Abstract:

When selecting the drawdown pressure during drill stem test (DST), it is generally necessary to consider various factors such as downhole safety, pipe string safety, construction efficiency, etc. For low porosity and permeability matrix sandstone formation, it is also necessary to consider removing near-well pollution as much as possible, reducing stress sensitivity and reservoir damage, etc. in order to obtain more accurate productivity data. Considering the requirements above, and based on the study of the sensitivity of matrix sandstone reservoir, in this paper, changes of the permeability field and stress field are analyzed around the well after considering the stress sensitivity, and a multi-factor drawdown pressure model of low porosity and permeability matrix sandstone gas reservoir test is established from three aspects, including wellbore stability, invasion backflow, and productivity restriction. The field application results show that this model can guide the selection of drawdown pressure of low porosity and permeability matrix sandstone gas reservoir, and provide a theoretical basis for the design of DST drawdown pressure.

Key words: low porosity and permeability, matrix sandstone, drill stem test (DST), drawdown pressure, stress sensitivity, well stability, productivity restriction