Oil content prediction of lacustrine organic-rich shale from wireline logs: A case study of intersalt reservoirs in the Qianjiang Sag, Jianghan Basin, China

2020 ◽  
Vol 8 (3) ◽  
pp. SL79-SL88
Author(s):  
Xin Nie ◽  
Jing Lu ◽  
Roufida Rana Djaroun ◽  
Peilin Wang ◽  
Jun Li ◽  
...  

Shale oil is an unconventional oil resource with great potential. Oil saturation ([Formula: see text]) is an essential parameter for formation evaluation. However, due to the complexity of matrix mineral components and pore structure, Archie’s law cannot be used directly to calculate [Formula: see text] in shale oil reservoirs. We have developed a new saturation model for shale oil reservoirs. This model allows us to separate the organic from the inorganic pores, eliminate the background conductivity mainly caused by the borehole fluid or conductive minerals and determine the effective conductive porosity, which rules out nonconductive porosity, including isolated pores and the pore space affected by the fluid distribution. By analyzing the logging and core experimental data from the Qianjiang Sag, Jianghan Oilfield, we found that the T2 cutoff porosities of nuclear magnetic resonance logging are strongly related to the nonconductive porosities. After we determine the T2 cutoff value using the core experimental data, we can use it to obtain nonconductive porosity fraction in each depth point, which allows us to efficiently calculate [Formula: see text]. We calculate oil saturation values and use them to estimate the oil content. The results are coherent with the core experimental data, which indicates the efficiency of this model.

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Xin Nie ◽  
Jing Lu ◽  
Jingyuan Chi ◽  
Peilin Wang ◽  
Chaomo Zhang

Organic-rich shales in between salt rock layers distribute widely in Qianjiang Sag, Jianghan Basin, central China. Due to the complexity of matrix mineral components and their distribution and tight pore structure, Archie’s law cannot be used directly to calculate oil saturation in those shale oil reservoirs. A new oil content model for shale oil reservoirs was introduced. By analyzing the logging and core experimental data from Qianjiang Sag, Jianghan Oilfield, we built the relationship between kerogen and the different well logging porosities including nuclear magnetic resonance (NMR) porosity, neutron porosity, and density porosity. And we used the dual- V sh method to calculate the total organic carbon (TOC). After calculating the volume fraction of the solid organic matters and separating it from the TOC, we acquired the hydrocarbon fluid content in the formations. The calculated oil content results are coherent with the core experimental data, which indicates the efficiency of this model. This model is simple and can be quickly applied. However, this method also shows its weakness in calculation precision when the TOC is not calculated precisely or the quality of the porosity logs is low.


2020 ◽  
Vol 8 (3) ◽  
pp. SL35-SL43
Author(s):  
Lichun Kuang ◽  
Zhenlin Wang ◽  
Cheng Feng ◽  
Peiqiang Zhao ◽  
Rui Mao ◽  
...  

Oil saturation is an important parameter in shale-oil reservoir evaluation. However, due to complex wettability and pore construction, we find that conventional resistivity and nuclear magnetic resonance (NMR) methods do not perform well in calculating oil saturation in shale-oil reservoirs. Hence, we have developed a practical NMR-based method to calculate the oil saturation of the Lucaogou shale-oil Formation, Permian, in Jimusar Sag, Junggar Basin, China. First, we analyze the relationships among the wettability, oil saturation, and [Formula: see text] distribution based on the theoretical formula and core analysis data. Results indicate that the ratio of the surface area wetted by water and oil is approximately equal to the ratio of water saturation and oil saturation. So we conclude that oil is mainly stored in relatively bigger pores and the surface relaxivity of the oil-wet surface is lower than that of the water-wet surface, resulting in long relaxation signals, that is, the long relaxation signals of NMR [Formula: see text] spectra of shale-oil reservoirs are primarily attributed to oil signals. We have made a series of NMR measurements of as-received samples and confirm this point. Thus, we propose a [Formula: see text] cutoff for water and oil to calculate the oil saturation, and we determine 6 ms as the [Formula: see text] cutoff based on the oil saturation analysis of cores and NMR logs. Finally, we verify and make application of our method and acquire good results.


2017 ◽  
Author(s):  
T. Chen ◽  
R. Salas-Porras ◽  
D. Mao ◽  
V. Jain ◽  
M. A. Thomas ◽  
...  

Geophysics ◽  
2018 ◽  
Vol 83 (5) ◽  
pp. B281-B287 ◽  
Author(s):  
Xiwu Liu ◽  
Fengxia Gao ◽  
Yuanyin Zhang ◽  
Ying Rao ◽  
Yanghua Wang

We developed a case study of seismic resolution enhancement for shale-oil reservoirs in the Q Depression, China, featured by rhythmic bedding. We proposed an innovative method for resolution enhancement, called the full-band extension method. We implemented this method in three consecutive steps: wavelet extraction, filter construction, and data filtering. First, we extracted a constant-phase wavelet from the entire seismic data set. Then, we constructed the full-band extension filter in the frequency domain using the least-squares inversion method. Finally, we applied the band extension filter to the entire seismic data set. We determined that this full-band extension method, with a stretched frequency band from 7–70 to 2–90 Hz, may significantly enhance 3D seismic resolution and distinguish reflection events of rhythmite groups in shale-oil reservoirs.


Sign in / Sign up

Export Citation Format

Share Document