基于比例积分控制原理预测钻井全过程原始地层温度的新方法研究

应用比例积分控制原理将瞬态传热模型预测结果与出口 温度实测数据逐步进行反馈可准确预测原始静态地层温度. 为此, 本文基于井下各控制组件质量、动量及能量守恒原理, 建立了实际井身结构与钻具组合条件下循环和停止循环期间井筒-地层温度分布全瞬态传热模型, 应用全隐式有限差分法进行求解, 并引入比例积分控制原理对比分析实测温度与预测温度的误差范围进而精确、 快速获取原始地层温度. 结合一口深井基础数据计算表明, 套管下入深度改变了井筒-地层间热交换效率, 进而影响了近井壁地层温度分布状况; 同时, 钻井过程中循环和停止循环作业过程改变了井下各控制组件的初始条件与边界条件, 致使近井壁原始地层温度分布距离产生变化. 建立的数学模型和研究方法可为石油钻井、地热井开采及地球深部原始地层温度信息准确、 经济、快速获取提供理论基础. 关键词： 原始地层温度 循环与停止循环 瞬态传热模型 比例积分控制原理

A new method of forecasting initial formation temperature during the whole drilling process based on proportional-integral control principle

A strategy based on proportional-integral feedback control was applied to gradually feedback the error between simulation of transient heat transfer model and logged date to forecast initial formation temperature. In this study, based on the each control unit of mass, momentum and energy conservation principles in a wellbore, the transient heat transfer model was developed between circulation and shut-in stages under real casing program and drilling string assembly condition, which were solved by full implicit finite difference method. Meanwhile, the proportional-integral control principle was introduced to compare the error range between measured temperature and prediction temperature, which can precisely and quickly obtain initial formation temperature. Combined with a deep well basic data, the results show that the heat exchange efficiency of wellbore and formation was changed by the casing pipe depth, thus affecting formation temperature distribution of the near-well zone. What’s more, the initial and boundary conditions of each control unit in the down-hole was also changed by circulation and shut-in operating time during the drilling process, leading to the variation of distribution distance of the initial formation temperature of the near-well zone. Development of the numerical models and the research methods can provide accurately, economically and quickly to obtain theoretical basis for oil drilling, geothermal well exploiting and the initial formation temperature information.
Keywords： initial formation temperature circulation and shut-in transient heat transfer model proportional-integral control principle