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Synthesis and analysis of drag reduction performance of the temperature-resistant polymer slickwater for high temperature reservoirs

Ziteng Yang,Mingwei Zhao,Weiyu Bi,Yunlong Cheng,Zhenfeng Ma,Kaiwen Liu,Ying Li,Caili Dai

Slickwater has been extensively utilised in deep reservoir fracturing owing to its excellent drag reduction performance, and the polymer drag reducer is the core of slickwater. However, polymer drag reducers may degrade at high temperatures, which limits the application of slickwater in high temperature reservoirs. To increase the temperature resistance of slickwater, a novel temperature-resistant polymer drag reducer was chemically synthesised through free-radical polymerisation using acrylamide (AM), acrylic acid (AA), 2-acrylamide-2-methylpropyl sulfonic acid (AMPS) and N,N-dimethylacrylamide (DMAA). The introduction of temperature-resistant monomers substantially increased the thermal stability of the drag reducer. The rheological measurements revealed that the aqueous polymer solution was a pseudoplastic fluid with good viscoelasticity and thickening properties. At 110 °C, the drag reduction rate of 0.03 wt% polymer aqueous solution could reach 72.57 %, and the drag reduction retention rate was 96.69 % when compared with that at 25 °C. The drag reduction performance was evaluated in relation to displacement, concentration, temperature, pipe diameter, and salinity. Simultaneously, the proportion of factors influencing the drag reduction performance was analysed. Finally, a drag reduction mechanism was proposed. This study is expected to extend the application of slickwater in high-temperature reservoir development.

Salt-tolerant and instant friction reducer for slickwater fracturing stimulation based on dispersion polymerization

Fu Chen,Dai Li,Zihan Liao,Yu Den,Lin Zhang,Heng Wang

The enhancement of performance and imbibition effect of slickwater-based fracturing fluid by using MoS2 nanosheets

Hang Xu,Yuan Li,Guo-Lin Yu,Sa-Sa Yang,Bo-Jun Li,Fu-Jian Zhou,Er-Dong Yao,Hao Bai,Zhi-Yu Liu

Slickwater-based fracturing fluid has recently garnered significant attention as the major fluid for volumetric fracturing; however, lots of challenges and limitations such as low viscosity, poor salt tolerance, and possible formation damage hinder the application of the conventional simple slickwater-based fracturing fluid. In addition, nanomaterials have proven to be potential solutions or improvements to a number of challenges associated with the slickwater. In this paper, molybdenum disulfide (MoS 2 ) nanosheets were chemically synthesized by hydrothermal method and applied to improve the performance of conventional slickwater-based fracturing fluid. Firstly, the microstructure characteristics and crystal type of the MoS 2 nanosheets were analyzed by SEM, EDS, TEM, XPS, and Raman spectroscopy techniques. Then, a series of evaluation experiments were carried out to compare the performance of MoS 2 nanosheet-modified slickwater with the conventional slickwater, including rheology, drag reduction, and sand suspension. Finally, the enhanced imbibition capacity and potential mechanism of the nanosheet-modified slickwater were systematically investigated. The results showed that the self-synthesized MoS 2 nanosheets displayed a distinct ultrathin flake-like morphology and a lateral size in the range of tens of nanometers. In the nano-composites, each MoS 2 nanosheet plays the role of cross-linking point, so as to make the spatial structure of the entire system more compact. Moreover, nanosheet-modified slickwater demonstrates more excellent properties in rheology, drag reduction, and sand suspension. The nanosheet-modified slickwater has a higher apparent viscosity after shearing 120 min under 90 °C and 170 s −1 . The maximum drag reduction rate achieved 76.3% at 20 °C, and the sand settling time of proppants with different mesh in the nano-composites was prolonged. Spontaneous imbibition experiments showed that the gel-breaking fluid of nanosheet-modified slickwater exhibited excellent capability of oil-detaching, and increase the oil recovery to ∼35.43%. By observing and analyzing the interfacial behavior of MoS 2 nanosheets under stimulated reservoir conditions, it was found that the presence of an interfacial tension gradient and the formation of a climbing film may play an essential role in the spontaneous imbibition mechanism. This work innovatively uses two-dimensional MoS 2 nanosheets to modify regular slickwater and confirms the feasibility of flake-like nanomaterials to improve the performance of slickwater. The study also reveals the underlying mechanism of enhanced imbibition efficiency of the nano-composites.

