。如何准确全面表征孔隙结构特征成为储集层研究的重要基础问题，对油气赋存状态、运移方式和渗流特征等基础地质问题研究异常重要。国内外学者对此均处于探索阶段。现有孔隙表征方法均无法全面得到储集层孔隙多尺度三维结构。本项目基于同步辐射先进光源高通量、高单色性等优点，利用同步辐射X射线多能显微CT(μCT)结合数据约束模型(DCM)的方法，实现单一能量CT无法达到的分辨率，对致密岩和页岩等储集岩孔隙进行纳米到毫米多尺度三维结构表征；建立其孔喉大小、形态及连通性的定量关系；探讨其孔隙结构形态、油气储集空间构成和赋存状态等。针对致密砂岩、致密灰岩及页岩等不同储集体，优化CT技术和DCM模型，使其成为非常规油气储集层孔隙定量研究的一种有效方法。

非常规油气资源作为油气勘探的热点，已成为国际能源战略的重要方向。我国非常规油气资源丰富，具有广阔的勘探开发前景。非常规油气储集层孔隙结构复杂多样，特征不清。如何准确全面表征孔隙结构特征成为储集层研究的重要基础问题，对油气赋存状态、运移方式和渗流特征等基础地质问题研究异常重要。现有孔隙表征方法均无法全面得到储集层孔隙多尺度三维结构。本项目基于同步辐射先进光源高通量、高单色性等优点，利用同步辐射X射线多能显微CT(μCT)结合数据约束模型(DCM)的方法，实现单一能量CT无法达到的分辨率，对致密岩和页岩等储集岩孔隙进行纳米到毫米多尺度三维结构表征；建立其孔喉大小、形态及连通性的定量关系；探讨其孔隙结构形态、油气储集空间构成和赋存状态等。针对致密砂岩、致密灰岩及页岩等不同储集体，优化CT技术和DCM模型，使其成为非常规油气储集层孔隙定量研究的一种有效方法。通过同步辐射多能显微CT结合数据约束模型的方法对碳酸盐岩、不同产地页岩进行孔隙结构研究。对四川盆地东北朱家1号井的三叠纪飞仙关组碳酸盐岩研究，得到该部分样品的孔隙率为3.8%，方解石和白云石的含量分别为11.5%和84.7%。陆相页岩取自中国四川盆地须家河组三叠纪页岩油气藏。该页岩的矿物组分复杂，通过简化模型，得到样品的孔隙率为6.5%，矿物组的含量分别为76.8%和16.7%。对来自准格尔盆地页岩不同区域的样品进行多尺度孔隙和矿物分析，得到两个区域的孔隙及矿物分布。结果发现，该页岩具有很强的各向异性，两个区域的孔隙率分别为1%和3%左右，另外两个区域中的主要矿物也不同，分别为长石和白云石。该结果其脆性矿物结构有助于压裂技术的选择。同时定量计算了两个区域页岩中最大孔隙的分形维数，分别为2.34和2.86。利用分形维数结果，可以建立数字模型，模拟流体渗流特性等。本项目为非常规油气储集层孔隙定量研究提供了一种有效手段。