Calculation of Horizontal Well Productivity in Low Permeable Gas Reservoirs Using Modified Isochronal Test
1Research Institute of Petroleum Industry
2Department of Petroleum and Natural Gas Engineering, Istanbul Technical University
3Dana Energy Company
Gas reservoirs are well-known as one of the most important energy sources in the world. By using horizontal wells, the production performance would be more efficient due to the larger contact surface of the well with the formation and drainage area. Although some methods have been presented for evaluating vertical well productivity in low permeability gas reservoirs, the detailed information regarding horizontal wells in low permeable gas reservoirs have not yet been deeply addressed. Direct use of isochronal test calculations in modified back pressure test would overestimate the pressure drawdown and therefore underestimate the productivity. To overcome this issue, in this study, the traditional back pressure test calculations were modified based on the isochronal test so the productivity of a gas well can be accurately determined. The “process conversion-flowing pressure correction” method was used to convert the modified back pressure test process into the isochronal test. By doing so, the isochronal test calculations could be used in modified back pressure and gas well productivity was correctly estimated. Here, this method was applied in horizontal gas wells at early-time flow and the productivity diagrams were plotted. Furthermore, a graphical comparison between the correct and inaccurate productivity are presented that validates the results of simulation