scholarly journals Evaluation method for resource potential of shale oil in the Triassic Yanchang Formation of the Ordos Basin, China

2020 ◽  
Vol 38 (4) ◽  
pp. 841-866
Author(s):  
Qiulin Guo ◽  
Xiaoming Chen ◽  
Xiaoxue Liuzhuang ◽  
Zhi Yang ◽  
Man Zheng ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Total Organic Carbon ◽  
Calculation Method ◽  
Evaluation Method ◽  
Ordos Basin ◽  
Oil Yield ◽  
Shale Oil ◽  
Recovery Coefficient ◽  
Evaporative Loss ◽  
Total Oil

The widely distributed, thick Chang 7 Shale is the richest shale oil formation in China. A calculation method for the evaporative hydrocarbon recovery coefficient based on formation volume factor is proposed considering the correction of heterogeneity-based total organic carbon differences to improve the adsorbed oil calculation method, and light hydrocarbon evaporative sampling losses, which can make mobile and total oil calculations more accurate. The adsorbed oil, S1 evaporative loss, total oil yield, and movable oil yield of 200 shale samples from the Chang 7 Member were calculated using the new methods. Results show that S1 evaporative loss accounts for 29% of S1, total oil yield is 3.5 times S1, and movable oil yield accounts for 37% of total oil yield. Based on the calculated total oil yield and movable oil yield results, the relationships among total oil yield, movable oil yield, and total organic carbon of the Chang 7 were established yielding total oil yield and movable oil yield estimates of 11.12 × 109 t and 4.01 × 109 t, respectively, revealing its tremendous shale exploration potential.

Logging Evaluation Method and its Application for Measuring the Total Organic Carbon Content in Shale

2014 ◽  
Vol 962-965 ◽  
pp. 51-54
Author(s):  
Zhi Feng Wang ◽  
Yuan Fu Zhang ◽  
Hai Bo Zhang ◽  
Qing Zhai Meng
Keyword(s):  
Organic Carbon ◽  
Total Organic Carbon ◽  
Shale Gas ◽  
Sichuan Basin ◽  
Evaluation Method ◽  
Organic Carbon Content ◽  
Geochemical Analysis ◽  
Data Logging ◽  
Longmaxi Formation ◽  
Sedimentary Structures

The acquisition of the total organic carbon (TOC) content mainly relies on the geochemical analysis and logging data. Due to geochemical analysis is restricted by coring and experimental analysis, so it is difficult to get the continuous TOC data. Logging evaluation method for measuring TOC is very important for shale gas exploration. This paper presents a logging evaluation method that the shale is segmented according to sedimentary structures. Sedimentary structures were recognized by core, thin section and scanning electron microscope. Taking Wufeng-Longmaxi Formation, Silurian, Muai Syncline Belt, south of Sichuan Basin as research object, the shale is divided into three kinds: massive mudstone, unobvious laminated mudstone, and laminated mudstone. TOC within each mudstone are calculated using GR, resistivity and AC logging data, and an ideal result is achieved. This method is more efficient, faster and the vertical resolution is higher than △logR method.

scholarly journals Total Organic Carbon Enrichment and Its Impact on Pore Characteristics: A Case Study from the Niutitang Formation Shales in Northern Guizhou

Energies ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1480 ◽  
Author(s):  
Liu ◽  
Tang ◽  
Xi
Keyword(s):  
Fractal Dimension ◽  
Organic Carbon ◽  
Total Organic Carbon ◽  
Vitrinite Reflectance ◽  
Guizhou Province ◽  
Type I ◽  
Pore Characteristics ◽  
Hill Model ◽  
Recovery Coefficient ◽  
Niutitang Formation

