Oil Content Prediction Method Based on the TOC and Porosity of Organic-Rich Shales from Wireline Logs: A Case Study of Lacustrine Intersalt Shale Plays in Qianjiang Sag, Jianghan Basin, China

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.

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

Interpretation ◽

10.1190/int-2019-0247.1 ◽

2020 ◽

Vol 8 (3) ◽

pp. SL79-SL88

Author(s):

Xin Nie ◽

Jing Lu ◽

Roufida Rana Djaroun ◽

Peilin Wang ◽

Jun Li ◽

...

Keyword(s):

Experimental Data ◽

Oil Content ◽

Pore Space ◽

Oil Reservoirs ◽

Fluid Distribution ◽

Shale Oil ◽

Oil Saturation ◽

Archie’S Law ◽

The Core ◽

Shale Oil Reservoirs

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.

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Study on mechanism of spontaneous imbibition and pressurized imbibition in shale oil reservoirs

Journal of Petroleum Exploration and Production Technology ◽

10.1007/s13202-020-01056-3 ◽

2020 ◽

Author(s):

Lanlan Yao ◽

Zhengming Yang ◽

Haibo Li ◽

Bo Cai ◽

Chunming He ◽

...

Keyword(s):

Oil Recovery ◽

Spontaneous Imbibition ◽

Oil Reservoirs ◽

Recovery Ratio ◽

Shale Oil ◽

Fracture System ◽

Matrix System ◽

Jianghan Basin ◽

Shale Oil Reservoirs ◽

Shale Permeability

AbstractImbibition is one of the important methods of oil recovery in shale oil reservoirs. At present, more in-depth studies have been carried out on the fracture system and matrix system, and there are few studies on the effect of energy enhancement on imbibition in shale oil reservoirs. Therefore, based on the study of pressurized imbibition and spontaneous imbibition of shale oil reservoirs in Qianjiang Sag, Jianghan Basin, nuclear magnetic resonance technology was used to quantitatively characterize the production degree of shale and pore recovery contribution under different imbibition modes, and analyze the imbibition mechanism of shale oil reservoirs under the condition of energy enhancement. The experimental results showed that with the increase in shale permeability, the recovery ratio of pressurized imbibition also increased. The rate of pressurized imbibition was higher than spontaneous imbibition, and pressurized imbibition can increase the recovery ratio of fractured shale. Spontaneous imbibition can improve the ultimate recovery ratio of matrix shale. Pressurized imbibition can increase the recovery contribution of macroporous and mesoporous.

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Characteristics of shale oil reservoirs in Qianjiang Formation, Qiangjiang Depression, Jianghan Basin, China

10.5194/egusphere-egu2020-1982 ◽

2020 ◽

Author(s):

Jing Luo ◽

Furong Wang

Keyword(s):

Pore Volume ◽

Salt Lake ◽

Nitrogen Adsorption ◽

Oil Reservoirs ◽

Oil Reservoir ◽

Shale Oil ◽

Type Ii ◽

Salt Rock ◽

Jianghan Basin ◽

Shale Oil Reservoirs

The Jianghan Basin is a typical eastern fault depression salt lake basin in China, in which the Paleogene strata of the Qianjiang Sag are rich in shale oil resources. As a salt lake sedimentary basin, the developed Qianjiang Formation is a set of inter-salt oil-bearing strata, in which the salt rock strata are especially developed. There are many salt rhythms in the study area and a salt rhythm consists of a argillaceous dolomite layer between a salt rock formation and a salt rock formation. This study focuses on the 10th rhythm of the Qian 34 section of Qianjiang Depression (Eq3410). The samples were investigated by organic geochemical analysis and X-ray diffraction, and the pore structure characteristics of the reservoir were studied by argon ion polishing scanning electron microscope and low temperature nitrogen adsorption test. The research indicates that the average TOC of Eq3410 in Qianjiang Depression is 2.11% and the main distribution is 1%~3%; the type of organic matter is mainly Type II2 and Type II1; the overall maturity of organic matter is low maturity stage(Tmax is 412~441&#8451;with an average of 423&#8451;). The XRD data indicates that the mineral composition of the Qianjiang Formation shale oil reservoir is complex and have strong heterogeneity(quartz content in 2.3%~18.6% with an average of 9.5%, calcite content in 6.9~43.8% with an average of 12.8%, dolomite content in 2.5%~ 61.2% with an average of 27.2%, clay mineral content in 1.0%~45.2% with an average of 20.5%, glauberite content from 7.1% to 92.7% with an average of 22.9%). The pore types of shale oil reservoirs in Qianjiang Sag are complex and diverse and mostly are intergranular pores, which are mainly developed between detrital minerals or between detrital minerals and carbonate minerals. In carbonate mineral particles and quartz particles, some intragranular pores are visible, including calcite dissolution pores, internal pores of calcite and clay minerals, and internal pores of pyrite particles. And organic pores are rare in reservoirs due to the low maturity(Ro ranges between 0.5% and 0.7%). Nitrogen adsorption experiments showed that the pore size distribution of Eq3410 samples was dominated by mesopores and macropores. And the pore volume of the Eq3410 sample was most affected by the macropore pore volume, averaging 66.22%, followed by the mesopore pore volume with an average of 31.45%. To study and understand the characteristics of shale oil reservoir in Qianjiang Depression is conducive to mastering the regularity of shale oil enrichment and provides a basis for the exploration and development of shale oil.

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