Study On Seepage Regularity Of Abnormal High Pressure Fractured Low Permeability Gas Reservoir

Low permeability with nature fracture gas reservoir occupies an important place in China’s petroleum industry. In this type of these gas reservoirs, the low permeability of matrix, nature fractured with high pressure gas reservoirs account for a large proportion, as Moxi and Dabei gas reservior. These reservoirs are characterized by:low permeability, reservoir fracture developed, not-high production, and unsteable economic efficiency. Meanwhile, a large number of experiments prove that the fracture has a strong effect of pressure-sensitive, high speed non-darcy flow accourd arround well porors media and the start-up pressure gradient in the low-permeability matrix; all of these factors are stimulated really complex.However, the model of dual-porosity in software Eclipse cannot be considered both low-speed non-darcy flow and stress sensitivity. This paper bases on the W-R model, for low-permeability, nature fracture with high pressure gas reservoirs is carried out within the framework of traditional percolation theory, the stress sensitivity of fracture and the start-up pressure gradient of matrix are considerated. And the causes of this type gas reservoir, geological characteristics and the development characteristics are analyzed, the flowing numerical-model which consideration the stress sensitivity of fracture, high speed non-darcy flow and the start-up pressure gradient of matrix and differential equations are established, and then gets its solution method. Finally, this paper writes software APGS-NFR for the special gas reservoirs (low-permeability, nature fracture with high pressure).The following key findings:(1)Productivity in low permeability fractured with high pressure gas reservoirs with Klinkenberg effect, non-darcy (high speed and low speed) flow and stress sensitivity. Confirm that the stress sensitivity have a stronger impact on the productivity compared with non-darcy (high speed and low speed) flow and Klinkenberg impact factor;(2)Establishs the flowing numerical-model which consideration the stress sensitivity of fracture, high speed non-darcy flow in fracture and the start-up pressure gradient of matrix, and then gives its solution method;(3)Writes numerical stimulate software APGS-NFR for the special gas reservoirs (low-permeability, nature fracture with high pressure);(4)APGR-NFR is stimulated for non-darcy (high speed and low speed) flow and stress sensitivity;(5)In considering the start-up pressure gradient and the stress sensitivity of abnomal pressure fractured low permeability gas reservoirs in the sensitivity analysis of the anisotropy, water body size(3 times is a boundary), water avoiding height on the productivity of wells (10m is well).