Productivity prediction, dynamic evaluation and reservoir heterogeneity analysis of HS 4 block carbonate gas reservoir

Productivity prediction and dynamic description of carbonate gas reservoirs are very important to improving development efficiency. In this paper, we study the productivity evaluation and reasonable production allocation of the carbonate gas reservoir in the HS 4 block. Through gas test and production data, the dynamic productivity equation of a gas well is established using various equations. The influencing factors of productivity change are analyzed, and the main control effects of geological, engineering, and production factors on productivity are discussed. Based on the study of the main controlling factors of gas reservoir productivity, the one-point method is modified to establish the gas reservoir productivity equation, predict the new drilling productivity, and put forward reasonable production allocation suggestions. The seepage model of a single well and well group based on a fractured-vuggy gas reservoir is constructed, and the reservoir permeability characteristics of the gas reservoir are described in detail. Notably, this study innovatively modifies the traditional one-point method by classifying reservoir types (pore-type and fractured-vuggy) to establish targeted productivity equations, effectively addressing the accuracy limitations of single-method applications in complex carbonate gas reservoirs. Furthermore, the integrated use of grey correlation analysis, Pearson method, and fractured-vuggy seepage models realizes the comprehensive quantification of geological, engineering, and production factors on productivity, which fills the gap of lacking a unified and multi-method collaborative productivity prediction framework for such reservoirs in previous studies. The research shows that (1) The thickness and physical properties of fractured-vuggy reservoirs are positively correlated with gas well productivity, and the water production of gas wells is negatively correlated with productivity. (2) The modified one-point method and the dynamic model method can effectively predict the new drilling productivity and optimize the gas well production plan. (3) Wellbore pressure loss and near-well pressure loss are the main influencing factors of gas well productivity. (4) The analysis of the grey correlation method and the Pearson method shows that there is a significant correlation between geological, development, and engineering parameters and gas well productivity, which provides a basis for gas reservoir development.