Study On Risk Prediction In Drilling Engineering Based On The Seismic Data

With the development of domestic oil and gas reservoir exploration,drilling depth is getting deeper and deeper.Due to the more and more complex geological environment,many kinds of engineering risks,such as leakage,kick,collapse,stuck and so on,frequently happen in the process of drilling,which seriously restrict the safety and efficient drilling operation.Accurate risk assessment of drilling engineering is not only the premise of preventing and controlling drilling engineering risk,ensuring the safe and sucessufully implementation of the project,but also an important basis for the invertment decision.Besides,it's of great significance to dirlling construction.However,the drilling risk assessment is mainly based on the three kind of formation pressures data.Where there are only a few exploratory wells or even no wells,using seismic data is the only method for formation pressures prediction.As for above problems,this paper dealed with the initial data from the original seismic data and calculated the interval velocity and the average velocity from stack velocity using Dix method.What's more,the conversion of interval velocity from time domain to depth domain is realized with the use of average velocity.A grid body is built for the whole work area in this paper and the data in the interval velocity segy model are resampled into the grid.Finally,an interval velocity attribution model which is convenient to extract data is getted.On the basis of the above,with the investigation and analysis of methods for calculating the formation pressure based on the interval velocity all over the world,the pressure calculation method which can be applied to this region is selected and the formation pressure is calculated.The comparison between the pressure from seismic data and logging data shows that the pore pressure is relatively accurate,while the collapse pressure and fracture pressure exist relatively more errors.The results are corrected by longitudinal depth correcton and lateral data correction.The correction results show that the method can not only preserve the original trend of the pressure data obtained from the seismic calculation,but also make the results closer to the log values.Besides,using Kriging interpolation method,based on the concept of "formation matrix",a regional three-dimensional pressure model is established and the three regional formation pressures description is also realized.Finally,the Monte-Carlo method is used to establish the formation pressure profile.And combined with the pressure constraint criterion,the safety drilling fluid density window is also established.What's more,based on the risk assessment method,this paper assessed the risk of well BD-1 and compared the theoretical results with the actual results.Although there are errors in risk prediction,the prediction results are basically consistent with the actual situation.Therefore,a complete set of drilling engineering risk prediction method based on seismic data is formed.