Research On Rate Decline Curve Based On Decline Rate Model

At present,there are some problems in traditional rate decline analysis,such as inaccurate properties of decline,imperfect theoretical system,small numbers of decline models and relatively simple modeling and analysis methods.With the increase of unconventional reservoirs in recent years,the law of decline is becoming more and more complex.In order to make a more accurate and effective analysis of rate decline,this paper focuses on the decline rate and carries out the following researches:The first is the study of decline properties.Because the decline rate can reflect the characteristics of production decline directly,and the decline rate and production are one-to-one corresponding relationship,this paper uses the decline rate as the core to carry out the rate decline analysis.By supplementing the decline rate properties,the existing decline property system is improved.At the same time,according to the new system,the decline models are reclassified,and the exponential decline and hyperbolic decline are extended to hyperbolic-decline rate inversion model.The second is the extension of the single property model.After pointing out the transformation modes of the decline models among different properties,the exponential decline rate inversion model is established based on the exponential decline rate model.And three hyperbolic expansion models are constructed for the most common class D11 property.It is pointed out that the power law exponential decline model and Duong model in recent years are also included in the decline rate inversion system,which can be simplified into the single property model.The third is the study of combinatorial property model.Two kinds of important characteristic curves are added to represent the decline rate model of complex properties.Then the linear-superposition combination model in general form is given.Under the new idea,three kinds of combination models with fixed weight and one kind of dynamic superposition relation are constructed.Finally,the example verification and analysis are given.Taking a typical gas well with weak water drive as an example,nine single property models and three combination models are validated.Taking a complex medium water drive gas well which cannot be accurately analyzed by the existing decline theory as an example,a complex combination model is demonstrated and verified.Examples show that the water drive gas reservoir has the character of rising decline rate at later period of decline.On the other hand,the single property model has high accuracy,while the combinatorial property model has higher accuracy,it also shows a wider application range.Generally speaking,the inversion system of decline rate has good breadth and accuracy in application,and increasing model parameters reasonably and effectively is the direction of traditional decline development.