The optimization of sensitive fluid factor removing the effect of porosity and its application to hydrocarbon detection

The deep-water turbidite sandstone reservoirs in Niger Delta basin have great oil-gas exploration potential.Drilling results in S Block area indicate that high-porosity water sandstones show "bright spot" and class II-III AVO anomaly,which are similar to features of oil sandstones. It is critical to remove the effect of porosity while fluid detection is conducted.However,conventional analysis method seldom considers the effect of porosity,and the selected fluid factor is sensitive to both hydrocarbon and porosity,which leads to inaccurate detection result.Therefore,in this study,a new quantitative evaluation method based on fluid and porosity substitution is proposed to choose the most sensitive fluid factor,which can highlight hydrocarbon and suppress the effect of porosity.The analysis result shows that λ/μ is the most suitable elastic parameter in this area and can be used to detect hydrocarbon.The real data application result shows that λ/μ can effectively distinguish "bright spot" water sandstones from oil sandstones, and the predicted results are well consistent with the drilling data, which proves the feasibility of this method.