An Experimental Investigation on the Chemical Stability of Selected Formation and Determination of the Proper Type of Water-Base Drilling Fluids. Part 2. Test Results

The objective of this study was to select the proper drilling fluid type and composition for drilling stable holes through the problems of the selected formations. This study was performed on shale samples taken from 10 wells in which hole instability was encountered to various extents during drilling the Germav formation. Both ionic and polymer inhibitions were utilized in formulating the proper drilling for the Germav formation. Ionic inhibition was obtained using KCl and NaCl. Polyanionic polymer (Pac-L) was used for providing the polymer encapsulation. Experimental results indicated that KCl is superior to NaCl in providing ionic inhibition. Both salts lowered the interaction between the drilling fluid and Germav formation, but better results were obtained with KCl. Minimum salt concentration up to 15% yields more inhibitive environment. Polymer inhibition tests indicated that minimum Pac-L concentration required for maintaining the polymer inhibition was about 2 lb/bbl for both systems. In conclusion, KCl/encapsulating polymer system seems to be the most proper water: base drilling fluid available for Germav formation achieving the required wellbore stability. The fluid loss and suspending properties of the proposed system must be controlled using the modified starch and XC polymer.     

提高井壁稳定性的途径及水基防塌钻井液研究与应用进展

针对泥页岩地层黏土含量高,容易水化,导致钻井过程中出现严重坍塌和膨胀缩径,以及严重造浆等问题,从4个方面(合适的钻井液密度,提高钻井液的抑制性,减少钻井液滤液进入地层,强化封堵)阐述提高井壁稳定性的途径,介绍国内在钻井用化学剂方面开展的研究工作,同时介绍近年来出现的通过添加不同新型化学抑制剂形成的强抑制水基钻井液,如聚合醇钻井液、强抑制胺基钻井液、有机硅聚合物钻井液、有机盐钻井液、甲基葡萄糖苷钻井液等.提出围绕提高井壁稳定性的研究方向:提高对钻井液中低密度固相控制的认识,重点考虑固相化学控制剂的研究,通过低密度固相的控制,提高钻井液抑制性;考虑在现场钻井液检测性能中增加抑制性检测指标和方法;以低相对分子质量聚胺为代表的钻井液抑制剂是阳离子钻井液的新发展,应加强其机理研究;重视铝基化合物或络合物的研发,强化钻井液的抑制性及封堵作用.     

页岩气水平井钻井液技术的难点及选用原则

我国页岩气资源勘探开发已全面铺开。针对页岩气的成藏特征,页岩气开发以浅层大位移井、丛式水平井布井为主。由于页岩地层裂缝发育、水敏性强,长水平段钻井中不仅易发生井漏、垮塌、缩径等问题,且由于水平段较长,还会带来摩阻、携岩及地层污染问题,从而增大了产生井下复杂情况的几率。解决井壁稳定、降阻减摩和岩屑床清除等问题是目前页岩气水平井钻井液选择和设计的关键。选择页岩气水平井钻井液的原则是确保井壁稳定、润滑、防卡和井眼清洗。油基钻井液可提高水润湿性页岩的毛细管压力,防止钻井液对页岩的侵入,从而有效保持井壁稳定,同时还具有良好的润滑、防卡和降阻作用,是国内外目前采用最多的钻井液体系。当采用水基钻井液的时,利用低活性高矿化度聚合物钻井液或CaCl2钻井液以降低页岩和钻井液相互作用的总压力;采用浓甲酸钾、Al3+盐,可以通过脱水、孔隙压力降低和影响近井壁区域化学变化的协同作用产生良好的井眼稳定作用;对于有裂隙、裂缝或层理发育的高渗透性页岩应使用有效的封堵剂进行封堵;但对于强水敏性页岩地层,水基钻井液在抑制性方面仍然存在局限性。从环境保护的角度出发,甲基葡糖苷钻井液在井壁稳定机理方面与油基钻井液相似,未来可望作为有效的钻井液体系之一。随着以页岩气为代表的非常规油气资源的不断开发,为了满足安全钻井和环境保护的需要,未来页岩气水平井钻井液技术的研究应围绕高效、低成本水基钻井液和低毒油基钻井液来展开。     

燃气互换性与火焰稳定性研究

随着燃气品种增多，品质变化，燃气互换性和火焰稳定性成为燃气燃烧理论与技术中极有意义的课题。本文从火焰稳定、热负荷、排烟量３个方面来研究适合于锅炉动力及工业加热类的气互换性；推荐了ＢＦＧ＋ＣＯＧ置换ＣＯＧ的互换准则。