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川渝东部地区由于钻井地质情况复杂，钻井成本高，大部分井完井井身结构设计为Φ152.4 mm井眼下Φ127 mm套管固井完井。川渝东地区碳酸盐岩深部地层井眼扩大率较小，一般在2%～5%，实际井径一般在Φ152 mm～Φ158 mm以内，在Φ152.4 mm井眼下Φ127 mm套管环空间隙小，长期以来固井优质率一直徘徊在20%左右，层间封隔质量难以保证。较低的固井优质率难以保证完井作业中的酸化、压裂质量和油气生产作业。为此，文章认真分析了小井眼固井质量低的主要原因是环空间隙值较小。为提高小井眼固井质量，开展了提高小井眼井径扩大率研究，对于全面钻进井段开展双心钻头、取心井段采用扩眼器提高井径扩大率研究，使小井眼井径扩大率达到10%以上、实际井径达到165 mm以上，保证和提高了小井眼的固井质量，固井优质率达50%左右。

RESEARCH ON ENHANCING THE CEMENT JOB QUALITY OF SLIM HOLE

Most of the wells in the east part of Sichuan—Chongqing region were completed with a casing program of Φ152.4 mm hole×Φ127 mm casing because of the complicated drilling geological conditions and high drilling cost in the region.The hole enlargement ratio of the deep seated carbonat rocks in the region was very small,being 2%—5% in general and the real hole diameter being commonly within Φ152—Φ158 mm.Because of a small annular clearance between Φ152.4 mm hole and Φ127 mm casing,the factor of merit of well cementing has been always fluctuated at about 20% and it was difficult to control the quality of interzonal isolation,thus influencing acid fracturing quality and oil/gas producing job.So,through analyzing in detail,it was thought that the principal reason causing the slim hole cement job quility low is the small annular clearance.In order to raise the quality,the research on enhancing the hole enlargement ratio was carried out.The result indicated that,through the bi center bit′s being used for full diameter drilling intervals and the reamer′s for coring intervals,the slim hole enlargement ratio was up to more than 10%,its real hole diamenter being up to over 165 mm,thus ensuring and raising the slim hole cement job quality,the factor of merit of well cementing being about 50%.