8. Reservoir Characterization
A Semi-theoretical Approach to Determine Shear Wave Velocity Log Through using of MLR Method with a Hypothetical Test on Core and Well Log Data
Javid Hasanzadeh Azar(1), Abdolrahim Javaherian(2) and Mohammad Reza Pishvaie(1)
(1) Sharif University of Technology, I. R. Iran. (2) University of Tehran, I. R. Iran.
Abstract
One of the most important and practical aspects of rock physics is to make some feasible models (theoretical, empirical or semi-theoretical) which can be used to predict the acoustic wave velocities (specifically shear wave velocity) in the fluid saturated reservoir rocks. Using of shear wave velocity information improve the hydrocarbon reservoir exploration and development. Shear wave velocity is essential to provide amplitude versus offset studies. In this way predicted shear wave velocity log from other measured well log data and core measurements is the main purpose of this study. Therefore, in addition to the usage of GassmannÃÔ low frequency and BiotÃÔ high frequency models (theoretical models), Multiple Linear Regression (MLR) method with a hypothesis test were applied to create valid relations for prediction of shear wave velocity log. Hypothesis test is a procedure to determine if an assertion about a characteristic of a population is reasonable. In this way, it was used Fisher test to determine whether the observed relationship between the dependent and independent variables occurs by chance or not. Also Student's tËÕest was used to determine whether each slope coefficients is useful in estimating the assessed value or not. Whereas the acoustic data obtained from laboratory measurements at ultrasonic frequencies are used to S-wave velocity log prediction and seismic interpretation. The magnitude of velocity dispersion was determined too. In this work, it was attempted to study and apply some practical rock physics models on 31 carbonate representative core samples. Thereby, based on the both theoretical and empirical approaches integrated with statistical discipline (semi-theoretical approach), shear wave velocity log was constructed through a carbonate reservoir interval. Also we integrated well log data with laboratory measurements of acoustic properties of these representative core samples. Therefore, based on the semi-theoretical approach, some relations were represented for predicting of S-wave velocity log. It is necessary to mention that MLR method used as a canned procedure is a dangerous tool because the resulting model may include more input variables only to improve the correlation of the represented model without any physical sense. Also the input variables may be as correlated with each other as they are with the response. If this is the case, the presence of one input variable in the model may mask the effect of another (multicollinearity).
Last modified: Tue May 23 13:34:57 2006