This study analyzes samples from the Lower Cambrian Niutitang Formation in northern Guizhou Province to enable a better understanding of total organic carbon (TOC) enrichment and its impact on the pore characteristics of over-mature marine shale. Organic geochemical analysis, X-ray diffraction, scanning electron microscopy, helium porosity, and low-temperature nitrogen adsorption experiments were conducted on shale samples. Their original TOC (TOCo) content and organic porosity were estimated by theoretical calculation, and fractal dimension D was computed with the fractal Frenkel–Halsey–Hill model. The results were then used to consider which factors control TOC enrichment and pore characteristics. The samples are shown to be dominated by type-I kerogen with a TOC content of 0.29‒9.36% and an equivalent vitrinite reflectance value of 1.72‒2.72%. The TOCo content varies between 0.64% and 18.17%, and the overall recovery coefficient for the Niutitang Formation was 2.16. Total porosity of the samples ranged between 0.36% and 6.93%. TOC content directly controls porosity when TOC content lies in the range 1.0% to 6.0%. For samples with TOC < 1.0% and TOC > 6.0%, inorganic pores are the main contributors to porosity. Additionally, pore structure parameters show no obvious trends with TOC, quartz, and clay mineral content. The fractal dimension D1 is between 2.619 and 2.716, and D2 is between 2.680 and 2.854, illustrating significant pore surface roughness and structural heterogeneity. No single constituent had a dominant effect on the fractal characteristics.

Effect of Demineralization on Shale Oil Yield by Bioleaching Process of Huadian (China) Oil Shale

2013 ◽  
Vol 295-298 ◽  
pp. 146-149
Author(s):  
Xue Qing Zhang ◽  
Lan Ying Zhang ◽  
He Jun Ren
Keyword(s):  
Organic Carbon ◽  
Surface Structure ◽  
Mixed Culture ◽  
Oil Shale ◽  
Thiobacillus Ferrooxidans ◽  
Oil Yield ◽  
Mineral Matter ◽  
Shale Oil ◽  
Temperature Programmed

In this study, the effect of the mineral matter of Huadian (China) Oil Shale on the conversion of organic carbon of oil shale to shale oil. The bioleaching process is taken in a mixed culture of the lithotrophic bacteria Thiobacillus ferrooxidans(Tf). The aim of bioleaching process was to dissolve the inorganic matters and improve the shale oil yield. A series of temperature-programmed pyrolysis operation was performed with raw and bioleached oil shale to find the best retorting temperature, 500oC is the best temperature to retort the oil shale. The oil shale samples were detected by SEM, DG, Fischer assay test, the results show that the surface structure was significantly different from the raw sample, and the shale oil yield improved from 8.9% to 11.7%.

scholarly journals Geochemistry and shale gas potential of the lower Permian marine-continental transitional shales in the Eastern Ordos Basin

2020 ◽  
pp. 014459872097924
Author(s):  
Jingyi Wei ◽  
Yongli Wang ◽  
Gen Wang ◽  
Zhifu Wei ◽  
Wei He
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Total Organic Carbon ◽  
Shale Gas ◽  
Higher Plants ◽  
Ordos Basin ◽  
Organic Matter Content ◽  
Lower Permian ◽  
Gas Desorption ◽  
Geochemical Parameters

Marine–continental transitional strata were widely developed in the Ordos Basin in Upper Carboniferous - Lower Permian. The Taiyuan - Shanxi Formation possesses promising shale gas exploration layers. Shale samples from two drilling wells of Shanxi-Taiyuan Formation in Shilou and Xixian, Ordos Basin, were investigated to study their carbon–sulfur contents and distribution characteristics of organic components using carbon/sulfur analyzer and gas chromatography–mass spectroscopy. Using results of total organic carbon analyses, Rock-Eval pyrolysis, X-ray diffraction analysis, shale gas desorption experiments, and other relevant experimental data, the shale samples were comprehensively analyzed. The exploitability of the shale in the study area was evaluated. The Shanxi-Taiyuan Shale in the Shilou and Xixian areas was characterized by high total organic carbon contents of 7.1% and 2.1% and high Tmax values of 499 and 505 °C, respectively. The organic matter of the shale is types II2 and III. Moreover, biomarker parameters including n-alkanes, Paq, Pwax, average carbon chain length, and the ternary diagram of C27-C28-C29 steranes show the organic matter constituted terrestrial higher plants and aquatic low biological algae. Multiple n-alkane parameters show the organic matter input in the Shilou area is mainly derived from terrestrial higher plants. The Pr/Ph value and trace element indicators show the deposition environment is dominated by weak oxidation–reduction conditions. A shale gas desorption experiment shows the average desorbed gas contents of the shale samples in the Shilou and Xixian areas were 1.79 and 0.37 m3/t, respectively. The organic matter content determined the differences in shale gas properties between the two areas in Ordos Basin. The composition and content of inorganic minerals affect the reservoir physical properties. According to the analyses, the shale in the Shilou area has good shale gas reservoir characteristics in terms of desorbed gas content and the above-mentioned geochemical parameters. Furthermore, the Shanxi shale has good potential for shale gas industrial exploitation.

