一种新型低密度矿渣固井液

A New Low Density Slag Cementing Slurry

针对漂珠、空心玻璃微珠等减轻剂价格昂贵、使用量大、其浆体与钻井液相容性较差等问题,借鉴钻井液转化为水泥浆(MTC)技术,直接以矿渣作为胶凝材料替代油井水泥配制固井液,并研究了配套的激活剂和缓凝剂。通过大量的室内实验,初步筛选出一种碱金属氢氧化物JHQ和一种碱金属硅酸盐JGY作为激活剂,并最终确定他们的掺量分别为3%和2%,此时固化体3 d的抗压强度可达到12.5 MPa;体系采用的缓凝剂HNJ主要靠分子中α和β位羟基羧酸基团能与Ca2+有很强的螯合作用,形成高度稳定的五元环或六元环,部分吸附于矿渣颗粒上,阻止水化产物性能,以达到延长工作液稠化时间的目的,浆体稠化时间与缓凝剂HNJ掺量几乎呈线性增长趋势;体系选用具有提高浆体稳定性和控制失水能力的膨润土类悬浮剂GYW-201,并配合使用悬浮稳定作用强的高聚物悬浮剂GYW-301。结果表明,矿渣固井液适用温度为50~90℃,密度在1.30~1.50 g/cm^3范围可调,具有成本低、失水量低、沉降稳定性良好、与钻井液相容性好、稠化时间线性可调、低温下强度发展迅速等优点。该体系已应用于江苏油田现场作业,固井质量良好。因此该矿渣固井液可替代低密度水泥浆,用于低压易漏井、长封固段、欠平衡井等固井施工,降低固井成本。

Floating beads and hollow glass beads are commonly used lightweight additives in cement slurries. These lightweight additives are expensive, and generally large amount of them are needed in formulating cement slurries of required density. Cement slurries treated with floating beads and hollow glass beads have poor compatibility with drilling fluids. A clue borrowed from MTC technology can be used to solve these problems, that is, using slag as a gelling material to replace oil well cement in formulating cementing slurries. Activators and retarders as assorted agents in this new technology have been studied. An alkaline metal hydroxide JHQ and an alkaline metal salt of silicate JGY were preliminarily screened out as the activators through large amount of laboratory experiments, and the concentration of the activators were determined to be 3% and 2%, respectively. At these concentrations of activators, the set cementing slurry had compressive strength of 12.5 MPa. The retarder selected, HNJ, has hydroxycarboxylic acid groups on the α and β carbon atoms that have strong chelating capacity to calcium ions. The result of the chelating was the formation of highly stable pentacyclic or hexacyclic structures. HNJ was adsorbed on the surface of slag particles to retard the hydration process and prolong the thickening time. The thickening time was almost in a positive linear relationship with the concentration of HNJ. A bentonitic suspending agent, GYW-201, was selected to enhance the stability of the cementing slurry and to control flter loss. GYW-301, a high polymer suspending agent, was used in combination with GYW-201. The slag cementing slurry is suitable for use at 50-90℃, and has density adjustable between 1.30 g/cm3 and 1.50 g/cm3. Low cost, low flter loss, good sedimentation stability, good compatibility with drilling fluids, linearly adjustable thickening time, fast-developing low temperature strength were the advantages of the cementing slurry. Good cementing job quality has been obtained in the Jiangsu oilfeld. As a low cost technology, this new slag cementing slurry has the potential to replace low density cement slurry in cementing low pressure wells liable to lost circulation, wells with long cementing section, and under-balanced wells.