Micro/nano structured oleophobic agent improving the wellbore stability of shale gas wells

Through embedding modified nano-silica particles on the surface of polystyrene using the method of Pickering emulsion polymerization,a kind of nano/micro oleophobic agent named OL-1 was developed.The effects of OL-1 on the rock surface properties and its performance in inhibiting the oil phase imbibition into the rock were explored.The performance and mechanisms of OL-1 in improving the wellbore stability of shale gas wells were evaluated and analyzed.OL-1 could absorb on the surface of the shale core to form a membrane with a micro-nano two-stage roughness,making the surface energy of the core decrease to 0.13 mN/m and the contact angle of the white oil on the core surface increase from 16.39°to 153.03°.Compared with the untreated capillary tube,when immersed into 3#white oil,the capillary tube treated by OL-1 had a reversal of capillary pressure from 273.76 Pa to-297.71 Pa,and the oil imbibition height inside the capillary tube decreased from 31 mm above the external liquid level to 33 mm below the external liquid level.The amount of oil invading into the rock core modified by OL-1 decreased by 64.29%compared with the untreated one.The shale core immersed into the oil-based drilling fluids with 1%OL-1 had a porosity reduction rate of only 4.5%.Compared with the core immersed in the drilling fluids without OL-1,the inherent force of the core treated by 1%OL-1 increased by 24.9%,demonstrating that OL-1 could effectively improve the rock mechanical stability by inhibiting oil phase imbibition.

OLEOPHOBIC AND HYDROPHOBIC FEATURE EXPERIMENTS OF FLUORINATED HIGH DENSITY POLYETHYLENE

The surface performances of directly fluorinated high density polyethylene （HDPE） are studied with Fourier transform infrared （FT-IR） spectra, scanning electron microscopy （SEM） and contact angle （CA） system. The SEM images show that there is a three-layer structure called the reaction, virgin and boundary layer structure. The depth of fluorinated layer is 5.75 ~m with 1 h fluorination time and 7.86 b^m with 2 h. The depths are 5.46 /~m and 5.07 /~m when fluorine density is 2G and 1~/0, respectively. CA indicates that the HDPE surface property becomes more hydrophobic with the increasing water contact angle from 78.5~ to 104.5~. Oleophobic and hydrophobic features of HDPE are identified by comparison of mass change experiments. It is shown that the in- crement rate of fluorinated HDPE is much lower than that of un-fluorinated HDPE filled in neither distilled water nor jet fuel.

Wettability Control between Oleophobic/Superhydrophilic and Superoleophilic/Superhydrophobic Characteristics on the Modified Surface Treated with Fluoroalkyl End-Capped Oligomers/Micro-Sized Polystyrene Particle Composites

Fluoroalkyl end-capped vinyltrimethoxysilane-N,N-dimethylacrylamide cooligomer [RF-(CH2-CHSi(OMe)3)x-(CH2-CHC(=O)NMe2)y-RF;RF = CF(CF3)OC3F7: RF-(VM)x-(DMAA)y-RF] was synthesized by reaction of fluoroalkanoyl peroxide [RF-C(=O)O-O(O=)C-RF] with vinyltrimethoxysilane (VM) and N,N-dimethylacrylamide (DMAA). The modified glass surface treated with the cooligomeric nanoparticles [RF-(VM-SiO3/2)x-(DMAA)y-RF] prepared under the sol-gel reaction of the cooligomer under alkaline conditions was found to exhibit an oleophobic/superhydrophilic property, although the corresponding fluorinated homooligomeric nanoparticles [RF-(VM-SiO3/2)n-RF] afforded an oleophobic/hydrophobic property on the modified surface under similar conditions. RF-(VM-SiO3/2)n-RF/RF-(VM-SiO3/2)x-(DMAA)y-RF/PSt (micro-sized polystyrene particles) composites, which were prepared by the sol-gel reactions of the corresponding homooligomer and cooligomer in the presence of PSt particle under alkaline conditions, provided an oleophobic/superhydrophilic property on the modified surface. However, it was demonstrated that the surface wettability on the modified surface treated with the RF-(VM-SiO3/2)n-RF/RF-(VM-SiO3/2)x-(DMAA)y-RF/PSt composites changes dramatically from oleophobic/superhydrophilic to superoleophilic/superhydrophilic and superoleophilic/superhydrophobic characteristics, increasing with greater feed ratios (mg/mg) of the RF-(VM)n-RF homooligomer in homooligomer/cooligomer from 0 to 100 in the preparation of the composites. Such controlled surfac

