【作者】 孙士慧；

【导师】 闫铁；

【作者基本信息】 东北石油大学 ， 石油与天然气工程， 2014， 博士

【摘要】 控压钻井是解决我国大规模、难动用深层油气资源勘探开发中普遍存在的由地层“窄安全压力窗口”现象引起的钻井漏喷同存难题，极大提高钻井安全性的一项革命性钻井新方法。精确的井筒流动模型是实现井筒压力精确控制的前提，是实现安全高效钻进的核心科学问题。由于井底恒压控制压力钻井技术在解决类似问题上体现出巨大的优势，为此本文展开详细研究。井底恒压钻井井筒流动模型是在传统稳态单相流、稳态多相流的基础上，更全面、系统、精确地研究不同工况条件下井筒流动规律与压力变化规律，它主要包括：正常钻进时稳态单相流流动模型和气侵后的瞬态多相流流动模型。论文从以下几方面开展研究：(1)在分析不同工况下井筒-地层之间热交换机制的基础上，考虑焦耳-汤姆逊效应、钻井液流动过程中摩擦生热和地层流体侵入的影响，应用传热学、流体力学相关理论，建立了钻井循环期间、停止循环和溢流期间的井筒和地层温度的物理模型和非稳态数学模型；通过全隐式差分方法进行数值求解，揭示钻井全过程井筒和地层温度的动态变化规律。(2)基于井筒动态温度剖面，分析钻井液密度随温度、压力的变化，建立了可准确描述钻井液当量静态密度随井深变化规律的钻井液当量静态密度计算模型，修正了静液柱压力计算模型；采用量纲分析理论研究钻具接头、钻具旋转和环空偏心对摩阻压耗的影响，综合钻井液密度特性、粘温特性、钻具接头、钻具旋转、钻具偏心及起下钻过程的波动压力等因素，完善了井底恒压钻井井筒稳态单相流流动模型，提高了井筒压力的预测精度。(3)根据不同井型下的气侵量，分析气泡的生成机理给出了不同气侵量下的气泡几何尺寸计算模型，通过分析不同尺寸气泡运动的受力情况，建立准确描述不同尺寸气泡动态运动行为的气泡上升速度模型。在此基础上，研究起钻、接单根、关井期间井筒流体流动特性和压力波动规律，给出了起钻、接单根期间的井筒流动计算模型，考虑关井后地层流体的续流效应，建立了关井工况下的井底压力和井口压力预测模型。揭示气泡在井筒中的动态运移规律，为瞬态流动模型的建立奠定基础。(4)综合考虑温度、地层渗流特性、油气相变、岩屑的影响，推导了环空多相流连续性方程、动量守恒方程以及能量守恒方程，建立了正常钻进、溢流、关井和压井不同工况下复杂多相流体的瞬态流动模型；并采用有限差分法对建立模型进行了数值求解，完成钻井过程中从溢流发生到压井的全过程模拟；基于瞬态多相流理论，建立了井口回压的动态计算模型，奠定了控压钻井动态井控与压力预测的理论基础，为实现控压钻井井筒压力的动态精确控制提供了有力的理论支撑。更多还原

【Abstract】 Managed preesure drilling (MPD) is an innovative approach which can be used to solvethe drilling problems induced by narrow safety pressure window in deep carbonate reservoirs.The precise wellbore flow model is not only the premise to realize accurate wellbore pressurecontrol, but also the key for safe and efficicent drilling. Constant Bottomhole Pressure MPD(CBHP MPD) technology displays great advantage in solving above problems, therefore adetailed study is described in this thesis.The entire process of CBHP MPD flow model was established based on the traditionalsingle and multiphase flow model. The model can be used to study flow pattern and pressurechange rules under different drilling conditions more comprehensively, systematically andaccurately. The model include single liquid phase steady flow in drilling and gas-liquidmultiphase transient flow after gas invasion.In the thesis, the research mainly focuses on the following aspects:(1) Based on the energy exchange mechanism of individual control-unit components ofwellbore and formation under different drilling conditions, the physical model and unsteadymodel during circulation, circulation-stop and gas kick were established by using heat transfertheory and fluid mechanics for predicting the temperature distributions of drilling fluids insidethe drill string and in annulus and formation. In the model, Joule-Thomson effect, frictionalheat of fluid flow and the inflow of formation fluid with certain internal energy were consideredand finite difference method was used to solve model. Dynamic wellbore and formationtemperature distribution is revealed in the whole drilling process.(2) Based on dynamic wellbore temperature profile, drilling fluid density change withtemperature and pressure were analyzed, equivalent static drilling fluid density model whichcan accurately describe equivalent static density along the wellbore was built. Hydrostaticcolumn pressure calculation model was corrected. The influence of tool joint, drilling toolrotation and eccentric annulus on friction pressure loss was studied. Considering the factors ofdrilling fluid density, viscosity-temperature characteristic, tool joint, rotation and eccentricannulus of drilling tool, and pressure fluctuation in the process of tripping, single-phase steadyflow model of constant bottomhole pressure drilling was improved, which enhanced wellborepressure prediction accuracy.(3) According to gas kick volume of different well types, gas bubble formation mechanismwas analyzed and gas bubble size calculation model under different gas kick volumes wasobtained. Starting from the force analysis of bubbles movement in different sizes, bubble risingvelocity model was developed, which was used to describe bubble dynamic behavior accurately.And on this basis, fluid flow characteristics and pressure fluctuation rules during the conditionof POOH, make a connection and well shut-in were researched and the relevant flow modelwas presented. With a view to wellbore storage effects during well shut-in, a prediction model of bottom wellbore pressure and wellhead pressure was established. Dynamic migration rulesof gas kick in wellbore was proposed, which laid a foundation for the establishment of transientflow model.(4) Considering the effect of temperature, reservoir flow characteristics, oil/gas phasechange and cuttings, mass, momentum and energy equations were deduced. And transientmultiphase flow model under the conditions of drilling, shut in and well killing process wereestablished to describe coupled multiphase flow quantitatively in wellbore. The dynamic modelwas solved by finite difference method. The dynamic model can truly simulate the wholeprocess from gas kick to well killing. Based on transient multiphase flow theory, dynamiccalculation model of wellhead back pressure was developed. The research results in this thesisnot only lay a theoretical foundation for dynamic well control and pressure prediction, butprovide a strong theoretical support for the precise dynamic control of wellbore pressure.更多还原