scholarly journals Evaluation of total organic carbon contents in carbonate source rocks by modified acid treatment method and the geological significance of acid-soluble organic matters

2018 ◽  
Vol 37 (1) ◽  
pp. 219-229 ◽  
Author(s):  
Peng Liu ◽  
Xiaofeng Wang ◽  
Juske Horita ◽  
Xuan Fang ◽  
Jianjing Zheng ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Total Organic Carbon ◽  
Carbonate Rocks ◽  
Acid Treatment ◽  
Treatment Protocol ◽  
Treatment Method ◽  
Source Rocks ◽  
Element Analysis ◽  
Organic Matters ◽  
Hydrocarbon Source Rocks

Total organic carbon contents are an important parameter in evaluating hydrocarbon source rocks and it shows the hydrocarbon-generating potential of hydrocarbon source rocks. In this study, the total organic carbon of 16 carbonate rocks with different maturity level was determined by a modified acid treatment protocol of the elemental analyzer method. In the modified method, montmorillonite is used to thicken the residue of acid treatment and remaining acid solution. Then, total organic carbon values of “clay-paste” sample were analyzed by the element analysis method. The results of 16 carbonate rocks show that the total organic carbon values with the new method were greater than the conventional total organic carbon test in a majority of the samples. Additionally, the fraction of acid-soluble organic matters was investigated and it shows no clear relationship of the fraction of acid-soluble organic matters with maturity and total organic carbon values in source rocks. Hence, it indicates that the released acid-soluble organic matters are characterized by complex factors that influence their occurrence and compositions.

scholarly journals Geochemical Characteristics of Released Organic Matters by Acid Decomposition of Hydrocarbon Source Rocks from Different Sedimentary Basins

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Peng Liu ◽  
Xiaofeng Wang ◽  
Xiaofu Li ◽  
Ting Zhang ◽  
Wenhui Liu
Keyword(s):  
Organic Carbon ◽  
Acid Solution ◽  
Total Organic Carbon ◽  
Acid Treatment ◽  
Geochemical Characteristics ◽  
Source Rocks ◽  
Hydrocarbon Generation ◽  
Carbonate Minerals ◽  
Important Indicator ◽  
Organic Matters

It has been acknowledged that carbonate was identified as the source rocks of a series of oil-gas fields worldwide. For evaluating the carbonate source rocks, total organic carbon (TOC) contents act as an important indicator. However, the acid solution, which has been generated during conventional TOC measurements, contain organic matters. Hence, the released organic matters in acid solution during carbonate decomposition may lead to underestimate the hydorcarbon generation potential. In this study, rock-eval pyrolysis technique was applied to bulk rock and residue after acid treatment. Meanwhile, the organic matters in acid solution were measured by Gas Chromatography-Mass Spectrometer (GC-MS) to investigate the geochemical characteristics. In addition, the hydrocarbon generation and alteration of TOC contents of released organic matters by acid treatment were studied by hydrous pyrolysis experiments. The results show that the acid solution contains organic compounds, including n-alkanes, saturated fatty acids and fatty acid methyl esters. Meanwhile, total organic carbon (TOC) contents and hydrocarbon generation potential (S1+S2) significantly decrease for bulk rocks after acid treatment in low maturity samples. Moreover, organic CO2 (S3) decreased after treating of acid, revealing that acidolysis process can affect and release organic matters containing oxygen-bearing functional groups. The S1, S2, S3, and TOC loss are positive correlation with the proportion of rock loss during acidolysis, indicating that the organic matters in acid solution are associated with carbonate minerals. The organic fractions may exist as adsorption state on the surface of carbonate minerals and (or) exist as organic acid salts. Moreover, the thermal simulation experiments reveal that the organic matter in acid solution, which is not recovered by the conventional measurement approach, could contribute to hydrocarbon generation.

OIL GEOCHEMISTRY AND POTENTIAL SOURCE ROCKS OF THE OFFICER BASIN, SOUTH AUSTRALIA

1980 ◽  
Vol 20 (1) ◽  
pp. 68 ◽  
Author(s):  
D.M. McKirdy ◽  
A.J. Kantsler
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Carbonate Rocks ◽  
Depositional Environment ◽  
South Australia ◽  
Source Rocks ◽  
Potential Source ◽  
Playa Lake ◽  
Oil Source ◽  
Extractable Organic Matter

Oil shows observed in Cambrian Observatory Hill Beds, intersected during recent stratigraphic drilling of SADME Byilkaoora-1 in the Officer Basin, indicate that oil has been generated within the basin. Shows vary in character from "light" oils exuding from fractures through to heavy viscous bitumen in vugs in carbonate rocks of a playa-lake sequence.The oils are immature and belong to two primary genetic families with some oils severely biodegraded. The less altered oils are rich in the C13 - C25 and C30 acyclic isoprenoid alkanes. Source beds within the evaporitic sequence contain 0.5 - 1.0% total organic carbon and yield up to 1900 ppm solvent-extractable organic matter. Oil-source rock correlations indicate that the oils originated within those facies drilled; this represents the first reported examples of non-marine Cambrian petroleum. The main precursor organisms were benthonic algae and various bacteria.Studies of organic matter in Cambrian strata from five other stratigraphic wells in the basin reveal regional variations in hydrocarbon source potential that relate to differences in precursor microbiota and/or depositional environment and regional maturation. Micritic carbonates of marine sabkha origin, located along the southeast margin of the basin, are rated as marginally mature to mature and good to prolific sources of oil. Further north and adjacent to the Musgrave Block, Cambrian siltstones and shales have low organic carbon values and hydrocarbon yields, and at best are only marginally mature. Varieties of organic matter recognised during petrographic studies of carbonates in the Officer Basin include lamellar alginite (alginite B) and "balls" of bitumen with reflectance in the range 0.2 to 1.4%.

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.

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