Shuangfang Lu

Research of CO 2 and N 2 Adsorption Behavior in K-Illite Slit Pores by GCMC Method

Understanding the adsorption mechanisms of CO2 and N2 in illite, one of the main components of clay in shale, is important to improve the precision of the shale gas exploration and development. We investigated the adsorption mechanisms of CO2 and N2 in K-illite with varying pore sizes at the temperature of 333, 363 and 393u2009K over a broad range of pressures up to 30u2009MPa using the grand canonical Monte Carlo (GCMC) simulation method. The simulation system is proved to be reasonable and suitable through the discussion of the impact of cation dynamics and pore wall thickness. The simulation results of the excess adsorption amount, expressed per unit surface area of illite, is in general consistency with published experimental results. It is found that the sorption potential overlaps in micropores, leading to a decreasing excess adsorption amount with the increase of pore size at low pressure, and a reverse trend at high pressure. The excess adsorption amount increases with increasing pressure to a maximum and then decreases with further increase in the pressure, and the decreasing amount is found to increase with the increasing pore size. For pores with size greater larger than 2u2009nm, the overlap effect disappears.

FRACTAL CHARACTERISTICS OF CONTINENTAL SHALE PORES AND ITS SIGNIFICANCE TO THE OCCURRENCE OF SHALE OIL IN CHINA: A CASE STUDY OF BIYANG DEPRESSION

Samples from seven major exploration wells in Biyang Depression of Henan Oilfield were compared using low-temperature nitrogen adsorption and shale oil adsorption experiments. Comprehensive analysis of pore development, oiliness and shale oil flowability was conducted by combining fractal dimension. The results show that the fractal dimension of shale in Biyang Depression of Henan Oilfield was negatively correlated with the average pore size and positively correlated with the specific surface area. Compared with the large pore, the small pore has great fractal dimension, indicating the pore structure is more complicated. Using S1 and chloroform bitumen A to evaluate the relationship between shale oiliness and pore structure, it was found that the more heterogeneous the shale pore structure, the higher the complexity and the poorer the oiliness. Clay minerals are the main carriers involved in crude oil adsorption, affecting the mobility of shale oil. When the pore complexity of shale was high, the content ...

FRACTAL NATURE OF POROSITY IN VOLCANIC TIGHT RESERVOIRS OF THE SANTANGHU BASIN AND ITS RELATIONSHIP TO PORE FORMATION PROCESSES

In this paper, in a case study of Santanghu Basin in China, the morphological characteristics and size distribution of nanoscale pores in the volcanic rocks of the Haerjiawu Formation were investigated using the results of low temperature nitrogen adsorption experiments. This research showed that within the target layer, a large number of nanoscale, eroded pores showed an “ink bottle” morphology with narrow pore mouths and wide bodies. The fractal dimension of pores increases gradually with increasing depth. Moreover, as fractal dimension increases, BET-specific surface area gradually increases, average pore diameter decreases and total pore volume gradually increases. The deeper burial of the Haerjiawu volcanic rocks in the Santanghu Basin leads to more intense erosion by organic acids derived from the basin’s source rocks. Furthermore, the internal surface roughness of these corrosion pores results in poor connectivity. As stated above, the corrosion process is directly related to the organic acids gene...

Pore characteristics of lacustrine mudstones from the Cretaceous Qingshankou Formation, Songliao Basin

AbstractCretaceous Qingshankou (K2qn) mudstone of lacustrine origin is the major source rock for conventional hydrocarbon currently being produced in the Daqing and Jilin oilfields of the Songliao Basin, which is one of the largest continental basins in the world. Therefore, elucidating the geochemical and petrological characteristics of the K2qn mudstone is important to help determine its quality as an economically viable source for shale oil production. In our study, eight dark mudstone core samples from the K2qn formation were subjected to total organic carbon (TOC), Rock-Eval pyrolysis, X-ray diffraction, scanning electron microscopy (SEM), field emission SEM (FE-SEM), and low-pressure N2 gas adsorption (LPGA-N2) experiments. Geochemical and petrological analysis results indicated the presence of a high TOC content, which originated mainly from alginate and some plant-derived organic matter, whereas bitumen was frequently present in mudstones with thermal maturity in the oil-generation stage. The K2qn...

