致密油储层基质渗吸规律及原油动用机理研究

Due to the characteristics of small pores, low formation pressure coefficient, high oil viscosity, fast decline of well production, high difficulty of energy supplement and hard to produce the oil in the matrix, it is key to solve the problem of how to produce the oil in the matrix effectively and keep or even enhance the well productivity after depletion. The main objective of this project focuses on the imbibition mechanism of the oil in matrix and oil producing method, and especially the law of imbibition and mass transfer in the micro-nano pores of the tight oil reservoir. Firstly, based on the static and dynamic imbibition tests and visualization model, the theory model of matrix imbibition under pore scale will be established. Secondly, the imbibition law of the elastic depletion stage in the typical tight oil reservoir will be analyzed by physical simulation. On this basis, mechanisms of energy supplement and imbibition strengthening by thermal expansion and thermal imbibition during steam flooding after depletion will be studied. The effect of temperature increase on heat transfer, expansion, wetability, and imbibition of fluid-solid coupling media in tight oil reservoir will be revealed. Then the thermal imbibition model considering heat expansion effect will be established. Thus, the development principle of the whole process including depletion, thermal expansion and thermal imbibition can be obtained. Finally, the developing mode of producing the matrix of the tight oil reservoir effectively and intensively with the characteristics of thermal expansion, viscosity declination, imbibition acceleration, threshold pressure decline was formed. The above research work will provide theoretical basis for the development of tight oil reservoir.

针对我国陆相致密油储层孔隙细微、地层压力系数低、原油粘度高、单井产量递减快、能量补充难度大、基质动用困难等特点，如何在衰竭开采后有效动用基质内的原油，提高及稳定单井产量，是急需解决的技术关键。本项目重点研究基质原油的渗吸机理，探索致密油储层微纳米孔隙中的渗吸、传质机理与规律。首先，通过静、动态渗吸实验及可视化物理模型，建立孔隙尺度下的致密油储层渗吸过程模型；其次，采用物模实验分析典型致密油储层弹性衰竭开采后渗吸规律；在此基础上，探索衰竭式开采后注蒸汽“注汽增能，热水渗吸”的动用方法及原理（包括热采条件下的热膨胀、热渗吸机理等），揭示升温对致密储层流固耦合介质中的传热、膨胀、润湿性和渗吸能力的影响，建立考虑热膨胀效应的热渗吸产量模型，获得衰竭-热膨胀-热渗吸整个过程的开发规律，形成以热膨胀、降粘、提高渗吸速度等为特点的致密油基质“强化动用”模式，为形成致密油高效开发技术提供理论支持。

针对我国陆相致密油储层孔隙细微、地层压力系数低、原油粘度高、单井产量递减快、能量补充难度大、基质动用困难等特点，通过静、动态渗吸实验及可视化物理模型、物模实验等方法分析了典型致密油储层弹性衰竭开采后渗吸规律，并在此基础上探索了衰竭式开采后注蒸汽“注汽增能，热水渗吸”的动用方法及原理，建立了考虑热膨胀效应的热渗吸产量模型，获得了衰竭-热膨胀-热渗吸整个过程的开发规律，形成了以热膨胀、降粘、提高渗吸速度等为特点的致密油基质“强化动用”模式。研究结果表明，渗吸过程中微孔作为动力孔，首先实现油水置换，渗吸采出程度最高；建立OEO、TEO、TEO-OW、AFO等不同边界渗吸模型，并提出秋困网络模型，将渗吸机理理论化和公式化。提高温度有助于提高渗吸效率，温度越高，提高幅度越大，但当温度高于150℃后，增幅下降。研究认为温度对渗吸效果的影响主要表现在原油黏度、原油膨胀和孔隙体积压缩三个方面的影响。通过研究，为形成致密油高效开发技术提供理论支持。