考虑井眼清洁条件下的小井眼钻井液性能优化研究

新疆油田玛湖部分区块采用长水平段(超2000 m)小井眼技术进行钻井和开发。在钻井过程中,井眼不清洁导致的卡钻,井筒压力过大导致的漏失问题严重制约了该区块的高效经济开发。钻井液性能的优化是解决上述问题的关键方法之一。为此,采用了CFD数值模拟的方法,建立了环空固液两相流模型,探究了不同钻进参数下钻井液不同流变参数(赫巴流变模型)对岩屑运移和环空压耗的影响。根据数值模拟结果可知:(1)提升钻井液密度有利于提高携岩能力;(2)不同钻进参数下,钻井液流变参数对岩屑运移作用效果不同;(3)钻井液流变参数并非越大越有利于岩屑运移;(4)结合玛湖区块特征,确立了最优钻井液流变参数范围,并将该范围成功的应用于现场。

Performance Optimization of Slim-Hole Drilling Fluids Under Hole Cleaning Condition

In Xinjiang Oilfield, part of the Mahu block is developed with long horizontal (exceeds 2000 m) slim holes. In drilling operation, pipe sticking resulted from poor hole cleaning and mud losses resulted from excessive wellbore pressure seriously restricted the efficient and economic development of the block. One of the key methods to solve these problems is the optimization of the drilling fluid properties. Using CFD numeric simulation method, a model describing the solid liquid two-phase flow in annular spaces was established, and the effects were investigated of different mud rheological parameters (Herschel-Bulkley rheological model) on the migration of the drilled cuttings and the annular pressure losses under different drilling parameters. Th numeric simulation results show that (1) an increase in drilling fluid density is beneficial to the carrying capacity of the drilling fluid; (2) the effects of the mud rheological parameters on the migration of drilled cuttings vary under different drilling parameters; (3) higher mud rheological parameters do not necessarily aid in cuttings migration; (4) an optimum mud rheology range was determined for the drilling operation in the Mahu block based on its characteristics, and the optimum mud rheology range has been successfully used in field operations.