Chimney Atlas to Quantify Top Seal and Charge Risk - Case Study from Maari Oil Field, Taranaki Basin, New Zealand

Many hydrocarbon producing basins of the world are dominated by vertical hydrocarbon migration. This hydrocarbon migration is often directly detected in the seismic record as zones of vertically aligned, chaotic, low energy data. We term these features gas chimneys, mud volcanoes, or gas clouds, depending on their morphology. However, at depth these "chimneys" can be very widespread, and are often related to oil migration. The diffuse nature of chimneys makes them difficult to map in seismic data. Thus a method was developed to highlight and visualize these chimneys in seismic data using a supervised neural network.

Chimneys have often been observed in relationship to producing oil and gas fields. However, this has not been systematically documented. To address this issue we are compiling an Atlas of chimney occurrences associated with known producing reservoirs and wet reservoirs drilled on valid structures. Traps are classified based on the morphology of the chimneys above and below the reservoir. The morphology of chimneys above the reservoir provides clues to the top seal integrity. The morphology of the chimneys beneath the reservoir provides an indication of the charge into the reservoir. These classifications can then be a guideline for risking untested structures.