Numerical Study on Eastern Nankai Trough gas Hydrate Production Test

2014 ◽  
Author(s):  
Mingliang Zhou ◽  
Kenichi Soga ◽  
Ermao Xu ◽  
Shun Uchida ◽  
Koji Yamamoto
Keyword(s):  
Gas Hydrate ◽  
Nankai Trough ◽  
Numerical Study ◽  
Production Test

Comparison of Simplistic and Geologically Descriptive Production Modeling for Natural-Gas Hydrate by Depressurization

SPE Journal ◽  
2019 ◽  
Vol 24 (02) ◽  
pp. 563-578 ◽  
Author(s):  
Yilong Yuan ◽  
Tianfu Xu ◽  
Yingli Xia ◽  
Xin Xin
Keyword(s):  
Gas Hydrate ◽  
History Matching ◽  
Nankai Trough ◽  
Flow Behavior ◽  
Test Site ◽  
Gas Production ◽  
Production Test ◽  
Hydrate Reservoir ◽  
Hydrate Saturation ◽  
Production Modeling

Summary Marine-gas-hydrate-drilling exploration at the Eastern Nankai Trough of Japan revealed the variable distribution of hydrate accumulations, which are composed of alternating beds of sand, silt, and clay in sediments, with vertically varying porosity, permeability, and hydrate saturation. The main purposes of this work are to evaluate gas productivity and identify the multiphase-flow behavior from the sedimentary-complex hydrate reservoir by depressurization through a conventional vertical well. We first established a history-matching model by incorporating the available geological data at the offshore-production test site in the Eastern Nankai Trough. The reservoir model was validated by matching the fluid-flow rates at a production well and temperature changes at a monitoring well during a field test. The modeling results indicate that the hydrate-dissociation zone is strongly affected by the reservoir heterogeneity and shows a unique dissociation front. The gas-production rate is expected to increase with time and reach the considerable value of 3.6 × 104 std m3/d as a result of the significant expansion of the dissociation zone. The numerical model, using a simplified description of porosity, permeability, and hydrate saturation, leads to significant underestimation of gas productivity from the sedimentary-complex hydrate reservoir. The results also suggest that the interbedded-hydrate-occurrence systems might be a better candidate for methane (CH4) gas extraction than the massive hydrate reservoirs.

Mechanical Response of Reservoir and Well Completion of the First Offshore Methane-Hydrate Production Test at the Eastern Nankai Trough: A Coupled Thermo-Hydromechanical Analysis

SPE Journal ◽  
2018 ◽  
Vol 24 (02) ◽  
pp. 531-546 ◽  
Author(s):  
Jun Yoneda ◽  
Akira Takiguchi ◽  
Toshimasa Ishibashi ◽  
Aya Yasui ◽  
Jiro Mori ◽  
...  
Keyword(s):  
Gas Hydrate ◽  
Mechanical Response ◽  
Nankai Trough ◽  
Water Pressure ◽  
Compressive Force ◽  
Gas Production ◽  
Production Test ◽  
Frictional Stress ◽  
Well Completion ◽  
Hydrate Saturation

Summary During gas production from offshore gas-HBS, there are concerns regarding the settlement of the seabed and the possibility that frictional stress will develop along the production casing. This frictional stress is caused by a change in the effective stress induced by water movement caused by depressurization and dissociation of hydrate as well as gas generation and thermal changes, all of which are interconnected. The authors have developed a multiphase-coupled simulator by use of a finite-element method named COTHMA. Stresses and deformation caused by gas-hydrate production near the production well and deep seabed were predicted using a multiphase simulator coupled with geomechanics for the offshore gas-hydrate-production test in the eastern Nankai Trough. Distributions of hydrate saturation, gas saturation, water pressure, gas pressure, temperature, and stresses were predicted by the simulator. As a result, the dissociation of gas hydrate was predicted within a range of approximately 10 m, but mechanical deformation occurred in a much wider area. The stress localization initially occurred in a sand layer with low hydrate saturation, and compression behavior appeared. Tensile stress was generated in and around the casing shoe as it was pulled vertically downward caused by compaction of the formation. As a result, the possibility of extensive failure of the gravel pack of the well completion was demonstrated. In addition, in a specific layer, where a pressure reduction progressed in the production interval, the compressive force related to frictional stress from the formation increased, and the gravel layer became thin. Settlement of the seafloor caused by depressurization for 6 days was within a few centimeters and an approximate 30 cm for 1 year of continued production.

