The Study Of Micro-seismic Source Place Inversion Methods

Micro-seismic technique is an advanced technique for fracture monitoring, which has been used to monitor oil-field production performance because of its high efficiency and low cost. However, in the actual process of oil reservoir exploitation, the information of micro-seismic generated is relatively weak, which brings great difficulty for locating the source accurately by inversion. To resolve this problem, a source inversion method in view of micro-seismic is studied in this paper.First, forward modeling of complicated geologic condition is carried out by ray tracing procedure, and then velocity models in different media are built to analyze the characteristics of wave spectrums in them, in order to guide the inversion process using actual data effectively. A series of measures, such as limiting picking range and picking first arrival peak, are taken in the paper, which making the picking results more dependable. Polarizing angles of the geophones are discriminated correctly by the methods of maximum, histogram and vector curve, which are used to identify the true micro-seismic events, do geophone community process and source location.Combining with three-component record and field data acquisition means of the actual micro-seismic data, a cooperative inversion method with three components being separately regulated is designed. With the trial inversion of some models and partly micro-seismic data, the results show that, the inversion of the micro-seismic data, obtained through the double drillings observation system, can constringe the solution to the right place easily in vertical direction, but diverge in horizontal direction. Combined with the model based on acoustic logging information and the restriction of perforating data, a cooperative inversion method suit for micro-seismic data observed in log is gained. On the basis of the forward modeling, vertical position variable and velocity are calculated by normal search method, but horizontal variable is computed by searching trust region. The optimum trust region is found out by means of combined inversion, and then the solution is searched and found out in the region. The explanation of some parameters, such as step length, precision and inversion velocity are also given, based on the distinguishing feature of micro-seismic data. The combined inversion method is verified feasible by the theory models and practical data. The cooperative inversion results of multi micro-seismic events show that, the inversion method based on forward modeling iteration and organic combination of various optimization methods overcomes the faults of single inversion method, reflects the real fracture location effectively.