Caprocks play an important role in the trapping of coalbed methane(CBM)reservoirs.To study the sealing capacities of caprocks,five samples with different lithologies of Neogene clayrock,Paleogene redbeds,Permian sands...Caprocks play an important role in the trapping of coalbed methane(CBM)reservoirs.To study the sealing capacities of caprocks,five samples with different lithologies of Neogene clayrock,Paleogene redbeds,Permian sandstone,Permian mudstone and Permian siltstone were collected and tested using experimental methods of microstructure observation,pore structure measurement and diffusion properties determination.Results indicate that with denser structures,lower porosities,much more developed micropores/transition pores and higher pore/throat ratios,mudstone and siltstone have the more ideal sealing capacities for CBM preservation when comparing to other kinds of caprocks;the methane diffusion coefficients of mudstone/siltstone are about 6 times higher than sandstone and almost 90 times higher than clayrock/redbeds.To further estimate the CBM escape through caprocks,a one-dimensional CBM diffusion model is derived.Modeling calculation result demonstrates that under the same thickness,the CBM sealing abilities of mudstone/siltstone are almost 100 times higher than those of clayrock/redbeds,and nearly 17 times higher than sandstone,which indicates that the coal seam below caprocks like clayrock,redbeds or sandstone may suffer stronger CBM diffusion effect than that below mudstone or siltstone.Such conclusion is verified by the case study from III3 District,Xutuan Colliery,where the coal seam capped by Paleogene redbeds has a much lower CBM content than that capped by the Permian strata like mudstone,siltstone and sandstone.展开更多
Maintaining caprock integrity is prerequisite for hydrocarbon accumulation. And gypsolyte caprock integrity is mainly affected by fracturing. Composition, damage behavior and mechanical strength of Paleocene Artashi F...Maintaining caprock integrity is prerequisite for hydrocarbon accumulation. And gypsolyte caprock integrity is mainly affected by fracturing. Composition, damage behavior and mechanical strength of Paleocene Artashi Formation gypsolyte rock that seals significant petroleum in the Kashi Sag of Tarim Basin had been revealed via X-ray diffraction and triaxial compression test. The results indicate the Artashi Formation can be lithologically divided into the lower and upper lithologic members. The lower member comprises gypsum as the dominant mineral, and the cohesion and friction coefficient are 8 MPa and 0.315, respectively. Similarly, the upper lithologic member consists mainly of anhydrite at the cohesion and coefficient of internal friction values of 18 MPa and 0.296. Given that the failure criterion and brittle-ductile transition factors during burial, the sealing integrity of Artashi Formation can be quantized for seven different stages. The reservoirs at the bottom of Artashi Formation caprock buried from 2285 m to 3301 m are expected to be the most favorable exploration target in the Kashi Sag.展开更多
The intra-formational seal capability was characterized by multi-layered shale baffles to act as the primary or ultimate cap system, were taken into account by homogeneous and heterogeneous models, respectively. In th...The intra-formational seal capability was characterized by multi-layered shale baffles to act as the primary or ultimate cap system, were taken into account by homogeneous and heterogeneous models, respectively. In this study, the relevant ranges of input parameter of porosity （20%-35%） and permeability （0.0001-1,000 mD）, respectively for the sandstone （storage layers） and shale （seals） have been selected, according to results of large amount of laboratory core, test from pilot 3,000 m drilling within Tai-Hsi Foreland Basin in Western Taiwan. By a comprehensive geological model, typical single well injected plume migration scenarios were stochastically simulated which covered a 20-year continuous injection （one Mt-CO2 per year） followed by a 1,000-year post-injection monitoring. The corresponding 2-D MHMD （maximum horizontal migration distances） of CO2 plume in the storage reservoir had been calculated with respect to heterogeneous reservoir models and their homogeneous counterparts. Moreover, the induced pressures at critical monitoring points above the injection zone were also evaluated. As a result, the shale baffles of intra-formational seal in a saline aquifers are proven to play a vital role, and capable of ensuring the safe carbon storage operation within a basin scale with a depth range about 2,100-2,500 mRT.展开更多
