Probabilistic Approach To Seismic Rock Physics Modeling In Huaibei Coalfield Limestone

With the degree of coalfield development increasing gradually, the current exploration target has been also transferred from the shallow part to the deep underground. The exploiting threaten resaults in lower group’s coal exploitation becomes more and more remarkable, and the seismic exploration technology has being took for one of the major methods to coalfield limestone structure prediction and fluid identification, so forward modelling the relationship between water saturation and porosity of coalfield limestone and its seismic response based on seismic rock physics is becoming a research hotspot.This paper aims to study the physical properties of limestone rock in coal bed from the perspective of modeling theory in carbonatite. Taking consider of the structure of the pores in coalfield limestone rocks, and these pores are divided into disconnected type and connected form. Based on the classification, different rock physical models are applied to modle each type pores step by step, and then coalfield limestone rock physics model is constructed. However, the uncertainty of the measurement data and the difference in scale between rock physics model and seismic inversion will result in the uncertainty of reservoir prediction and fluid identification. In this paper, we also using the probability distribution function of random variable instead of a constant value as the input of rock physics model, therefore, uncertain information is included in the rock physics model. On the premise of deriving the analytical expression of the probability distribution of predicted variable in coalfield limestone rock physics models, rock physics probability model is constructed.According to well log data in Huaibei coalfield, and combining coalfield limestone rock physics probability model with the analysis results of limestone samples test, compressional and shear wave velocity were predicted. The actual log data of P-wave velocity indicates that the predicted p-wave velocity precision can meet the actual production needs. The resault also shows that the forecasting accuracy of S-wave velocity at the same time is acceptable. Finally, the synthetic seismogram with uncertainty in seismic scale was obtained by using the theory of rock physicas boundary.