川深1井钻井液关键技术

Key Drilling Fluid Technology for Well Chuanshen-1

川深1井是中石化部署在川东北地区的一口超深预探井,完钻井深为8420.00 m。该井面临着井温高、地层条件复杂、地质资料少及井壁易失稳等诸多技术难点。针对高密度钻井液技术难点,通过室内实验优选出抗高温处理剂:2%SPNH、2%SMP-3、0.5%SMPFL(DSP-1)、3%SMT(SMS-H)、3%RHJ-3、1%HPA、3%纳米SiO_2。通过钻井液体系正交实验得出了流变性好、抑制性强、抗温性强、沉降稳定性好、抗污染能力强的高密度聚磺钻井液,并在该井四开井段取得了成功应用。最后,对现场应用过程中的钻井液关键技术进行了系统的阐述,如气液转换技术、特殊地层处理方法、钻井液的现场维护技术措施及保护油气层技术等,主要取得以下认识:①加重时循环混入低黏度切力的高密度钻井液,逐步降低膨润土含量;②通过固控设备严格控制固相含量;③钻遇盐膏层时可提高钻井液密度,并严格控制滤失量,保证钻井液pH值不低于10;④酸性地层可适量提高Cl^-含量对钻井液进行预处理提高其抗盐性能;⑤破碎地层须提高钻井液密度并加入相应处理剂,从力化耦合角度防止井壁失稳;⑥易漏地层应严格控制钻井液密度,适当减少排量及提高黏度和切力,可加入不同粒径可酸化的封堵材料,进行屏蔽暂堵。

Well Chuanshen-1 is an ultra-deep exploratory well drilled in northeast Sichuan by Sinopec.Drilling of this well was faced with several technical difficulties such as high formation temperature,complex formations penetrated,less geological data available,borehole wall instability and high mud density etc.Drilling fluid additives were selected through laboratory experiment to deal with the high-density problem.The additives selected and their concentrations were:2%SPNH,2%SMP-3,0.5%SMPFL(DSP-1),3%SMT(SMS-H),3%RHJ-3,1%HPA,3%nanophase SiO2.A high-density polymer sulfonate drilling fluid with good rheology,strong inhibitive capacity,high temperature resistance,good settling stability and high resistance to contamination,was formulated through orthogonal experiment.This drilling fluid was successfully applied in the fourth interval of the well Chuanshen-1.Difficulties encountered in filed operations and technical measures(such as gas-liquid conversion,drilling fluid treatment for special formations,mud property maintenance in field operations and reservoir protection etc.)are discussed in this paper.The major technical measures include:1)When weighing the active mud,high density mud with low viscosity low gel strength should be used and the MBT of the mud should be reduced gradually.2)Solids control equipment should be used to control solids content strictly under designed value.3)Drilling fluid density can be increased when drilling into salt and gypsum formations and filter loss should be strictly controlled.pH value of the drilling fluid should be no less than 10.4)When drilling formations with acidic fluids,pretreat the drilling fluid with high chloride content,thereby enhancing its ability to resist salt contamination.5)High density with some additives can be used to drill broken formations,borehole instability can be resolved through coupling of mechanical and chemical measures.6)Drilling fluid density should be strictly controlled when drilling formations at which mud losses are easy to take place.Meanwhile the flow rate should be appropriately reduced,and mud viscosity and gel strength should be increased to some extent.Temporary plugging with acid soluble lost circulation materials of different particle sizes can be used to control mud losses.