页岩气水平井低油水比油基钻井液研制及应用

针对页岩气水平井钻探过程中井壁失稳风险大、钻井液性能要求高和商业开发降本提效的迫切需求,基于页岩储层特征、水平井工程施工要求,构建、研制了一套性能稳定的低油水比油基钻井液体系。室内试验表明,该油基钻井液具有良好的热稳定性、抗污染性、封堵性和乳化稳定性,而且塑性黏度较低、切力适中、流变性能较好,可以满足页岩气水平井钻井的要求。低油水比油基钻井液在涪陵页岩气田5口井进行了现场应用,通过采取低油水比胶液维护、固相控制和随钻封堵等配套措施,实现了将油水比控制在70/30以下,较该气田以往油基钻井液基础油用量降低15%,获得良好的降本效果。页岩气水平井低油水比油基钻井液能有效降低涪陵页岩气田钻井成本,有力支撑了页岩气低成本商业开发,对国内其他地区页岩气开发也具有借鉴意义。 

Development of Oil-Based Drilling Fluid with Low Oil-Water Ratio and Its Application to Drilling Horizontal Shale Gas Wells

In order to meet the requirement of wellbore stabilization and good performance of drilling fluids during the drilling of shale gas horizontal wells and realize commercial development at a low cost and with high efficiency, a stable oil-base drilling fluid system with low oil-water ratio was developed to accommodate the characteristics of shale reservoirs and the engineering requirements of horizontal wells. It is shown from experimental tests that this oil-base drilling fluid system is good in terms of thermal stability, contamination resistance, plugging capacity and emulsion stability. In addition, it has lower plastic viscosity, moderate shear and better rheological property. Therefore, a stable oil-based drilling fluid system can satisfy the unique conditions in drilling horizontal of shale gas wells. The oil-based drilling fluid system has been applied in 5 horizontal wells drilling in Fuling Shale Gas Field. Through low oil-water ratio gel maintenance, solid phase control and plugging while drilling, the oil-water ratio was kept below 70/30, 15% lower than previously used oil based drilling fluids in this gas field. Further, drillings cost were reduced significantly. In summary, drilling costs in the Fuling Shale Gas Field could be reduced effectively by using an oil-based drilling fluid system with a low oil-water ratio in horizontal shale gas wells. This system will provide strong support in the low-cost commercial development of shale gas and used as a model in the development of shale gas in other areas within China.