Research Of Flow Mechanism Of Fissure-cavern Carbonate Reservoirs

In company with our country's increasing energy demand, the exploration and development of unconventional reservoirs became more and more important. Because of its large reserve volume and high productivity, naturally fractured vuggy carbonate reservoirs are signified to our national petroleum strategy. Be different with conventional classic reservoirs, the most outstanding problem of fractured vuggy carbonate reservoirs are extreme heterogeneity and the various scales of fracture and vuggy fabric and multifold connection. All these made a great deal of difficulty in the development of carbonate reservoirs. By now, there is no efficient method of development of this kind of reservoir home and abroad. So in order to provide the technique support for developing the reservoir scientifically, it is essential to carry on the percolation mechanism research of naturally fractured vuggy carbonate reservoirs.Firstly, the character of the core of Tahe oil field is systematically studied based on NMR, CT scanning technique, and much profound knowledge of fractured vuggy carbonate reservoir is acquired. Secondly, The single-phase flow in fracture and cave is studied on the base of numerical computation and experiment. The flow law , which can provide theoretical support to establish flow equation of fractured vuggy carbonate reservoir, is studied . Result showed that swirl in the cave will be bigger if flow velocity is faster. Based on the experiment result and numerical simulation result, we can know that the law of flow in fracture and cave is accordance with fluid mechanics equation. Lastly, in accordance with the characteristics of fractured vuggy carbonate reservoir, a basic idea for studying the flow law in this kind of media is put forward: this kind of fractured vuggy reservoir system is decomposed into big fracture vug units and microscopic fracture and corroded hollow units, and in the big fracture vug units there not exists porous media, the fluids belongs to free flow and can be simplified to tube current.; the law of flow of minute crack and corroded hollow is accordance with Darcy's law. The numerical model is put forth and calculated through projection method. Flow field in fracture and cave is obtained and distribution of pressure and velocity is also given in this paper. Numerical computation and experiment show that the flow from fracture to cave is similar to jet flow if the velocity is big enough. A new hydrodynamic model, which is based on the tubing flow theory, is put forth in this paper. Exploitation performance and water cut changes are also simulated in this paper.Innovates of this paper are as follows:(1) The characteristics of carbonate reservoir are studied, and experimental results show that matrix can not be as effective reservoir, store ability and permeability of the rock core are provided by micro fracture, so the reservoir is divided into macro fracture system and micro fracture system, not the classical triple-medium.(2) A new coupled hydrodynamic model, which is based on the tubing flow theory and knowledge of seepage , is put forth in this paper, the pressure distribution is calculated, Exploitation performance and water cut changes are also simulated in this paper.