DISCUSSION ON THE GEOLOGIC CHARACTERISTICS AND OFFTAKE STRATEGY OF LOW PERMEABILITY SANDSTONE GAS RESERVOIRS

The main geologic characteristics of low permeability sandstone gas reservoirs are high antisotropic,small pore-throats radius,high shale content and high water saturation.Its exploitation's characteristics are:the natural productivity of gas wells are generally low and distribution is non-equilibrium,the producing pressure differential is high ,the condition of stable production are bad,it is necessary for a majority of gas wells to sand fracturing before they are putted into production.Its offtake strategy are:the techniques of gas reservoirs fine description are used to determine the distribution area of all sorts of reservoirs,dense well pattern in high-permeability area and infill drilling are used in hole pattern,the technologies of preventing gas reservoir are emphasized during drilling and well completion,the effect of sand fracturing is increased to improve permeable capacity of gas reservoir,and adopting superchange method and drainage gas recovery method prolong producing time of gas well in late production period.