Pore structure characterization of Chang-7 tight sandstone using MICP combined with N2GA techniques and its geological control factors.
Understanding the pore networks of unconventional tight reservoirs such as tight sandstones and shales is crucial for extracting oil/gas from such reservoirs. Mercury injection capillary pressure (MICP) and N2gas adsorption (N2GA) are performed to evaluate pore structure of Chang-7 tight sandstone. Thin section observation, scanning electron microscope, grain size analysis, mineral composition analysis, and porosity measurement are applied to investigate geological control factors of pore structure. Grain size is positively correlated with detrital mineral content and grain size standard deviation while negatively related to clay content. Detrital mineral content and grain size are positively correlated with porosity, pore throat radius and withdrawal efficiency and negatively related to capillary pressure and pore-to-throat size ratio; while interstitial material is negatively correlated with above mentioned factors. Well sorted sediments with high debris usually possess strong compaction resistance to preserve original pores. Although many inter-crystalline pores are produced in clay minerals, this type of pores is not the most important contributor to porosity. Besides this, pore shape determined by N2GA hysteresis loop is consistent with SEM observation on clay inter-crystalline pores while BJH pore volume is positively related with clay content, suggesting N2GA is suitable for describing clay inter-crystalline pores in tight sandstones.
State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249 PR, China.|College of Geosciences, China University of Petroleum, Beijing, 102249 PR, China.|Department of Geology and Geophysics, Texas A&M University, College Station, TX 77843-3115, USA.
Zhe
Z
Cao
State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249 PR, China.|College of Geosciences, China University of Petroleum, Beijing, 102249 PR, China.
Guangdi
G
Liu
Department of Geology and Geophysics, Texas A&M University, College Station, TX 77843-3115, USA.
Hongbin
H
Zhan
State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249 PR, China.|College of Geosciences, China University of Petroleum, Beijing, 102249 PR, China.
Chaozheng
C
Li
Research Institute of Petroleum Exploration and Development of Changqing Oilfield Company, PetroChina, Xi'an 710018 PR, China.
Yuan
Y
You
State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249 PR, China.|College of Geosciences, China University of Petroleum, Beijing, 102249 PR, China.
Chengyu
C
Yang
Strategic Research Center of Oil and Gas Resource, Ministry of Land and Resources, Beijing 100034 PR, China.
Hang
H
Jiang