Introduction. Gut microbiota is involved in the progression of metabolic diseases such as obesity and type 2 diabetes. The ob/ob and db/db mice are extensively used as models in studies on the pathogenesis of these diseases. The goal of this study is to characterize the composition and structure of gut microbiota in these model mice at different ages. Materials and methods. High-throughput sequencing was used to obtain the sequences of the highly variable 16S rRNA V3-V4 region from fecal samples. The taxa with high abundance in both model mice were identified by bioinformatics analysis. Moreover, the taxa with divergent abundance in one model mice at different ages or in both model mice at the same age were also recognized. Discussion and conclusion. The high abundance of Bacteroidetes and Firmicutes in microbiota composition and their imbalanced ratio in both model mice reflect the state of metabolic disorders of these mice. Differences in microbiota composition between the two model mice of the same age or in one model mice with different ages were assumed to be closely linked to the fluctuation of their blood glucose levels with age. The data on gut microbiota in ob/ob and db/db mice investigated herein has broad implications for the pathogenesis study and drug discovery on obesity and related complications.
Although foamy oil can improve the
performance of solution gas
drive in heavy oil, only about 5–15% original oil in place
(OOIP) can be recovered under primary production. In this study, a
series of micromodel flood experiments and sandpack flood tests were
performed to evaluate the performances of water flooding, surfactant
flooding, gas flooding, and foam flooding for enhancing the recovery
of Orinoco Belt heavy oil after solution gas drive. Water flooding
tests show that the sweep efficiency of water flooding was low as
a result of the adverse mobility ratio caused by gas bubbles dispersed
in the oil; about 10.57% OOIP was obtained in the sandpack study.
Surfactant flooding tests indicate that the penetration of the surfactant
solution into the heavy oil and the subsequent formation of gas bubbles
and emulsified oil droplets in surfactant solution could reduce the
mobility of water phase, thereby improving sweep efficiency, and oil
recovery of 15.09% OOIP was recovered in the sandpack. Because of
the viscous fingering, only 4.57% OOIP was obtained in the gas flooding
test. The micromodel test of foam flooding shows that gas bubbles
could reduce the mobility of the gas phase and the residual oil droplets
could be pulled into oil threads by the viscoelasticity of gas bubbles,
thereby reducing the residual oil saturation of foam flooding. The
sandpack flood result shows that the oil recovery of foam flooding
can reach 23.92% OOIP.
Wormlike micelles formed by amidosulfobetaine surfactants present advantage in increasing viscosity, salt-tolerance, thermal-stability and shear-resistance. In the past few years, much attention has been paid on rheology behaviours of amidosulfobetaine surfactants that normally bear C18 or shorter tails. Properties and oil displacement performances of the wormlike micelles formed by counterparts bearing the long carbon chain have not been well documented. In this paper, the various properties of C22-tailed amidosulfobetaine surfactant EHSB under high salinity (TDS = 40g/L) are investigated systematically, including solubility, rheology and interfacial activity. Moreover, its oil displacement performance is studied for the first time. These properties are first compared with those of C16-tailed counterpart HDPS. Results show that the Krafft temperature( TK) of EHSB decreases from above 100°C to 53°C with the increase of TDS to 40 g/L. Increasing concentration of EHSB in the semidilute region induces micelle growth from rod-like micelles to wormlike micelles, and then the worms become entangled or branched to form viscoelastic micelle solution, which will increase the viscosity by several orders of magnitude. The interfacial tension with oil can be reduced to ultra-low level by EHSB solution with concentration below 4.5 mM. Possessing dual functions of mobility control and reducing interfacial tension, wormlike micelles formed by EHSB present a good displacement effect as a flooding system, which is more than 10% higher than HPAM with the same viscosity. Compared with the shorter tailed surfactant, the ultra-long tailed surfactant is more efficient in enhancing viscosity and reducing interfacial tension, so as to enhance more oil recovery. Our work provides a helpful insight for comprehending surfactant-based viscoelastic fluid and provides a new viscoelastic surfactant flooding agent which is quite efficient in chemical flooding of offshore oilfield.
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