Long-Lasting Filtration of Oily Water by Anti-Fouling Underwater Oleophobic Sand Particles

The produced water from the oilfield was purified with filter material and then injected back into the ground.The serpentine filter material was easy to harden with the increase in filtration amount,which affected the water quality.A superhydrophilic/underwater oleophobic serpentine filter material was successfully prepared by a simple method of coating modification,which exhibited long-lasting filtration of oily water,good filtration and anti-fouling properties,and resistance to harden.The film-forming material of the superhydrophilic/underwater oleophobic coating was composed of SiO_(2) particles with small size,which could completely and evenly cover the filter particle.The weight loss was only 7.6%after mechanical stirring for 90 min.Compared with the original filter material,the superhydrophilic/underwater oleophobic serpentine filter material showed a better anti-fouling ability and resistance to harden.The filtration of crude oil emulsion and oil slick sewage showed a better backwashing performance.After 35 cycles of continuous filtration of suspended solids in wastewater,the backwashing rate reached 78.4%.The results provided an effective method for the filtration of oily wastewater in the oilfield.

New strategy for reducing the EHL friction in steel contacts using additive-formed oleophobic boundary films

In this study we present a mechanism for the elastohydrodynamic(EHD)friction reduction in steel/steel contacts,which occurs due to the formation of oleophobic surface boundary layers from common boundary-lubrication additives.Several simple organic additives(amine,alcohol,amide,and fatty acid)with different molecular structures were employed as the model additives.It was found that the stronger chemisorption at 100℃,rather than the physisorption at 25℃,is more effective in friction reduction,which reaches 22%.What is more,EHD friction reduction was obtained in steel/steel contacts without use of the diamond-like carbon(DLC)coatings with their wetting or thermal effect,which was previously suggested as possible EHD friction reduction mechanism;yet about the same friction reduction of about 20%was obtained here—but with much simpler and less expensive technology,namely with the adsorbed oleophobic surface layers.A small variation in the additive’s molecular structure results in significant changes to the friction,indicating good potential in future EHD lubrication technology,where these additives could be designed and well optimised for notable reduction of the friction losses in the EHD regime.

Surface treatment technology of downhole water cut sensor

Based on the structure,working principle,and working conditions of conductance water cut sensor,it is revealed that the early failure of the metal electrode of the sensor is due to the comprehensive influence of well fluid erosion,electrochemical corrosion,and oil pollution during its long-term service in the downhole.A technology for electrode surface treatment is proposed using boron-doped diamond(BDD)films to improve the service performance of the modified electrode.The hot wire chemical vapor deposition method was adopted to fabricate BDD film,the boron doping concentration and deposition time were optimized,and fluorination treatment was applied to improve the wear resistance,electrochemical corrosion resistance,and oleophobic property of the BDD film comprehensively.The results showed that BDD film with boron doping concentration of 6×10^(-3) exhibited high wear resistance and good electrochemical corrosion resistance,and endowed the modified electrode with superior erosion resistance and corrosion resistance.The friction coefficient and wear rate of BDD modified electrode were 92%and 78%lower than those of Invar alloy,also,the low-frequency impedance modulus value of the modified electrode was higher than 1×10^(4) Ω·cm^(2).The BDD film prepared with a deposition time of 8 h had a favorable micro-nano structure owing to small grain size and uniform distribution.Such morphology was conducive to enhancing the oleophobic performance of the modified electrode,and its contact angle in the simulated well fluid was high to 102°.The engineering applicability of BDD film modified electrode under simulated working conditions indicated that,the modified electrode had excellent comprehensive performances of erosion resistance,electrochemical corrosion resistance and oil adhesion resistance,and can realize the long-term stable operation of the conductance water cut sensor under harsh downhole conditions.

Fluorinated Hyperbranched Poly(urea-urethane)s Containing Reactive Groups: Synthesis, Characterization and Application on Cotton Fabric

A series of hyperbranched poly(urea-urethane)s (HPUs) containing short fluoroalkyl chain and reactive groups (HPUFs) capable as hydrophobic and oleophobic coating materials were synthesized. The obtained polymers were characterized by FTIR(fouier transform-infrared spectroscopy), 1H NMR(nuclear magnetic resonance), 13C NMR, 19F NMR, GPC(gel permeation chromatography), TGA(thermogravimetric analyzer), and XPS(X-ray photoelectron spectroscopy) analyses. Highly hydrophobic and oleophobic cotton fabrics could be achieved from these fluorinated hyperbranched polymers by solution-immersion coating method. The static contact angles reached to 143°, 114°, and 92° for water, hexadecane, and decane, respectively. The water and oil repellency ratings were 90 and 6, respectively, and still kept 80 and 5, respectively, after 10 soaping cycles at 50℃.

