Tight Oils Research Articles

Detailed investigation on the oxidation behavior and kinetic triplet of tight oil via TG-DSC-PDSC analyses

It remains some barriers for continental tight oils to enhance oil recovery owing to low or ultra-low permeability in China. Whether low temperature combustion mode (or deflagration fracturing) could be employed to expand the fracture, is an interesting but debatable topic in consideration of the not well-understood oxidation behavior and kinetic mechanism for the tight oil. This study initiated a comprehensive characterization on the oxidation behavior and kinetic triplet for the Mahu tight oil via the combination of atmospheric and pressurized thermal analyses (TG/DTG, DSC/DDSC, PDSC) and unconventional Popescu method. Threshold, peak, and end temperatures were shifted to higher temperature ranges following lower cumulative heat emission (from 13.21 to 9.15 kJ·g−1) with the heating rate increment from 5 to 15 K·min−1. Inversely, a more thorough oxidation process with higher cumulative heat releases (8.69 kJ·g−1 for LTO, 4.48 kJ·g−1 for HTO) was presented under elevated pressure condition. In order to elucidate the latent reaction mechanism, seven sequential temperature subzones were divided to acquire the most probable mechanism function G(α) and corresponding kinetic parameters. The results indicated that, owing to the high reservoir pressure, generated enormous heat in LTO stage had a significant acceleration to initiate and sustain the low temperature combustion process, which in some degree was conducive to update and expand the understanding of the low temperature in-situ combustion mode of air injection in low permeability and tight oil reservoirs via fracturing reservoir matrix.

COMPOSITION OF LIGHT HYDROCARBONS IN JURASSIC TIGHT OILS IN THE CENTRAL SICHUAN BASIN, CHINA: ORIGIN AND SOURCE ROCK CORRELATION

Crude oil reserves in tight Middle and Lower Jurassic reservoirs are of increasing exploration interest in the central Sichuan Basin, SW China. However, the origin of these “tight oils” is poorly understood. In this study, sixteen samples of light oils/condensates from tight Middle and Lower Jurassic reservoir rocks were analysed using gas chromatography (GC) and isotope ratio mass spectrometry to investigate the oils’ origin and to classify them into genetic families. The tight oils can be divided into two families. Family I oils occur in the Gongshanmiao oilfield where reservoir units comprise the Da'anzhai Member of the Lower Jurassic Ziliujing Formation, the Lower Jurassic Lianggaoshan Formation, and the First Member of the Middle Jurassic Shaximiao Formation. Family I oils are characterized by relatively low values of the methylcyclohexane (MCH) and cyclohexane (CH) indexes, low values of Mango's parameter K2 for light hydrocarbon composition, and relatively negative δ13C values ranging from ‐30.8‰ to ‐28.9‰. Family I oils are inferred to be self‐sourced by lacustrine shales in the Da'anzhai Member and the Lianggaoshan Formation in the study area, both of which are rich in sapropelic organic matter. These source rocks also charged reservoirs in the First Member of the Shaximiao Formation. By contrast, the newly discovered Family II oils, which occur at the Jinhua oilfield and the as‐yet undeveloped Qiulin and Bajiaochang structures, are reservoired in the Second Member of Shaximiao Formation. Family II oils have higher values of the MCH index, CH index and Mango's K2 parameter, and δ13C values varying from ‐27.5‰ to ‐25.4‰. These oils have similar light hydrocarbon compositions and δ13C values to oils derived from source rocks in the Upper Triassic Xujiahe Formation which contain dominantly humic organic matter. Family II oils are therefore inferred to be derived from the coaly mudstones in the Xujiahe Formation.The different compositions of the tight oils in the First and Second Members of the Shaximiao Formation appear to be controlled by the distribution and thickness of source rocks in the study area. Thus, the Gongshanmiao oilfield where Family I oils occur in the First Member is close to the depocentre of source rocks in the Da'anzhai Member and Lianggaoshan Formation. These source rocks are inferred to have charged the First Member reservoirs which may also be present in nearby oil‐ and gas‐bearing structures such as Nanchong and Yingshan. By contrast, Family II oils occur in tight reservoirs in the Second Member in areas with thick successions of Upper Triassic Xujiahe Formation mudstone source rocks, such as the Jinhua oilfield. In areas where both source rocks are present such as the Zhongtaishan and Lianchi oilfields, Shaximiao Formation reservoirs appear to contain both Family I and Family II oils.

