Staude Dominik, Plank Johann
Technical University of Munich, Construction Chemistry, Lichtenbergstraße 4, 85747, Garching, Germany.
Heliyon. 2024 Oct 4;10(19):e38921. doi: 10.1016/j.heliyon.2024.e38921. eCollection 2024 Oct 15.
For well cementing at temperatures above 120 °C, thermal thinning depicts a major problem, promoting particle sedimentation decreasing slurry viscosities. This is partly caused by dispersing properties of common high temperature retarder systems and can lead to imperfect zonal isolation, endangering the stability of the wellbore. Counteracting additives tend to start losing their effectiveness at temperatures >140 °C. Other options are often not economically sufficient, increase system complexity or show negative interactions with other additives. Hence, this work presents a comprehensive study on the sodium ethylenediamine tetra(methylene phosphonate) (Na-EDTMP)/borax retarder system, which was found to combine sufficient retardation with low thermal thinning, leading to an enhanced slurry stability at high temperatures. Thickening times (TT's) from 7 to 13 h (increasing with temperature) were achieved from atmospheric pressure and 50 °C up to high pressures and temperatures (HP/HT) of 19.0 kpsi and 200 °C bottom hole circulating temperature (BHCT). Furthermore, On/off-cycle HP/HT consistometer tests at 160 and 190 °C and rheological measurements were performed to examine stability of the slurry's viscosity. Experiments with fluid-loss additives show potential compatibility with other additives. Total retarder dosages of 0.97-2.64 % bwoc (by weight of cement) were applied. Compared to prior literature, higher Na-EDTMP/borax ratios (0.29-0.34 vs. 0.055) were found to improve retarding performance probably by enhancing synergetic effects. The slurries featured a sufficient initial viscosity (<40 Bc) and a constant pumpability (10-25 Bc) during the tests followed by a swift setting and compressive strength (CS) development. Additionally, high slurry stability was shown and compatibility with common fluid-loss additives is probable. Main disadvantage was the relatively high sensitivity of the system, especially at moderate temperatures, requiring exact dosage. Summarizing, the Na-EDTMP/borax retarder system might present a low-complexity opportunity for common high temperature retarders, avoiding thermal thinning while improving slurry stability.
对于在120℃以上温度下的固井作业，热稀释是一个主要问题，它会促使颗粒沉降并降低水泥浆粘度。这部分是由常见高温缓凝剂体系的分散特性引起的，可能导致封隔不完善，危及井筒稳定性。抗作用添加剂在温度>140℃时往往会开始失去效力。其他选择通常在经济上不可行，会增加体系复杂性或与其他添加剂产生负面相互作用。因此，本文对乙二胺四亚甲基膦酸钠（Na-EDTMP）/硼砂缓凝剂体系进行了全面研究，发现该体系兼具足够的缓凝作用和低热稀释特性，能在高温下提高水泥浆稳定性。在常压和50℃至井底循环温度（BHCT）为19.0 kpsi和200℃的高压高温（HP/HT）条件下，稠化时间（TT）达到了7至13小时（随温度升高）。此外，还进行了160℃和190℃的开/关循环HP/HT稠化仪测试以及流变学测量，以考察水泥浆粘度的稳定性。使用降滤失添加剂的实验表明其与其他添加剂可能具有相容性。缓凝剂总用量为0.97 - 2.64%bwoc（占水泥重量）。与先前文献相比，发现较高的Na-EDTMP/硼砂比例（0.29 - 0.34对0.055）可能通过增强协同效应来提高缓凝性能。在测试过程中，水泥浆具有足够的初始粘度（<40 Bc）和恒定的可泵性（10 - 25 Bc），随后迅速凝结并发展抗压强度（CS）。此外，该体系显示出高水泥浆稳定性，并且可能与常见的降滤失添加剂相容。主要缺点是该体系的敏感性相对较高，尤其是在中等温度下，需要精确的用量。总之，Na-EDTMP/硼砂缓凝剂体系可能为常见高温缓凝剂提供了一个低复杂性的选择，既能避免热稀释，又能提高水泥浆稳定性。
