Research Of Flow Mechanism Of Fracture-cavern Carbonate Reservoirs In Tahe Oil Field

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 fracture-cavern carbonate reservoirs are signified to our national petroleum strategy.The Tarim Oil Field is the biggest marine carbonate oil field in our country, whose major reservoirs are the fracture-cavity type carbonate reservoirs in Yijianfang and Yingshan formation of middle-lower palaeozoic ordovician group, which are characterised by deep burial, strong heterogeneity, complex factors affecting the development of reservoirs, and the big difficulty to describe the reservoirs. So these reservoirs could be said as the most complex and special carbonate reservoirs in the world. By now, there is no equivalent method or theory 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 fracture-cavern carbonate reservoirs, witch is the theoretical base of rational development in naturally fracture-cavern carbonate reservoirs;Firstly, based on the analysis of poroperm characteristics,apparent knowledge of core,NMR,CT scanning technique,Cast thin section analysis,constant velocity mercury injection technique and displacement experiment of core, the character of the core of Tahe oil field is systematically studied; The testing indicates that: the storage and penetrability of the core are mainly contributed by micro-fracture in the matrix reservoir. It is then demonstrated that the micro-fractures and the core are considered as equivalent continuum, which maybe named rock mass. Without considering micro-fractures, when theory of medium of fracture-cavern carbonate reservoirs is made research;Secondly, based on the analysis of the character of the fracture-cavern carbonate reservoirs, laboratory flowing experiments are developed. The experimental study indicates that: the porosity and penetrability of the core are low, meanwhile non-Darcy flow is objective in matrix, and the apparent penetrability is the functional relation of pressure gradient; Finally, the seepage model has been established.Finally, the single-phase flow in combination model of fracture and cave is studied on the base of numerical computation and experiment. It indicates that pressure and production of cave present exponential decline characteristic in elastic production experiment for closed single cavity -fractured system. The decline models of pressure and production for cave are theorized based on the law of material balance and hydraulic theory. The volume of cavity may be calculated by the exponential decline models, meanwhile the average flow conductivity of fracture may be developed by the decline models of pressure and production. What 's more, it has been pre-established for the exchange theory for non-stabilized flow from matrix to insular cavity as well as from matrix to infinite conductivity fracture, which is the base of research of flow mechanism of fracture-cavern carbonate reservoirs.