Development of a High-Temperature Thixotropic Cement Slurry System

Cementing carbonate reservoirs is generally a difficult task.The so-called thixotropic cement slurry has gained considerable attention in this regard as it can help tofix some notable problems.More precisely,it can easilyfill the leakage layer;moreover,its gelling strength can grow rapidly when pumping stops,thereby increasing the resistance to gas channeling,effectively preventing this undesired phenomenon in many cases.High-temperature thixotropic cement slurry systems,however,are still in an early stage of development and additional research is needed to make them a viable option.In the present study,using a self-developed composite high-temperature thixotropic additive as a basis,it is shown that the compressive strength can be adjusted by tuning the proportion of silica sand,the high-temperature retarder,fluid loss additive and dispersant(compatible with the thixotropic additive).According to the tests,the developed high-temperature thixotropic cement slurry system has a 14 d compressive strength of 29.73 MPa at 150°C,and a thickening time of 330 min when the dosage of retarder is 2%.At the same time,the rheological property,water loss,permeability,water separation rate,and settlement stability of the cement slurry system meet the requirements of cementing construction.

Plugging property and displacement characters of a novel high-temperature resistant polymer nanoparticle

The goal of the research was to investigate the profile control and oil displacement characteristics of the polymer nanoparticles after high temperature swelling.The displacement parameters showed considerable influence on the plugging effect of the high-temperature swelled polymer nanoparticles,such as the core permeability,concentration of nanoparticles in the suspension,swelling time and swelling temperature,which makes it flexible to control the plugging effect by controlling displacement experiments conditions.Experimental results show that polymer nanoparticles dispersion system with a concentration of 500 mg/L is suitable for cores plugging with a permeability of 30×10^(-3)-150×10^(-3)μm^(2),even after aging at 150℃ for three months.The shunt flow experiments show that when the displacement factors are optimal values,the polymer nanoparticles after high temperature swelling to plug the high-permeability layer selectivity and almost do not clog the low-permeability layer.Oil recovery of homogeneous artificial core displacement experiment and a heterogeneous double-tube cores model are increased by 20%and 10.4%on the basis of water flooding.The polymer nanoparticles can be a great help for petroleum engineers to better apply this deep profile control and flooding technology.

Laboratory Study on 210°C High Temperature and Salt Resistant Drilling Fluid

Combined with the current research status in this area at home and abroad, with the improvement of salt and high temperature resistance as the research goal, the laboratory research of salt and high temperature resistant drilling fluid system has been carried out, and lubricants, inhibitors and stabilizers have been optimized. The final drilling fluid formula is: water + 3% sepiolite + 0.3% Na2CO3 + 3% RH-225 + 3% KCOOH + 3% G-SPH + 3% CQA-10 + 1.5% ZX-1 + Xinjiang barite, density 2.2 g/cm3, using hot-rolling furnace, environmental scanning electron microscope, high temperature and high pressure plugging instrument and Zeiss microscopes and other instruments use core immersion experiments, permeability recovery value experiments, and static stratification index methods to perform temperature resistance, reservoir protection, plugging performance, and static settlement stability performance of the configured drilling fluid., Inhibition performance, biological toxicity, salt resistance, anti-pollution performance have been tested, and it is concluded that the temperature resistance is good under the condition of 210°C, and the salt resistance can meet the requirements of 20% NaCl + 0.5% CaCl2 concentration. It has a good reservoir protection effect, the permeability recovery value can reach more than 90%, the performance of restraining water dispersion and cuttings expansion is good, the heat roll recovery rate can reach more than 85%, and the SSSI value shows that its settlement stability performance is good;Its plugging performance is good under high temperature and high pressure. It laid the foundation for the next step to promote the field application of the drilling fluid system.

3D-printed controllable gradient pore superwetting structures for high temperature efficient oil-water separation

Superwetting surfaces have the potential to address oil pollution in water,through their ability to separate the two.However,it remains a great challenge to fabricate stable and efficient separation structures using conventional manufacturing techniques.Furthermore,the materials traditionally used for oil-water separation are not stable at high temperature.Therefore,there is a need to develop stable,customizable structures to improve the performance of oil-water separation devices.In recent years,3D printing technology has developed rapidly,and breakthroughs have been made in the fabrication of complicated ceramic structures using this technology.Here,a ceramic material with a gradient pore structure and superhydrophobic/superoleophilic properties was prepared using 3D printing for high-efficiency oil-water separation.The gradient pore structure developed here can support a flux of up to 25434 L/m^(2)h,which is nearly 40%higher than that an analogous structure with straight pores.At 200℃,the oil-water separation performance was maintained at 97.4%.Furthermore,samples of the material exhibited outstanding mechanical properties,and chemical stability in a variety of harsh environments.This study provides an efficient,simple,and reliable method for manufacturing oil-water separation materials using 3D printing,and may have broader implications for both fundamental research and industrial applications.

