用于深水/超深水低温固井的纳米水化硅酸钙/明胶接枝磺化醛酮晶种早强剂

Nano Calcium Silicate Hydrate/Gelatin Grafted Sulfonated Acetone-formaldehyde Seed Crystals as Early Strength Agents for Deepwater/Ultra-deepwater Well Cementing at Low Temperature

针对深水/超深水低温固井作业面临着水泥浆强度发展缓慢、候凝时间长的难题,纳米水化硅酸钙(CSH)晶种可通过晶核作用有效促进水泥水化速率。然而,CSH易团聚,造成粒径不均匀,且制备过程中用到的分散剂又会延迟水泥水化,无法满足深水/超深水低温固井作业要求。为此,以明胶、甲醛、丙酮等为原料制备明胶接枝磺化醛酮缩聚物(SG);以SG为高分子有机分散底液,采用溶液法制备纳米水化硅酸钙/明胶接枝磺化醛酮晶种(SG-CSH)。通过激光粒度分析仪、透射电镜、等温量热仪、X射线衍射仪等,分析了SG-CSH的微观结构、水化放热规律、水化产物和低温早强性能。结果表明,SG具有优异的插层分散能力,与CSH形成的晶种具有低钙硅比(1.0)、粒径分布(3~100 nm)窄和分散性好的特性,体系在长久保存下稳定无沉淀;加入SG-CSH后在水化反应早期生成更多的氢氧化钙和钙钒石,加快水泥水化速率。水泥浆稠化实验和抗压强度检测结果表明,与空白实验相比,加入SG-CSH后水泥浆的稠化时间明显缩短,30℃下的稠化时间从210 min缩短至125 min;加入4%SG-CSH的水泥浆在10、15、30℃下候凝1 d后的抗压强度分别提升1.9、1.3、5.0 MPa,表现出优良的低温早强性能。

In response to the challenges of slow development of cement slurry strength and long waiting time for cementing in deepwater/ultra-deepwater cementing operations at low temperature,nano calcium silicate hydrate(CSH)seeds can effectively promote cement hydration rate through crystal nucleation.Nevertheless,CSH tends to agglomerate and leads to uneven particle sizes.Additionally,the dispersants used during the preparation process can delay cement hydration,which does not meet the requirements for low-temperature cementing in deepwater/ultra-deepwater environments.For this reason,a gelatin grafted sulfonated acetone-formaldehyde condensate(SG)was prepared using gelatin,formaldehyde and acetone as raw materials.With SG as the polymer organic dispersion base solution,nano calcium silicate hydrate/gelatin grafted sulfonated acetone-formaldehyde seed crystals(SG-CSH)was prepared by the solution method.The microstructure,hydration exothermic law,hydration products and low-temperature early strength properties of SG-CSH were analyzed through laser particle size analyzer,transmission electron microscope,isothermal calorimeter and X-ray diffractometer,etc.The results showed that SG had excellent intercalation and dispersion ability,which could form a low calcium-silicon ratio(1.0),narrow particle size distribution(3—100 nm),good dispersibility,stable and precipitation free long-term storage seeds with CSH.After adding SG-CSH,more calcium hydroxide and perovskite were generated in the early stage of hydration reaction,accelerating the cement hydration rate.At the same time,the results of cement slurry thickening experiment and compressive strength testing showed that compared with the blank experiment,the thickening time of cement slurry was significantly shortened after adding SG-CSH.The thickening time of cement slurry at 30℃was shortened from 210 minutes to 125 minutes.The compressive strength of cement slurry containing 4%SG-CSH increased by 1.9,1.3 and 5.0 MPa after initial setting for 1 day at 10,15,and 30℃,respectively,demonstrating excellent low-temperature early strength performance.