Liu Kecheng, Wang Ren, Rong Kesheng, Yin Zebin, Lu Tiemei, Yu Yongsheng, Li Yingying, Yang Zexing, Yang Jie, Zhao Zhen
Engineering Technology Research Institute, PetroChina Xinjiang Oilfield Company, Karamay 834000, China.
CNPC Engineering Technology R&D Company Ltd., Beijing 102206, China.
Gels. 2023 Apr 1;9(4):290. doi: 10.3390/gels9040290.
As shale gas recovery progresses to deep layers, the wellbore instability during drilling in applications of oil-based drilling fluids (OBFs) becomes increasingly severe. This research developed a plugging agent of nano-micron polymeric microspheres based on inverse emulsion polymerization. Through the single-factor analysis with respect to the permeability plugging apparatus (PPA) fluid loss of drilling fluids, the optimal synthesis conditions of polymeric microspheres (AMN) were determined. Specifically, the optimal synthesis conditions are as follows: the monomer ratio of 2-acrylamido-2-methylpropanesulfonic acid (AMPS): Acrylamide (AM): N-vinylpyrrolidone (NVP) were 2:3:5; the total monomer concentration was 30%; the concentrations and HLB values of emulsifier (Span 80: Tween 60) were 10% and 5.1, respectively; the oil-water ratio of the reaction system was 1:1; the cross-linker concentration was 0.4%. The polymeric microsphere (AMN) produced via the optimal synthesis formula had the corresponding functional groups and good thermal stability. The size distribution of AMN ranged mainly from 0.5 to 10 μm. The introduction of AMND in OBFs can increase the viscosity and yield point of oil-based drilling fluids and slightly decrease the demulsification voltage but significantly reduce high temperature and high pressure (HTHP) fluid loss and permeability plugging apparatus (PPA) fluid loss. The OBFs with 3% polymeric microsphere dispersion (AMND) reduced the HTHP and PPA fluid loss by 42% and 50% at 130 °C, respectively. In addition, The AMND maintained good plugging performance at 180 °C. The AMN particles can block leakoff channels of artificial cores, effectively prevent the invasion of oil-based drilling fluids into formations and suppress pressure transfer. OBFs with 3% AMND enabled the corresponding equilibrium pressure to decrease by 69%, compared with that of the OBFs. The polymeric microspheres had a wide particle size distribution. Thus, they can well match leakage channels at various scales and form plugging layers via compression-deformation and packed accumulation, so as to prevent oil-based drilling fluid from invading formations and improve wellbore stability.
随着页岩气开采向深层推进，在油基钻井液（OBF）应用中钻井过程中的井壁失稳问题日益严重。本研究基于反相乳液聚合开发了一种纳米-微米聚合物微球堵漏剂。通过对钻井液渗透率堵漏仪（PPA）滤失量的单因素分析，确定了聚合物微球（AMN）的最佳合成条件。具体而言，最佳合成条件如下：2-丙烯酰胺基-2-甲基丙磺酸（AMPS）：丙烯酰胺（AM）：N-乙烯基吡咯烷酮（NVP）的单体比例为2:3:5；单体总浓度为30%；乳化剂（Span 80：Tween 60）的浓度和HLB值分别为10%和5.1；反应体系的油水比为1:1；交联剂浓度为0.4%。通过最佳合成配方制备的聚合物微球（AMN）具有相应的官能团和良好的热稳定性。AMN的粒径分布主要在0.5至10μm之间。在油基钻井液中引入AMND可以增加油基钻井液的粘度和屈服点，并略微降低破乳电压，但能显著降低高温高压（HTHP）滤失量和渗透率堵漏仪（PPA）滤失量。含有3%聚合物微球分散体（AMND）的油基钻井液在130℃时分别将高温高压和PPA滤失量降低了42%和50%。此外，AMND在180℃时仍保持良好的堵漏性能。AMN颗粒可以封堵人造岩心的漏失通道，有效防止油基钻井液侵入地层并抑制压力传递。与不含AMND的油基钻井液相比，含有3%AMND的油基钻井液能使相应的平衡压力降低69%。聚合物微球具有较宽的粒径分布。因此，它们能够很好地匹配各种尺度的漏失通道，并通过压缩变形和堆积形成封堵层，从而防止油基钻井液侵入地层并提高井壁稳定性。