Excellent electromagnetic wave absorption of MOF/SiBCN nanomaterials at high temperature

Electromagnetic wave absorbing materials at high-temperature are urgently needed for stealth aircrafts or aero-engines worked in harsh environments.In this contribution,cobaltcontaining siliconboron carbonitride(MOF/SiBCN)nanomaterials were prepared by pyrolyzing metal–organic framework,i.e.cobalt 2-methylimidazole(ZIF-67),and hyperbranched polyborosilazane.The rhombic dodecahedral ZIF-67 and cobalt element promoted in situ formation of dielectric loss phases,including SiC nanocrystals,CoSi nanocrystals and turbostratic carbons.The ZIF-67/SiBCN nanomaterials showed excellent microwave absorption both at room and elevated temperature.The minimum reflection coefficient(RC_(min))was-51.6dB and effective absorption bandwidth(EAB)is 3.93GHz at room temperature.At an elevated temperature of 600℃,the RC_(min) reached-30.29 dB and EAB covered almost the whole X-band(3.95GHz,8.45–12.4GHz).The ZIF-67/SiBCN nanocomposites are promising and useful platform for microwave absorbing materials at high-temperature.It may shed light on the downstream applications in designing next generation areo-engines and stealth aircrafts.

Study on a Polyamine-Based Anti-Collapse Drilling Fluid System

In complex strata, oil-based drilling fluid is the preferred drilling fluid system, but its preparation cost is high, and there are hidden safety risks. Therefore, the new progress of high-performance anti-collapse water-based drilling fluid at home and abroad is analyzed. It is difficult to prevent and control the well collapse. Once the well wall instability problem occurs, it will often bring huge economic losses to the enterprises, and the underground safety accidents will occur. In order to ensure the stability of the well wall and improve the downhole safety, the key treatment agent of water-based collapse drilling fluid is selected, the anti-collapse drilling fluid system is formulated, the evaluation method of drilling fluid prevention performance is established, and a set of water-based drilling fluid system suitable for easy to collapse strata in China is selected to ensure the downhole safety. The development trend of high performance anti-collapse water-based drilling fluid is expected to provide a reference for the research of high performance anti-collapse water-based drilling fluid system and key treatment agent.

Hyperelastic Graphene Aerogels Reinforced by In‑suit Welding Polyimide Nano Fiber with Leaf Skeleton Structure and Adjustable Thermal Conductivity for Morphology and Temperature Sensing

Graphene-aerogel-based flexible sensors have heat tolerances and electric-resistance sensitivities superior to those of polymer-based sensors.However,graphene sheets are prone to slips under repeated compression due to inadequate chemical con-nections.In addition,the heat-transfer performance of existing compression strain sensors under stress is unclear and lacks research,making it difficult to perform real-temperature detections.To address these issues,a hyperelastic polyimide fiber/graphene aerogel(PINF/GA)with a three-dimensional interconnected structure was fabricated by simple one-pot compound-ing and in-situ welding methods.The welding of fiber lap joints promotes in-suit formation of three-dimensional crosslinked networks of polyimide fibers,which can effectively avoid slidings between fibers to form reinforced ribs,preventing graphene from damage during compression.In particular,the inner core of the fiber maintains its macromolecular chain structure and toughness during welding.Thus,PINF/GA has good structural stabilities under a large strain compression(99%).Moreover,the thermal and electrical conductivities of PINF/GA could not only change with various stresses and strains but also keep the change steady at specific stresses and strains,with its thermal-conductivity change ratio reaching up to 9.8.Hyperelastic PINF/GA,with dynamically stable thermal and electrical conductivity,as well as high heat tolerance,shows broad applica-tion prospects as sensors in detecting the shapes and temperatures of unknown objects in extreme environments.

Fabrication of high-stability Ni-PSF@PAO40 microcapsules and their lubricating properties in polyamide 6

Novel Ni-PSF@PAO40 microcapsules(NPPMS)with high stability were prepared by using a combined processing method of electroless nickel plating and solvent volatilization.The results indicate that Ni is completely assembled on the surfaces of PSF/PAO40 microcapsules with the encapsulation capacity of NPPMS achieved at 50%.Organic solvents immersion shows that NPPMS have an excellent chemical stability.Macro thermal stability tests reveal that the softening temperature of NPPMS is increased up to over 400℃ while it becomes lower than 200℃ for PSF/PAO40 microcapsules.Furthermore,NPPMS were embedded into polyamide 6(PA6)to prepare PA6/NPPMS composites.The cross-sectional morphology shows that NPPMS are intact in PA6 matrices.The microhardness of PA6 is effectively improved with the incorporation of NPPMS.As compared with neat PA6,the coefficient of friction(COF)for PA6/NPPMS composites with 10%NPPMS could be reduced by 87.7%(from 0.49 to 0.06)and the wear rate could be decreased by 96.8%(from 1.29×10^(-5) to 4.15×10^(-7) mm^(3)/(N·m)).Further studies confirmed that increasing test loads and test temperatures was beneficial to improve the lubrication performance of NPPMS despite the opposite trend occurred when increasing the sliding speeds.It has been demonstrated that synergistic effects between PAO40 and Ni layer play an important role in improving the tribological properties of PA6.Therefore,NPPMS significantly improve the ability of microcapsules to resist a harsh environment,which has important scientific significance for expanding the use of microcapsules more practically in self-lubricating composites.