固平28-21大位垂比水平井钻井液技术

Drilling Fluid Technology for Horizontal Well Guping 28-21 of High Horizontal Displacement to Vertical Depth Ratio

固平28-21井水平段长2 006 m,位垂比为1.70,是长庆油田水平段最长的油井水平井,属低孔、超低渗、低电阻高泥质含量的孔隙性油层。室内优选出了CQSP-2复合盐水钻井完井液,现场三开应用结果表明,应用CQSP-2钻井完井液能使井壁稳定,在2 000 m的水平段钻进过程中,泥岩和炭质泥岩钻遇率为20.84%,总长度达418 m,井壁稳定,井下无任何掉块,井径规则,水平段井径扩大率最大为1.61%,最小为0.05%,平均为0.63%;体系润滑性能好,水平段体系摩阻系数控制为0.03~0.05,起下钻摩阻较小;悬浮携带能力强,井眼净化能力好,钻进施工顺利,没有出现任何复杂情况和工程事故;油层保护效果好,产量创该区块同目的层水平井新高,投产初期出现自喷现象,日产油量为83.6 t/d,是合水油田平均单井日产量的近7倍。

The well Guping 28-21 is a horizontal well having the longest horizontal length（2,006 m） in Changqing Oilfield.It has a ratio of horizontal displacement to vertical depth of 1.7.The reservoir is of low porosity,ultra-low permeability,low electric resistance and high shale content.A CQSP-2 compound salts drill-in fluid was formulated to drill the reservoir section.CQSP-2 helped stabilize borehole wall in horizontal section of the well which is 418 m in length,having 20.84%of mudstone and carbonaceous mudstone penetrated along the hole.A gauge hole was obtained,with maximum hole enlargement of 1.61%,minimum of 0.05%,and an average of 0.63%.Friction coefficient in the horizontal drilling was kept at 0.03-0.05,showing good lubricity for the drilling.Hole cleaning performance was satisfactory,with no downhole troubles arising with hole cleaning.Good reservoir protection was achieved as selfflow was found when the well was initially put into production,giving a daily production of 83.6 t,seven times of the average daily production of other wells in Block Heshui.