Evolution and recovery of original total organic carbon for carbonate source rocks with different total organic carbon in the Tazhong area, Tarim Basin, China

2016 ◽  
Vol 34 (5) ◽  
pp. 471-477 ◽  
Author(s):  
Z. P. Huo ◽  
M. Zou ◽  
S. Q. Qin ◽  
X. Q. Pang ◽  
W. Y. Wang ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Total Organic Carbon ◽  
Tarim Basin ◽  
Source Rocks ◽  
Tazhong Area ◽  
Carbonate Source

scholarly journals Quantitative prediction model of present-day low-TOC carbonate source rocks: Example from the Middle–upper Ordovician in the Tarim Basin

2018 ◽  
Vol 36 (5) ◽  
pp. 1335-1355 ◽  
Author(s):  
Junqing Chen ◽  
Xiongqi Pang ◽  
Hong Pang
Keyword(s):  
Organic Carbon ◽  
Prediction Model ◽  
Total Organic Carbon ◽  
Tarim Basin ◽  
Quantitative Model ◽  
Source Rocks ◽  
Upper Ordovician ◽  
Oil Accumulation ◽  
Hydrocarbon Expulsion ◽  
Carbonate Source

Plenty of marine crude oil generated by the Middle–Upper Ordovician source rocks has been discovered in the Tabei Uplift, Tarim Basin. Previous studies on the extensively distributed low organic matter source rock total organic carbon ≤ 0.5%) imply that this contributes to oil accumulation. Thus, the identification of present-day low-total organic carbon source rocks that experience hydrocarbon expulsion and evaluation of their contribution is of considerable significance to analyze marine oil accumulation and to assess the resources in the Tarim Basin. Using the mass balance approach, we identify and verify present-day low-total organic carbon carbonate source rocks and present a quantitative model using well-logging data to predict the present-day low-total organic carbon carbonate source rocks in order to evaluate their contribution in the Tarim Basin. Hydrocarbon expulsion has occurred in the Yijianfang formation, which has present-day low-total organic carbon, between 6452 and 6487 m in the Yangwu 2 well. In the horizons depicting carbonates with hydrocarbon expulsion, the porosity is relatively high and the daily oil production is 0.19 m3 according to the perforation tests. The extracts have similar biomarker signatures to that of the crude oils in the Tabei Uplift. In this study, a quick and cost-effective quantitative model is developed using double lateral resistivity and uranium/thorium well-logging data. By applying the prediction model, the contribution of present-day low-total organic carbon carbonate source rocks in the Middle–Upper Ordovician formation of the Tarim Basin is primarily evaluated to be 363.38 × 109 bbl oil equivalent.

scholarly journals A New Evaluation Method of Total Organic Carbon for Shale Source Rock Based on the Effective Medium Conductivity Theory

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Jian Fu ◽  
Xuesong Li ◽  
Yonghe Sun ◽  
Qiuli Huo ◽  
Ting Gao ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Total Organic Carbon ◽  
Clay Minerals ◽  
Pore Water ◽  
Effective Medium ◽  
Source Rocks ◽  
Model Parameters ◽  
Hydrocarbon Generation ◽  
Tight Sandstone

In the evaluation of source rocks, the total organic carbon (TOC) is an important indicator to evaluate the hydrocarbon generation potential of source rocks. At present, the commonly used methods for assessing TOC include △ log R and neural network method. However, practice shows that these methods have limitations in the application of unconventional intervals of sand-shale interbeds, and they cannot sufficiently reflect the variation of TOC in the vertical direction. Therefore, a total organic carbon (TOC) evaluation model suitable for shale and tight sandstone was established based on the effective medium symmetrical conduction theory. The model consists of four components: nonconductive matrix particles, clay minerals, organic components (solid organic matter and hydrocarbons), and pore water. The conductive phase in the model includes clay minerals and pore water, and other components are treated as nonconductive phases. When describing the conductivity of rock, each component in the model is completely symmetrical, and anisotropic characteristics of each component are considered. The model parameters are determined through the optimization method, and the bisection iteration method is used to solve the model equation. Compared with the classic TOC calculation method, the new model can evaluate the abundance of organic matter in shale and tight sandstone, which provides a new option to assess the TOC of rocks based on logging methods.

