Integration of 3D CSEM and MMT with Seismic and Well Data Yields New Geologic Insights in North Flemish Pass Basin, Offshore Canada

Abstract:

The North Flemish Pass is a structurally complex Mesozoic rift basin offshore eastern Canada. The basin comprises a series of tilted fault blocks, fault bounded horsts, and inversion anticlines forming potential traps for hydrocarbons. A regional 3 x 3 km grid 3D CSEM (2014) data was inverted to 3D resistivity volumes. The recorded data recovered resistivity anomalies across drilled Jurassic oil discoveries.

Additionally, 3D marine Magneto-Telluric data acquired simultaneously, reveal new geologic insights at the sub-regional scale. Lateral resistivity differences were observed between sub-basins and anticlines. The Mizzen anticline is interpreted as cored by a mobile lithology such as shale and not hard rock like Paleozoic metamorphic rocks. In contrast, to the east, we interpret that deep sub-basins are characterized by in-folded resistive rocks, possibly Early Mesozoic limestone or Paleozoic rocks.

At the basin to sub-basin scale we have identified dominant resistive features at Jurassic and Cretaceous stratigraphic levels on leased and open acreage. The anomalies are integrated with 2D seismic and available well data. 3D CSEM data show excellent lateral resolution, resistivity anomalies stop abruptly at faults, and stratigraphic boundaries. CSEM data are sensitive to resistors of a certain threshold in size, determined by both the background resistivity and the reservoir properties such as depth, areal extent, pay thickness, and resistivity. This implies that the strength and size of the anomaly can be indicative of the net rock volume. Well logs allow us to evaluate the resistivity range of a hydrocarbon-filled versus a water-wet sandstone. In this paper, we present the anomaly recovered over the Mizzen discovery, how it correlates with well data and show the estimated areal extent of the accumulation. We discuss potential leads and how by integrating CSEM data in an early phase of exploration, drilling risk can be reduced and pre-drill volumetric estimates are improved.

We conclude that 3D inversion of the CSEM data and the integration of all available data sets can significantly improve and better frame the interpretation of the major anticlines that underlie the oil discoveries and the generation of new leads at both the prospect and sub-regional scale offshore East Canada.