固井水泥石低温强度诱导纳米水化硅酸钙晶核

Low-temperature Strength Induced Nano-hydrated Calcium Silicate Nucleus for Well Cementing

高继超 蒋 平 雒 闯 吕鹏程 卢海川 熊钰丹

GAO Jichao JIANG Ping LUO Chuang LYU Pengcheng LU Haichuan XIONG Yudan

针对低温或表层固井水泥浆候凝时间长、水泥石早期强度低且发展慢等问题，以硝酸钙、硅酸钠、梳型聚羧酸减阻剂、聚丙烯类稳定剂为原料，采用化学沉淀法+磁力搅拌+超声分散的制备工艺提高混合效率，制得水泥石低温强度诱导晶核（LTI）。通过透射电镜观察LTI 的微观形貌、分析其元素组成，研究了其对水泥浆低温稠化性能和静胶凝过渡时间、水泥石低温强度发展的影响。结果表明，LTI 的基本单元结构为堆叠的类锡箔状和絮片状，伴有少量棒状和规则方形晶体，尺寸为100～200 nm，周围延伸出类纤维状物质，比表面积较大。LTI 借助自身模板成核作用促进水泥水化进程，降低堆积产物成核势垒，促使低温稠化曲线由爬坡向直角转变，可在 10 ℃下将稠化时间之比控制在0.47 以内。LTI 可诱导水泥石早期强度快速发展，随LTI 掺量增加、温度升高，水泥石低温抗压强度增大。在 20 ℃下，掺有 1.5%、5.0% LTI 水泥石的 24 h 抗压强度分别提高 89.1%、257.8%；在 30 ℃下，掺有1.5%、5.0% LTI 水泥石的6 h抗压强度分别为4.1、6.5 MPa，相比于刚成型的净浆水泥石，抗压强度实现跨越式发展。掺有LTI的水泥浆在30 ℃下的静胶凝过渡时间可由78 min 缩短至18 min，有助于提高水泥浆的防窜性能。纳米水化硅酸钙晶核LTI可缩短低温浅层或高寒区域油气井建井周期、提高固井质量。

Low temperature or surface cementing often faces problems such as long waiting time of cement slurry，low early strength of cement and slow development. Using calcium nitrate，sodium silicate，comb type polycarboxylic acid drag reducer and polypropylene stabilizer as raw materials，by optimizing the preparation process using solution chemical precipitation method， magnetic stirring and ultrasonic dispersion，a low-temperature strength induced nucleus material（LTI）for cement stone was prepared. The microstructure and elemental composition of LTI were observed by transmission electron microscopy. The influence of LTI on the low-temperature thickening property，static gelling transition time and the development of low-temperature strength of cement was studied. The results showed that the basic unit structure of LTI was stacked tinfoil-like and float-like，accompanied by a small number of rod and regular square crystals，the size of 100—200 nm，and the surrounding extension of fiber-like material. The specific surface area was large. By utilizing its own template nucleation function，nucleus LTI promoted the hydration process of cement，reduced the nucleation potential barrier of accumulated products，and then promoted the transition of low-temperature thickening curve from climbing to right angle. The thickening time ratio could be controlled within 0.47 at 10 ℃. LTI could induce the rapid development of early strength of cement. With increasing LTI dosage and temperature，the low-temperature compressive strength of cement increased. At 20 ℃，the 24-hours compressive strength of cement stone mixed with 1.5% and 5.0% LTI increased by 89.1% and 257.8%. At 30 ℃，the 6-hours compressive strength of cement stone mixed with 1.5% and 5.0% LTI was 4.1 MPa and 6.5 MPa，respectively. Compared with freshly formed cement stone，the compressive strength achieved a leapfrog development. The static gelation transition time of cement slurry mixed with LTI at 30 ℃ could be shortened from 78 min to 18 min，which helped to improve the anti channeling function. Nanoscale hydrated calcium silicate nucleus LTI could shorten the construction cycle of oil and gas wells in low temperature shallow or high cold areas，and then improve the quality of cementing.

10.19346/j.cnki.1000-4092.2024.03.001