环氧树脂乳液改性油井水泥的性能研究

Properties of Oil-Well Cement Modified by Epoxy Resin Emulsion

随着油气井勘探领域的不断扩展和深入,油井水泥脆性较大的弊端越来越明显,在复杂的压力和温度条件下,水泥石容易产生裂缝从而造成强度损失,甚至会进一步导致水泥环的完整性失效,对油气井的安全生产有着严重的危害.为克服油井水泥的脆性,聚合物乳液因其能有效改善水泥的韧性、保水性而得到广泛应用.针对深井、超深井高温高压固井需求,制备了水性环氧树脂乳液改性水泥,并对其流变性能、稠化性能、抗折抗压强度和弹性模量等应用性能进行了研究,同时利用X射线衍射(XRD)、固体核磁共振(NMR)和热失重(TG)等表征手段探究了环氧树脂乳液体系在水泥中的作用机理.结果表明,环氧树脂乳液的加入改善了水泥浆的静态滤失性能,对水泥浆的流变性能和稠化行为没有负面影响.改性水泥石的抗折强度显著提高,尤其是当环氧树脂乳液掺量为15%时,90℃养护7 d、14 d和28 d的水泥抗折强度分别提高了25%、111%和100%.同时,与空白试样相比,环氧树脂乳液掺量为5%、15%和20%的水泥弹性模量分别降低了39.4%、42.8%和58.1%.环氧树脂乳液不会改变水泥的水化产物,只会在水泥水化早期起到一定的延缓和阻碍作用;环氧树脂在水泥基体中发生固化交联反应,在水泥水化过程中水化产物之间形成了联结,从而提高了水泥石的抗折性能,降低了水泥石的弹性模量.

With the continuous expansion and deepening of oil and gas well exploration,the disadvantages of the high brittleness of oil-well cement are becoming increasingly apparent.Under complex pressure and temperature conditions,the cement stone is susceptible to cracking,causing a loss of strength and ultimately leading to the failure of the cement sheath,which adversely impacts the safe production of oil and gas wells.Polymer emulsions are widely used to combat the brittleness of oil-well cement because they can effectively improve its toughness and water retention.To meet the requirements of high-temperature and high-pressure cementing in deep and ultradeep wells,waterborne epoxy emulsion-modified cement was prepared,and its application properties,such as rheological property,thickening property,flexural and compressive strength,and elastic modulus,were investigated.The mechanism of the epoxy resin emulsion system in the cement was investigated using X-ray diffraction(XRD),solid nuclear magnetic resonance(NMR),and thermogravimetric(TG)analysis.The results showed that the addition of epoxy resin emulsion improved the static filtration performance of the cement slurry without affecting its rheological property or thickening behavior. The flexural strength of the modified cement stone was considerably improved, particularly when the epoxy resin emulsion content was 15%. Further,the flexural strength of cement cured at 90℃ for 7 d,14 d,and 28 d increased by 25%,111%,and 100%,respectively. In comparison to the blank sample,the elastic modulus of the modified cement with epoxy resin emulsion content of 5%,15%,and 20% decreased by 39.4%,42.8%,and 58.1%,respectively. Epoxy resin emulsion does not affect the hydration products of cement but delays and inhibits the early hydration of cement. The curing cross-linking reaction of epoxy resin in the cement ma-trix forms a connection between the hydration products during the cement hydration process,enhancing the flexural performance and decreasing the elastic modulus of the cement stone.