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Daigang Wang
Beijing International Center for Gas Hydrate, Peking University, Beijing 100871, China

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Journal article
Published: 08 November 2018 in Sustainability
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Coalbed Methane (CBM) has become an important gas resource in recent decades. The brittle property of coal matrix and overactive operation make the migration of coal fines inevitable. Blockage by coal fines that plugs flow paths is a non-negligible issue that results in a significant decline in gas production. By setting different experimental conditions with the following factors—coal fines concentration of the mixture displacing fluids, constant flow pump rate, inlet pressure, outlet pressure and confining pressure—six experimental schemes were designed to investigate the two-phase water and coal fines flow in natural core samples. When the differential pressure and flooding flow reach a pseudo-steady status, the equivalent permeability of coal samples can be approximately calculated considering coal fines migration. Furthermore, the influences of coal fines migration on the cleat opening and permeability variation are analyzed in the porous coal medium. The study will benefit CBM development and save pump maintenance costs. In this work, we found that maintaining the differential pressure for a longer period may result in new cleat openings and severe coal rock damage during the single-phase water flooding process. While coal fines may plug some natural cleats and pores, especially in the core samples with micro-cleats during the two-phase flooding stage, coal fines migration significantly reduces the equivalent permeability and dewatering ability of the coal rock in the earlier flooding. While enlarging the differential pressure in two-phase water and fines flooding, breakthrough of coal fines from the samples contributes to widened cleats. While coal fines are difficult to flood into the core pores for low-permeability core samples, coal fines gather in the inlet, and it is also difficult to reach the pseudo-steady status even under higher differential pressure. The damage to permeability mainly occurs in the early stage of coal fines migration, and an abrupt increase in the flow velocity can damage reservoirs and induce substantial coal fines generation. Thus, maintaining a stable effective strength and a controlled depressurization rate during drainage can effectively constrain coal fines output and decrease permeability damage within coal reservoirs.

ACS Style

Dapeng Gao; Yuewu Liu; Tianjiao Wang; Daigang Wang. Experimental Investigation of the Impact of Coal Fines Migration on Coal Core Water Flooding. Sustainability 2018, 10, 4102 .

AMA Style

Dapeng Gao, Yuewu Liu, Tianjiao Wang, Daigang Wang. Experimental Investigation of the Impact of Coal Fines Migration on Coal Core Water Flooding. Sustainability. 2018; 10 (11):4102.

Chicago/Turabian Style

Dapeng Gao; Yuewu Liu; Tianjiao Wang; Daigang Wang. 2018. "Experimental Investigation of the Impact of Coal Fines Migration on Coal Core Water Flooding." Sustainability 10, no. 11: 4102.

Journal article
Published: 01 September 2018 in Energy
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The addition of solvent to steam injection, known as Solvent-Assisted Steam-Gravity Drainage (SA-SAGD), has recently been regarded as a more economically-efficient and environmentally-friendly alternative to Steam-Assisted Gravity Drainage (SAGD). In this paper, we present a mathematical model for estimating greenhouse gas (GHG) emissions and chamber evolution considering non-uniform property distribution along the horizontal well for SA-SAGD. In addition, oil price, carbon tax and liquid pool corresponding to the influences of the market, environmental needs and technology are incorporated into the model to analyze the economic benefits. The calculated results show that, when the liquid-pool level is 3 m, the reduction in GHG emissions is 30% by injecting C3/C5 solvents and 16.5% when the solvent is C7. If the liquid level is as high as 5 m, there will be no reduction in carbon emissions for the C5/C7 solvent injection. When both oil price and the carbon tax are at high levels, the C5/C7-assisted SAGD has the best economic performance. The C3-assisted SAGD is best when the oil price is low and the carbon tax is high. When the oil price and carbon tax are low, there is no economic advantage for the solvent-assisted SAGD.

ACS Style

Linsong Cheng; Hao Liu; Shijun Huang; Keliu Wu; Xiao Chen; Daigang Wang; Hao Xiong. Environmental and economic benefits of Solvent-Assisted Steam-Gravity Drainage for bitumen through horizontal well: A comprehensive modeling analysis. Energy 2018, 164, 418 -431.

AMA Style

Linsong Cheng, Hao Liu, Shijun Huang, Keliu Wu, Xiao Chen, Daigang Wang, Hao Xiong. Environmental and economic benefits of Solvent-Assisted Steam-Gravity Drainage for bitumen through horizontal well: A comprehensive modeling analysis. Energy. 2018; 164 ():418-431.

Chicago/Turabian Style

Linsong Cheng; Hao Liu; Shijun Huang; Keliu Wu; Xiao Chen; Daigang Wang; Hao Xiong. 2018. "Environmental and economic benefits of Solvent-Assisted Steam-Gravity Drainage for bitumen through horizontal well: A comprehensive modeling analysis." Energy 164, no. : 418-431.