河探1井超高密度钻井液技术

Ultra-High Density Drilling Fluid Technology for the Well Hetan-1

河探1井是中油股份公司在华北油田河套盆地临河坳陷部署的一口重点风险探井,完钻井深为6460.44 m,钻探目的为探索兴隆构造带光明背斜古近系、新近系生储盖特征及其含油气性。该井三开钻遇四套不同压力系数复杂地层,钻井液密度窗口窄,现场顺利实施了提密度压井、堵漏,控压钻进等作业,四开钻遇异常高压流体层,应用超高密度钻井液体系一次性将钻井液密度从1.80 g/cm^(3)提高至2.55 g/cm^(3),并安全实施完井作业,储备压井高密度钻井液(ρ=2.60 g/cm^(3)),达到国内应用水基钻井液采用重晶石粉加重的极限。在钻井施工过程中先后出现井塌、膏泥岩层蠕变缩径卡钻、高压盐水侵以及井漏等事故复杂,采用超高密度抗高温复合盐钻井液,现场应用随钻封堵提高地层承压能力工艺,分段完成七次承压堵漏,同时强化一级固控有效使用,应用高目筛布、优化钻井液体系配方、优选加重材料、调节膨润土含量及合理控制低密度固相含量等手段,成功解决了窄密度窗口和超高密度水基钻井液高温、高固相流变性能调整困难等技术难题,确保了压井和试油作业期间高温条件下超高密度钻井液体系具有良好的稳定性。该井创地区同期六项钻井技术指标,日产302.4 m^(3)高产工业油流,实现巴彦油田最深井勘探发现,为钻井及完井试油作业提供了技术支撑。

The well Hetan-1 is a key exploratory well drilled by CNPC at the Linhe depression in the Hetao basin in Huabei oilfield.The completion depth of this well is 6,460.44 m and was drilled to explore the reservoir characteristics of the Paleogene and the Neogene systems in the Guangming anticline in the Xinglong tectonic belt.The third interval of this well penetrated formations of four different formation pressure coefficients,and the safe drilling windows of the formations are narrow.Killing the well by raising mud weight,controlling mud losses and drilling with managed pressure were used in drilling this interval.When drilling into the formation with ultra-high pressure fluids,the mud density was increased in one step from 1.80 g/cm^(3) to 2.55 g/cm^(3),and the well was successfully completed.The kill mud stored at the rig site had a density of 2.60 g/cm^(3),a density limit of water based drilling fluids weighted with barite.Several downhole troubles were encountered during drilling,such as borehole collapse,pipe sticking because of creeping tight hole in mudstone formations containing gypsum,high pressure saltwater invasion as well as mud losses.The interval was drilled with a high temperature ultra-high density compound saltwater drilling fluid,and controlling mud losses while drilling technique was used seven times to enhance the pressure bearing capacity of the formations.During drilling,finer screens were used on shale shakers for better solids control,the drilling fluid was continually optimized for its composition,the weighting materials were carefully selected,the content of bentonite in the mud was adjusted to satisfy the needs of stabilizing mud rheology,and the content of the low-gravity solids in the mud was carefully controlled at as low as possible level.With these measures,problems such as narrow drilling windows,difficulties in controlling the rheology of a high temperature high solids content drilling fluid with ultra-high density were successfully solved,ensuring the stability of the properties of the ultra-high density drilling fluid in high temperature drilling and completion operations.The drilling of this well has created six drilling technical indicators in this area at the same period.An industrial oil flow of 302.4 m^(3) was produced daily,realizing the target of exploring oil and gas in the deepest well in the Bayan oilfield,and of providing technical support to the drilling and completion operations.