scholarly journals Shale favorable area optimization in coal-bearing series: A case study from the Shanxi Formation in Northern Ordos Basin, China

2017 ◽  
Vol 36 (5) ◽  
pp. 1295-1309 ◽  
Author(s):  
Wei Guo ◽  
Weijun Shen ◽  
Shangwen Zhou ◽  
Huaqing Xue ◽  
Dexun Liu ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Total Organic Carbon ◽  
Shale Gas ◽  
Ordos Basin ◽  
Sedimentary Facies ◽  
Gas Content ◽  
Burial Depth ◽  
Organic Carbon Content ◽  
River Channels

Shales in the Well district of Yu 106 of the Shanxi Formation in the Eastern Ordos Basin is deposited in the swamp between delta plains, distributary river channels, natural levee, the far end of crevasse splay, and depression environments. According to organic geochemistry, reservoir physical property, gas bearing capacity, lithology experimental analysis, combined with the data of drilling, logging, testing and sedimentary facies, the reservoir conditions of shale gas and the distribution of an advantageous area in Shanxi Formation have been conducted. The results show that the total organic carbon content of the Shanxi Formation is relatively high, with an average content value of 5.28% in the segment 2 and 3.02% in segment 1, and the organic matter is mainly kerogen type II2 and III. The maturity of organic matter is high with 1.89% as the average value of Ro which indicates the superior condition for gas generation of this reservoir. The porosity of shales is 1.7% on average, and the average permeability is 0.0415 × 10−3 µm2. The cumulative thickness is relatively large, with an average of 75 m. Brittle mineral and clay content in shales are 49.9% and 50.1%, respectively, but the burial depth of shale is less than 3000 m. The testing gas content is relatively high (0.64 × 104 m3/d), which shows a great potential in commercial development. The total organic carbon of the segment 2 is higher than that of the segment 1, and it is also better than segment 1 in terms of gas content. Based on the thickness of shale and the distribution of sedimentary facies, it is predicted that the advantageous area of shale gas in the segment 2 is distributed in a striped zone along the northeast and the northsouth direction, which is controlled by the swamp microfacies between distributary river channels.

scholarly journals Total Organic Carbon Content Prediction in Lacustrine Shale Using Extreme Gradient Boosting Machine Learning Based on Bayesian Optimization

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-18
Author(s):  
Xingzhou Liu ◽  
Zhi Tian ◽  
Chang Chen
Keyword(s):  
Machine Learning ◽  
Organic Carbon ◽  
Total Organic Carbon ◽  
Bayesian Optimization ◽  
Gradient Boosting ◽  
Support Vector ◽  
Shale Oil ◽  
The Core ◽  
Extreme Gradient Boosting ◽  
Lacustrine Shale

The total organic carbon (TOC) content is a critical parameter for estimating shale oil resources. However, common TOC prediction methods rely on empirical formulas, and their applicability varies widely from region to region. In this study, a novel data-driven Bayesian optimization extreme gradient boosting (XGBoost) model was proposed to predict the TOC content using wireline log data. The lacustrine shale in the Damintun Sag, Bohai Bay Basin, China, was used as a case study. Firstly, correlation analysis was used to analyze the relationship between the well logs and the core-measured TOC data. Based on the degree of correlation, six logging curves reflecting TOC content were selected to construct training dataset for machine learning. Then, the performance of the XGBoost model was tested using K -fold cross-validation, and the hyperparameters of the model were determined using a Bayesian optimization method to improve the search efficiency and reduce the uncertainty caused by the rule of thumb. Next, through the analysis of prediction errors, the coefficient of determination ( R 2 ) of the TOC content predicted by the XGBoost model and the core-measured TOC content reached 0.9135. The root mean square error (RMSE), mean absolute error (MAE), and mean absolute percentage error (MAPE) were 0.63, 0.77, and 12.55%, respectively. In addition, five commonly used methods, namely, Δ log R method, random forest, support vector machine, K -nearest neighbors, and multiple linear regression, were used to predict the TOC content to confirm that the XGBoost model has higher prediction accuracy and better robustness. Finally, the proposed approach was applied to predict the TOC curves of 20 exploration wells in the Damintun Sag. We obtained quantitative contour maps of the TOC content of this block for the first time. The results of this study facilitate the rapid detection of the sweet spots of the lacustrine shale oil.