The occurrence of tight oil in the Chang 8 lacustrine sandstone of the Huaqing area, Ordos Basin, China: Insights into the content of adsorbed oil and its controlling factors

Tight oil is a great potential resource for unconventional oil exploration and development. Determining the content of adsorbed tight oil in sandstone reservoirs and the factors controlling its content is crucial for the evaluation and development of tight oil resources. Using fluorescence petrography, environmental scanning electron microscopy, porosity as well as permeability analyses, high-pressure mercury intrusion, and nuclear magnetic resonance imaging, the present study analyzed the occurrence form, location, and relative content of free and adsorbed tight oils and effect of controlling factors on the content of adsorbed tight oil in sandstone reservoirs of the Chang 8 member in the Huaqing area of the Ordos Basin. The free tight oil mainly exists in residual intergranular, intergranular dissolved, intragranular dissolved, and dissolution-enlarged pores as well as some throats in the form of flakes with various areas and slender strips. The adsorbed tight oil mainly occurs on the surfaces of the mineral particles and mica fragments as well as in fractures, some throats or the intragranular as well as intergranular dissolved pores in the form of films with variable thicknesses and long strips. The lower limit of the pore radius at which free tight oil occurs in sandstone is approximately 0.1 μm and the adsorbed tight oil occurs on the surface of mineral particles and in spaces with pore radii of 0.02–0.3 μm. The contribution of free tight oil to total tight oil in the present study has highest and lowest content of 60.95% and 32.48%, respectively, with an average content of 50.14%. The contribution of adsorbed tight oil to total tight oil has highest and lowest content of 67.52% and 39.05%, respectively, with an average content of 49.86%. The content of adsorbed tight oil is generally proportional to the median pressure and inversely proportional to the porosity as well as permeability of the reservoir; particularly, porosity is relevant. The content of adsorbed tight oil is inversely proportional to the quartz content and directly proportional to the feldspar, carbonate cement, and clay mineral content of the sandstone.

Depositional conditions and accumulation models of tight oils in the middle Permian Lucaogou Formation in Junggar Basin, northwestern China: New insights from geochemical analysis

Depositional conditions and accumulation models of tight oils in the middle Permian Lucaogou Formation in Junggar Basin, northwestern China: New insights from geochemical analysis

How Is Ultrasonic-Assisted CO2 EOR to Unlock Oils from Unconventional Reservoirs?

CO2 enhanced oil recovery (EOR) has proven its capability to explore unconventional tight oil reservoirs and the potential for geological carbon storage. Meanwhile, the extremely low permeability pores increase the difficulty of CO2 EOR and geological storage processing in the actual field. This paper initiates the ultrasonic-assisted approach to facilitate oil–gas miscibility development and finally contributes to excavating more tight oils. Firstly, the physical properties of crude oil with and without ultrasonic treatments were experimentally analyzed through gas chromatography (GC), Fourier-transform infrared spectroscopy (FTIR) and viscometer. Secondly, the oil–gas minimum miscibility pressures (MMPs) were measured from the slim-tube test and the miscibility developments with and without ultrasonic treatments were interpreted from the mixing-cell method. Thirdly, the nuclear-magnetic resonance (NMR) assisted coreflood tests were conducted to physically model the recovery process in porous media and directly obtain the recovery factor. Basically, the ultrasonic treatment (40 KHz and 200 W for 8 h) was found to substantially change the oil properties, with viscosity (at 60 °C) reduced from 4.1 to 2.8 mPa·s, contents of resin and asphaltene decreased from 27.94% and 6.03% to 14.2% and 3.79%, respectively. The FTIR spectrum showed that the unsaturated C-H bond, C-O bond and C≡C bond in macromolecules were broken from the ultrasonic, which caused the macromolecules (e.g., resin and asphaltenes) to be decomposed into smaller carbon-number molecules. Accordingly, the MMP was determined to be reduced from 15.8 to 14.9 MPa from the slim-tube test and the oil recovery factor increased by an additional 11.7%. This study reveals the mechanisms of ultrasonic-assisted CO2 miscible EOR in producing tight oils.

Imidazole-Based Ionic Liquids with BF4 as the Counterion Perform Outstanding Abilities in Both Inhibiting Clay Swelling and Lowing Water Cluster Size.

