Array acoustic logging to evaluate gas-bearing property in tight sandstone gas reservoirs
Tight sandstone gas reservoirs of the Middle Jurassic Shaximiao Formation,Tianfu gasfield,central Sichuan Basin,have developed into the hot and key exploration domain in recent years.Different from conventional ones,such reservoirs,however,have complex lithology and poor reservoir conditions.Some variations on their gas-bearing property cannot be accurately reflected by using traditional electrical logging.Thus,array acoustic data were used to analyze curve sensitivity to this property.And two methods of longitudinal wave moveout and Lame coefficient-volume compressibility curve overlap were selected for property evaluation.Further-more,acoustic-wave experiments were conducted in rocks with different saturation to create one way to quantitatively calculate gas saturation using array acoustic data.Results show that(ⅰ)for the tight sandstone reservoirs in central Sichuan Basin,one way of curve envelope based on array acoustic data may achieve much higher coincidence of gas-bearing logging interpretation than electrical log-ging,and can better estimate the gas-bearing property;and(ⅱ)combining the ratio of longitudinal-wave velocity to transverse-wave velocity(Vp/Vs)and the bulk modulus,the calculated water saturation has a good correlation with that from sealed coring,which may not only provide basis for reservoir classification and parameter calculation but guide the evaluation on the gas-bearing property in other tight sandstone reservoirs in Sichuan Basin.
Sichuan BasinMiddle JurassicTight sandstone gas reservoirArray acoustic waveEvaluation on gas-bearing propertyCurve envelopeVp/Vs ratio
国家科技期刊平台
NSTL
万方数据
