scholarly journals A method to determine nuclear magnetic resonance T 2 cutoff value of tight sandstone reservoir based on multifractal analysis

2020 ◽  
Vol 8 (4) ◽  
pp. 1135-1148 ◽  
Author(s):  
Yunbing Hu ◽  
Yinghai Guo ◽  
Junjian Zhang ◽  
Jingwen Shangguan ◽  
Mi Li ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Multifractal Analysis ◽  
Tight Sandstone ◽  
Cutoff Value ◽  
Sandstone Reservoir ◽  
Nuclear Magnetic

Nuclear-Magnetic-Resonance Study on Mechanisms of Oil Mobilization in Tight Sandstone Reservoir Exposed to Carbon Dioxide

SPE Journal ◽  
2017 ◽  
Vol 23 (03) ◽  
pp. 750-761 ◽  
Author(s):  
Haitao Wang ◽  
Zengmin Lun ◽  
Chengyuan Lv ◽  
Dongjiang Lang ◽  
Weiyi Pan ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Relaxation Times ◽  
Co2 Injection ◽  
Tight Sandstone ◽  
Initial Exposure ◽  
Exposure Experiment ◽  
Sandstone Reservoir ◽  
Nuclear Magnetic

Summary Nuclear magnetic resonance (NMR) was used to investigate the exposure between carbon dioxide (CO2) and the sandstone matrix with a permeability of 0.218 md and a porosity of 9.5% at 40°C and 12 MPa (immiscible condition). Minimum miscibility pressure (MMP) between oil and CO2 was 17.8 MPa, determined by slimtube test at 40°C. The exposure process between CO2 and the sandstone matrix included first, second, third, and fourth exposure experiments. Before each exposure experiment started, there was a CO2-injection stage with a CO2 injection under a constant pressure of 12 MPa and at a constant rate to keep fresh CO2 (concentration of CO2 is 100% in gas phase) in the system. Each exposure experiment ended when the obtained T2 spectrum was unchanged (total amount of oil in tight matrix remains constant). These processes were similar to CO2 huff ’n’ puff. The results showed that (1) oil in all pores could mobilize as exposure time increases in the first exposure experiment. (2) The total original-oil-in-place (OOIP) recovery is 46.6% for oil in big pores (29 ms < T2 ≤ 645 ms)—this result is higher than the recovery (12.8%) for oil in small pores (T2 ≤ 29 ms). (3) Oil is mobilized fast in the initial exposure hours, and then the rate drops gradually until no more oil is produced. (4) Initially, the oil exists in pores with maximum relaxation times of 645 ms in the originally saturated core. After the CO2 injection, oil flows to pores with relaxation times slower than 645 ms, suggesting that oil in tight matrix is mobilized to the surface of core by swelling caused by CO2 diffusion. (5) The final OOIP recoveries of first, second, third, and fourth exposure experiments are 23.7, 7.2, 2.6, and 1.5%, respectively, and they decline exponentially. Oil mobilization in a tight-sandstone reservoir exposed to CO2 was observed by NMR T2 spectra under multiple exposure experiments. Mechanisms of oil mobilization were investigated (i.e., oil swelling, concentration-driven diffusion of hydrocarbons, and extraction of light components). The CO2 enhanced oil recovery (EOR) with multiple injections under immiscible conditions is acceptable and satisfactory in a tight-sandstone reservoir. CO2 huff ’n’ puff with optimized injection, soaking, and production process is an economic development method in a tight sandstone reservoir.

Nuclear magnetic resonance T2 cutoffs of coals: A novel method by multifractal analysis theory

Fuel ◽  
2019 ◽  
Vol 241 ◽  
pp. 715-724 ◽  
Author(s):  
Sijian Zheng ◽  
Yanbin Yao ◽  
Dameng Liu ◽  
Yidong Cai ◽  
Yong Liu ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Multifractal Analysis ◽  
Analysis Theory ◽  
Novel Method ◽  
Nuclear Magnetic

scholarly journals Petrophysical characterization of high-rank coal by nuclear magnetic resonance: a case study of the Baijiao coal reservoir, SW China

2018 ◽  
Vol 5 (12) ◽  
pp. 181411 ◽  
Author(s):  
Dongming Zhang ◽  
Yapei Chu ◽  
Shujian Li ◽  
Yushun Yang ◽  
Xin Bai ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Coalbed Methane ◽  
High Rank ◽  
Free Fluid ◽  
Permeability Model ◽  
Cutoff Value ◽  
Coal Reservoir ◽  
Nuclear Magnetic

To better apply nuclear magnetic resonance (NMR) to evaluate the petrophysical characterization of high-rank coal, six anthracite samples from the Baijiao coal reservoir were measured by NMR. The porosity, T 2 cutoff value, permeability and pore type were analysed using the transverse relaxation time ( T 2 ) spectrum before and after centrifugation. The results show that the T 2 spectrum of water-saturated anthracite can be divided into a discontinuous and continuous trimodal distribution. According to the connectivity among pores, three T 2 spectrum peaks were identified at the relaxation times of 0.01–1.7 ms, 1.7–65 ms and greater than 65 ms, which correspond to the micropores (less than 100 nm), mesopores (100–1000 nm) and macropores (greater than 1000 nm), respectively. Based on the T 2 cutoff value, we divided the T 2 spectrum into two parts: bound fluid and free fluid. By comparing two classic permeability models, we proposed a permeability model to calculate the permeability of anthracite. This result demonstrates that NMR has great significance to the exploration of coal reservoirs and to the understanding of the development of coalbed methane.

scholarly journals Multifractal characteristics of shale and tight sandstone pore structures with nitrogen adsorption and nuclear magnetic resonance

2020 ◽  
Vol 17 (5) ◽  
pp. 1209-1220
Author(s):  
Fu-Yong Wang ◽  
Kun Yang ◽  
Yun Zai
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Specific Surface ◽  
Pore Size ◽  
Ordos Basin ◽  
Tight Sandstone ◽  
Pore Structures ◽  
Pore Size Distributions ◽  
Multifractal Spectra ◽  
Nuclear Magnetic

Abstract Based on the experiments of nitrogen gas adsorption (N2GA) and nuclear magnetic resonance (NMR), the multifractal characteristics of pore structures in shale and tight sandstone from the Chang 7 member of Triassic Yanchang Formation in Ordos Basin, NW China, are investigated. The multifractal spectra obtained from N2GA and NMR are analyzed with pore throat structure parameters. The results show that the pore size distributions obtained from N2GA and NMR are different, and the obtained multifractal characteristics vary from each other. The specific surface and total pore volume obtained by N2GA experiment have correlations with multifractal characteristics. For the core samples with the similar specific surface, the value of the deviation of multifractal spectra Rd increases with the increase in the proportion of large pores. When the proportion of macropores is small, the Rd value will increase with the increase in specific surface. The multifractal characteristics of pore structures are influenced by specific surface area, average pore size and adsorption volume measured from N2GA experiment. The multifractal characteristic parameters of tight sandstone measured from NMR spectra are larger than those of shale, which may be caused by the differences in pore size distribution and porosity of shale and tight sandstone.

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