Abstract
Pressure response behavior of two-layered reservoir with a vertical mixed boundary is easy to be mistaken for that of the radial composite reservoir or dual-pore reservoir. It is difficult to fit the pressure response curve and easy to obtain abnormal parameter values using a misunderstood model. In this paper, we present the interpretation of three different types of pressure responses of vertical mixed boundary reservoir by our proposed models, where the diagnostic window and feature value are captured for different mixed boundary types. Results show that the mixed boundary with closed boundary and infinite-acting boundary induces the fake pressure response of a radial composite reservoir with poor permeability outer zone. The mixed boundary with the main constant-pressure and non-main closed boundary produces a fake pressure response of a dual-porosity reservoir. The diagnostic window of pressure response curves shape can easily capture the mixed boundary type, and the feature value of the feature values of pressure response value can quickly obtain the permeability ration of one layer. Aiming at different representative types of pressure response cases in the western Sichuan XC gas field, China, we innovatively analyze them from a different perspective and get a new understanding of pressure response behavior of vertical mixed boundary, which provides a guideline for the interpretation of layered oil and gas reservoir with the complex boundary in the vertical direction.
Highlights
This work intends to show a comprehensive analysis of pressure response in the vertical commingled well considering the influences of the mixed boundary in the vertical direction
According to the analysis and application results of the vertical mixed boundary model, the following observations are highlighted: 1. The pressure response of three types mixed boundary model shows that the type of mixed boundary can be quickly captured by the shape of the pressure response curve in the log–log coordinate system and the permeability ratio of one-layer can be obtained by the feature value of pressure or pressure derivative
The application of the mixed boundary model in the XC gas field can solve the problem of difficulty in fitting the well test curve
Summary
Given the poor matching of the pressure response and abnormal parameter values of the XC gas field interpreted by the conventional radial composite reservoir and the dual-pore reservoir model, the results interpreted based on these misleading pressure response behaviors are likely to be wrong To solve this problem and better understand this misleading pressure response phenomenon, this paper, based on the theoretical research of reference [11], reviews and extends three representative pressure responses behavior of the vertical mixed boundary reservoir. Pressure responses of three typical production gas well in the XC gas field, Western Sichuan Basin, are interpreted by the models we proposed to give the transient pressure well-testing engineer and analyzer a new and comprehensive understanding of the pressure response behaviors in the vertical mixed boundary reservoir. Notes: “IARF” is Infinite-Acting Radial Flow, “CBF” is Closed Boundary Flow, “CpBF” is the Const-Pressure Boundary flow
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