Combining rate-controlled porosimetry and NMR to probe full-range pore throat structures and their evolution features in tight sands: A case study in the Songliao Basin,China |
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| Institution: | 1. Research Institute of Unconventional Oil & Gas and Renewable Energy, China University of Petroleum (East China), Qingdao 266580, China;2. State Key Laboratory of Oil & Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu, Sichuan 610059, China;3. Energy & Geoscience Institute, The University of Utah, Salt Lake City, UT 84102, USA;1. Department of Geophysical Sciences, National Research Centre, Cairo, Egypt;2. Ecole Nationale Supérieure de Géologie, Université de Lorraine, Nancy, France;1. State Key Laboratory of Petroleum Resource & Prospecting, College of Geosciences, China University of Petroleum, Beijing, 102249, China;2. Sinopec Shengli Oilfield Company, Dongying, Shandong, 257061, China;3. Geophysical Research Institute, Bureau of Geophysical Prospecting, China National Petroleum Corporation, Zhuozhou, Hebei, 072751, China;1. EMR | Energy and Mineral Resources Group, Reservoir-Petrology, RWTH Aachen University, Germany;2. Wintershall Holding GmbH, Germany;3. Institute of Applied Geosciences, Structural Geology & Tectonics, Karlsruhe Institute of Technology, Germany;4. TTE Reservoir-Geology, KIT Campus Transfer GmbH, Karlsruhe, Germany;1. School of Geosciences, China University of Petroleum (East China), Qingdao, 266580, China;2. Research Institute of Unconventional Oil & Gas and Renewable Energy, China University of Petroleum (East China), Qingdao, 266580, China;1. State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing, 102249, China;2. Institute of Geophysical and Geochemical Exploration, CAGS, Langfang, 065000, China;3. Basin and Reservoir Research Center, China University of Petroleum, Beijing, 102249, China;4. Wuxi Research Institute of Petroleum Geology, SINOPEC, Wuxi, China |
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| Abstract: | To better understand reservoir quality and to produce accurate petrophysical interpretations, it is necessary to understand complex and heterogeneous pore throat structures in tight sands and to develop a technique to reveal the full range of pore and throat distributions. In this study, in order to characterize the features and evolutions of pore throat structures, nine samples from the Lower Cretaceous tight gas sandstone in the Songliao Basin of China are measured by nuclear magnetic resonance (NMR), rate-controlled porosimetry (RCP) and scanning electron microscopy (SEM). Throats with bifractal structures are found in these tight sands and can be divided into a backbone formation (BF) region and a percolation region using RCP data. Because (i) throats in the percolation region record treelike pore structures and are predominant in small pore spaces and (ii) a good correlation exists between NMR-derived T2 relaxation times and the RCP-derived radius of throats, the throat distribution obtained via RCP can be used to calibrate the NMR PSD and then to partition the PSD into distributions of pore bodies and throats. These data indicate that (i) throats are more common than pore bodies in pore spaces of tight sands with lower permeability, (ii) pore bodies are connected to throats from both the BF and percolation regions, in which the fluid mobility in pore bodies is mainly controlled by the pore to throat ratio (PTR), which is related to the intersection throat of these two regions, and (iii) compaction, dissolution, clay cementation and sediment properties (e.g., rock compositions) have different impacts on the evolutions of pore bodies and throats, in which larger PTR values in tight sands are mainly produced by compaction and pore-bridging clay cementation, and lower contents of pore bodies are commonly related to abundant plastic compositions and pore-bridging clay cementation. |
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| Keywords: | Pore throat structure Pore throat evolution Fluid mobility Porosimetry NMR Tight sands |
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