雁探1“四高”井钻井液应用技术

Drilling Fluid Technology for “Four-High” Well Yantan-1

雁探1井是中国石油天然气股份有限公司青海油田分公司的一口重点矿权保护井,是青海油田柴达木盆地一里坪地区落雁山构造一口四开直井型风险井,完钻井深为5 909.95 m,钻探主要目的是探索落雁山构造E32～N1含油气性;了解落雁山地区古-新近系暗色泥岩发育情况以及生烃能力,为下步盆地腹部大型区带热成因气勘探研究及部署提供依据。该井地质条件复杂,没有任何实钻参考资料,存在高温、高密度、高压盐水层、高浓度CO_2等叠加复杂因素,实际使用钻井液密度高达2.50 g/cm^3,井底实测温度高达205℃,CO_2侵高达100%,加之多层高压盐水存在,是一口典型的"四高"井,钻井施工难度极大。优选采用了BH-WEI钻井液体系,围绕高温稳定性、抗酸性气体污染、抗盐水污染、高密度流变性、滤失量与流变性矛盾等技术难点,精细调整钻井液配方及维护处理措施,较好地解决了一系列技术难题和矛盾,顺利钻至设计井深5 700 m,后加深钻进至5 909.95 m突遇设计外的异常高压盐水层,由于关井压井时间过长,事故完井。该井技术难点典型,积累了宝贵的现场施工经验,具有很好的借鉴指导意义。

The well Yantan-1 is a key well of mining rights protection of PetroChina Qinghai Oilfield Company.It is a vertical fourinterval exploration well drilled in the Luoyanshan structure in Yiliping in Qaidam Basin.The well was drilled to 5,909.95 m.The objectives of the well were to ascertain the potential of oil and gas production of the Luoyanshan Structure E3 2-N1;to understand the developmental state and hydrocarbon-generating potential of the Paleogene-Neogene dark-colored mudstones in Luoyanshan area,which will provide bases on which study and deployment of thermogenic gas exploration in the large-scale belt zone in the hinterland of Qaidam Basin can be performed in the future.Geological conditions of this well are quite complex,and no drilling data are available for reference.As a typical“four-high”well,the actual mud density used during drilling was as high as 2.50 g/cm3,the bottom hole temperature measured was as high as 205℃,CO2 concentration of the mud was 100%during CO2 invasion,and multiple high pressure salt water zones were encountered.A BH-WEI drilling fluid was selected to deal with these difficulties.Formulation of the mud and maintenance of the properties of the mud were focused on technical issues such as high temperature stability,resistance to sour gas contamination,resistance to salt water contamination,mud rheology at high density and filtration control.By elaborate adjustment of mud formulation and mud property maintenance,these technical difficulties were successfully resolved,and the well was successfully drilled to 5,700 m.When the well was then deepened to 5,909.95 m,an abnormally high pressure saltwater zone was encountered.Since the well was shut in and killed in a prolonged time,the well had to be abnormally completed.Technical difficulties encountered during the drilling of this well are quite typical,and valuable experiences gained from the field operation are of good reference value in dealing with the same drilling difficulties.