Cheng Wang,Jinsheng Sun,Yifu Long,Hongjun Huang,Juye Song,Ren Wang,Yuanzhi Qu,Zexing Yang
Lost circulation control remains a challenge in drilling operations. Self-healing gels, capable of self-healing in fractures and forming entire gel block, exhibit excellent resilience and erosion resistance, thus finding extensive studies in lost circulation control. In this study, layered double hydroxide, Acrylic acid, 2-Acrylamido-2-methylpropane sulfonic acid, and CaCl2were employed to synthesize organic-inorganic nanocomposite gel with self-healing properties. The chemical properties of nanocomposite gels were characterized using X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscope, X-ray photoelectron spectroscopy and thermogravimetric analysis. layered double hydroxide could be dispersed and exfoliated in the mixed solution of Acrylic acid and 2-Acrylamido-2-methylpropane sulfonic acid, and the swelling behavior, self-healing time, rheological properties, and mechanical performance of the nanocomposite gels were influenced by the addition of layered double hydroxide and Ca2+. Optimized nanocomposite gel AC6L3, at 90 °C, exhibits only a self-healing time of 3.5 h in bentonite mud, with a storage modulus of 4176 Pa, tensile strength of 6.02 kPa, and adhesive strength of 1.94 kPa. In comparison to conventional gel, the nanocomposite gel with self-healing capabilities demonstrated superior pressure-bearing capacity. Based on these characteristics, the nanocomposite gel proposed in this work hold promise as a candidate lost circulation material.
Lost circulation has been a serious problem to be solved in many drilling practices during oil, gas and geothermal well drillings. Many materials have been developed and evaluated for the purpose. However, their performance to plug severe leakoff is very limited. Herein, an injectable self-healing hydrogel based on polyampholyte with sulfonated and quaternary ammonium functionalities (P(MPTC- co -NaSS)) was developed and comprehensively evaluated to prevent the severe loss of fluids to formation. By incorporating cation-π (π is for aromatic residues) interaction, the hydrogel shown self-healing property and robustness in severe environment (temperature, salt) by comparison with other hydrogels merely consisting of cation-anion and H-bonding interactions. Aromatic residues enhanced thermal stability above 310 °C. The plugging measurement shown that an addition of 2 wt% dried gel particles can plug high-permeability formation and endure a high pressure of 6 MPa, produce much lower circulation loss and result in a dramatically increased loss volume reduction rate (63.5%) compared with a commercial polymer gel product and an inert material (9.4%) after a self-healing process. Markedly, P(MPTC- co -NaSS) can be used in a wide range of formation temperature (as high as 150 °C) and salt concentrations (NaCl, CaCl 2 , as high as 15 wt %). In addition to suitable particle size and mechanically robustness, it was also attributed to the soft, swelling, deformable, toughness and self-healable features of P(MPTC- co -NaSS) gel particles as well as the strong adhesion to negatively charged formations in water, even under high thermal and saline condition. These characteristics also contributed to a long-term plugging performance, beneficial to avoid repeated lost circulation in drilling operation. Besides, this self-healing polyampholyte gel particles dispersed well in saline fluid and maintained stable rheological properties after hot rolling, which was favorable to drilling fluid circulation. This study shown the application potential of self-healing materials as plugging material candidate in petroleum drilling industry.
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