Evaluation of the total organic carbon of source rocks in lacustrine basins using the variable-coefficient ΔLgR technique — A case study of the Xujiaweizi Fault Depression in the Songliao Basin

2019 ◽  
Vol 7 (4) ◽  
pp. SJ67-SJ75
Author(s):  
Chao Liu ◽  
Lidong Sun ◽  
Jijun Li ◽  
Shuangfang Lu ◽  
Lei Tian ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Total Organic Carbon ◽  
Variable Coefficient ◽  
Prediction Equation ◽  
Songliao Basin ◽  
Source Rocks ◽  
High Quality ◽  
Natural Gamma ◽  
The Individual ◽  
Fourth Member

To lay the foundation for the exploration of shale gas, we calculated the total organic carbon (TOC) of Shahezi Formation source rocks in the Xujiaweizi Fault Depression in the Songliao Basin by using the measuring data and the logging curves. Because the source rocks in the study area were formed in a lacustrine basin, they are characterized by strong organic heterogeneity, making it difficult to objectively characterize any changes in the TOC of the underground source rocks based on discrete and limited sampling. In addition, because the source rock is relatively rich in shale and poor in organic matter, the logging response features of high natural gamma, medium-high interval transit time, and medium-low resistivity, making it easily identified. However, because the logging parameters to predict the TOC of source rocks are not universal, it is impossible to establish a prediction equation that is universally applicable. To solve the above problems, we used the variable-coefficient [Formula: see text] technique to predict the TOC of the source rocks in the study area. We defined the two key parameters that affect the TOC prediction in the classic [Formula: see text] technique as the undetermined coefficients, and the coefficients were determined according to the logging and geologic data of the individual wells. The application results indicate that the variable-coefficient [Formula: see text] technique has an average relative error of 17.5% in the prediction of the TOC, which is 16.1% lower than that of the classic [Formula: see text] technique. Thus, the prediction results can effectively reflect the vertical variation in the TOC of source rocks. Based on the logging evaluation results for the TOC of source rocks in 35 wells throughout the study area, the thickness of the high-quality source rocks in the fourth member of the Shahezi Formation was mapped. The thickness of the high-quality source rocks in the fourth member of the Shahezi Formation is generally [Formula: see text]. There are two centers of greater thickness in the plane, with the maximum thickness of more than 70 m.

scholarly journals Geochemical characterization and possible hydrocarbon contribution of the Carboniferous interval natively developed in the Chepaizi Uplift of Junggar Basin, northwestern China

2019 ◽  
Vol 38 (3) ◽  
pp. 654-681 ◽  
Author(s):  
Lixin Mao ◽  
Xiangchun Chang ◽  
Youde Xu ◽  
Bingbing Shi ◽  
Dengkuan Gao
Keyword(s):  
Organic Carbon ◽  
Total Organic Carbon ◽  
Junggar Basin ◽  
Source Rocks ◽  
Hydrocarbon Generation ◽  
Exploration Process ◽  
Potential Source ◽  
Hydrocarbon Generation Potential ◽  
Northwestern Region ◽  
Effective Source

