The Jackalope gas hydrate system in the northeastern Gulf of Mexico

Abstract

Abstract We present a new gas hydrate system, Jackalope, in the US Gulf of Mexico ~110 km from the Louisiana coast primarily in Mississippi Canyon (MC) Blocks 127 and 128. Jackalope is a relatively shallow prospect (~1650 m water depth) and is associated with a submarine channel-levee depositional system. Several kilometers below the seafloor, an extended sub-circular salt ridge rooted into the allochthonous salt canopy creates a system of faulted anticlinal folds. Accordingly, the distribution of bottom simulating reflections mapped at ~250–300 m below seafloor (mbsf) is structurally controlled, indicating that gas tends to accumulate above the hinge of the salt ridge in sand-dominated turbidites. The Jackalope system is not a single accumulation; it comprises two primary prospects (Saint Petersburg and Columbus) and several secondary prospects. The primary prospects are defined based on seismic data by peak-leading reflections and phase reversals at the base of the gas hydrate stability zone: a strong peak-leading amplitude above it changes to trough-leading amplitude below. We interpret strong peak-leading amplitudes as gas hydrate in sand-rich intervals, which is confirmed by resistivity and gamma ray logs at the margin of the Saint Petersburg prospect. Continuous gas-water contacts below the primary prospects characterize them as permeable three-component reservoirs comprising gas hydrate above gas, and gas above water. Both prospects are located at ~230–300 mbsf occupying a total area of ~5.9 km2. Low and high estimates of in place gas at standard pressure and temperature conditions in the primary prospects range between 1.5 and 10.6 BCM. These characteristics define Jackalope as a promising, cost- and time-efficient gas hydrate system for further drilling exploration. Moreover, Jackalope demonstrates there is potential for new discoveries in the US Gulf of Mexico in particular due to expanding public 3D seismic and well log datasets.