ROCK PHYSICS INVERSION WORKFLOW ON RESERVOIR PARAMETERS: A CASE STUDY OF SEISMIC HYDROCARBON DETECTION IN LARGE-AREA TIGHT DOLOMITE RESERVOIRS

摘要

Lateral heterogeneities of the geological characteristics in hydrocarbon reservoirs pose a major challenge for the wide application of rock physics modeling and relevant hydrocarbon detection techniques. In the application of 3D seismic inversion in a large work area, studies on improving hydrocarbon seismic prediction accuracy by effectively utilizing multiple-well log data and multi-scale wave responses is still a hotspot and difficulty in the research area of quantitative seismic interpretation. By combining the rock physics model with the pre-stack seismic inversion, quantitative estimate of reservoir properties can be performed. However, due to the different observation scales of seismic, well log and laboratory observation, the rock physics model established at each scale is different and the data between different scales cannot be effectively related in a combined application. This paper probes into the dolomite gas reservoirs with low porosity and low permeability in the MX work area. We consider the reservoir environment, lithology and pore fluid to predict the wave response dispersions on the basis of poroelasticity theory, and produce the multi-scale rock physics models to relate wave data between different scales. By analyzing the models and the well production reports, we adjust the log interpretation results and perform fluid sensitivity analysis on rock physics parameters at acoustic and ultrasonic scales, respectively. Comparison shows that the pattern and sequence of sensitivity parameters from the two scales are basically consistent. The parameters which are the most sensitive to porosity and gas saturation are selected. Based on the single-well rock physics templates which is built in the analysis of each key reference wells, optimization is made to output the standard template for the work area. The standard template takes into account the general geological and petrophysical characteristics of the target stratum. By analyzing the lateral variation and heterogeneity of reservoir geological characteristics in the large work area, the input parameters of rock physics modeling at each well coordinates are adjusted according to the gas production reports, and optimization is made in the 3D work area to establish the 3D data volume of rock physics template. In combination with the pre-stack seismic inversion, the porosity and saturation are estimated in the target stratum, and the estimate results are smoothed to output the final inversion data volume. By comparing with the log interpretation and production testing results, it is proved that the prediction results are correct and the methodology is effective.