Unsteady State Flow Behavior And Its Application For Two Composite Gas Reservoirs

Although many composite gas reservoirs have been explored at home and abroad, there are only a few of researches about the behavior of unsteady fluids flow through porous media for composite gas reservoirs. Thus, it makes practical significance to analysis the behavior of unsteady fluids flow through porous media for composite gas reservoirs.A lot of scholars at home and abroad have studied on composite reservoirs, while most researches are focused on pressure distribution for oil rather than gas reservoirs. Based on the investigation of most literatures, this thesis has developed a method to analysis the characteristics of unsteady fluids flow for composite gas reservoirs, which based on the theory of unsteady fluids flow through porous media in homogeneous reservoirs.First of all, this thesis derived the formula of pressure distribution for infinite,closed circle and constant pressure circle composite gas reservoirs, and gave the curve plate for dimensionless well pressure and its derivation, and we found that the history of well pressure and its derivation are similar for composite reservoirs when their boundaries are changed. (1) The feature of well pressure and its derivation are just like that of infinite composite gas reservoirs when pressure disturbance did not contact the external boundary. (2) The well pressure derivation has two horizontal period, the value of the first one is 0.5, which responses the reaction of I area, and the second value of horizontal period is 1/2M, which responses the reaction ofâ…¡area.Secondly, we evaluated the time when different flow periods appeared through asymptotic analysis.Thirdly, this thesis analyzed factors that affect the decline of production for composite gas reservoirs. It emphasized on the changing of production and cumulative production vs. time at outer boundary conditions of infinite,closed circle and constant pressure circle. This thesis also probed the effects of inner radius and mobility ratio and some other parameters which affect the decline of production. What's more, this thesis mainly studied on two aspects of the method of deliverability analysis. The first is the research of the method of conventional deliverability analysis. It derived the binomial deliverability formula for composite gas reservoirs and discussed the reasonable condition for its application. The second is the research of the method of modern deliverability analysis. On the basis of the method of RTA, it derived Fetkovich/Arps decline curves of combined production which are suitable for composite gas reservoirs systems, analyzed the curve plate of production and cumulative production. It is great practical value to develop the method of Blasingame type curves analysis and mapped the curve plate on the basis of Fetkovich/Arps decline curves of combined production for composite gas reservoirs systems.Finally, we list an example to use the curve plate of well pressure and that of Blasingame production rate decline curve for composite gas reservoirs to study the field production data. The reservoir parameters can be determined by this method, which may provide reliable criterion both to estimate the characters of gas reservoirs and to establish the development program.