Research On The Influence Of Fluid Pressure On The Acoustic Properties Of Carbonate Reservoirs

Acoustic characteristic of rock is very important.The relevant characteristics of the rock can be obtained by processing acoustic information.However,the acoustic information is complex,which is affected by some factors.And the fluid pressure is the important factor that affect the acoustic information.The internal structure of fracture-cave carbonate is complex and its heterogeneity is strong result in that it is more difficult to deal with acoustic information of fracture-cave carbonate.Therefore,the investigation of acoustic characteristics under different pore pressure is very importance to deal with acoustic information of carbonate reservoir.In this paper,the fracture-cave carbonate of Longwangmiao Formation are studied.The acoustic experiment under different fluid pressure is carried out.On the basis,the influence of pore pressure on the acoustic characteristics of different types of carbonate are investigated.From the view of qualitative:the influence of different pore pressure on the acoustic time and time-frequency characteristics of different types of fracture-cave carbonate is stated.From the view of quantitative:using the wavelet transform to dispose the acoustic information under different pore pressure and the relationship between pore pressure and acoustic anomaly information of different types of carbonate is investigated.Experimental research and the result show that:(1)for the carbonate cores without pore pressure,the acoustic time decrease with the increase of ultrasonic frequency,and the longitudinal time is smaller than transverse time at the same frequency;The attenuation coefficient tends to increase with the increase of ultrasonic frequency.(2)For hole-type carbonate under the different pore pressure.,With the increase of pore pressure,the acoustic time increase significantly and the energy of waves decreased significantly;The main frequency offset of longitudinal wave is obvious and the main frequency offset of transverse wave is small.There is a good linear relationship between pore pressure and acoustic anomaly information.(3)For fracture-cave carbonate under the different pore pressure.With the increase of pore pressure,there is an obvious increase of acoustic time.The main frequency offset of longitudinal wave is small.There is bad linear relationship between pore pressure and acoustic anomaly information,and the changes are chaotic.(4)For dense carbonate under the different pore pressure.With the increase of pore pressure,the acoustic time increases obviously,the energy of wave decreases obviously,and the main frequency offset of longitudinal wave is the smallest.There is a good linear relationship between pore pressure and acoustic anomaly information.