Wu S.,Petrochina |
Wu S.,National Energy Tight Oil & Gas R & nter |
Wu S.,China National Petroleum Corporation |
Zhu R.,Petrochina |
And 23 more authors.
Shiyou Kantan Yu Kaifa/Petroleum Exploration and Development | Year: 2015
With low mature Triassic Chang 7 Member shale samples from the Ordos Basin as study object, the 3-D porosity evolution with temperature increase and its main controlling factors are analyzed based on the physical modeling under high temperature & pressure and nano-CT scanning data. More and more nano-pores were developed in Chang 7 Member organic-rich shale with the increase of maturity. The porosity calculated from the nano-CT scanning model increased from 0.56% to 2.06%, more than 250% times larger, when temperature increased from 20 ℃ to 550 ℃. The process of porosity evolution can be divided into three phases. Firstly, porosity decreased rapidly from immature to low mature stage because of weak hydrocarbon generation and strong compaction; Secondly, porosity increased rapidly when the maturity increased from low mature stage to mature and post-mature stage, organic matter cracked into hydrocarbon (HC) massively, and clay minerals transformed intensively; Thirdly, porosity system kept stable when the shale entered into post-mature stage and the intensity of both HC generation and clay mineral transformation decreased. Organic matter thermal evolution, clay mineral transformation and brittle mineral transformation make different contribution to the porosity of shale, and the ratio is 6:3:1 respectively. It is inferred abundant organic matter pores occur when Ro is over 1.2%. ©, 2015, Science Press. All right reserved.
Wang X.,Petrochina |
Wang X.,National Energy Tight Oil & Gas R & nter |
Wang X.,China National Petroleum Corporation |
Zhai Z.,Beijing University of Chemical Technology |
And 15 more authors.
Shiyou Kantan Yu Kaifa/Petroleum Exploration and Development | Year: 2016
To reveal competitive absorption behavior between CH4 and CO2 in organic matter (OM) nanopores, OM pore structure was first characterized using focused ion beam-scanning electron microscope (FIB-SEM) and pore-size distribution was studied using N2 adsorption, using Lower Silurian Longmaxi shale in Sichuan Basin as sample. Then a simplified pillar-layer model was used to study CH4 adsorption behavior and competitive adsorption effect between CO2 and CH4, using grand canonical Mote Carlo (GCMC) method. Research indicates that nanopores with good connectivity widely exist in OM, offering important storage space for absorbed shale gas. The amount of absorbed CH4 can increase with lower temperature and increased pressure, and overpressure will significantly increase the amount of CH4 absorbed underground; CO2 shows high competitive absorption ability; CO2/CH4 selectivity coefficient decreases dramatically with increasing temperature or pressure, or both, and it corresponds to deeper burial depth. CO2 EGR during shale gas exploration will be more efficient if it is conducted after the pressure drops to a certain degree. © 2016, The Editorial Board of Petroleum Exploration and Development. All right reserved.