Combining reactive transport modeling with geochemical observations to estimate the natural gas hydrate accumulation

Recent Advances on Natural Gas Hydrate Exploration and Development in the South China Sea

“…35 Tian et al applied numerical simulation and also suggested that biogenic and thermogenic methane are both the gas source of a high saturation hydrate system and their ratio was about 1:3 with geochemical observations in the Shenhu area, SCS. 76 Similar gas sources for hydrate accumulation were interpreted in the QDNB as well, and Sha et al speculated that the hydrate-bonded gas in this area may have experienced fractionation, admixture, or degradation during the gas migration from deeper source rock 32,37,38 Lai et al conducted geochemical analyses to investigate the source of gas hydrate from site GMGS5-W08 in the QDNB. It is derived that the microbial methane within the gas hydrates was mainly originated from source rock in the shallow gas reservoir during microbial alternation.…”

“…81 Furthermore, an integrated simulation package (TOUGH + Hydrate + React) was developed by coupling reactive transport modeling and geochemical observation of hydrate-bearing system on the basis of observed data at site SH2. 76 It can provide a more reliable solution for evaluating the accumulation of gas hydrate in the SCS. Su et al simulated the gas hydrate evolution and accumulation process using a petroleum system modeling method.…”

“…At first, Liu et al compared the gas compositions of gas hydrate recovered from the SCS and terrestrial areas in China and supposed that methane from hydrate in the SCS is primarily from biogenic origin. , In contrast, Wei et al examined the gas composition and isotope composition, and the results showed that hydrate-bond gases were mainly thermogenic gas with a small amount of biogenic gas . Tian et al applied numerical simulation and also suggested that biogenic and thermogenic methane are both the gas source of a high saturation hydrate system and their ratio was about 1:3 with geochemical observations in the Shenhu area, SCS . Similar gas sources for hydrate accumulation were interpreted in the QDNB as well, and Sha et al speculated that the hydrate-bonded gas in this area may have experienced fractionation, admixture, or degradation during the gas migration from deeper source rock ,, Lai et al conducted geochemical analyses to investigate the source of gas hydrate from site GMGS5-W08 in the QDNB.…”

A New Dynamic Modeling Approach to Predict Microbial Methane Generation and Consumption in Marine Sediments

“…According to the literature, there are significant gradients of methane and DIC at lower boundary conditions, indicating that dissolved species are released in deeper sediments and transported to the surface by diffusion [9]. For simplification, in most cases, they considered a constant value or zero concentration gradients at the bottom of their modeled columns [1,9,15,43,44,53]. In this study, according to the depth and time, two boundary conditions were considered because of the sedimentation evolution.…”

“…The current study's approach is to use a new numerical model to enhance the general understanding of biogeochemical processes by considering progressive sedimentation over time and provide a more reliable dynamic approximation of processes in the marine sediments. In contrast with other studies [1,4,6,9,12,19,[39][40][41][42][43][44], which used the data of seafloor and bottom of sediments, the major advantages of our transport-reaction model are using the seafloor data as the only input and simulating sedimentation over time with progressive compaction of sediments. Since most of the time, it is hard or impossible to obtain the data in the deeper part of sediments, in this model, we provide a unique tool to predict methane in all phases (pore water, gas hydrate, and free gas), in addition to the concentration of sulfate, dissolved inorganic carbon, calcium, and magnesium in pore water.…”