Promoting fluid transportation in porous media has important applications in energy, pedology, bioscience, etc. For this purpose, one effective way is to prevent swelling through surface modification; however, it is far from enough in real cases, such as ultra-low permeability reservoirs and tight oils. In this study, we considered the comprehensive effects of inhibiting clay swelling, flocculation performance, reducing water clusters and interfacial tension and developed a series of imidazole-based tetrafluoroborate ionic liquids (ILs) with different lengths of alkyl chains. Through measurements of anti-swelling rates, XRD, SEM, 17O NMR, molecular dynamics simulation, zeta potential, flocculation evaluation, interfacial tension and a core flooding experiment based on ultra-low permeability reservoirs, the relationships between the molecular structure and physicochemical properties of ILs have been revealed. Interestingly, one of the selected ILs, imidazole-based tetrafluoroborate ILs (C8-OMImBF4), shows excellent performance, which is helpful to design an effective strategy in promoting fluid transportation in narrow spaces.

Method for Determining Lowest Oil Price Limit by Developing Tight Peripheral Oil in Daqing

The outer oil field of Daqing is a low-permeability oil field, which has a large proportion of the tight oil reserves. Due to the high development costs of the tight oils, many fields are difficult to reach the standard of economic evaluation. It increases the difficulty in optimizing reserves and use of reserves. In the process of the development of the tight oil field, it is important to determine the limit of starting oil price. It is also an important basis for determining the launch of the oil field development project. The evaluation of present value method does not consider the change process of external conditions and has certain limitations. However, the introduction of investment option value method for evaluation can fully consider changes in oil prices and other external factors, and provide a more realistic assessment of the oilfield development process. In the case of low oil prices, some tight oil fields can also be used effectively, which improves the efficiency of resource utilization, increases the scale of reserves utilization, and solves the problem of optimization and evaluation of reserves.

Impact of Centrifuge-Separated Fractions from Light Tight Oils on the Propensity and Mechanisms of Fouling, and Improved Crude Oil Fouling Potential Prediction Model

Processing of light tight oils (LTOs) and their blends is challenged with their high fouling propensity. In this study, their fouling potential was attributed to fractions from centrifuge-accelerat...

Application of Rare-Earth Elements and Comparison to Molecular Markers in Oil–Source Correlation of Tight Oil: A Case Study of Chang 7 of the Upper Triassic Yanchang Formation in Longdong Area, Ordos Basin, China

The biomarker features of 10 Chang 7 crude oil samples were investigated by gas chromatography–mass spectrometry (GC–MS), and the rare-earth element (REE) compositions of 16 Chang 7 and Chang 8 crude oil samples were determined by inductively coupled plasma–mass spectrometry (ICP–MS) for the first time in Longdong area. Oil–source correlation analysis was improved by biomarkers and REEs. The distribution and relative ratios of a series of biomarker parameters in saturated hydrocarbons and aromatic hydrocarbons of crude oil samples indicate that Chang 7 tight oil has already reached the mature stage. The organic matter mainly comes from lower aquatic organisms of algae, with some contribution of micro-organisms and bacteria, while the forming environment of tight oil is mainly the transitional environment of sub-oxidizing to sub-reducing. The V/(V + Ni) and Ni/Co ratios of crude oil samples suggest that the specific redox conditions of Chang 71 and Chang 72 samples were slightly oxic, while Chang 73 and Chang 8 samples were formed under an anoxic environment. The results of both biomarker-based and REE-based oil–source correlation analysis indicate that Chang 71 and Chang 72 tight oils come from Chang 7 mudstone, while most of the Chang 73 tight oils are from Chang 7 oil shale, with part of mixed from Chang 7 mudstone. This recognition may indicate that Chang 7 mudstone and oil shale are two relatively independent hydrocarbon self-generation and near-storage systems. The analysis results demonstrate that the REE composition in crude oil is an efficient and accurate tool for oil–source correlation in the petroleum system.