Multi-component segmentation of X-ray computed tomography (CT) image using multi-Otsu thresholding algorithm and scanning electron microscopy:

X-ray computed tomography is an efficient method for quantitatively estimating the characteristics and heterogeneity of shales in three dimensions. A threshold is commonly used to separate pore-fractures from the background image. However, few studies have focused on the multi-component segmentation of computed tomography images. To obtain the distribution characteristics of different components in three dimensions, a segmentation method was proposed that combines a multi-Otsu thresholding algorithm with scanning electron microscopy. The gray value distributions of different components were first determined using this method. Then, the shale components were divided into several groups based on these gray values. The threshold of each component group was determined using the multi-Otsu thresholding algorithm. The computed tomography image stacks of two shale samples were processed using this segmentation method, and another computed tomography image stack was used to verify the method. The results showed that (1) the multi-component segmentation method can successfully segment computed tomography image stacks using the calculated values determined by computed tomography, which agree well with the measured values obtained from X-ray diffraction, total organic carbon, and porosity tests in the laboratory; (2) samples with similar provenances and mineral compositions have the same gray value distribution in the back scattering scanning electron microscopy and computed tomography images; (3) this method is superior in both the effectiveness and efficiency of the computed tomography image stack segmentation of samples according to the gray value distribution, as determined by samples with similar provenances and mineral compositions.

Quantitative Evaluation on the Elastic Property of Oil-Bearing Mudstone/Shale from a Chinese Continental Basin

This study aims at quantitatively evaluating the impact of material compositions on the elastic property (static Youngs modulus) of oil-bearing mudstone and shale (MS). Six samples (two mudstone and four shale) from a Chinese continental basin (Bohai Bay basin) were investigated under different hydrostatic triaxial compression conditions. The primary findings of this study include the following: (a) the elastic property of MS rocks are sensitive to the hydrostatic confinement condition. In response, the MS Youngs modulus gradually increases with increasing confining stress. (b) The mineralogical compositions impacting the MS Youngs modulus primarily include quartz, plagioclase, calcite and clay. Overall, the total content of siliceous (calcareous) minerals has a positive (negative) effect on Youngs modulus. Clay also contributes to the decrease of Youngs modulus. (c) Due to its relatively low stiffness and strength, organic matter has a substantially negative impact on Youngs modulus. (d) MS reservoirs that contain a high siliceous mineral content will be favorable to hydraulic fracturing. Finally, an empirical model evaluating MS Youngs modulus was established by coupling Youngs modulus with material compositions; the model shows a good fit with the experimental results. Thus, the MS Youngs modulus is comprehensively affected by multiple constituents found in MS rocks and can be expressed as a function of material composition.

Thermal effect of intrusive rock on hydrocarbon generation from organic matter

Igneous intrusions may contain sufficient heat that can have an effect on the generation of hydrocarbons from the source rock. This model is tested in the Yingtai Fault Depression of the southern Songliao Basin, where intrusive rocks are abundant. A heat conduction model and kinetic models of hydrocarbon generation are calibrated by using the hydrocarbon yield data from pyrolysis experiment and vitrinite reflectance values of source rocks adjacent to intrusive rocks. Our analysis shows that the intrusive rock contributes to the hydrocarbon generated from organic matter in the neighboring rock nearby the intrusive rock. For instance, as the distance to the contact surface is decreased, the maturity of the organic matter of neighboring rock increases gradually, H/C and TOC decreases gradually. The results have revealed that the extents affected by intrusive rocks with different thicknesses at various initial temperatures are basically not more than twice of the thickness of the intrusive rock. For multiple intrusive rocks, the extent and the degree of the thermal effect during a contemporaneous emplacement and emplacement at different stages are obviously different. The extent and degree of the thermal effect during contemporaneous emplacement are normally large. The degrees of thermal effect are different for neighboring rocks with different initial maturity, which is affected by the intrusive rock with the same parameters (such as thickness or initial temperature). Setting 0.9xa0% as the maturity (Ro) limit, at maturity less than 0.9xa0%, the Ro thermal effect (increment amount of Ro) increases as the initial maturity of the neighboring rock rises. At maturity of more than 0.9xa0%, it decreases as the initial maturity of neighboring rock rises. The results of the geological application have shown that the hydrocarbon generation history of source rock in an area with intrusive rocks can be solved effectively by an integrated use of the heat conduction model and the kinetic model of hydrocarbon generation.

