The
oil and gas industry is plagued by inevitable formation damaged
in the wellbore proximity during entire life of the well. Therefore,
it is indispensable to ameliorate the damaged permeability by either
using conventional applied techniques or ultrasonic-assisted stimulation
method. The latter is characterized by efficient, simple and convenient,
and environmentally secure method. Due to these distinguished characteristics,
the demand of this physical Enhanced Oil Recovery (EOR) technique
increased in petroleum industry. In this study, ultrasonic waves and
hydrochloric acid (HCl) were used separately as well as in combination
to recover the lost productivity caused by calcium carbonate (CaCO3) inorganic plugs in low permeability sandstone core samples.
Results showed that permeability recovery increased with irradiation
time up to 100 min; however, it decreased with further irradiation.
This deviation could be due to particles bridge formation at later
stage. In addition, optimum frequency and power of ultrasonic waves
(20 kHz and 1000 W) significantly recovered the damaged permeability.
Although maximum frequency (25 kHz) could not achieve maximum permeability,
but higher power was quite effective. The damaged permeability recoveries
of HCl and ultrasonic waves were 44.5% and 37.6% respectively, but
the permeability recovery was escalated to 61.5% when HCl and ultrasonic
techniques were applied together. Inorganic plugs using ultrasonic
waves could chiefly be caused by cavitation, acoustic streaming, and
heat generation in three different ways, such as cavitation, boundary
friction and transformation upon hitting the medium.
A 2-D finite element model of human cochlea is established in this paper. This model includes the structure of oval window, round window, basilar membrane and cochlear duct which is filled with fluid. The basilar membrane responses are calculated with sound input on the oval window membrane. In order to study the effects of helicotrema on basilar membrane response, three different helicotrema dimensions are set up in the FE model. A two-way fluid-structure interaction numerical method is used to compute the responses in the cochlea. The influence of the helicotrema is acquired and the frequency selectivity of the basilar membrane motion along the cochlear duct is predicted. These results agree with the experiments and indicate much better results are obtained with appropriate helicotrema size.
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