Challenges in Quantifying Subsalt Structural Uncertainty

Subsalt deep-water exploration and production (E&P) is one of the most challenging and risky businesses. In particular, drilling in the deep-water environment is becoming increasingly complex and expensive. Uncertainty is inherent in every stage E&P business, and understanding uncertainty enables mitigation of E&P risks. Therefore, quantification of uncertainty is beneficial for decision-making, and uncertainty should be managed along with other aspects of business. For example, decisions on well-positioning subsalt should take into account the structural uncertainties related to non-uniqueness of the velocity model used to create the seismic depth image. Even with our best efforts to combine all available data, there is still intrinsic ambiguity in our velocity models, i.e., multiple feasible models can fit the data equally well. The velocity model ambiguity exacerbates significantly in the presence of salt. The paper discusses the challenges for structural uncertainty analysis for subsalt targets.