Previous studies on Chepaizi Uplift mainly focused on its reservoirs, and the potential source rocks natively occurred was ignored. During the exploration process, dark mudstones and tuffaceous mudstones were found in the Carboniferous interval. These possible source rocks have caused great concern about whether they have hydrocarbon generation potential and can contribute to the reservoirs of the Chepaizi Uplift. In this paper, the potential source rocks are not only evaluated by the organic richness, type, maturity, and depositional environment, but also divided into different kinetics groups. The Carboniferous mudstones dominated by Type III kerogen were evolved into the stage of mature. Biomarkers indicate that the source rocks were deposited in a marine environment under weakly reducing conditions and received mixed aquatic and terrigenous organic matter, with the latter being predominant. The effective source rocks are characterized by the total organic carbon values >0.5 wt.% and the buried depth >1500 m. The tuffaceous mudstone shows a greater potential for its lower active energy and longer hydrocarbon generation time. Considering the hydrocarbon generation potential, base limits of the total organic carbon and positive correlation of oil–source rock together, the native Carboniferous mudstones and tuffaceous mudstones might contribute to the Chepaizi Uplift reservoirs of the northwestern region of the Junggar Basin, especially the deeper effective source rocks should be paid enough attention to.

DETERMINATION FROM WELL LOGS OF THE TOTAL ORGANIC CARBON CONTENT IN POTENTIAL SOURCE ROCKS

1994 ◽  
Vol 34 (1) ◽  
pp. 307
Author(s):  
J.L. Lin ◽  
H.A. Salisch
Keyword(s):  
Organic Carbon ◽  
Total Organic Carbon ◽  
Source Rocks ◽  
Well Logs ◽  
Organic Carbon Content ◽  
Well Log ◽  
Single Model ◽  
Geochemical Properties ◽  
Comparison Of The Results ◽  
Immature Source Rock

This paper discusses, in some detail, the log responses to total organic carbon (TOC) in the Upper and Middle Velkerri Formation in an area of the McArthur Basin, Northern Territory, Australia. The Formation Density log was found to be superior to other standard well logs in assessing values of TOC in the area studied. A theoretical model was used to estimate TOC from the Formation Density log. The model was established and its applicability was verified by comparison with other models. Based on geochemical properties the Upper and Middle Velkerri Formation is classified into three categories: nonsource rocks, mature source rocks and immature source rock. They show significant differences in the well log responses, and different models had to be established for the three categories to determine the TOC content from well logs. Comparison of the results of using a different model for each category instead of a single model to cover the three categories shows that the former approach gives more meaningful answers.

Lithofacies-dependent rock physics templates of an unconventional shale reservoir on the North Slope, Alaska

2020 ◽  
pp. 1-49
Author(s):  
Minh Tran ◽  
Tapan Mukerji ◽  
Allegra Hosford Scheirer
Keyword(s):  
Organic Carbon ◽  
Total Organic Carbon ◽  
Source Rock ◽  
Velocity Ratio ◽  
Rock Physics ◽  
Hydrogen Index ◽  
Source Rocks ◽  
Rock Properties ◽  
North Slope ◽  
Petrophysical Properties

Over the past 20 years, oil and gas companies have turned their attention to producing petroleum directly from organic-rich shale. Successful exploration, appraisal, and production strategies for source rocks critically depend on reliable identification of their organic components (kerogen, in particular) and generation potential. There is mounting demand to evaluate organic richness in terms of quantity (i.e. total organic carbon) and quality (i.e. hydrogen index) from seismic data, which is usually the only source of information in the early development period of emerging shale plays. We delineated major seismic lithofacies on the Alaska North Slope using elastic, seismic, and petrophysical properties. We performed a well-established quantitative seismic interpretation workflow to integrate geochemical data in the lithofacies definition. Rock physics templates of seismic parameters, Acoustic Impedance, (AI), versus P-wave to S-wave velocity ratio, (VP/VS), are constructed for each lithofacies to assess variations in pore fluid and lithology. We proposed correlations between source rock properties (hydrogen index, total organic carbon) and petrophysical properties (bulk density, porosity, sonic velocity ratio) of the major lithofacies. These correlations, together with facies-specific rock physics templates, can be utilized to predict organic richness and source rock properties away from drilled wells. The models are validated by training data from 2 regional wells to observe their applicability on the Alaska North Slope.

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