Revitalizing biopolymers to prepare temperature-resistant and salt-tolerant filtrate reducer by combining light-driven lignin depolymerization and subsequent photopolymerization on MIL-100(Fe)-NH2(20) photocatalyst.

For the first time, this study integrate the light-driven depolymerization/activation of industrial grade sodium lignosulfonate and its subsequent photo-induced radical polymerization with acrylamide (AM) and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) into one-pot using MIL-100(Fe)-NH2(20) as a photocatalyst to synthesize fluid loss agent LSMP. Due to the significant hydrogen bonding effect, the agent owns excellent rheological and filtration properties. The filtrate volumes of drilling fluids containing 2.0 wt% agent before and after aging at 150 °C are only 3.6 and 4.6 mL, reducing by 85.0 % and 88.5 %, respectively, compared with pure fluids. Even at high temperatures and high salinity, LSMP still gives stunning performances with significant filtrate volumes decline of 96.58 % and 86.52 % under erosion of 25 wt% NaCl and 2.0 wt% CaCl2, separately. Meanwhile, the filtration reduction mechanism of LSMP is presented, and the probable photocatalytic mechanism is also explored: 1, under depolymerization process, the selective cleavage of ubiquitous C - O/C - C linkage bonds (ß-O-4, ß-5, α-O-4, ß-ß, 4-O-5, ß-1, dibenzodioxocin, etc.) occur, accompanied by the aromatic rings intact; 2, with the action of photo-induced carriers generated on MIL-100(Fe)-NH2(20), absorbed photons are transformed into thermal energy and the radical polymerization of green synthesis are ultimately achieved.

Development of a Low-Molecular-Weight Filtrate Reducer with High-Temperature Resistance for Drilling Fluid Gel System.

Currently, conventional polymeric filtrate reducers with high-temperature resistance for use in drilling fluids have high molecular weights, which greatly affects the rheological properties. Therefore, to address the challenges in regulating the rheology and filtration performance of high-density drilling fluids at high temperatures, it is essential to develop low-molecular-weight filtrate reducers with high-temperature resistance. In this study, a low-molecular-weight filtrate reducer with high-temperature resistance (LMF) was prepared via free radical polymerization from acrylamide and 2-acrylamido-2-methyl-1-propanesulfonic acid as monomers, tertiary dodecyl mercaptan as a chain transfer agent, and ammonium persulfate as the initiator. LMF was then characterized by infrared spectroscopy, thermogravimetric analysis, and gel permeation chromatography. The obtained filtrate reducer exhibits a weight-average molecular weight (Mw) of 3819 and an initial thermal decomposition temperature of 300.7 °C, indicating good thermal stability. The effects of LMF dosage, temperature, and NaCl dosage on the rheology and filtration performance of mud samples were also investigated, and the mechanism of action was revealed by zeta potential, particle size distribution, scanning electron microscopy, and adsorption measurements. The results reveal that LMF increases the mud sample viscosity and reduces its filtration. For example, the filtration of the mud sample with 2 wt% LMF was 7.2 mL, a reduction of 70% compared to that of a blank mud sample. Further, after aging at 210 °C for 16 h, the filtration of the same sample was 11.6 mL, and that of a mud sample with 2 wt% LMF and 35 wt% NaCl after aging at 180 °C for 16 h was 22 mL. Overall, we have reported a scheme to prepare a low-molecular-weight filtrate reducer with high-temperature resistance and superior filtrate-reducing effects, laying the foundation for the investigation and development of low-molecular-weight filtrate reducers.

Preparation of MOF-Based Core-Shell Gel Particles with Catalytic Activity and Their Plugging Performance.

Drilling fluid systems for deep and ultra-deep wells are hampered by both high-temperature downhole environments and lengthy cycle periods. Suppose that the gel particle-plugging agent, the primary treatment agent in the system, fails to offer durable and stable plugging performance. In such a scenario, the borehole wall is susceptible to instability and landslide after prolonged immersion, leading to downhole accidents. In this study, novel core-shell gel particles (modified ZIF) with ZIF particles employed as the core material and organosilicon-modified polyethylene polyamine (PEPA) as the polymer shell were fabricated using PEPA, in-house synthesized (3-aminopropyl) triethoxysilane (APTS), and the ZIF-8 metal-organic framework (MOF) as the raw materials to enhance the long-term plugging performance of gel plugging agents. The modified ZIF particles are nanoscale polygonal crystals and differ from conventional core-shell gel particles in that they feature high molecular sieve catalytic activity due to the presence of numerous interior micropores and mesopores. As a result, modified ZIF exhibits the performance characteristics of both rigid and flexible plugging agents and has an excellent catalytic cross-linking effect on the sulfonated phenolic resin (SMP-3) and sulfonated lignite resin (SPNH) in drilling fluids. Consequently, a cross-linking reaction occurs when SMP-3 and SPNH flow through the spacings in the plugging layer formed by the modified ZIF particles. This increases the viscosity of the liquid phase and simultaneously generates an insoluble gel, forming a particle-gel composite plugging structure with the modified ZIF and significantly enhancing the long-term plugging performance of the drilling fluid.