Directional Wells Anti-Collision Technology Based on Detecting the Drill Bit Vibration Signal and its Application in Field

摘要

With the deepening of exploration and development of onshore and offshore oilfields, cluster wells and infill wells are more and more popular. It will greatly increase the possibility of well collision during the drilling and would have great harm to drilling and the production of oilfield. The normal detecting technique of anti-collision is based on the measured well trajectory data and the judgment on the abnormality during drilling. The error of measured data and the uncertainty of downhole situation will result a high risk of collision. Based on detecting the drill bit vibration, a new anti-collision technology is proposed. Firstly, the acceleration sensors are installed on the casing head of risky well to collect the drill bit vibration signal transmitted by the formation and casing. Secondly, the signals are feature extraction by the calculation analysis software based on the time domain analysis and frequency domain analysis to recognize the approach motive of the drilling bit to the risky well. Thirdly, the characteristic signals are shown in real time. When the characteristic value is greater than the threshold value, an alarm will be given for the directional drilling engineer to do the anti-collision scanning in time and decide whether or not to change the well trajectory. This technology was applied in an offshore block in Bohai Oilfield and some fields in South China Sea. The results showed that the risk casing head vibration signal induced by drill bit vibration had a characteristic frequency range and the vibration signal characteristics were related with the distance between drill bit and the risk casing definitely. The vibration signals at the drilling casing head were very strong when cement plug was drilled, which could be used to judge whether bit was close to the cement sheath and casing of risky wells. The signal amplitude acquired at the casing head of risky well declined with the increase of distance between the drilling well and risky well. It can be used to judge the risk of wellbore collision. The results of field tests showed that new technology could monitor the well anti-collision and alert. It can improve the cluster and infill drilling effectively. This is a new anti-collision technology based on detecting the drill bit vibration signal collected by the acceleration sensors installed on the casing head of drilling and risky wells.