高温高压钻井液P-d-T特性及其对井眼压力系统的影响

THE P-ρ-T (PRESSURE-DENSITY-TEMPERATURE) BEHAVIOR OF HPHT DRILLING FLUID AND ITS EFFECT ON WELLBORE PRESSURE CALCULATION

汪海阁 郝明惠 杨丽平

Wang Haige Hao Minghui Yang Liping

石油勘探开发科学研究院, 北京 100083 河南油田勘探处 海洋石油总公司渤海公司, 天津塘沽 300452

在高温高压环境下的钻井与完井,既困难,危险性又大。文中阐述了地温梯度、入口钻井液温度、钻井液类型等因素对当量静态钻井液密度的影响;建立了高温高压井中当量静态钻井液密度的计算模型;分析了钻井液密度变化对井底静压、动压、当量钻井液循环密度和动态波动压力的影响。结果表明,利用地面测量的钻井液密度计算井下压力,只适用于浅井和中深井;对于安全密度窗口很窄的高温高压井,必须考虑井筒温度和压力变化对钻井液密度及井内压力系统的影响,才能确保高温高压井的施工安全。

High risks exist in drilling and completing HPHT wells. This paper estimates the effects of formation temperature gradient, inlet mud temperature and mud types on the equivalent static density (ESD), and presents the calculation model of ESD under HPHT environment. In addition, the effects of ESD variations on wellbore static pressure, flowing pressure, equivalent circulation density (ECD), surge and swab pressure are also investigated. The results show that errors resulting from ignoring variations in mud properties are small in relative shallow wells, however, in HPHT wells, especially in those wells with narrow safe density margins available, changes in mud density due to elevated temperature and pressure and its effects on wellbore pressure system must be taken into account to ensure safe drilling and completion.

10.3969/j.issn.1000-7393.2000.01.005