Global Search for Intrusive Mud Systems: Analogues for the Subsurface

Katie Roberts¹, Richard Davies¹, Simon A. Stewart², and Kenneth McCaffrey^1
1Earth Sciences, University of Durham, Durham, United Kingdom
²BP, Baku, Azerbaijan

Mud volcanoes are an important global mechanism for the escape of fluids from sedimentary basins, however, little is known about the 3D geometry of their feeder systems. Two end-member theories on geometry currently exist; (a) mud transport takes place through linked mud-dyke complexes and (b) mud moves diapirically. Detailed investigation is required to assess how such systems intrude the crust and how fluid-sediment mixes utilize the conduit system. The conduits penetrate some of the largest hydrocarbon reservoirs in the world (South Caspian Sea), providing opportunities to optimise hydrocarbon production.

Recent reconnaissance has yielded several types of intrusion where: (1) muds intrude through sandstone beds utilizing thrust faults as pathways (Yasamal valley (Az)); (2) mud infills pre-existing joints in the centre of anticlines (Kichik Harami (Az)); (3) breccia pipes (Koturdag, (Az); and (4) mud intrudes through small scale, sinuous hydrofractures (Kichik Harami (Az)). Ongoing work will test the hypothesis that mud transport is through linked mud dykes forming highly efficient systems capable of transporting tens of cubic kilometres of mud and fluid. If this hypothesis is correct, it would counter the conception of kilometre-wide mud-diapirs, downgrading the role of diapirism to an ancilliary process. We intend to employ a scaled approach to the problem: Seismic interpretation of several mud volcano systems within the AGC fields (including shallow seismic data), will be combined with field-based studies, focused in Trinidad, Azerbaijan and Brunei. In addition, various intrusive mud system morphologies will be identified with an interpretation of controls on their evolution. The structure of these conduits is still unknown and the global search for a subsurface analogue has an important role in understanding the subsurface roots of volcanoes in more detail.

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