Flow description of gas well in basement granite reservoir from well test analysis

Abstract

A sweet gas exploration well, penetrating 3286 feet thickness of Granite Basement with 200 feet thickness of extensive fracture was tested. Initial step was to study all geological and petrophysical aspects of reservoir and well. These data were used to obtain the sense of reservoir shape model and its fracture flow behaviour. Interpreting the log gives the presents of partial fracture and open fracture, which are shown in the early time region as a fracture dominated flow and very small wellbore storage effect. The bilinear flow before middle time region and followed by two porosity fracture model at middle time region are shown afterward. Constant pressure circle boundary is shown in the late time period. In summarized, the well flow model is in infinite acting conductivity with two porosity pseudo steady state reservoir model and constant pressure circle boundary. The permeability is 1.45 mD, with -0.52 skin and 1962 Psia reservoir pressure; meanwhile the fracture coefficient is 50 mD-ft, storativity is 0.51, and interporosity flow coefficient is 4.38x10-6 mD-ft. All well and reservoir data pertaining well test is very important for getting a reliable well test interpretation result; to get better understanding reservoir flow behaviour; in this case the reservoir is tight with expected better reservoir outside circle boundary.