Research And Evaluation Of Formation Pressure Analysis Method By Mechanical Specific Energy

Formation pressure refers to the pressure of the fluid in the formation pore.The correct evaluation of formation pressure is the premise of achieving high quality,high efficiency and safety drilling.At present,with the increase of drilling depth and difficulty,the requirement of formation pressure evaluation technology is increasing.The accuracy of traditional formation pore pressure monitoring method will be greatly reduced in the face of the change of bit type,especially PDC bit and complex lithology formation.Based on the concept of mechanical specific energy,a new pore pressure prediction method is proposed in this paper.The mechanical specific energy is the total energy required to break and remove the unit volume of rock.With the increase of the depth and the increase of the confining pressure and the vertical effective stress,the total energy needed to destroy and remove the rock per unit volume is larger.But in the abnormally high pressure section,the pore fluid bears a part of the overburden pressure,and the effective stress of the rock decreases,resulting in the decrease of the mechanical specific energy.Therefore,the formation pressure can be quantitatively evaluated according to the mechanical specific energy.This paper optimizes the mechanical specific energy formula according to the actual drilling conditions.The new formula is more suitable for PDC and cone bit,eliminates the influence of overbalance drilling,and greatly improves the accuracy of formation pressure prediction.The formation pressure software is developed by using C#.NET.The software is used to predict some typical wells in Yingxi area and carbonate block of Qaidam Basin.The application process of the model is introduced in detail.Compared with the measured formation pressure,the relative error is kept within 12%.The results show that the mechanical specific energy model analysis method is suitable for carbonate formation with complex lithology,PDC bit,and not limited to high pressure formation with uncompacted formation,which proves that the method is very practical.At the same time,this paper uses the function of artificial intelligence algorithm which can self train and study,takes the calculation parameters of mechanical specific energy as the learning samples for training,takes the formation pressure as the output layer,uses Python to write the depth neural network model and carry out the optimization training,forecasts the formation pressure in the west of England,the relative error is less than 15%,which opens a new way for the formation pressure prediction.