Tight Gas Reservoir Production Analysis Method

There are a wide range of distribute tight gas reservoirs in our country. The gas reserve in tight gas reservoirs occupies a great amount of proportion in the whole gas reserve. The gas flow mechanism in the tight gas reservoir is very complicated and the research about it is very difficult, which makes us analysis the production performance of tight gas reservoir usually by using general gas reservoir analysis method. This makes the analysis result inaccurate. This paper takes deliverability analysis method of tight gas reservoir as the research goal, Based on surveying and studying the documents systematically, deeply analyzing and studying the current research situation both at home and abroad, a series of research achievements are gotten through synthetically applying knowledge in many aspects such as reservoir geology, fluid flow theory through porous media, partial differential equation, optimization theory and computation mathematics etc. Many achievements are firstly presented both at home and abroad. At the same time, this paper indicates that these achievements have very wide application through a large number of case studies. Generally speaking, this paper has made the important breakthrough in the following several respects:1, Analyzing the forming factors, the factors that affect permeability,the characteristics and the influence mechanism of tight gas reservoir from the angle of gas reservoir geology.2, Basing on the practical flow characteristics of tight gas reservoir, the exponential flow equation is simplified to Darcy's flow equation in low speed, which simplify the problem and consider the effects of constant flow speed, constant pressure gradient and starting pressure gradient to the dropdown performance of tight gas reservoir. Using Laplace transformation and Green's function method, the solution of this model in Laplace zone is obtained, then, we have made theory curves and discussed the effects of constant flow speed, constant pressure gradient and starting pressure gradient to the dropdown performance of tight gas reservoir.3, Generally, the influence equations producing with positive output and negative output have different forms, which holdback the application of the superpose principle to the pressure. The tow forms in different cases are transformed to a single equation in this paper, and then the solution of different cases is unified, which establish the foundation for deducing general formula of pressure build-up equation and pressure drop-off equation in multi-rate testing.4, On the basis of the nature of Laplace and inverse transformation, we obtain the concise solution in real space by introducing additional function conception5, As the solution is abstained successfully about the flow of gas in tight gas reservoir, the general formula of pressure buildup about the flow of gas in tight gas reservoir and the formula in multi-rates testing are deduced in this paper.6, The productivity analysis method of tight gas reservoir is presented in this paper, then, we establish the optimal model of gas well productivity analysis and discuss the method to solve the model.7, We establish the gas reservoir productivity analysis model when the formation pressure isn't determined accurately. At last, we analyze the practical testing data of 11 wells in ChuanXi gas field. The results of analysis indicate that has strong reliability and extensive practibility.On the basis of the research of this paper, we have formed a set of theoretical system about tight gas reservoir deliverability analysis, which makes the gas reservoir engineering perfect and abundant. The achievements have high theory value and wide application prospect and established the theoretical foundation for guiding the development of low permeability gas reservoir and determining the rational working system of gas wells.