Numerical Modeling of Gas Migration and Hydrate Formation in Heterogeneous Marine Sediments

Abstract

The formation of marine gas hydrates is controlled by gas migration and accumulation from lower sediments and by the conditions of the hydrate stability zone. Permeability and porosity are important factors to evaluate the gas migration capacity and reservoir sealing capacity, and to determine the distribution of hydrates in the stable region. Based on currently available geological data from field measurements in the Shenhu area of Baiyun Sag in the northern South China Sea, numerical simulations were conducted to estimate the influence of heterogeneities in porosity and permeability on the processes of hydrate formation and accumulation. The simulation results show that: (1) The heterogeneity of the hydrate stability zone will affect the methane migration within it and influence the formation and accumulation of hydrates. This is one of the reasons for the formation of heterogeneous hydrates. (2) When the reservoir is layered heterogeneously, stratified differences in gas lateral migration and hydrate formation will occur in the sediment, and the horizontal distribution range of the hydrate in a high porosity and permeability reservoir is wider. (3) To determine the dominant enrichment area of hydrate in a reservoir, we should consider both vertical and lateral conditions of the sedimentary layer, and the spatial coupling configuration relationships among the hydrate stability region, reservoir space and gas migration and drainage conditions should be considered comprehensively. The results are helpful to further understand the rules of hydrate accumulation in the Shenhu area on the northern slope of the South China Sea, and provide some references for future hydrate exploration and the estimation of reserves.

The Effects of the Length and Conductivity of Artificial Fracture on Gas Production from a Class 3 Hydrate Reservoir

“…The reliability of T + H has been validated in the two International Methane Hydrate Simulator Code Comparison Studies [29,34]. T + H can be used to fit the experimental results of methane hydrate formation and dissociation in the lab [35], and it can also be applied in large-scale simulation to evaluate the accumulation [36,37] and exploitation [38,39] of hydrate reservoirs. There are two models of hydrate dissociation and formation in T + H, i.e., the equilibrium model and kinetic model; the equilibrium model was recommended for field-scale hydrate production for the justified results and less computational demands [40], which was why it was adopted in the current simulations.…”

Active Methanotrophs and Their Response to Temperature in Marine Environments: An Experimental Study

“…The BB sediment sample used in this study was collected during the same sampling. 3 ORP is the abbreviation for oxidation-reduction potential.…”

“…2 R 2 values were the correlation coefficients from the linear regression. 3 One-way ANOVA was conducted with CH 4 oxidation rates obtained from all six experimental treatments. 4 d.f is degree of freedom in one-way ANOVA.…”

“…At present, gas hydrates are the most abundant source of methane on the earth [1][2][3]. A great amount of methane is released due to the decomposition of gas hydrates from submarine reservoirs [4], which are gradually consumed by anaerobic methanotrophic archaea (ANME) in anoxic sediment layers and aerobic methanotrophs in oxic layers [5,6].…”

Physio-Chemical and Mineralogical Characteristics of Gas Hydrate-Bearing Sediments of the Kerala-Konkan, Krishna-Godavari, and Mahanadi Basins

“…The molecules of water and gas chemically interact to construct an ice-like crystalline structure [2], which is stable at an absolute pressure and temperature range [3]. The bottom of the stability area of hydrate structures is designated with the Bottom-Simulating Reflectors (BSR), which are parallel to the seafloor at a sub-bottom depth of a specific hundred meters [4,5]. These BSRs are formed by a sharp elastic contrast between the methane hydrates bearing and the underlying sediments, which are either brine or gas saturated [6].…”