Sequence stratigraphy and controls on gas hydrate occurrence in the eastern Nankai Trough, Japan

2016 ◽  
Vol 4 (1) ◽  
pp. SA73-SA81 ◽  
Author(s):  
Yuhei Komatsu ◽  
Kiyofumi Suzuki ◽  
Tetsuya Fujii
Keyword(s):  
Gas Hydrate ◽  
System Analysis ◽  
Nankai Trough ◽  
Tectonic Setting ◽  
Sedimentary Facies ◽  
Production Test ◽  
Data Sets ◽  
Sea Level Changes ◽  
Accumulation Mechanism ◽  
Sequence Boundaries

The first offshore gas hydrate production test was conducted within the gas-hydrate-concentrated zone (reservoir) of the eastern Nankai Trough, which is considered to be a stratigraphic accumulation. However, the accumulation mechanism for this concentrated zone was not yet well understood. We used core and geophysical log data sets to determine the subsurface geologic architecture and stratigraphic evolution most likely responsible for the stratigraphic accumulation of gas hydrate in the eastern Nankai Trough. Seven depositional sequences were identified based on grain size, bed thickness, sedimentary structure, and stacking patterns. The sequence boundaries were also identified by terminations of seismic reflection. These sequences were attributed to a fourth to fifth-order eustatic sea-level changes because the stacking pattern cycle was in phase with global oxygen isotope curves; the cycle was also identified in the onshore formation during the same period. The reservoir was interpreted as falling-stage systems tract (FSST) and lowstand systems tract (LST). FSST and LST consisted mostly of trough-fill channel deposits. The deposits were represented by alternations of very fine- to fine-grained sand and silt. The reservoir is located in association with the structural wing of the Daini-Atsumi Knoll. The uplift of the knoll was strongly controlled by tectonic events associated with subduction of the pacific plate during Pleistocene time. The muddy deposits above the reservoir were interpreted as condensed section. We identified channel facies pinched out against structural highs, and together, these result in stratigraphic traps. Consequentially, the gas hydrate trapping system was constrained by sedimentary facies, systems tracts, and geographic and tectonic setting. Concepts and data generated in this study can be used for gas hydrate petroleum system analysis such as basin simulation.

Numerical Analysis of the Behavior of Gas Hydrate Layers After Cementing Operations

2021 ◽  
Author(s):  
Sukru Merey ◽  
Tuna Eren ◽  
Can Polat
Keyword(s):  
Numerical Simulations ◽  
Gas Hydrates ◽  
Gas Hydrate ◽  
Cement Hydration ◽  
Nankai Trough ◽  
Heat Of Hydration ◽  
Production Test ◽  
Hydrate Saturation ◽  
Gas Channeling ◽  
Heat Released

Abstract Since the 2000s, the number of gas hydrate wells (i.e., exploration wells, production test wells) has increased. Moreover, in the marine environment, gas hydrate zones are drilled in conventional hydrocarbon wells. Different than conventional hydrocarbon wells, the heat released with cement hydration cannot be ignored because gas hydrates are heat sensitive. In this study, by analyzing different cement compositions (conventional cement compositions and novel low-heat of hydration cement), it is aimed to investigate the effect of the heat of cement hydration on gas hydrate zones near the wellbore. For this purpose, numerical simulations with TOUGH+HYDRATE simulator were conducted in the conditions of the Nankai Trough gas hydrates. According to the numerical simulations in this study, if the increase in temperature in the cemented layer is above 30°C, significant gas hydrate dissociation occurs, and free gas evolved in the porous media. This might cause gas channeling and poor cement bond. The heat released with cement hydration generally affects the interval between the cemented layer and 0.25 m away from the cemented layer. Within a few days after cementing, pressure, temperature, gas hydrate saturation, and gas saturation returned to almost their original values.

Prediction and validation of gas hydrate saturation distribution in the eastern Nankai Trough, Japan: Geostatistical approach integrating well-log and 3D seismic data

2016 ◽  
Vol 4 (1) ◽  
pp. SA83-SA94 ◽  
Author(s):  
Machiko Tamaki ◽  
Kiyofumi Suzuki ◽  
Tetsuya Fujii ◽  
Akihiko Sato
Keyword(s):  
Gas Hydrate ◽  
Seismic Data ◽  
Nankai Trough ◽  
Test Site ◽  
Geostatistical Simulation ◽  
Production Test ◽  
Well Log ◽  
Log Data ◽  
Saturation Distribution ◽  
Well Data

Accurate reservoir potential evaluation requires reliable 3D reservoir models. Geostatistical simulation techniques can reproduce the heterogeneity and quantify the uncertainty in a reservoir. We have applied sequential Gaussian simulation with collocated cokriging to generate the spatial distribution of gas hydrate (GH) saturation around a gas production test site in the eastern Nankai Trough. The simulation was performed using well-log data obtained from the exploration and production tests as a primary variable and inversion-derived seismic impedance data as a secondary variable under the good correlations between two variables. The integrated model adequately described the reservoir heterogeneity and effectively interpolated the seismic trend with respect to the well data. To confirm the usability of the seismic data for the accurate representation of the GH saturation distribution, we ran two model simulations: one using well data only and the other using well and seismic data. Each model was validated using the well-log data obtained at the production test site that were not included during the simulation. The model generated using well and seismic data appropriately reproduced the trend of well-log data at the production test site, especially for the low-GH-saturation unit within the reservoir. However, the model generated using well data only was insufficient to predict the trend of the well data. The results demonstrated that the seismic data were effective for the prediction of the GH saturation distribution, and integration of the well and seismic data could improve the accuracy of the reservoir model.

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