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基质酸化是碳酸盐岩油气藏中应用范围最广、最经济有效的增产方式之一,而酸化最典型的特征是形成酸蚀蚓孔。由于酸岩反应影响因素多、蚓孔形态多样、生长随机性强,目前仍未形成对蚓孔的定量描述方法。对碳酸盐岩酸蚀蚓孔的定量描述主要包括确定单蚓孔形态及多蚓孔分布2部分内容,这是优化施工设计、经济有效开发此类油气藏的重要前提。为此,通过多组岩心流动实验,采用三维CT扫描后重组的手段得到了蚓孔的真实形态,并验证了岩心线性和径向流动下蚓孔的分形特征,得到了其分形维数。运用分形几何学方法,建立了单蚓孔等效长度分形计算模型,为从长度和平面分布2个维度定量描述单蚓孔提供了可能。其次,为了明确不同蚓孔在空间分布情况,建立了多蚓孔间竞争分布数学模型,并对其进行了求解和模拟分析,验证了蚓孔间竞争分布的分形性特征。在此基础上,建立了蚓孔分布双重分形模型,为定量描述三维酸蚀蚓孔形态奠定了基础,也为更准确优化酸化施工提供了可能。
Matrix acidification is one of the most widely used and most economical and effective stimulation methods in carbonate reservoirs. The most typical feature of acidification is the formation of erodible wormholes. Due to many factors affecting the acid-rock reaction, the morphology of wormholes is diverse and the growth is random, so far no quantitative description of wormholes has been made. Quantitative description of the carbonate eroded wormholes mainly includes the determination of the morphology of the wormhole and the distribution of the wormhole in two parts, which is an important prerequisite for optimizing the construction design and economically effective development of such reservoirs. Therefore, through the experiments of multi-groups of core flow, the real shape of wormholes was obtained by three-dimensional CT scanning and recombination, and the fractal characteristics of wormholes under linear and radial flow were verified. The fractal dimension was obtained. The fractal geometry method is used to establish the fractal calculation model of the wormhole equivalent length, which provides the possibility to quantitatively describe the wormhole from the two dimensions of length and plane distribution. Secondly, in order to clarify the spatial distribution of different wormholes, a mathematical model of the competition distribution among the wormholes was set up, and the fractal characteristics of the competition distribution between wormholes were verified by solving and simulating the wormworms. On this basis, a dual fractal model of wormhole distribution was established, which laid the foundation for the quantitative description of wormhole morphology of three-dimension acid erosion and provided the possibility of optimizing the acidification construction more accurately.