RETRACTED ARTICLE: Light hydrocarbon geochemistry: insight into oils/condensates families and inferred source rocks of the Woodford\u2013Mississippian tight oil play in North-Central Oklahoma, USA

The Woodford–Mississippian “Commingled Production” is a prolific unconventional hydrocarbon play in Oklahoma, USA. The tight reservoirs feature variations in produced fluid chemistry usually explained by different possible source rocks. Such chemical variations are regularly obtained from bulk, molecular, and isotopic characteristics. In this study, we present a new geochemical investigation of gasoline range hydrocarbons, biomarkers, and diamondoids in oils from Mississippian carbonate and Woodford Shale. A set of oil/condensate samples were examined using high-performance gas chromatography and mass spectrometry. The result of the condensates from the Anadarko Basin shows a distinct geochemical fingerprint reflected in light hydrocarbon characterized by heptane star diagrams, convinced by biomarker characteristics and diamantane isomeric distributions. Two possible source rocks were identified, the Woodford Shale and Mississippian mudrocks, with a variable degree of mixing. Thermal maturity based on light hydrocarbon parameters indicates that condensates from the Anadarko Basin are of the highest maturity, followed by “Old” Woodford-sourced oils and central Oklahoma tight oils. These geochemical parameters shed light on petroleum migration within Devonian–Mississippian petroleum systems and mitigate geological risk in exploring and developing petroleum reservoirs.

Study on Influencing Factors of Microscopic Occurrence of Tight Oil in Nanoscale Pore Throat.

Tight oil is widely distributed around the world, and industrialized exploitation has been developed and applied in North America, greatly alleviating the contradiction between supply and demand of energy. The main storage space of tight oil reservoirs is micro-nano pores, and a reliable method for studying the occurrence of tight oil in micro-nano pores has not been studied. In this paper, the microscopic occurrence of tight oils in the Songliao Basin, Ordos Basin, and Tarim Basin in China are studied in combination with nuclear magnetic resonance (NMR) and field emission scanning electron microscopy (FE-SEM) scanning techniques. A method for characterizing the storage space, occurrence state, and influencing factors of tight oil based on SEM and NMR was proposed. The results show that the storage space of tight oil reservoirs is nanoscale cracks and pores. Mainly, these are distributed on the scale of less than 1 μm and more than 10 μm, the volume of porecracks is less than 1 μm, which account for more than 80% of the total volume. This indicates that the tight oil mainly exists in the nanoscale pore throat. The scattered distribution of crude oil in the black shape of oil spot is mainly in the micro-nano pores, and the crude oil content in the micro-cracks is small, indicating that nanoscale cracks are the main space for the occurrence of tight oil. However, some micro-cracks can penetrate oil spots or oil stains, and can connect the oil spots with scattered distribution, which will greatly improve the mobility of crude oil. In addition, oil spot accumulation areas often develop illite and illite/smectite mixed-layer, and clay minerals have developed nanoscale pores. The crude oil and clay minerals have certain associated characteristics. This study is of great significance for understanding the law of the occurrence and migration of tight oil and the basic theoretical research and technological innovation of the development of tight oil reservoir.

ENGlobal signs $20 M-plus contract to supply modular hydrogen plant for renewable diesel facility

Light tight oils are in general high API gravity feedstocks and lesser amounts of contaminants than many conventional crude oils. However, there is a series of challenges that need to be solved to ensure uninterrupted transportation and refining of these tight oils. Unlike most conventional crude oils, tight oils are light, sweet crude oils, with a high paraffin content, high volatility, and low acidity. They also have minimal asphaltene and resin constituents as well as varying contents of filterable solids, hydrogen sulfide (H2S), and mercaptans (RSH). In addition, the streams from a tight oil production region can have significant variability, with colors ranging from pale amber to black.The challenges associated with the production of tight oils are a function of their compositional complexities and the varied geological formations where they are found. These oils are light, but they are very waxy and reside in oil-wet formations. These properties create some of the main difficulties associated with tight oil extraction. Such problems include scale formation, salt deposition, paraffin wax deposits, destabilized asphaltenes, corrosion and bacteria growth. Multi-component chemical additives are added to the stimulation fluid to control these problems.This chapter presents an introduction to the main challenges encountered with these feedstocks, including issues related to storage, transportation, and refining.

High abundance of carotanes in the brackish-saline lacustrine sediments: A possible cyanobacteria source?

