弱胶结储层微观出砂机理与颗粒级尺度出砂过程模拟研究

For the sand production issue in petroleum and natural gas industry, the present macroscopical sanding mechanisms mainly involve tensile failure, compression failure and shear failure. But really, these mechanisms are essentially difficult to describe and explain the actual sand production characteristics on site. The objective of this project is to establish a new integrated theory and method for sanding mechanism and sand production prediction by microcosmic particle-scale sanding process simulation in weak consolidated reservoir including gas hydrate reservoir. Firstly, based on the casing-perforated and open-hole well completion mode, a stochastic distribution model of cement skeleton particle within the area close to the wellbore will be set up, considering the vertical and horizontal heterogeneity of rock strength. With the particle distribution model, the methodology for microcosmic particle desquamating and immigrating conditions will be developed within stress field and fluid flowing velocity field. Then a systematic visually numerical model and software package will be evolved to simulate the microcosmic sanding process. The simulation results will be furtherly verified and re-corrected by experiments work in laboratory. Finally, the new microcosmic sanding mechanism, which maybe concerns porosity liquefying, analogous earthworm cavity and continuous collapse, will be distinguished by visual simulation of sand production process. As a result, based on all of the above study, a new integrated sanding prediction model will be put forward to quantitatively predict the critical sanding pressure drawdown and productivity, sand production rate and the size of produced particles. This project and its result will provide theoretical support for the sanding prediction, sand control design and development optimization of traditional oil and gas reservoir, and newly emerging gas hydrate reservoir.

对于石油天然气领域储层出砂机理和出砂预测，现有的拉伸、压缩和剪切破坏等宏观出砂机理与预测方法难以准确有效地解释现场出砂现象和规律。项目拟针对弱胶结疏松储层（含天然气水合物储层），开展颗粒级微观出砂机理及出砂过程模拟研究，建立一套全新的微观出砂模拟和预测理论与方法。项目首先依托弱胶结储层射孔和裸眼完井模式，考虑胶结强度的纵向及平面非均质性，构建近井地带储层颗粒骨架微观随机分布模型；然后研究微观颗粒在地应力场和流速场影响下的剥离和运移条件，建立颗粒级微观出砂过程模拟的数值模型，开发可视化模拟软件，并利用微观实验装置进行验证。基于可视化数值模拟，研究孔隙液化、类蚯蚓洞以及连续坍塌三种微观出砂机理的界限条件，形成一套全新的基于微观出砂过程模拟的出砂临界条件、出砂速度和出砂粒径定量预测理论与方法。项目研究成果将对石油天然气传统能源以及天然气水合物等新能源弱胶结储层出砂与防砂及开发优化提供理论基础。

项目针对不同类型弱胶结储层的出砂问题，构建了一套弱胶结常规砂岩、泥质粉砂型天然气水合物等不同类型储层颗粒级尺度微观结构随机描述和物理建模方法，为后续微观可视化数值模拟提供了关键基础。通过可视化出砂模拟实验，创新发现了非均质岩心孔隙液化、单分支类蚯蚓洞、多分支类蚯蚓洞、连续坍塌的复杂出砂形态和机理，以及孔洞前沿单颗粒剥落离散和团簇式剥落的两种剥落形式；提出了诱发类蚯蚓洞延伸扩展的前沿砂剥落竞争机制和多分支类蚯蚓洞的非均质并发剥落机理，建立了定量表征方法及指标。实验结果为可视化出砂数值模拟提供了关键指导。基于微观可视化出砂模拟实验揭示的出砂形态，在颗粒级尺度微观结构建模的基础上，研究形成一套不同类型弱胶结储层微观出砂过程可视化数值模拟方法。基于可视化出砂模拟，研究构建了弱胶结储层的精细划分方法和界限标准。构建了一套适用于不同类型复杂条件储层的全新出砂规律预测与出砂亏空剖面精细预测方法，以及非均质储层长井段生产段的砂液产出剖面预测方法；研制开发了自主国产化的定量出砂预测软件系统；适用于弱胶结常规砂岩、水合物储层、储气库储层和聚合物衍生物聚结等复杂条件储层。延伸探索性研究了基于亏空预测的高饱和充填、分级分段砂水协同控制方法，实现出砂预测从笼统到精细亏空刻画的关键突破，为不同类型易出砂储层的精细固体(出砂)控制提供了变革性关键基础。项目共发表学术论文21篇，其中行业顶尖期刊论文8篇；出版学术专著 1部。获授权发明专利 6项，软件著作权2项。主办专业领域国内学术会议1次，参加国际学术会议3次和国内学术会议1次，共发表大会主题报告3次，分会报告8个。培养博士后1名，博士研究生1名，硕士研究生6名。项目作为现场出砂工程问题的应用基础研究，已支撑和转化应用于工程研究项目6项，成果已在指导现场出砂预测和固体控制领域的工程应用方面初见成效，并在碳酸盐岩、储气库、地热等领域也有广阔应用前景。