基金Project(2016YFC0801608) supported by the National Key Research and Development Plan,ChinaProject(51574148) supported by the National Natural Science Foundation of China
文摘Caprocks play an important role in the trapping of coalbed methane(CBM)reservoirs.To study the sealing capacities of caprocks,five samples with different lithologies of Neogene clayrock,Paleogene redbeds,Permian sandstone,Permian mudstone and Permian siltstone were collected and tested using experimental methods of microstructure observation,pore structure measurement and diffusion properties determination.Results indicate that with denser structures,lower porosities,much more developed micropores/transition pores and higher pore/throat ratios,mudstone and siltstone have the more ideal sealing capacities for CBM preservation when comparing to other kinds of caprocks;the methane diffusion coefficients of mudstone/siltstone are about 6 times higher than sandstone and almost 90 times higher than clayrock/redbeds.To further estimate the CBM escape through caprocks,a one-dimensional CBM diffusion model is derived.Modeling calculation result demonstrates that under the same thickness,the CBM sealing abilities of mudstone/siltstone are almost 100 times higher than those of clayrock/redbeds,and nearly 17 times higher than sandstone,which indicates that the coal seam below caprocks like clayrock,redbeds or sandstone may suffer stronger CBM diffusion effect than that below mudstone or siltstone.Such conclusion is verified by the case study from III3 District,Xutuan Colliery,where the coal seam capped by Paleogene redbeds has a much lower CBM content than that capped by the Permian strata like mudstone,siltstone and sandstone.
基金Project(41672121)supported by the National Natural Science Foundation of ChinaProject(D1438)supported by the China Geological Survey
文摘Maintaining caprock integrity is prerequisite for hydrocarbon accumulation. And gypsolyte caprock integrity is mainly affected by fracturing. Composition, damage behavior and mechanical strength of Paleocene Artashi Formation gypsolyte rock that seals significant petroleum in the Kashi Sag of Tarim Basin had been revealed via X-ray diffraction and triaxial compression test. The results indicate the Artashi Formation can be lithologically divided into the lower and upper lithologic members. The lower member comprises gypsum as the dominant mineral, and the cohesion and friction coefficient are 8 MPa and 0.315, respectively. Similarly, the upper lithologic member consists mainly of anhydrite at the cohesion and coefficient of internal friction values of 18 MPa and 0.296. Given that the failure criterion and brittle-ductile transition factors during burial, the sealing integrity of Artashi Formation can be quantized for seven different stages. The reservoirs at the bottom of Artashi Formation caprock buried from 2285 m to 3301 m are expected to be the most favorable exploration target in the Kashi Sag.
文摘The intra-formational seal capability was characterized by multi-layered shale baffles to act as the primary or ultimate cap system, were taken into account by homogeneous and heterogeneous models, respectively. In this study, the relevant ranges of input parameter of porosity （20%-35%） and permeability （0.0001-1,000 mD）, respectively for the sandstone （storage layers） and shale （seals） have been selected, according to results of large amount of laboratory core, test from pilot 3,000 m drilling within Tai-Hsi Foreland Basin in Western Taiwan. By a comprehensive geological model, typical single well injected plume migration scenarios were stochastically simulated which covered a 20-year continuous injection （one Mt-CO2 per year） followed by a 1,000-year post-injection monitoring. The corresponding 2-D MHMD （maximum horizontal migration distances） of CO2 plume in the storage reservoir had been calculated with respect to heterogeneous reservoir models and their homogeneous counterparts. Moreover, the induced pressures at critical monitoring points above the injection zone were also evaluated. As a result, the shale baffles of intra-formational seal in a saline aquifers are proven to play a vital role, and capable of ensuring the safe carbon storage operation within a basin scale with a depth range about 2,100-2,500 mRT.
