Many
experimental studies have been conducted in the recent past
to assess the inclusion of different types of surfactant in a frac
fluid in hydraulic fracturing of low-permeable formations. These lab
studies either corresponded to spontaneous imbibition testing using
Amott cells or dynamic core-flooding tests to assess the hydrocarbon
permeability after the invasion of the frac fluid. Both these tests
have been considered independently by different authors but have not
been analyzed as one holistic approach to assess the oil recovery
potential of a surfactant. It is prudent to understand the superiority
of the specific interfacial mechanism of the surfactant that correlates
to the best-case scenario of oil recovery by considering both the
tests that lead to leak-off and follow the leak-off of frac fluid
into the matrix. In this experimental study, two tests related to
soaking and production processes are conducted simultaneously using
surfactants with different interfacial properties of interfacial tension
(IFT) reduction and wettability alteration for both low-permeable
and high permeable core samples. The oil recovery from soaking tests
are compared to the oil productivity of dynamic production tests assessed
from the calculated parameters of effective permeability of oil recovered
and flowback efficiencies. The results obtained in this study indicate
that the surfactant which simultaneously reduces the IFT and alters
the wettability of the low-permeable rock from oil-wet to water-wet
is not conducive for oil productivity during dynamic production process
despite it being very effective in oil recovery during the soaking
process. Rather, a neutral-wetting surfactant seems to produce optimal
results when the whole process of oil recovery from hydraulic fracturing
is considered. The trend in the results for flowback efficiency and
effective permeability of oil post leak-off observed in this study
across the high and low-permeable rocks could be extended to unconventional
shale rocks to safely infer that with regards to oil productivity,
it would be beneficial to avoid any leak-off of the surfactant fluid,
which showcases both IFT reduction and wettability alteration. The
insights provided in this study motivate the reader to analyze beyond
the common experimental methods of static imbibition testing in labs
to embrace the methods that consider a complete hydraulic fracturing
process for assessing enhanced oil recovery of low-permeable formations.
The invasion of hydraulic fracturing fluids into the matrix through a relatively conductive fracture network causes capillary entrapment of the fluids that lead to the reduction of relative permeability of oil during production. Such a formation damage could be alleviated by the use of surfactants, however, their use does not always guarantee an efficient oil recovery. Through a microfluidic-chip based experimental study, the present work highlights the factors that control the later oil productivity and flowback especially through an oil-wetting matrix. The results from this study indicate that for an oil-wet formation, at shallow invasions, a water-based fracture fluid gives higher later oil production rates than a moderate IFT-reducing surfactant, and at deep invasions, the latter fluid gives better later oil production rates than the former. These results are very useful to the oil industry in making well informed decisions for selecting appropriate fracture fluids to stimulate oil-wet formations.
The purpose of the present work was to study the effect of guava pomace and pulse powder incorporation in to rice based extrudates on physical characteristics. Guava pomace collected after juice extraction was dried and milled. It was then added with pulse powder-rice flour blend at different combinations based on Central Composite Rotatable Design (CCRD). The independent variables were moisture content (17 – 21%), temperature (115 – 135°C), screw speed (230 – 270rpm), and varying proportion of rice, pulse and guava pomace. Higher feed moisture content resulted in extrudates with a higher density, lower expansion, higher water absorption index, lower water soluble index, and higher hardness. Higher barrel temperature resulted in reduced density, increased expansion, and water solubility index. Addition of guava pomace resulted in increase in water absorption index, hardness and decreased bulk density, expansion and water solubility index. The study suggested the guava pomace may be utilized up to the level of 10% to in Ready to Eat Snacks.
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