The organic-rich oil shales of low maturity and tight oils from the Middle Permian Lucaogou Formation were formed in a brackish-saline lacustrine environment in the Jimusaer Sag, Junggar Basin. They are characterized by remarkably abundant β-carotane and γ-carotane. The biological sources and favourable sedimentary environments of carotanes formation remain obscure. Organic geochemical analyses of 17 oil shales and 20 tight oils from the Jimusaer Sag reveal that reducing, evaporitic and carbonate-rich, shallow water environment is favourable for β-carotane accumulation. Geochemical studies show that carotane abundance is controlled by both source of organic matter and sedimentary environment rather than thermal maturity in the study area. Even though both higher plants and microalgae are reported to be precursors of carotanes, cyanobacteria may be the main biological sources of carotanes in the Lucaogou Formation based on cyanobacteria-derived biomarkers, such as the C39 2,6-dimethyl benzene-substituted isoprenoid, 2α-methylhopanes, 7- and 8-monomethylhepadecanes. The airborne volcanic ash containing ample elements (e.g. Mg and Fe) caused by the intermittent volcanic eruptions during the Middle Permian most likely contributed to the flourish of cyanobacteria in the study area.

Influence of Gas and Oil State on Oil Mobility and Sweet-Spot Distribution in Tight Oil Reservoirs from the Perspective of Capillary Force

Summary The coexisting free gas, solution gas, and oil in a tight oil reservoir, constrained by the capillary force of the micrometer/nanometer pore/pore-throat system, are of crucial importance to the sweet spot of a tight oil reservoir. Equations of modified total capillary force for the liquid phase are proposed to indicate the tight oil mobility in situ, and are derived from the Kelvin capillary force equation, the Peng-Robinson (PR) equation of state (EOS) (Robinson et al. 1977), and the Van-Laar (VL) equation (Renon and Prausnitz 1968). In addition, relationships between the vapor/liquid state, phase-flow state for production, and gas/oil ratio (GOR) are established in correspondence with the production data of North American and Chinese (Yanchang) tight oil plays. The following conclusions can be drawn. We proposed a modified total capillary force function to indicate the tight oil mobility in situ, using the PR EOS method and the EOS+λ (VL equation) method. We identified five phase stages according to the gas volume ratio ( yi) in situ: the single-phase oil flow stage, the multiphase transient-flow stage, the multiphase stable-flow stage, the multiphase supercritical-flow stage, and the single-phase gas flow stage. Tight oils are more mobile in three stages: near the critical point of yi-critical(1), such as in the Yanchang and Bakken tight oils; at the transition zone between oil and wet-gas zones before yi-critical(2), such as in the Eagle Ford tight oil; and between the yi-critical(2) and yi-critical(3) in a gas-condensate state, which is at the transition zone between wet-gas and dry-gas zones.

Analysis of Test Method for Oil and Water Relative Permeability Curve in Tight Reservoirs

With the development of the international economy, the global demand for oil and gas resources has continued to increase in recent years. The development of high-permeability reservoirs has reached the middle and late stages, and resources are depleting. With the large-scale successful exploitation of tight oils in North America, low-permeability tight reservoirs have gradually become the main object of development. Compared with conventional reservoirs, tight reservoirs mainly develop nano- scale pore systems. It causes poor reservoir properties, high interlayer heterogeneity, low porosity and permeability, and generally no natural productivity in reservoirs. In tight reservoirs, the flow of oil-water phases is not affected by the scale, but also the wettability, they make the oil and water phases seepage more complicated. In this paper, the natural core of a tight reservoir in Daqing was selected. Experiments were carried out using two experimental methods: steady-state method and non-steady-state method. The characteristics of oil and water phases percolation in tight reservoirs were analyzed. The results by comparing the two experimental methods showed the steady state method is suitable for measuring the oil and water relative permeability curve of tight reservoirs.

Classification Approach to Assay of Crude Oils with Different Physicochemical Properties and Quality Parameters

An approach to crude oil assay based on the consistent application of two heterogeneous classifications of oils is proposed: according to the quality index and physicochemical parameters. The methodological issues of the classification approach to oil analysis, implemented in the form of a two-stage procedure, are described. The approach is illustrated by an example of analysis of the characteristics features of different types of tight oils in Russia. The analysis used data from 25.190 oil samples with abnormal properties and 10 500 oil samples with complex modes of occurrence. At the first stage, the analysis has been carried out using the classification of tight oils according to the quality index; as a result, the oils were divided into three homogeneous classes: low, medium, and high quality oils. At the second stage of the analysis, the classification of oils by physicochemical characteristics has been used, taking into account the density; viscosity; sulfur, resin, asphaltene, wax, vanadium, nickel, and light end contents; gas saturation of oil; etc. The analysis made it possible to establish the characteristic features of the physicochemical properties of tight oils belonging to different quality classes.

