伊拉克米桑Fauqi油田水平井造斜段钻井液技术

Drilling Fluid Technology for Angle Build Section of Horizontal Wells in Iraq Missan Fauqi Oilfield

Fauqi油田水平井的造斜和稳斜井段一般在3 350~4 480 m,该井段属于白垩系,主要由灰岩、泥岩及页岩组成,地层岩性易发生垮塌,长期开采造成压力系数低,施工过程中又易发生井壁坍塌、黏附卡钻和井漏等复杂事故。针对该地层的特点,FQCS**井采用BZ-KSM钻井液体系。现场施工中,在BZ-KSM钻井液中引入了BZ-YRH,对改进钻井液流变性能,防止岩屑床形成起到了明显的作用;加入了BZ-YFT、纳米封堵剂及硅酸盐等处理剂,对提高钻井液的防塌抑制性能、防止钻屑分散具有明显的作用;由于地层易漏易塌,在五开直井段钻进过程中钻井液密度维持在1.22~1.28 g/cm^3之间,起钻换定向钻具前再将密度提高到1.35 g/cm^3。应用结果表明,该钻井液充分利用了K^+离子的抑制作用、硅酸盐的聚结封堵效果及高分子量聚合物的降滤失作用等,解决了抑制与分散、井壁垮塌与岩屑携带的问题,保证了施工井的顺利完成。

In horizontal drilling in the Fauqi oilfield,the angle build and hold sections are generally at depths between3350-4480m,the Cretaceous system,which mainly composed of limestone,mudstone and shale.Long time of hydrocarbon development has resulted in low formation pressure.During drilling,borehole collapse,differential pressure pipe sticking and lost circulation have been encountered frequently.Based on the formation characteristics,a BZ-KSM drilling fluid was used in drilling the well FQCS**.To improve the rheology of the drilling fluid and to prevent the formation of cuttings beds,an additive BZ-YRH was introduced into BZ-KSM.BZ-YFT,a nano plugging agent and a silicate were used to improve the inhibitive capacity of the drilling fluid.To avoid lost circulation,mud density was maintained between1.22g/cm3and1.28g/cm3in the5th interval.Prior to POOH to change to directional drilling tool,the mud density was increased to1.35g/cm3.Field application has shown that this drilling fluid had good inhibitive and plugging capacity,as well as superior filtration control performance and rheology.Downhole problems such as shale dispersion,borehole instability and difficulties in cuttings carrying have been greatly mitigated,ensuring the success of the drilling operation.