Stratigraphic Trap Potential in the Middle East – Examples from the Mesozoic

The Mesozoic stratigraphy of the Middle East is endowed with multiple world-class, economically significant petroleum systems. Since the first discovery of a major oilfield in an anticline structure in 1908 (Masjed-e-Suleyman, Iran), exploration and production in the Middle East has been largely focussed on relatively low-risk, large structural traps. However, across the Arabian Plate, unexplored structural traps at similar scales are becoming scarce. Therefore, in this mature petroleum province, attention must now focus on identifying the presence of subtle stratigraphic traps, especially within the hydrocarbon-rich Mesozoic stratigraphy. In order to locate and evaluate subtle stratigraphic traps, we have applied sequence stratigraphic principles across the Mesozoic strata of the Arabian Plate. This approach provides a regional, robust age-based framework which reduces lithostratigraphic uncertainty across international boundaries and offers predictive capabilities in the identification and extent of stratigraphic plays. Herein, we focus on three intervals of Mesozoic stratigraphy, namely Triassic, Middle-Late Jurassic and middle Cretaceous strata, in which regional sequence stratigraphic based correlations have identified stratigraphic trap potential. Each of these stratigraphic intervals are associated with the following stratigraphic traps:Triassic: Sub-crop traps associated with a base Jurassic regional unconformity and intra-Triassic unconformities. Onlap geometries associated with differential topography on the Arabian Plate.Middle-Late Jurassic: Pure stratigraphic trap geometries associated with basin margin progradation and pinch-out plays either side of the Rimthan Arch related to late Oxfordian/early Kimmeridgian sea-level fall.Middle Cretaceous: Sub-crop potential beneath the regional mid-Turonian unconformity, basin margin progradation and stratigraphic pinch-out geometries associated with onlap onto basin margins. This regional sequence stratigraphic approach highlights the remaining exploration and production opportunities within these hydrocarbon-rich stratigraphic intervals.

Seismic imaging of Deccan-related lava flows at the K-T boundary, deepwater west India

Continuous improvements in geophysical technology have enabled seismic imaging of Mesozoic strata under the K-T transition boundary — a thick lava blanket spread along the continental margin of India's west coast. The new images reveal features of the subbasalt geology of this large offshore region. The relationship of the offshore lava flows with the equally vast lava flows of the onshore Deccan Traps adds a parameter of comparison to the whole Mesozoic stratigraphy of the south, west, and northwest coasts of India. The lava flows are part of the deepwater margin that embraces several basins, the largest being the southernmost underexplored Kerala-Konkan Basin. Newly acquired and processed regional seismic data sets were integrated with new data sets of potential field data to better uncover the Mesozoic stratigraphy. The 3D seismic data, acquired with long spreads and broadband processing through time and depth migration, enabled imaging of the complex structure of layers under basalt. India detached from Madagascar during Cretaceous time; the northward path to its present position was affected by Reunion hotspot activity that melted the west coast near the K-T transition time. The volcanic lithology observed at the K-T boundary is related to episodic emplacement of intrusive dykes and extrusive sills. A possible cause-effect event in that span of time is the Chicxulub meteorite impact that may have increased the volume of Deccan lava flows. The deepwater lava volumes estimated from interpretation of seismic data from the offshore region at the end of Cretaceous time are comparable to, or perhaps much greater than, the volumes estimated for the precisely age-dated Deccan Traps basalts exposed onshore. This suggests an enormous outpouring of flood basalts (onshore and offshore) at K-T time that was comparable to other major flood basalt events, such as the Siberian traps, and associated with mass extinctions.