Nano-SiO2 enhanced slickwater fracturing fluid for improved imbibition recovery in tight gas reservoirs: Performance and mechanism

Tiantian Zhang,Jie Yang,Zhiping Li,Mingwei Gao,Caspar Daniel Adenutsi,Qing You

Inspired by the exceptional performance of nanomaterials in oilfield development, yet it is rarely applied in tight gas reservoir. In this study, focusing on the tight gas reservoir of the Liuyangbao, Ordos Basin, a slickwater fracturing fluid was synthesized by incorporating nano-SiO 2 and surfactant to enhance its stability and activity, aiming to optimize the utilization efficiency of slickwater. The prepared SiO 2 -enhanced slickwater fracturing fluid exhibited excellent interfacial regulation properties involving surface tension reduction (71.65–28.31 mN/m) and wettability alteration (69.3–21.5º). In addition, SEM images indicated that the self-assembled nano-SiO 2 adsorbed on the core surface, sequentially forming a large number of micro/nano structures in “spot adsorption”, “sheet adsorption”, “lobe adsorption” and “cluster adsorption” shapes, altering the original pore structure. Meanwhile, LP-N 2 GA results showed an upward shift in the hysteresis loop of isotherms after nano-SiO 2 was adsorbed on the core samples, with a considerable increase in specific surface area (SSA) and transitional pores. Moreover, the system showed an outstanding capacity for imbibition gas production, and finally recovered 78.2 % (∼21.4 % higher than slickwater system). The underlying mechanism responsible for the system enhanced gas recovery were attributed to capillary pressure, structural disjoining pressure and Jamin effect. This work provides feasibility of the application of nano-SiO 2 in the development of tight gas reservoirs.

Development of polymer powder-based multifunctional variable-viscosity slickwater systems assisted by viscoelastic surfactants for enhanced unconventional reservoir fracturing

Wenlong Zhang,Yonghao Chen,Jizhen Tian,Dong Wang,Hao Zeng,Longyao Wang,Hetian Su,Jincheng Mao,Xiaojiang Yang

The study presents a groundbreaking advancement in variable-viscosity slickwater technology for unconventional reservoir stimulation through the development of a novel hydrophobically associating water-soluble polymer (TAE 23 C 12 N) and its synergistic systems with viscoelastic surfactants (VESs), which successfully addresses the challenge of real-time preparation of polymer powder-based slickwater. The innovative pentameric copolymer, synthesized via strategic incorporation of lauryl polyoxyethylene ether methacrylate, AMPS, and sulfobetaine monomers, demonstrates exceptional performance characteristics, including a high molecular weight (5.59 × 10 6  g/mol), superior salt tolerance (>10 4  mg/L mineralization resistance), and excellent thermal stability (50 % mass loss at 393 °C). A custom-designed continuous powder-liquid mixing system enabled real-time preparation of polymer powder-based slickwater, effectively solving the critical issue of polymer powder hydration and positioning TAE 23 C 12 N as a superior alternative to conventional emulsion and suspension dispersion systems for slickwater formulation. This technological breakthrough offers significant advantages, including reduced operational costs, minimized formation damage (<16.39 % permeability reduction), and enhanced transportation efficiency. Comprehensive characterization revealed remarkable synergistic effects between TAE 23 C 12 N and three VESs in polymer powder-based slickwater systems, with the EDAC/TAE 23 C 12 N system exhibiting optimal performance: rapid preparation (34 s for low-viscosity formulation), maximum drag reduction (79.1 %), and robust thermal/shear stability. All VES-enhanced polymer powder-based slickwater systems demonstrated complete gel breaking within 2 h at 120 °C, meeting stringent industry standards. These advancements address critical challenges in hydraulic fracturing through enhanced proppant transport, reduced environmental impact, and cost-effective large-scale applications of polymer powder-based slickwater, representing a paradigm shift in fracturing fluid technology with potential applications extending to enhanced oil recovery and geothermal energy development.