针对新疆油田南缘深井、超深井的一些地质特点,阐述了固井的主要技术难点,重点从水泥浆技术方面提出了技术难题和解决措施.运用颗粒级配原理,通过大量的室内实验,选取粒径合适的加重材料和充填材料,并确定合适的加量,设计出最高密度范围2.70 g/cm3、最高温度200℃,各项性能满足固井技术需求的超高温超高密度水泥浆,解决了超高密度水泥浆在超高温环境下稳定性差、浆体流变性差、抗压强度发挥慢、难相容等技术难题.该体系在新疆油田南缘区块上已成功使用.

针对中拐凸起储层油水关系复杂、储层裂缝发育、裸眼段较长等固井难点,室内研究出韧性膨胀水泥D600G体系,该水泥浆体系具有较好的膨胀率、流动性和抗冲击能力.通过固井软件仿真优化施工参数,确保水泥浆体系的有效充填.现场应用该固井技术,固井质量达到优质.

准噶尔盆地环玛湖地区储集着丰富的油气资源,近年来为实现环玛湖地区的钻井提速,在该地区加大了对PDC钻头的应用.当前环玛湖地区钻头的优选和应用主要在侏罗系以上地层和三叠系地层,侏罗系上部地层可钻性好,但进入侏罗系底部及三叠系地层后,地层可钻性变差,对钻具的要求高.根据环玛湖地区地层情况分析了该地区使用个性化PDC钻头及配套工具的优势.阐述了PDC钻头及配套工具近年来在环玛湖地区的发展应用,并结合现场探索试验,通过对比钻头的使用效果,在不同地层层段对PDC钻头进行了合理的优选.最后优选出适应于侏罗系上部地层的X3切削齿、六刀翼PDC钻头(FX65DX3)和适应于三叠系克拉玛依组层段的扭力冲击器+PDC钻头,为推动环玛湖地区钻井提速进程起到了较大作用.

在对压力系数低、易漏地层,特别是裂缝型地层的固井作业中,采用常规密度的水泥浆进行固井极易引起井漏,造成固井失败或质量不合格.为此,根据准噶尔盆地西部隆起克百断裂带百口泉鼻隆构造上的百泉1井钻井复杂情况和地层情况,采用了2种超低密度水泥浆柱结构,以确保固井时上部防漏下部压稳,该井固井过程中无漏失,测井结果表明,低密度水泥浆固井质量合格.结论认为:①在压力系数低和有易漏地层存在的情况下,从固井设计到施工都应采用以“高效顶替、整体压力平衡”为核心的平衡压力固井工艺技术,控制环空形成的动液柱压力约大于地层压力和小于地层破裂压力；②正确选用和合理搭配固井施工压力、水泥浆密度和施工排量这3个参数,分析前期技术难点并制订合理的应对措施是保证固井成功的关键；③由于采用了超低密度水泥浆,降低了环空液柱压力与地层压力之间的正压差,减小了水泥浆的失水量,有利于保护油气层.

For the formations with low pressure coefficient and easy lost circulations, and especially for fractured formations, the conventional density slurry will usually lead to lost circulations, resulting in cementing failure or poor cementing quality. Through the study on the downhole drilling events and formation conditions in Well Baiquan 1 on the Baikouquan structure located at uplifted Kebai fracture belt in the west Junggar Basin, two cement slurry systems with ultra-low density are proposed and applied, to ensure no lost circulation in upper cementing and low kicks from the lower cementing. The final logging data shows that the cementing quality is good. The following conclusions are drawn. (1) For low-pressure thief zones, a balanced cementing technology, which has the core principle of high-efficiency displacement and overall pressure balance, can be applied during the cementing planning and operation to keep the dynamic hydraulic pressure in the annulus slightly above formation pressure and below the formation breakdown pressure. (2) Proper combination of operating pressure, slurry density and pump rate, and correct pre-job analysis and planning of countermeasures are critical for the success in cementing operation. (3) The application of ultra-low-density slurry will lower the positive pressure differential between the annulus hydraulic pressure and the formation pressure, reduce the water loss of the cement slurry, and be helpful for reservoir protection.