With the rapid increase of oil production and offshore transportation, the probability of accidental oil leakage is rising. Utilization of superhydrophobic materials constitutes an effective method to solve oil pollution on the water surface. In this study, a modified superhydrophobic sepiolite (SEP) layer was loaded onto the skeleton surface of three-dimensional (3D) porous polyurethane (PU) sponges through a one-step ultrasonic dip-coating process. The as-prepared superhydrophobic sponges can rapidly and selectively absorb multiple oils and nonpolar solvents that are more than 29 times the weight of the sponge, while completely repelling water. In addition, the as-prepared composite material could be reused for oil–water separation for more than 10 times with a high separation efficiency of over 99.45%. The composite material also exhibited robust superhydrophobicity in corrosive liquids and hot water. The results of this research may provide a promising absorbent material that might be used to effectively remove oil spills from the surface of water.

The hydration and swelling of shale formations are serious problems for well drilling. The use of an efficient shale inhibitor is one of the most important methods for overcoming the wellbore instability issue. In this work, poly-L-arginine (PArg) was synthesized and used as an efficient and biodegradable shale inhibitor. This inhibitor was systematically evaluated through measuring the swelling degree of the bentonite (Bent) pellet, the rheological behavior of the Bent suspensions, and the recovery percentage of shale cuttings. The results demonstrated that 2.0 wt % PArg could reduce the swelling degree of Bent to 70.53%, improve the shale recovery percentage to 71.40% at 180 °C, and inhibit 12.0 wt % Bent mud-making. The PArg displayed a highly inhibitive performance and excellent high-temperature resistance property, better than common inorganic KCl and organic polyether diamine. The underlying inhibition mechanism was also proposed based on measuring the variation of the interlayer spacing of the Bent, observing the exterior morphologies of Bent particles, and assessing the particle size distribution and electrokinetic potential. The results indicated that the PArg displayed its inhibitive effect mainly by adsorbing onto the Bent, encapsulating the Bent particles efficiently, and decreasing the interlayer spacing in a certain degree with 0.9 Å. This study can contribute to designing highly inhibitive water-based drilling fluids containing PArg.

Various water-based drilling fluids (WBDFs) are increasingly being used in oil and gas exploitation, for more environmentally acceptable and low-cost advantages than oil-based drilling fluids (OBDFs). However, WBDFs without an effective inhibitor easily facilitate shale swelling, hydration, and dispersion and even induce well instability, which is quite disadvantageous for well drilling. Thus, high-performance and environmentally friendly shale inhibitors are desperately needed for WBDFs, especially in deep and other challenging wells. Previously, gelatin was adopted as an environmentally friendly shale inhibitor in our group. However, the shale inhibition performance was limited at a high temperature. In this work, gelatin was further modified by 2,3-epoxypropyltrimethylammonium chloride (EPTAC, denoted as GT) to introduce quaternary amine functionalities and improve shale inhibition performance. The inhibitive property of GT was systematically evaluated through the linear swelling test, hot-rolling recovery test, and Na−bentonite (Na−BT) inhibition test. Results indicated that GT displayed better inhibition performance, especially at a high temperature, than pure gelatin and other common inhibitors. GT can be strongly adsorbed on the negatively charged clay surface via electrostatic attraction and hydrogen bonding, effectively decreasing the ζ potential of Na−BT particles and suppressing the double electrical layers. Meanwhile, GT effectively encapsulated and gathered the clay particles together, therefore preventing water ingress into clay and shale. GT showed great potential as a high-performance and environmentally friendly shale inhibitor for WBDFs.

Drilling fluids with poor filtration property are disadvantageous for well drilling, easily causing wellbore instability and formation collapse. This work reports the novel utilization of tea polyphenols (TPs) as a fluid loss additive in the bentonite− water-based drilling fluids (BT-WDFs). The influence of TP concentration and temperature on the filtration property of the fluids was described. The results showed that an increase in the TP concentration contributed to a decrease in fluid loss. Especially BT-WDFs added with 3.0 wt % TP exhibited a low fluid loss (less than or approximately 10 mL) at room temperature and high temperatures (∼150 °C), displaying better filtration property and temperature resistance than common fluid loss agents. Through the investigations on the viscosity, the particle size of TP/BT-WDFs, and micromorphology of filter cakes, the dispersion effect of TP was considered as the dominant factor for the filtration property of TP/BT-WDFs. TP molecules, containing many functional groups, could attach to the surface of bentonite platelets, improve the hydration of bentonite particles, and promote the dispersion of bentonite particles. At room temperature, TP facilitated the dispersion of hydrated bentonite. The existing "house-of-cards" structure was weakened, decreasing the particle size and viscosity of TP/BT-WDFs. At high temperature, bentonite dehydrated and aggregated, thereby increasing the particle size of bentonite particles, decreasing the viscosity of bentonite dispersion, and resulting in a high fluid loss. The addition of TP dispersed bentonite from faceto-face (FF) attraction to edge-to-face (EF) attraction, recovered the house-of-cards structure, and increased the viscosity of TP/BT-WDFs. Under the dispersion effect of TP, an appropriate grain composition of bentonite particles was formed and the pore throats were plugged to prevent the penetration of water. Finally, a compact and thin filter cake was built and the fluid loss was greatly reduced. The TP/BT-WDFs exhibited good filtration property. TP is a prospective candidate to be a high-performance and biodegradable fluid loss additive in well-drilling applications.

Shale wellbore instability is a complex difficulty encountered during drilling all over the world. And the most important factor to determine shale wellbore stability is the distribution and expansion of micro-cracks in hard brittle shale. The usual ways to avoid collapse of shale wellbore mainly include increasing the inhibition of drilling fluid filtrate, improving the quality of drilling fluid cake and sealing the pores and micro-cracks near the wellbore surface. However, the shale wellbore collapsing difficulty was not solved effectively in field, which mainly because that the effective sealing is difficult to achieved in the case of crack width is unknown. Furthermore the drilling fluid cake is more difficult to be formed on shale sections because of the filtration rate is very low compared to sand sections under the same differential pressure. A kind of nanomaterial has been applied to achieve a sealing film rapidly, improve the sealing strength of the cake and reduce the mud cake permeability, which have been verified through the use of sound wave propagation speed, the pressure transmission experiment and cake strength. The technology had also been used in Well Exp1, which exhibited a smooth borehole and the borehole enlargement rate was below the wells in the same block.