32 research outputs found
Quantum algorithms for the subset-sum problem
Abstract. This paper introduces a subset-sum algorithm with heuristic asymptotic cost exponent below 0.25. The new algorithm combines the 2010 Howgrave-GrahamâJoux subset-sum algorithm with a new streamlined data structure for quantum walks on Johnson graphs
Noble gases in deepwater oils of the U.S. Gulf of Mexico
Hydrocarbon migration and emplacement processes remain underconstrained despite the vast potential economic value associated with oil and gas. Noble gases provide information about hydrocarbon generation, fluid migration pathways, reservoir conditions, and the relative volumes of oil versus water in the subsurface. Produced gas HeâNeâArâKrâXe data from two distinct oil fields in the Gulf of Mexico (Genesis and HooverâDiana) are used to calibrate a model that takes into account both waterâoil solubility exchange and subsequent gas cap formation. Reconstructed noble gas signatures in oils reflect simple (twoâphase) oilâwater exchange imparted during migration from the source rock to the trap, which are subsequently modified by gas cap formation at current reservoir conditions. Calculated, oil to water volume ratios ( urn:x-wiley:15252027:media:ggge21714:ggge21714-math-0001) in Tertiaryâsourced oils from the HooverâDiana system are 2â3 times greater on average than those in the Jurassic sourced oils from the Genesis reservoirs. Higher urn:x-wiley:15252027:media:ggge21714:ggge21714-math-0002 in HooverâDiana versus Genesis can be interpreted in two ways: either (1) the Hoover reservoir interval has 2â3 times more oil than any of the individual Genesis reservoirs, which is consistent with independent estimates of oil in place for the respective reservoirs, or (2) Genesis oils have experienced longer migration pathways than HooverâDiana oils and thus have interacted with more water. The ability to determine a robust urn:x-wiley:15252027:media:ggge21714:ggge21714-math-0003, despite gas cap formation and possible gas cap loss, is extremely powerful. For example, when volumetric hydrocarbon ratios are combined with independent estimates of hydrocarbon migration distance and/or formation fluid volumes, this technique has the potential to differentiate between large and small oil accumulations