PRESSURE TRANSIENT RESPONSE OF PARTIALLY FRACTURED RESERVOIRS

This paper presents a new approach for modeling partially fractured reservoirs. In many fractured reservoirs, fractures can be found in limited zones; however, most of the existing models idealize naturally fractured reservoirs by assuming a continuous uniform fracture network oriented parallel to the principle axes of permeability. The multiple porosity-Dual permeability model that is presented in this work gives us the possibility of modeling partially fractured reservoirs. First, the continuity equations based on the multiple porosity-dual permeability model are expressed and solved. Then, the pressure transient response based on this model is obtained for some synthesized cases. For a partially fractured reservoir, the block size of some of the elements in the synthesized cases is considered so big that the effective permeability, shape factor and fracture porosity of those elements tend toward zero. The connection between the matrix blocks in this model causes fluid to move through the matrix blocks in the element without a fracture network or with zero effective permeability. The results show that the effect of partial fracturing on the pressure transient response depends on the thickness and distribution of conventional layers in a naturally fractured reservoir. It is shown that a thick conventional layer in a naturally fractured reservoir is characterized by a straight line of slope more than unity on the pressure derivative during buildup periods. However, thin and scattered conventional layers could not be characterized by use of pressure transient response.