Preparation of Fluoroalkyl End-Capped Oligomers/Hexagonal Boron Nitride Nanocomposites Possessing No Weight Loss Behavior in Nanocomposites Even after Calcination at 800°C

Fluoroalkyl end-capped acrylic acid oligomer [RF-(ACA)n-RF]/hexagonal boron nitride (h-BN) nanocomposites [RF-(ACA)n-RF/h-BN] were prepared by reaction of the corresponding oligomer with h-BN nanoparticles (mean diameter: 50 nm) under non-catalytic or alkaline conditions, respectively. Fluoroalkyl end-capped N,N-dimethylacrylamide oligomer/h-BN nanocomposites [RF-(DMAA)n-RF/h-BN] were also obtained under similar conditions. It was demonstrated that RF-(ACA)n-RF/h-BN nanocomposites, which were prepared under alkaline conditions, afforded a clear weight loss in proportion to the contents of the oligomer in the composites after calcination at 800°C;however, the non-catalytic conditions enabled the RF-(ACA)n-RF/h-BN nanocomposite to give no weight loss behavior corresponding to the contents of the oligomer even after calcination. In fact, it was demonstrated that the RF-(ACA)n-RF/h-BN nanocomposites possessing a clear weight loss property could afford the fluorescent peak around 370 nm related to h-BN in the composites;however, the same fluorescent intensity of this nanocomposite after calcination at 800°C as that of the original h-BN was observed, indicating that this nanocomposite could give a clear weigh loss behavior corresponding to the content of the oligomer during the calcination process. In contrast, the RF-(ACA)n-RF/h-BN nanocomposites possessing no weigh loss behavior were found to exhibit the similar fluorescent intensity before and even after calcination at 800°C, suggesting that the corresponding nanocomposites could provide no weight loss ability corresponding to the contents of the oligomer in the composites even after calcination. Similarly, RF-(DMAA)n-RF/h-BN nanocomposites, which were prepared under non-catalytic or alkaline conditions, were found to provide no weight loss corresponding to the contents of the oligomer even after calcination, respectively. These fluorinated h-BN nanocomposites were applied to the surface modification of PMMA [poly(methyl methacrylate)] to exhibit an oleophobic property on the modified PMMA surface. RF-(ACA)n-RF/h-BN nanocomposites possessing a clear weight loss behavior, whose composites were calcinated at 800°C, afforded not oleophobic but oleophilic property on the modified PMMA surface, quite similar to that of the pristine PMMA film surface;however, more interestingly, we found that RF-(ACA)n-RF/ and RF-(DMAA)n-RF/h-BN nanocomposites possessing no weight loss characteristic, whose composites were calcined at 800°C, could supply a good oleophobic property related to the fluoroalkyl segments in the composites on the modified PMMA surfaces, respectively.

Identifying the optimal interfacial parameter correlated with hydrodynamic lubrication

The effects of boundary (liquid/solid) slip on hydrodynamics are well recognized.However,it is extremely difficult to quantify in-situ boundary slip in a lubrication contact.Therefore,an effective interfacial parameter that is well correlated with the lubrication effect is of practical significance.This paper presents an examination of common interfacial parameters,including surface tension,contact angle,contact angle hysteresis,and a recently proposed spreading parameter.Specimen surfaces of different hydro/oleophobicity were prepared and characterized using the aforementioned interfacial parameters.These samples were further used as bearing surfaces in hydrodynamic lubrication tests.The correlations of these parameters with the measured lubricating film thickness were examined and compared.The key parameter closely related to the hydrodynamic effect was identified.

Aggregation-induced demulsification triggered by the hydrophilic fabric for the separation of highly emulsified oil droplets from water

A functional fabric with hierarchical structure consisting of basalt fibre fabric as a substrate and polyvinyl alcohol as a coating was developed,aiming at providing a low cost and high-performance way to separate highly emulsified oil in water.The coating functioned as a hydrophilic gate for the penetration of water in the emulsion,whereas the micro-channels formed in the fabric offered capillary force for the continuous flow of water.The synergy of these two materials led to the increase on the oil concentration in the liquid,which in turn enhanced the collision of emulsified oil droplets to aggregate into large ones in the emulsion and resulted separation from the water.Based on these findings,an aggregation-induced demulsification process was proposed to explain the above phenomenon,and the mechanism was confirmed by studying the distribution of oil droplets in emulsion with a controlled separation degree.