DP19井小井眼欠平衡长水平段水平井的钻井技术

Technology for drilling prolonged horizontal section in an under-balanced slim hole:A case history of DP19 well,Daniudi Gas Field,Ordos Basin

DP19井是中国石油化工股份有限公司在鄂尔多斯盆地大牛地气田部署的第一口小井眼氮气泡沫全过程欠平衡长水平段水平井。该井为探索在小井眼条件下开发低压低孔低渗致密砂岩的自然建产潜力,设计水平段井眼尺寸为152.4mm,水平段长1 200m。针对该井所面临的技术难点,在施工过程中采取了以下技术措施:应用了小井眼钻井、长水平段钻井、裸眼悬空侧钻、氮气泡沫钻井液、全过程欠平衡及地质导向等多项国内先进技术,在氮气泡沫钻井液条件下应用了英国GEOLINK公司生产的E-LINK MWD无线随钻测量仪器,跟踪传递井底井眼轨迹参数和地层特性参数,使井眼轨迹能够安全有效地沿着目的层钻进;在地层自然伽马值稳定的井段,成功地实施2次裸眼悬空侧钻作业,保障了钻遇泥页岩夹层后井眼轨迹的顺利调整。多种先进适用技术在该井集成应用成功,为低效气藏的高效开发提供了新的工程技术手段和思路。

The DP19well launched by the Sinopec is the first slimhole well with long horizontal section in the Daniudi Gas Field,which adopts nitrogen foam and underbalanced drilling technology in the whole process.This slimhole well was drilled to explore the natural flowing potential of the tight sandstone gas reservoir with low pressure,porosity and permeability.The designed borehole size was φ152.4mm and the length of horizontal section was 1200m.In order to overcome technical difficulties during the drilling,many advanced domestic technologies have been adopted,such as slimhole drilling,long horizontal section drilling,sidetracking in open holes,nitrogen-foam drilling fluid,under-balanced drilling and geosteering in the whole process.Besides,the E-LINK MWD instrument produced by GEOLINK was selected to track and transmit borehole trajectory parameters and formation attribute parameters in order to make sure that the well was drilled targeting the pay zone.Open-hole sidetracking was successfully conducted twice at the section with stable natural gamma for the smooth adjustment of borehole trajectory after through the interlayer between mudstone and shale.This case history shows that the above advanced technologies have been successfully used in this well,providing a new technical means for the effective development of low-efficiency gas reservoirs.