钻井机器人的连续油管钻压和钻速控制模型

连续油管钻井机器人利用机身内外的钻井液压力差作为动力源，可在牵引连续油管的同时加载钻压。以钻井机器人为基础，建立连续油管钻柱动力学模型，并推导出通过钻井液排量控制钻压和钻速的单参数控制数学模型；对钻井机器人引入调速回路，建立具有调速功能的钻柱动力学模型；在溢流阀调定压力大于机身内外压差时，推导出利用钻井液排量和节流阀流通面积两种参数控制钻压、钻速的数学模型，在溢流阀调定压力小于机身内外压差时，推导出利用钻井液排量、节流阀流通面积和溢流阀调定压力3种参数控制钻压、钻速的数学模型；以11.43 cm（4.5英寸）井眼为例，对上述3种数学模型进行了分析。分析结果表明：钻压、钻速随钻井液排量的增加基本呈线性增加，在钻井液排量大于0.005 m³/s时，钻井机器人能够向前爬行，在钻井液排量大于0.005 7 m³/s时，钻头能够正常钻进；调节节流阀流通面积和溢流阀调定压力，可以在一定范围内无级调钻压和钻速；3种控制方法相结合，可以实现小排量、大钻压，及大排量、小钻压等钻井参数的控制。以控制模型为基础，针对不同井下工况建立钻进工艺的专家数据库，以钻井机器人为"大脑"，结合井下随钻测量数据就能够实现闭环控制，自动钻进。

Research on WOB and ROP control model of coiled tubing based on drilling robot

The coiled tubing drilling robot uses the differential pressure of inside and outside drilling fluid as a power source to load the weight on bit (WOB)while pulling the coiled tubing. Based on the drilling robot, this study establishes the dynamics model of coiled tubing drill string, and further derives the mathematical model of single parameter control for WOB and rate of penetration (ROP)through the control of drilling fluid displacement. A speed regulating circuit is introduced into the drilling robot to establish a dynamics model of drill string with ROP control function. When the set pressure of relief valve is greater than the differential pressure, the mathematical model is derived for the control of WOB and ROP using two parameters of drilling fluid displacement and throttle valve flow area. When the set pressure of relief valve is smaller than the differential pressure, the mathematical model is derived for the control of WOB and ROP using three parameters of drilling fluid displacement, throttle valve flow area and set pressure of relief valve. Taking the 4.5 in borehole as an example, this paper analyzes the above three mathematical models. The results show that the WOB and ROP of coiled tubing drill string linearly increase when the drilling fluid displacement increases. The drilling robot can crawl forward when the drilling fluid displacement is more than 0.005 m³/s, and the bit can drill normally when the drilling fluid displacement is more than 0.005 7 m³/s. The WOB and ROP can be adjusted steplessly within a certain range by adjusting the flow area of throttle valve and the set pressure of relief valve. The control of drilling parameters such as small displacement, large WOB, large displacement and small WOB can be realized by the combination of three control methods. Based on the control model, the expert database of drilling process can be established according to different downhole conditions. Closed-loop control and automatic drilling can be realized with the help of drilling robots and data measured while drilling.