Application And Research On The Technology Of Formation Pressure Predication

Abnormal formation pressure is a common phenomenon in hydrocarbon-bearing basins, which is closely related to the generation, migration and accumulation of hydrocarbon reservoir. Study on the change of formation pressure to find the direction of migration and concentration characteristic of hydrocarbon, and the basic laws between the pressure of hydrocarbon and lithological change. Abnormal formation pressure, especially abnormal pressure, is directly related to the drilling safety, then is involved with the safety of persons and property security, and finally affects the process of the exploration. It is of significance that the prediction of the abnormal pressure is favorable to discover a new oil/gas reservoir, the allocation for the density of the reasonable drilling fluid, the structure of well profile, ensuring drilling safety, improving the success rate of drilling wells, reducing the cost of drilling wells, and protecting the hydrocarbon reservoir.The research on genesis and distribution of abnormal pressure benefited to their prediction, reducing the potential risk of drilling well and production, the analysis of the migration, accumulation and distribution for discovering new oil/gas pools. The effect on reservoir forming factor of abnormal pressure is the theoretical basis of formation pressure predication .We have to grasp formation pressure during the drilling well, and then confirm the structure of well bore , the density of the drilling fluid, wellhead equipment and the measures of drilling construction; Based on the deeply analyze the cause of abnormal pressure and category, combining the characteristic of geology and reservoir bed in M area in Sichuan, this study is carried out for the abnormal pressure and the distribution in research area. Through diversified method on analyzing and evaluating formation pressure, it is proposed that the synthetically prediction of formation pressure based on the data of the seismic, well logging and stack velocity spectrum.The key of prediction for formation pressure through seismic data focuses on precise calculation interval velocity. Analyzing and comparing the stack velocity spectrum and post-stack inversion, combining the factual data in work area, formation velocity finally is obtained by neural network inversion and seismic velocity spectrum. Neural network inversion use fully of the existing advantages of the inversion methods, and overcome depending seriously on initial model in the course of inversion, so it is easy to fall into local optimum insufficient quality. The neural network has low requirement for the quality of data, having self-organizing and self-adaptation abilities which can learn from input sample, having the characteristic of strongly non-linear processing and the strong anti-noise ability. The results have unreliable low frequency component with neutral network inversion because seismic data lacks of low frequency. Thus the velocity obtained by inversion carries out high pass filter in frequency domain. Meanwhile the velocity obtained by stack velocity carries out low pass filter, and then we get the result with the above velocities as final interval velocity, the final velocity obtained has coincidence with the velocity of well logging. It is indicated the method greatly improve the precision of interval velocity and have the feasibility. Obtained interval velocity transforming the data volume of the formation pressure using Fillippone, the prediction of formation pressure in space came true in research area. the predicted formation pressure is more accurate than measured formation pressure, and their accuracy error is controlled within 10%, the results show that this method has the high predicted precision. In the meantime, There are some relationships between the distribution of predicted abnormal pressure and the distribution of hydrocarbon, Combining the structure, velocity and formation pressure, it is indicated the area of the favorable oil/gas accumulation and benefits to the study on oil/gas migration pathway, rational allocation for drilling fluid and gives important basis for the exploitation of nature gas.