Research On PDC Bits Structure Optimization Design In Middle-deep Well Of Daqing Oil Field

In recent years, with the constant increase of the depth of drilling, the geological conditions have also changed, and many new difficulties appear in the process of middle-deep drilling. In the process of middle-deep drilling, with the increasing of well depth, the temperature and the pressure of formation is increasing, which will lead to significant changes in a series of mechanical parameters, such as the strength, the drilling resistance, the hardness and so on. Especially when the rock transforms from brittle fracture to plastic collapse, fundamental changes have taken place in the mechanical properties of the rock, if the drill bit is not suitable for the formation at this time, the rate of penetration will be greatly reduced. Therefore, in this article, we regard the problems in the process of middle-deep drilling in Daqing oil field as the foundation, and have a research on PDC bits structure optimization design.Firstly, this article have a research on the Central Depression of Songliao Basin District which is the main area of middle-deep well distribution in Daqing oil field, and analyze the elastic parameters, compressive strength, hardness, ductility coefficient and drillability extremes of the rock formations. Through it, we found the drillability extremes are mostly in the range of6-9, and the structure is complex, the hardness is uneven. We also take statistical analysis of PDC bits application in this area and PDC bits-PFM635which is commonly used in field, so we can know its advantages and disadvantages. Meanwhile, through the analysis of the structural characteristics of PDC bits, we reveal the operating principle of cutting teeth, such as breaking rocks, erosion and so on, and analyze the influencing factors of PDC bits working. Based on existing research, we discuss and analyze the structural design principles of PDC bits, including:crown shape of drill bit, cutting structure, hydraulic structures and so on. Then PDC bits design theory and method of each structure is given. Finally, the structure optimization design of six-wing PDC bits which is applied in middle-deep well of Daqing oil field is conducted, and use Solidworks for three-dimensional solid modeling of PDC bits. Then we produce sample of PDC bits and conduct on-site experimental. The results showed that:optimization design of the six-wing PDC bits is rational, and achieve the goals of improving drilling speed at maximum limit, and reducing drilling costs.This study has some practical significance and practical value in improving drilling speed and reducing drilling costs in middle-deep well formations during the process of development of the oil and gas exploration.