The Post-stack Impedance Inversion And Reservoir Prediction

The deep marine carbonate formation of western Sichuan foreland basin has alarge thickness and plentifulnaturalgasresources whose exploration rate is extremelylow. The reliability of reservoirprediction has become a key issue of theoil-gasexploration of marine carbonate in western Sichuan basin. Developing newreservoir prediction methods with highprecision to predict the distribution of thereservoir is the foundation of the further breakthrough on exploration in westernSichuan.To further enhance the accuracy of reservoirprediction in western Sichuan, wecalibrate the reservoir subtly and built the wave impedance model constrained by theinterpolation of well logs based on high resolution seismic data. We study three inversemethods include model-based inversion, stochastic Inversion and sparse spikeInversion. Combining the contrastiveanalysis for practical situation of study area, theoptimum method, sparse spike Inversion, is selected to be used in the post-stack seismicinversion for the whole work area. We first estimate the relationship between waveimpedance and porosity from their convergence analysis. Then porosity data can beobtained from the wave impedance data for the porosity inversion. In this paper,impedance and porosity distribution of the3rd and4th member of Leikoupo formationand Ma’antang formation are obtain by studying to provide a strong basis for reservoirproperty study and well location selection.The results show that: the impedance and porosity of Ma’antan formation at theXins1well are the best; but these properties of Ck1well are relatively poor; and Xs1well’s are the worst, basically cannot form the effective reservoirs. The impedance andporosity of the4th member of Leikoupo formation at the Xins1well are still the best;Ck1well’s are relatively good, while Xs1well’s are the worst, basically cannot formthe effective reservoirs. In the3rd member of Leikoupo formation, the impedance andporosity of Xins1Well, Ck1Well and Xs1well are all poor, failing to form an effectivereservoir.In conclusion, using above method, we can predict the distribution of theimpedance and porosity of carbonate formation in western Sichuan more accurately.Then the preliminaryevaluation for distributioncharacteristics ofreservoirphysicalproperty can be obtained to provide the basis for the drilling deployments, to achieve the purpose of guiding the carbonate oil-gas exploration inwestern Sichuan.