改善煤岩润湿性的强化煤层固井胶结技术

煤层有机质含量高、节理发育、节理面光滑,导致煤岩与固井水泥石界面胶结强度弱、煤层段固井质量差,严重制约了煤层气的经济有效开发。为此,依据煤岩组成、成分和润湿特性分析,重点以改善煤岩的亲水润湿性为技术突破点,测试分析不同表面活性剂及其浓度、浸泡时间等对煤岩表面润湿角、界面胶结强度的影响规律,优选煤岩高效亲水润湿改性物质,研发出强化煤层胶结前置液体系,并在山西沁水盆地进行了现场应用。室内研究与现场应用结果表明:通过含醚、硫酸根的表面活性剂在煤岩表面的致密吸附,可在浓度0.3%、30 s内使煤岩表面润湿改性为强亲水性,能够显著提高煤岩—水泥石界面的胶结强度(胶结强度达65.5%);现场煤层气井固井应用效果也表明,采用该强化煤层胶结型前置液能够将煤层段固井质量由过去的不合格提高到优良水平,对于提高煤层段固井质量具有显著的效果。结论认为,该技术为解决煤层段固井质量差的难题及顺利实施后续压裂增产等改造措施提供了有效的保证。

Bonding-strengthening technology in coalbed cementing through wettability improvement

Coalbeds are characterized by high organic matter content, presence of joints and smooth joint surface, which lead to weak bonding between coal and set cement and poor cementing quality of coalbeds, and consequently the economic and effective development of coalbed methane (CBM) is restricted seriously. In this paper, components, compositions and wetting characteristics of coal, were analyzedin order to improve the water wettability of coal, the effects of different surfactants and their concentration and soaking time on the surface wetting angle of coal and interfacial bonding strength were tested and measured. The high-efficiency hydrophilic wettability modifierwas optimized. The strengthened coalbed bonding prepad fluid system was developed and applied practically in the Qinshui Basin, Shanxi province. The results of laboratory tests and field applications show that the compact adsorption of surfactant containing ether and sulfate radical on the surface of coal can convert the surface wettability into strong hydrophilicity at the concentration of 0.3% within 30 seconds, thus improving significantly the interface bonding strength (up to 65.5%) between coal and set cement. The field application in CBM well cementing shows that the strengthened coalbed bonding prepad fluid can improve the cementing quality from unqualified level to high level, and play a significant role in improving CBM hole interval cementing quality. It is concluded that this technology provides an effective guarantee for coalbed cementing quality improvement and smooth implementation of stimulation measures like fracturing.