钻井液中生物增黏剂对固井水泥浆性能及结构的影响

Impact of a biological tackifier in a drilling fluid system on the performance and structure of a cement slurry

固井中由于环空绕流等原因会造成水泥浆和钻井液掺混,现场相容性评价实验发现钻井液中的生物增黏剂会引发混浆流动性急剧变差,致使施工作业泵压快速升高,严重时将有可能导致固井失败。为此,开展了生物增黏剂对水泥浆性能及结构的影响实验:1用红外光谱、X射线衍射仪、扫描电镜对掺入生物增黏剂前后的水泥浆的结构、物相和微观形貌进行观察对比;2用原子吸收分光光度计分析水泥浆滤液的离子种类及含量,并考察水泥浆滤液中金属离子对钻井液和生物增黏剂溶液的影响。结果表明,生物增黏剂造成混浆流动性变差的机理在于:水泥浆与钻井液掺混后,生物增黏剂与水泥浆水化产生的Al 3+、Fe3+交联形成凝胶并大量包裹吸附水;混浆中维持其流动性的自由水显著减少,使得混浆流动性急剧变差;混浆出现"假凝",表现为稠化时间显著缩短;水泥浆水化进程延缓表现为水泥环抗压强度发展缓慢。

Cement slurry and drilling fluid will mix due to the annular streaming.The test of assessing the compatibility between a cement slurry and a drilling fluid showed that a biological tackifier in a drilling fluid caused a bad mobility of the mixture,quick pressurization of operation pumps,and even cementing failures.Therefore,we conducted tests on the impact of a biological tackifier on the performance and structure of a cement slurry.First,we observed and compared the structure,phase and microstructure of a cement slurry with infrared spectroscopy,X-ray diffraction instrument and SEM before and after adding a biological tackifier.Then,we analyzed the types and contents of ions of the filtrate in a cement slurry with atomic absorption spectrophotometer,and inspected the impact of metal ions in a cement slurry filtrate on the drilling fluid with a biological tackifier.Test results revealed the mechanism of how a biological tackifier caused a bad mobility of the mixture：after a cement slurry and a drilling fluid were mixed,Al3＋ and Fe3＋ produced by the hydration of the biological tackifier and the cement slurry were cross-linked to form a gel to wrap and adsorb a large amount of water; so free water making the mixture flow was obviously decreased,thereby to make the mobility of the mixture worse sharply; ＂mendacious congealing＂ of the mixture obviously shortened the thickening time; and the delay of the cement slurry hydrating process was represented by a slow increase in the compressive strength of cement sheath.