Yongming Li

A novel gemini viscoelastic surfactant (VES) for fracturing fluids with good temperature stability

A category of gemini surfactants with novel structures were designed and synthesized as thickening agents of clean fracturing fluids in this research. The desired products were characterized by high resolution mass spectrometry (ESI-HRMS) and infrared spectrometry (FT-IR GX). Fluid samples with a formula of 5 wt% of products and 1 wt% of KCl were evaluated. The SEM studies revealed a good network microstructure and obvious viscoelasticity, which is favorable for a proppant suspension. Furthermore, the evaluation of their rheological properties at high temperatures revealed good thermal stabilities of these fluids up to 139 °C, particularly for VES-M (the spacer for the surfactant using methylamine and epoxy chloropropane). Comparative analysis of the rheological properties showed that since long chains of N-substituents in the middle of the molecules could enhance steric hindrance and rigidity, it is unfavorable for molecular entanglement and increases the viscosity of the VES aqueous solution. Proppant-support and gel breaking evaluations were also performed. It can be seen that nearly 100% proppant suspension was observed for 180 min at ambient temperature and complete gel breaking was achieved.

Effective Synthesis of Benzyl 3-Phenylpropiolates Via Copper(I)-Catalyzed Esterification of Alkynoic Acids with Benzyl Halides Under Ligand-Free Conditions

AbstractnWe developed an efficient way to prepare benzyl 3-phenylpropiolates via copper-catalyzed coupling between corresponding benzyl halides and alkynoic acids under ligand-free condition. This methodology is also suitable for aromatic and α,β-unsaturated acids. The desired esters could be obtained in good yields.Graphical AbstractWe developed an efficient way to prepare benzyl 3-phenylpropiolates via copper-catalyzed coupling between corresponding benzyl halides and alkynoic acids under ligand-free condition. This methodology is also suitable for aromatic and cinnamic acids. The desired esters could be obtained in good yields.

A Comprehensive Model of a Hydraulic Fracture Interacting with a Natural Fracture: Analytical and Numerical Solution

In this paper, a comprehensive model combining analytical and numerical solution has been developed to study the interaction between a hydraulic fracture (HF) and a natural fracture (NF). A new analytical solution is presented to analyze the interaction mechanism with consideration of fluid lag and stress singularities near the HF tip, and to predict whether the HF crosses the NF when the propagating tip reaches the interface and the fluid front remains farther back. A new numerical solution based on the displacement discontinuity method and finite-volume method is derived to solve the problem of coupled rock deformation, fluid transport, stress interference, interface slipping, and opening, and to investigate the interaction between an HF and an NF after the fluid front reaching the interface. Based on the comprehensive model, sensitivity analyses of key influence parameters are implemented. The analyses indicate that the HF tends toxa0cross the NF under conditions of high principal stress difference, high intersection angle, high interfacial friction, high injection rate, high fracturing fluid viscosity, and low initial conductivity of the NF. Moreover, the morphology of HF is significantly affected by two engineering parameters, the injection rate and the fracturing fluid viscosity. The same value of the product of these two parameters results in the same HF morphology at the times of the same injected fluid volumes. The new comprehensive model is validated with published analytical and numerical criterions and laboratory tests.