Abstract
In order to effectively evaluate shale gas reservoirs with low porosity, extra-low permeability, and no natural productivity, dipole array acoustic logging, which can provide various types of information including P-wave slowness (DTC) and S-wave slowness (DTS), is widely used. As the dipole array acoustic logging tool has a larger investigation depth and is suitable for complex borehole environments, such as those with a high wellbore temperature, high drilling fluid column pressure, or irregular borehole wall, it has been mainly applied to the evaluation of lithology, gas potential, fractures, and stimulation potential in shale gas reservoirs. The findings from a case study of the Sichuan Basin in China reveal that the acoustic slowness, S-P wave slowness ratio (RMSC), and S-wave anisotropy of the dipole array acoustic logging can be used to qualitatively identify reservoir lithology, gas potential, and fractures. Using the relationship between DTC and the total porosity of shale gas reservoirs, and combined with the compensated neutron (CNL) and shale content (Vsh) of the reservoir, a mathematical model for accurately calculating the total porosity of the shale gas reservoir can be established. By using the relationship between the RMSC and gas saturation in shale gas reservoirs and tied with density log (DEN), a mathematical model of gas saturation can be established, and the determination of gas saturation by the non-resistivity method can be achieved, delivering a solution to the issue that the electric model is not applicable under low resistivity conditions. The DTS, DTC, and DEN of shale can be used to calculate rock mechanic parameters such as the Poisson’s ratio (POIS) and Young’s modulus (YMOD), which can be used to evaluate the shale stimulation potential.
Highlights
Unconventional oil and gas resources, including shale gas, are very richly concentrated around the world [1]
A dipole array acoustic logging tool usually consists of three parts: the acoustic system, the
This paper describes the application of dipole array acoustic logging in shale gas reservoir evaluation and verified this method using typical shale gas wells in two blocks in the Sichuan Basin
Summary
Unconventional oil and gas resources, including shale gas, are very richly concentrated around the world [1]. Evaluation of the stimulation potential in reservoirs is an important low permeability, and no natural productivity, so shale development requires large-scale hydraulic part of shale gas reservoir evaluation and is different from conventional oil and gas reservoir fracturing. From the prospective of shale gas dipole logging, rapid and efficient evaluation of shale gas reservoirs should be carried out in terms of lithology, array acoustic logging, rapid and efficient evaluation of shale gas reservoirs should be carried out in fractures, gas potential, and stimulation. We studied the methods and features of dipole array acoustic them to the qualitative identification of the lithology, gas potential, and fracture effectiveness of shale logging in detail and applied them to the qualitative identification of the lithology, gas potential, and gas reservoirs and the quantitative evaluation of the porosity, saturation, and reservoir stimulation fracture effectiveness of shale gas reservoirs and the quantitative evaluation of the porosity, potential.
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