环空附加当量循环密度的计算方法

China University of Petroleum, Beijing 102249, China Designing Institute, China National Petroleum Offshore Engineering Co.Ltd., Beijing 100028, China Research Institute of Drilling and Production, Qinghai Oilfield Company, PetroChina, Dunhuang 736202, China Dingbian Oil Production Plant, Yanchang Oilfield Co. Ltd., Dingbian 718600, China

面对日益复杂的地质条件和钻井技术的革新要求，井底当量循环密度计算的重要性越来越引起钻井工作者的重视。一般而言，当量循环密度等于当量静态密度与环空压耗的当量密度之和。将循环过程附加的环空压耗折算成相当的密度值，则为环空附加当量循环密度，其计算与监测对于大位移井、深水井或超深井的控压钻井尤为重要。文中通过优选钻井液流变模式选取幂律模式作为实际钻井液的流变模式，对不同尺寸的管柱采取分段求和的处理方法计算钻井液循环压耗，并运用环空水力模型和U型管原理这2种方法计算环空附加当量循环密度，最后结合具体实例进行了计算。研究结果表明，环空附加当量循环密度的计算结果能够满足工程设计的计算要求。

With the increasingly complex geological conditions and new requirements of drilling technology, drilling workers have paid much more attention to the calculation of equivalent circulating density(ECD). In general, the ECD of drilling fluid is the sum of the equivalent static density(ESD) of fluid and the pressure loss in the annulus due to the flow. Additional equivalent circulating density(AECD) can be defined as putting the additional circulating pressure loss into a density value, which is important to MPD technology for extended reach well(ERW), deep water, and ultra-deep wells. This paper calculates the circulating pressure loss by the way of choosing drilling fluid rheological models and using the stepwise summation methods, and the annulus hydraulic model and U tube principle are used to get AECD. At last, combined with the example, the calculation is analyzed. Results meet the requirements of engineering design and calculation.

10.6056/dkyqt201405030