Determining Petrophysical Properties of Low Resistivity Reservoirs Using Nuclear Magnetic Resonance Logs

With the deepening of exploration and development, many low-resistivity reservoirs have been found in the XP area. We have found that the genesis of these low-resistivity reservoirs is that they contain a lot of very fine sand, which leads to the high content of bound water in the reservoirs and reduces resistivity. Compared with normal oil reservoirs, these reservoirs show low resistivity and high natural gamma, which makes it difficult to identify reservoirs qualitatively and calculate parameters quantitatively. Using conventional logging interpretation methods, the wrong shale content and porosity will be obtained, and such reservoirs may even be judged as mudstones. To solve this problem, we extract a characteristic parameter from the T2 spectrum of nuclear magnetic resonance (NMR) logging, which can effectively identify such reservoirs. In addition, we have innovatively adopted an optimized logging interpretation method for integrated NMR logging and conventional logging, which has effectively improved the parameter calculation accuracy of this type of reservoir and achieved a good application effect in the XP area.

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Influence of CO 2 injection on the pore size distribution and petrophysical properties of tight sandstone cores using nuclear magnetic resonance

Energy Science & Engineering ◽

10.1002/ese3.663 ◽

2020 ◽

Vol 8 (7) ◽

pp. 2286-2296

Author(s):

Jinsheng Zhao ◽

Pengfei Wang ◽

Yanming Zhang ◽

Liang Ye ◽

Yu Shi

Keyword(s):

Nuclear Magnetic Resonance ◽

Magnetic Resonance ◽

Pore Size Distribution ◽

Pore Size ◽

Size Distribution ◽

Petrophysical Properties ◽

Tight Sandstone ◽

Nuclear Magnetic

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Petrophysical properties difference of organic-rich and organic-poor shale reservoir using low-field nuclear magnetic resonance experiment in the Sangzhi block, South China

Interpretation ◽

10.1190/int-2019-0219.1 ◽

2020 ◽

Vol 8 (4) ◽

pp. T895-T905

Author(s):

Gang Zhao ◽

Wenlong Ding ◽

Yaxiong Sun ◽

Siyu Shi ◽

Baocheng Jiao ◽

...

Keyword(s):

Nuclear Magnetic Resonance ◽

Magnetic Resonance ◽

Shale Gas ◽

Hunan Province ◽

Organic Carbon Content ◽

Petrophysical Properties ◽

Low Field ◽

Porosity And Permeability ◽

Shale Reservoir ◽

Nuclear Magnetic

The petrophysical properties of rocks have an important influence on shale quality. To characterize the difference of petrophysical properties between organic-rich and organic-poor shale reservoirs, we used the low-field nuclear magnetic resonance (NMR) technique and field emission scanning electron microscopy analysis after argon-ion polishing or natural section to measure porosity and permeability from six core samples from well SY6 in the Sangzhi block, Northwest Hunan province. Some information about pore types, pore structure, residual porosity, movable porosity, and permeability based on the T2 spectrums’ difference of organic-rich and organic-poor shale samples were discussed. The shale sample test results show that the main pores size is mesopore, which provide most of shale gas reservoir space. The continuous peaks demonstrated the pores’ connectivity better than the isolated peaks, and shale gas can migrate freely between these connected pores and fractures. The permeability of all samples calculated by the classic Coates model is extremely low, which is not conducive to the migration of shale gas. We evaluated the dominating factors of NMR porosity and permeability and found that the relationships between NMR porosity and permeability and total organic carbon content, quartz minerals, and clay minerals are not clear, which may be a comprehensive influence. The research results have important guiding significance for shale reservoir quality evaluation in this area.

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