海域天然气水合物钻井液用多功能处理剂制备与性能评价

Preparation and properties evaluation of multifunctional drilling fluid additive for marine natural gas hydrate

摘要:

针对海域天然气水合物钻井过程中由于储层水合物分解引起的井壁失稳难题，以2-丙烯酰胺基-2-甲基丙磺酸、二甲基二烯丙基氯化铵和二甲氧基甲基乙烯基硅烷改性纤维素为原料，制备了一种具有天然气水合物分解抑制性和降滤失性的双效处理剂。通过红外光谱表征了产物的分子结构，热重分析显示产物开始分解的温度约290 ℃，具有良好的热稳定性。水合物分解评价实验表明，1%双效处理剂作用下水合物的完全分解时间延长约1倍，水合物分解量降低了19.8%，具有良好的水合物分解抑制性能。在淡水基浆和5 wt% NaCl盐水基浆中的滤失量分别为6.8和8 mL，对于水合物储层具有良好的降滤失性。低温时淡水基浆滤失量为6.5 ml，表明双效处理剂具有良好低温流变性。本文为天然气水合物高性能钻井液的构建提供了重要支撑。

Abstract:

To address the issue of wellbore instability resulted from hydrate decomposition during offshore drilling for natural gas hydrate， this paper developed a dual-purpose additive which possess both hydrate decomposition inhibition and filtration reduction properties. It was synthesized using 2-acrylamido-2-methylpropane sulfonic acid， dimethyldiallyl ammonium chloride and dimethoxy methylvinylsilane-modified cellulose as the starting materials （named as “CAD”）. The molecular structure was characterized through infrared spectroscopy. Thermal analysis revealed that the product decomposition initiated at around 290°C， demonstrating commendable thermal stability. The hydrate decomposition evaluation experiments indicated that the presence of 1% of the dual-function additive extended the total decomposition time of hydrates by approximately 1-fold and reduced the hydrate decomposition rate by 19.8%， which highlights the outstanding performance of hydrate decomposition inhibition. Filtration in freshwater-based slurry and 5 wt% NaCl saline-based slurry measured to be 6.8 and 8 mL respectively， signifying effective filtration reduction capabilities for hydrate reservoirs. The filtration for the freshwater-based slurry amounted to 6.5 mL at low temperatures， indicating the dual-function additive has favorable performance of low-temperature rheology. All these research offers substantial support for the advancement of high-performance drilling fluids designed for natural gas hydrates.