Papers by Keyword: Air Drilling

Abstract: Plugged tee is the easilyworn part of an exhaust pipe during air drilling because of the flow of the compressed air with the entrained cutting particles. The effects of the particle size on the erosion of the plugged tee are studied by computational fluid dynamics (CFD). Mathematical models of the flow of the compressed air with the entrained cutting particles through the plugged tee are built and imported into the CFD through embedding procedures. After boundary conditions and the parameter of the particle size are given, the motion paths of cuttings in the different particle size in the plugged tee and its effects on erosion of the plugged tee are obtained. Erosions in the plugged tee are mainly distributed in the wall of the buffer segment and the joints and mainly caused by the scope of the particle size of cuttings. The motion paths and the residence time of cuttings with different particle size are different, so the erosions of the joints and the buffer segment are different.

Abstract: To ensure the normal drilling and well site safety, a monitoring system is necessary in air drilling to monitor the real-time information in total drilling. By using the LMS algorithm and adaptive delayed transversal filter, a mathematical model of underground blasting monitoring is established, and an information monitoring system is also developed based on wireless communication and field bus technologies. The system is characterized by miniaturization, lower cost, convenient operation and transportation, powerful function. The experiment results show that this system can not only provide accurate air drilling parameters and stratum information, but also can monitor the real-time contents of flammable, explosive and toxic gas, which provides a guide for the identify of water-oil-gas layer, supervising drilling and preventing the occurrence of safety accidents in well site.

Abstract: The dynamic mechanics model was built up to analyze the contact-impact between drill string and wellbore according to the characteristics of contact-impact, based on non-linear finite element method and Lagrange method. The dynamic mechanics equations were deduced by the dynamic mechanics model. The stress and deformation field of drill string with different parameters of bottom hole were obtained and tested by experiments and numerical simulation respectively. And also, the propagation laws of stress wave generated by contact-impact in drill pipe were studied. The comprehensive results indicate that the numerical results agree well with the actual dynamic process of contact-impact. The stress waves generated by contact-impact cause the change of stress. The contact-impact between drill string and wellbore under air drilling is the main reason for early drill string failure.

Abstract: Based on the failure mode of air hammer bit, a mechanical model of the tooth on the inclined plane is established. And then a new air hammer flat bit with double declined planes and a big central plat (the outer inclined plane is 40° and the inner one is 20°) is designed. In order to reduce the design cost and cut down the design cycle, we establish a 3D contact model of 12 1/4″ full-scale flat bit, teeth and rock to choose a better end face structure from single and double declined planes, verify the rationality of bit parameters and tooth arrangement, design reasonable shrink range between tooth and tooth-Hole. This 3D FEM methodology for air hammer bit design is economical and useful, it can be used to optimize bit structure and design a new bit.

Abstract: In order to reveal the physical mechanism of air hammer drilling process, using the finite element methods (FEM), a three-dimensional (3D) contact model of full-scale bit, full-scale teeth and rock is established by using free meshing method. We use a Mohr-Coulomb type material model to describe when and how rock fails, and a triangular wave to replace the stress wave. Using the finite element analysis software (ANSYS), the 3D contact analysis of the bit, teeth and rock is carried out. The results show that: aggressive tensile failure may be primarily responsible for rock breakage in air hammer drilling, while compressive failure (or shear failure) may only contribute as a minor player; the distribution of the fragmentation dents can be used to verify the rationality of tooth arrangement; the larger tooth-hole stress of the outside rows mainly responses for the bit failure, while the larger tooth stress of the inside rows contributes as a secondary factor. The results are further calibrated with a series of field applications and research results.

Abstract: Bottom hole assemblies (BHA) of oil drilling engineering were simplified as simply supported beam, and parametric resonances of BHA in mud drilling and air drilling were studied. Lateral vibration of BHA, which was induced by bit/formation interaction, was described and reduced into Mathieu equation by means of separation of variables and Galerkin method. Modified strained parameter method was adopted in stability analysis. The parametric resonance zones expressed by weight on bit (WOB) are presented here. It is found that drilling method, speed of rotation (SOR), material properties, and length of compression drillstring all can influence parametric resonance zones. So unstable responses can be avoided by adjusting these parameters.