scholarly journals Characteristics of the mud shale reservoirs in coal-bearing strata and resources evaluation in the eastern margin of the Ordos Basin, China

2019 ◽  
Vol 38 (2) ◽  
pp. 372-405
Author(s):  
Yue Chen ◽  
Dongmin Ma ◽  
Yucheng Xia ◽  
Chen Guo ◽  
Fu Yang ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Specific Surface ◽  
Total Organic Carbon ◽  
Surface Area ◽  
Shale Gas ◽  
Pore Volume ◽  
Ordos Basin ◽  
Thermal Maturity ◽  
Unconventional Gas ◽  
The Ordos Basin

As the co-exploration and co-production of unconventional gas have become a new trend of the unconventional gas exploration and development in the eastern margin of the Ordos Basin, this study focuses on the distribution, pore characteristics, geochemical properties, and mineral composition of the mud shale in the coal-bearing strata. The results show that the mud shale in the coal-bearing strata is distributed relatively stably with an average cumulative thickness of 77.60 m and a buried depth of 200–2400 m, increasing from east to west. The total organic carbon content of mud shale is relatively high, ranging from 0.14% to 39.9%, and the thermal maturity ranges from 0.23% to 2.49%, affected by both buried depth and magmatic intrusion. The organic matter type of the mud shale is dominated by type III, favorable for gas generation. The mineral composition of mud shale is mainly clay minerals and quartz, with low brittle minerals content (averaging 30.34%) and high kaolinite content (averaging 59.23%). Pores and micro-fissures are relatively developed in the mud shale, dominated by intergranular pores, organic pores, and the micro-fissures developed between brittle mineral crystals, within crystals and between clay mineral particles, with a porosity of 1.05%–1.59% and a permeability of 0.001–0.142 (×10−3µm2). The specific surface area of pores in mud shale is 12.31–28.99 m2/g, and the total pore volume is 0.0146–0.0483 cm3/g. Mesopores and micropores (mainly slit shaped pores) provide the main pore volume of mud shale, and micropores contribute most of the specific surface area. The controlling factors on pore development include the total organic carbon, thermal maturity, and inorganic minerals composition. The total amount of shale gas resources is 2.49 × 1012 m3, and the Linxian-Xingxian area and Shilou-Daning area are the potential favorable zones for shale gas exploration and development.

A logging-curve separation scale overlay method for total-organic-carbon estimation in organic-rich shale reservoirs

2017 ◽  
Vol 5 (3) ◽  
pp. T387-T398 ◽  
Author(s):  
Jingling Xu ◽  
Yangyang Li ◽  
Baoying Zhang ◽  
Lei Xu ◽  
Yuxing Qin
Keyword(s):  
Organic Carbon ◽  
Total Organic Carbon ◽  
Shale Gas ◽  
Evaluation Method ◽  
Gamma Ray ◽  
Quantitative Estimation ◽  
Well Logs ◽  
Reservoir Evaluation ◽  
Overlay Method ◽  
Shale Reservoirs

Quantitative estimation of total-organic-carbon (TOC) content using well logs is very important for shale-gas reservoir evaluation, especially when core data are limited. Even though many techniques have been developed to calculate TOC from well logs, they all have their limitations and accurate assessment of TOC in organic-rich tight shales is still challenging. We have used an improved log-overlay method for evaluating TOC content in organic-rich tight shale reservoirs by overlying the properly scaled gamma-ray, sonic transit time, and bulk density curves on top of the compensated neutron log (CNL) curve based on the same concept to the original [Formula: see text] technique. These logging curves are overlapped with the CNL in nonsource intervals, and they are separated in organic-rich shale reservoirs. The separation magnitude increases along with the increase in TOC content of the shale, and this relationship is transformed to calculate TOC. This method was tested and verified by doing a case study using well-log data from the Jiaoshiba tight shale-gas play in the Sichuan Basin. The results illustrated that the new TOC evaluation method is more practical and effective compared with existing TOC evaluation methods.

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