WuM1-1羽状分支水平井充气钻井液技术

Aerated Drilling Fluid for Feather Horizontal Well of WuM1-1

WuM1-1井由1口多分支水平井和1口采气的直井组成。该井斜井段短,井斜率在30°/100 m以上,主井眼和10个分支井段总进尺6182 m,98%以上在煤层中钻进,煤层脆、压实性较好,更易发生掉块。为满足钻井对井壁稳定性、润滑性、井眼净化以及煤层保护等的要求,采用钾铵基聚合物防塌钻井液进行充气欠平衡钻井,在钻进中保持钻井液有合适的粘度、切力,选用合适的注气压力和注气量以及当量钻井液密度;每钻完一个立柱坚持循环几分钟,上下划眼一次,并泵入CMC高粘钻井液,配合有效使用固控设备,尽量使井眼干净;复配使用粉末状固体润滑剂和液体润滑剂。该钻井液性能稳定,易于维护,悬浮携岩能力强,润滑性好,井眼畅通,保证了WuM1-1井安全、快速、优质施工。该井在煤层钻进中无阻卡现象,井壁稳定,没有出现井壁掉块或井垮现象,水平连通一次成功,10口分支井悬空侧钻一次成功,只用57 d即顺利完井,比该地区常规钻井快49倍。

Wum1-1 well is composed of a multilateral horizontal section and a vertical section.The well has a short deviation section and a deviation angle of more than 30°/100 m.Wum1-1 well with a original hole and 10 branch holes has a total depth of 6182 m.More than 98% penetration are in coal formation in which collapse accidents frequently occur as a result of it is brittle and has a better compactability.The potassium-ammonium polymer base anti-sloughing drilling fluid was employed in aerated underbalanced drilling operation to maintain borehole stability and meet the requirement of lubrication,clean drilling and coal formation protection.And maintaining appropriate viscosity, yield,gas injection pressure and equivalent density of drilling fluid were also required.Several minutes circulation and once reciprocate reaming were necessary each vertical column depth and then maintain a clean borehole by pumping CMC high viscosity fluid coupled with effective solid phase control.The combination product composed of powered solid lubricant and liquid lubricant was also employed.Results indicated that this drilling fluid assured WuM1-1 well safe,quick and high quality drilling operation because it presented stable performance,easy maintenance,stronger cuttings suspension and transportation,favorable lubrication and provided a unrestricted borehole.No sticking and collapse accidents occurred in coal reservoir.The horizontal connection and pending sidetrack drilling 10 branches were all operated successfully at first time.A drilling period of only 57 days was acquired.Drilling speed of WuM1-1 well was 49 times faster than conventional drilling operation in this area.