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The Influence of Nozzles on Bottomhole Flow Field of Dual-diameter PDC Bit
Yan Yan,Zhichuan Guan,Cai Yang,Han Yan 한국유체기계학회 2020 International journal of fluid machinery and syste Vol.13 No.1
In order to improve cleaning efficiency of dual-diameter PDC bit, the total flow area, inclination angle and azimuth angle of bit’s pilot and reaming nozzles were analyzed. By numerical simulation, the velocity, pressure and particle distribution of bottomhole are obtained. The results show that low pressure area of pilot downhole decreases while low pressure of reamer downhole increases with the increase of total flow area. The mud velocity of central bottomhole has the negative relationship with inclination angle and positive relationship with azimuth angle. Best cleaning efficiency can be achieved when total flow area is 12 ㎠, inclination angles of pilot and reamer are respectively 15° and 25°, and azimuth angles of pilot and reamer are respectively 60° and 30°.
Modeling of micro-annulus propagation along cementing interface in stimulated horizontal wellbore
Yan Yan,Guan Zhichuan,Yan Weijun 한국자원공학회 2021 Geosystem engineering Vol.24 No.5
Once there are micro-annulus at cementing interfaces in the process of reservoir stimulation, it is easy to form fluid channeling in the later development. Fluid channeling reduces the efficiency of reservoir development and even the service life of oil and gas wells. Based on the characteristics of ‘multi-stage’ in stimulated reservoir volume, a mathematical model was set up to calculate the interface debonding length driven by hydraulic pressure. The propagation process of microannulus in stimulated reservoir volume was also analyzed. The results show that the propagation speed of the micro-annulus gradually slows down with the progress of fracturing. Meanwhile, the debonding azimuth of the micro-annulus and the cement elastic modulus have dominant effects on the propagation length. It is recommended that the setting position of the packer be outranged from the debonding area of the cementing interface in the design of the stimulated reservoir volume scheme to avoid fluid channeling between the stages. This study can predict the unsealing length of cement sheath during hydraulic fracturing as a reference for the optimization of fracturing parameters.