Directional PDC bit is mainly used to solve a series of problems in directional wells,including big anti-torque,unstable tool surface and occasional pauses of deflecting operation.With compact structure,the bit is designed based on the low-torque and high rock breaking theory,the re- broken tooth placement technique and the bottom flow field simulation technique.Using the bit,the impact of cutting anti-torque on directional orientation tool surface is minimized,drilling torque changes little,tool surface is placed stably and it has effective directional capability,good deflecting effect,fast ROP and long life.Directional PDC bit,as a characteristic bit,has a broad application prospect.

Drilling in complicated formation can easily result in collapse,shortening diameter and high abrasiveness,which causes low average mechanical drilling velocity,difficult drilling and difficulty in meeting the demand of high-efficiency drilling regarding the common drill bit.Therefore,the study of a kind of new PDC bit used in complicated formation is put forward according to regional feature.The advanced means are used to carry out the individuated design in terms of teeth-distribution way,crown head shape,hydraulic structure and force balance of the PDC bit.The goal of increasing mechanical drilling velocity,reducing running and pulling times,preventing drilling accident,shortening drilling period and saving drilling cost can be reached by using the new bit in the complicated formation.The field application shows that the bit significantly increases drilling velocity,shortens drilling period and saves drilling cost with obvious economic benefit.

针对小井眼PDC钻头的实际工作条件,提出了在小井眼钻井中具有普遍意义的PDC钻头的横向力自平衡抗回旋技术.分析了钻头的受力状态与钻头回旋运动之间的关系,并对自平衡抗回旋技术的基本原理、设计方法和技术准则作了阐述.将该技术应用到小尺寸PDC钻头设计中,开发出可在直井、定向井以及水平井等各种小井眼钻井中使用的新型直径为114mmPDC钻头.简要介绍了该钻头的设计原理、结构特点和重要的技术参数.小井眼PDC钻头在大港油田直径为140mm套管开窗侧钻井的钻井工程中取得了良好的技术效益和经济效益.磨损分析结果表明,切削齿磨损速率低,磨损量均衡,聚晶金刚石层未见明显的脆性崩裂,具有良好的抗回旋性能.