摘要
提高固井注水泥浆顶替效率是保障水泥环密封性能的前提,已有的理论和实验室方法多集中于两相流(钻井液/隔离液、隔离液/水泥浆、钻井液/水泥浆)顶替模拟,而与实际工况下钻井液与隔离液先掺混、再被水泥浆顶替的动态过程特征相距甚远。为此,基于流体顶替过程中掺混与扩散机理,建立流体动态顶替过程数学模型,借助流动仿真软件探讨隔离液性能变化对顶替钻井液和被水泥浆顶替的内在演变机理,结合仿真数据,建立了水泥浆顶替效率评估的新计算模型。研究结果表明:①在顶替初期,低黏度、低密度隔离液体系与钻井液混浆严重,但有利于降低壁面钻井液黏滞力,清除滞留钻井液,进而改善水泥浆顶替效率;②高密度、低黏度隔离液虽然能快速清洗井筒钻井液,但也容易产生指进现象,进而导致水泥浆提前返出井口,容易被误认为顶替效率较好;③隔离液密度处于钻井液和水泥浆之间时,低黏度隔离液有助于清除壁面钻井液和被水泥浆顶替;④隔离液排量高于临界值时,顶替效果改善明显;⑤所建立的注水泥浆顶替效率评价新模型与数值仿真结果吻合度高,误差仅为4.6%。结论认为,该新模型有助于更好地认识与解释复杂流动机理,为改善注水泥井筒浆柱结构、浆体性能及提高顶替效率奠定了理论基础。
The precondition for ensuring the sealing property of cement sheath is to improve the displacement efficiency of cement slurry. Existing theories and laboratory methods focus on the displacement simulation of two-phase flows (drilling fluid/spacer fluid, spacer fluid/ cement slurry, drilling fluid/cement slurry). However, such simulations are far different from the characteristics of the actual dynamic process of first mixing drilling fluids with spacer fluids and then displacing the mixture with cement slurry. For this reason, a mathematical model for the dynamic displacement process of fluids was set up based on the mixing and diffusion mechanisms during the fluid displacement process;fluid emulation software was used to analyze the impact of spacer fluid property changes on the internal evolution mechanism of displacing drilling fluids and being displaced with cement slurry;based on the emulation data, a new calculation model for evaluating the displacement efficiency of cement slurry was set up. The study results show that:(1) at the initial stage of displacement, low-viscosity and low-density space fluids are mixed with drilling fluids, which are favorable for reducing the viscous force of drilling fluids on the borehole wall, clearing residual drilling fluids, and thereby improving the displacement efficiency of cement slurry;(2) high-density and low-viscosity spacer fluids can quickly flush drilling fluids in the borehole, but they may easily cause fingering, thereby causing the cement slurry to return to the wellhead ahead of schedule. This may be mistakenly considered for better displacement efficiency;(3) when the spacer fluid density is between the density of drilling fluids and that of cement slurry, low-viscosity spacer fluids are favorable for clearing drilling fluids on the borehole wall and being displaced by cement slurry;(4) when the spacer fluid pump rate is higher than the critical pump rate, the displacement efficiency is significantly improved;(5) the new model for evaluating the displacemen
作者
杨谋
唐大千
袁中涛
张俊
徐力群
陈英
Yang Mou;Tang Daqian;Yuan Zhongtao;Zhang Jun;Xu Liqun;Chen Ying(State Key Laboratory of Oil & Gas Geology and Exploration//Southwest Petroleum University,Chengdu,Sichuan 610500,China;Oil and Gas Engineering Institute,PetroChina Tarim Oilfield Company,Korla,Xinjiang 830011,China;Research Institute of Petroleum Engineering Technologies,Sinopec Northwest Oil Field Company,Korla,Xinjiang 830011,China)
出处
《天然气工业》
EI
CAS
CSCD
北大核心
2019年第6期115-122,共8页
Natural Gas Industry
基金
国家自然科学基金项目“深井井筒—地层传热传质环境下井筒温度压力时变特性研究”(编号:51504210)
关键词
固井
注水泥浆
顶替效率评估
数值模拟
隔离液
浆柱结构
浆体性能
Cementing
Cement slurry injection
Displacement efficiency evaluation
Numerical simulation
Spacer fluid
Slurry column structure
Slurry properties
