Xianbin Huang,Fengbao Liu,Pengxin Zhang,Zhenzhen Wei,Jinsheng Sun,Kaihe Lv,Jian Li
Fractured formations are complex formations often encountered during oil and gas drilling. Conventional methods such as plugging formation fractures and pores, improving cutting-carrying efficiency, and inhibiting hydration of cements cannot effectively solve the problem of wellbore instability in fractured formations. In this paper, an adhesive microgel latex (MGL) was prepared to improve the cementing strength of fractured formations. The morphology and thermal property were analyzed by differential scanning calorimetry (DSC), scanning electron microscopy (SEM), etc. The plugging effect of MGL was then studied by visualized plugging experiments and high temperature and high pressure (HTHP) plugging experiments. The evaluation methods for strengthening fractured formation were established, including immersion test, single lap test and compressive strength test, and applied to evaluate MGL. The experimental results show that MGL were spherical particles with a median particle size of 38.9 μm and a glass transition temperature of 61.98 °C. MGL could effectively decrease drilling fluid intrusion and plug fractured formations. Wellbore strengthening experiment showed that MGL could enhance the cementing strength of fractured formations. MGL greatly improved the tensile shear strength between core pieces and cementation strength of the fractured formation. After treatment of MGL, the tensile shear strength between core pieces increased by 81.2% compared to asphalt, and the compressive strength substantially increased for both wet and dry sand cores. The mechanism analysis suggests that the adsorption between MGL and rock matrix and the self-adhesion among MGL particles are responsible for wellbore strengthening. This paper innovatively proposes the use of adhesive particles to enhance wellbore stability in fractured formations.
Absorption enhancing effects of chitosan oligomers with different type and varying concentration on the intestinal absorption of low molecular weight heparin (LMWH) were examined by an in situ closed loop method in different intestinal sections of rats. Chitosan hexamer with the optimal concentration of 0.5% (w/v) showed the highest absorption enhancing ability both in the small intestine and large intestine. The membrane toxicities of chitosan oligomers were evaluated by morphological observation and determining the biological markers including amount of protein and activity of lactate dehydrogenase (LDH) released from intestinal epithelium cells. There was no obvious change both in levels of protein and LDH and morphology in the intestinal membrane between control and various chitosan oligomers groups, suggesting that chitosan oligomers did not induce any significant membrane damage to the intestinal epithelium. In addition, zeta potentials became less negative and amount of free LMWH gradually decreased when various chitosan oligomers were added to LMWH solution, revealing that electrostatic interaction between positively charged chitosan oligomers and negative LMWH was included in the absorption enhancing mechanism of chitosan oligomers. In conclusion, chitosan oligomers, especially chitosan hexamer, are safe and efficient absorption enhancers and can be used promisingly to improve oral absorption of LMWH.
Y. Chen,Y. Yang,F. Wang,X. Yang,F. Yao,K. Ming,W. Yuan,L. Zeng,J. Liu
ABSTRACT Duck hepatitis A virus type 1 ( DHAV-1 ) is one of the main pathogens of ducklings and causes a high mortality rate. Baicalin ( BA ) has potent antiviral effect, but the solubility is very poor. In order to increase the absorption, solubility, and pharmacological activity, the phospholipid complex was used to modify BA in present study. Therefore, BA phospholipid complex ( BAPC ) was prepared. The anti-DHAV-1 abilities of BA and BAPC in vitro was evaluated by cell counting kit-8 and reverse transcription quantitative PCR. The curative effects of BA and BAPC on ducklings which were infected by DHAV-1 in addition to the ALT and AST levels were also detected. The results indicated the anti-DHAV-1 ability of BAPC was stronger than that of BA both in vitro and in vivo . To explore the anti-DHAV-1 mechanism, the influence of BAPC on DHAV-1 adsorption, replication, and release was studied. Furthermore, the anti-oxidative and immuno-enhancing abilities of BAPC in the treatment of infected ducklings were also determined. The results showed BAPC inhibited DHAV-1 adsorption, replication and release. Furthermore, it played anti-oxidative and immno-enhancing roles in the treatment, and the immno-enhancing role was crucial to the treatment.
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