Basin modelling of gas migration and accumulation in volcanic reservoirs in the Xujiaweizi Fault-depression, Songliao Basin

The Xujiaweizi Fault-depression of Songliao Basin has developed typical and widespread volcanic gas reservoirs. We studied the formation process of volcanic gas reservoirs by using basin modelling software and evaluated the influence of volcanic porosity, the 3D spatial and temporal field of the thermal history, and the 3D fault patterns on the basin modelling results. The 1D basin modelling results indicate that hydrocarbon generation of deep layer source rocks has a relay characteristic in time (128–0xa0Ma) and space (sag and slope zone) in the Xujiaweizi Fault-depression. The 2D basin modelling results show that (i) the distribution of volcanic reservoirs was controlled by the volcanic apparatus, (ii) gas source faults facilitated the vertical migration of natural gas, and (iii) the development of volcanic porosity controlled the lateral migration and accumulation of natural gas in the carrier bed. The 3D basin modelling results demonstrate that JHM, JHC, KSHC, and KSHM (source rocks) started hydrocarbon generation during the late deposition of the Denglouku Formation (113xa0Ma), the main hydrocarbon expulsion period was during the deposition of the late Quantou Formation (100xa0Ma), when the largest volcanic gas reservoir was formed; and from 84xa0Ma to the present (0xa0Ma), the area of the volcanic gas reservoir has decreased gradually. The insight gained from the basin modelling results of the volcanic gas-bearing system of the Xujiaweizi Fault-depression is that volcanic porosity, the 3D spatial and temporal field of the thermal history, and the 3D fault patterns have important influences on gas reservoir formation history and accumulation location. We are the first to establish different patterns for relations between different volcanic lithofacies porosity and burial depth, and we expect to provide a reference for basin model of other volcanic oil- and gas-bearing systems.

Palaeoenvironment and Its Control on the Formation of Miocene Marine Source Rocks in the Qiongdongnan Basin, Northern South China Sea

The main factors of the developmental environment of marine source rocks in continental margin basins have their specificality. This realization, in return, has led to the recognition that the developmental environment and pattern of marine source rocks, especially for the source rocks in continental margin basins, are still controversial or poorly understood. Through the analysis of the trace elements and maceral data, the developmental environment of Miocene marine source rocks in the Qiongdongnan Basin is reconstructed, and the developmental patterns of the Miocene marine source rocks are established. This paper attempts to reveal the hydrocarbon potential of the Miocene marine source rocks in different environment and speculate the quality of source rocks in bathyal region of the continental slope without exploratory well. Our results highlight the palaeoenvironment and its control on the formation of Miocene marine source rocks in the Qiongdongnan Basin of the northern South China Sea and speculate the hydrocarbon potential of the source rocks in the bathyal region. This study provides a window for better understanding the main factors influencing the marine source rocks in the continental margin basins, including productivity, preservation conditions, and the input of terrestrial organic matter.

Controls on the organic carbon content of the lower Cambrian black shale in the southeastern margin of Upper Yangtze

Control of various factors, including mineral components, primary productivity and redox level, on the total organic carbon (TOC) in the lower Cambrian black shale from southeastern margin of Upper Yangtze (Taozichong, Longbizui and Yanbei areas) is discussed in detail in this article. Mineral components in the study strata are dominated by quartz and clay minerals. Quartz in the Niutitang Formation is mainly of biogenic origin, and the content is in positive correlation with TOC, while the content of clay minerals is negatively correlated with TOC. Primary productivity, represented by the content of Mobio (biogenic molybdenum), Babio (biogenic barium) and phosphorus, is positively correlated with TOC. The main alkanes in studied samples are nC18–nC25, and odd–even priority values are closed to 1 (0.73–1.13), which suggest the organic matter source was marine plankton. Element content ratios of U/Th and Ni/Co and compound ratio Pr/Ph indicate dysoxic–anoxic bottom water, with weak positive relative with TOC. In total, three main points can be drawn to explain the relationship between data and the factors affecting organic accumulation: (1) quartz-rich and clay-mineral-poor deep shelf–slope–basin environment was favorable for living organisms; (2) high productivity provided the material foundation for organic generation; (3) the redox conditions impact slightly on the content of organic matter under high productivity and dysoxic–anoxic condition.