A Study On Productivity Forecast For Gas Wells In Both YiNan 2 And Tuziluoke Reservoirs With Low Permeability

Up to 60%~70% oil and gas proved reserves is in low permeability formation in recent exploration with 5000 X 1012m3of gas, and most of gas reserves are located in Tarim and Erdos Basin , which are the main resource of "west gas to east" project. In order to meet the national energy strategy, the key issue is to develop the tight gas fields with high efficiency and profit. The production is generally very low in low permeability field, and stress-sensitivity makes it worse because the formation stress-sensitivity makes the permeability drop down with the decrease of pore pressure during reservoir producing. Meinzer pointed out plastic deformation phenomena in porous media in 1928, and exponent and nilpotent formulations could characterize the relation between pressure and permeability. A nonlinear transient flows model for stress-sensitive formation were built, and the one classical and two classical approximately solution and t column source solution in Laplace domain were go by Pedrosa, Kikani, Wang Xiaodon, etc.The stress-sensitivity study main focus on Tuziluoke and Yinan2 gas fields in Tarim Basin: The core samples stress-sensitivity is analyzed by the servo tri-axes rock mechanics test system. The data points plot on the semi-log plot does not show a single linear curve but two or multiple stage linear curves. The main reason is that the different pore structure type has different capability to against the compress. The permeability decreased rapidly at the beginning with the increasing of confining pressure. When the confining pressure exceed a transition stage, the permeability drops down slowly at the pore compression period. These phenomena can be well characterized by two or multiple stages exponent formulation. Permeability variation equation and it's solution at three boundary conditions has got in Laplace domain. The production forecast model and the IPR curve equation for the producing well in permeability variation formation is established, and it is very useful to guide the gas field producing. The stress-sensitive index of Tuziluoke and Yinan2 gas reservoir are acquired and the well production are predicted respectively.