Natsukawaishi and Nishiyama oil field

The writer presents an outline of the paper, which is entitled “Natsukawaishi” and Nishiyama oil field and written by Ikebe （1955）, and examines the migration and accumulation of crude oils in the Nishiyama field using new geological and geochemical data. The deeper part of this field is probably the remnant exploration target because of poor structural control and the possibility of tight oils.

Tight reservoir oiliness numerical simulation based on a Markov chain Monte Carlo (MCMC) method: A case study of the upper Triassic Yanchang-6 formation (T3ch6 Fm.) outcrop of Ordos Basin

Numerical simulation of the tight reservoir oiliness has always been an important issue in tight oil resources exploration. It is hard to take some special situations into simulations such as the micro-nano thermodynamic system, the multi-fluid phase behavior, and the superimposed tectonic stress field of tight oil reservoirs. In our research, we use MCMC methods to simulate the tight reservoir oiliness constrained by some visualized, spatial-related and interacted geological parameters based on the statistic Bayesian theory, instead of taking the complicated accumulation mechanism into consideration. In this research, we built a posterior probability density distribution (Post-PDD) matrix using the spatial relation between oiliness, fracture, and lithofacies parameters of a typical Yanchang tight oils outcrop. In the simulation, one Monte Carlo Step (MCS) was settled N = 80 × 36 × 5000, where 80 and 36 represent the horizontal and longitude grid number respectively, and 5000 represents the sampling times for each grid. In total, simulations of 50000 MCSs were made for each realization. For the simulation results, the variation in the fluctuating trends of the fitted and actual values matched well with the analytic variogram for the MCMC realizations. Additionally, we found that the simulation uncertainty was consistent with the reservoir heterogeneity. Even though the lamina, intercalation or the barrier was not defined in the grid model, the oiliness realization of the different types was remarkably consistent with the reservoir heterogeneity, which may be caused by the sedimentary rhythm similitude between different scale sedimentary cycles, particularly in the lacustrine tight reservoir.

Palaeostructure, evolution and tight oil distribution of the Ordos Basin, China

Whether or not the tight oil in the Triassic Yanchang Formation of the Ordos Basin is controlled by structural factors is a controversial issue, the relationship between the structural factors of the strata and the distribution of tight oil is limited to the study of current structures. The traditional view is that structural factors have no obvious control over the formation and distribution of the oil reservoir. Taking the Chang 8 member of the Triassic Yanchang Formation in the Ordos Basin as an example, this paper studies respectively the burial of strata-hydrocarbon generation history of the individual well and the structural evolution history of strata in the basin by using software tools of the Genex burial-hydrocarbon generation history restoration and TemisFlow evolution of stratigraphic structures. It is considered that the hydrocarbon generation period of the source rock of the Triassic Yanchang Formation in the Ordos Basin is from early Middle Jurassic to end of Early Cretaceous. By reconstructing the evolution and structure of the Chang 8 member during the hydrocarbon accumulation period, combined with a comprehensive analysis on the distributional characteristics of the Chang 8 oil reservoir, we found the palaeoslopes and palaeohighs of the Chang 8 reservoir to represent areas in which tight oils were distributed. Palaeo-structural characteristics of the target layer exhibit control over the Chang 8 reservoir. The new theory underlying tight oil exploration, which is based on the recovery of the palaeogeomorphology of the target layer during the hydrocarbon generation period, incorporates the vital roles of key controlling factors over tight oil accumulation, so that the mind-set on tight oil exploration in the Ordos Basin has evolved.

Geochemical characteristics of the Triassic Chang 7 lacustrine source rocks, Ordos Basin, China: Implications for paleoenvironment, petroleum potential and tight oil occurrence

The fact that high-quality lacustrine source rocks (generally shale and mudstone) control the formation and distribution of conventional and unconventional oil and gas reservoirs in lacustrine basins has been well-accepted in petroleum exploration and exploitation. Taking the Chang 7 lacustrine source rocks in the Ordos Basin as an example, several points having been reached are as follows. (1) The Chang 7 source rocks possess an excellent source rock potential, and the shales hold a better potential than the mudstones. (2) The paleoenvironments of the Chang 7 source rocks were sub-reducing to sub-oxidizing conditions and fresh- and brackish-water depositional environments with a maximum water depth of 150 m. The organic matter origins of the source rocks are mainly plankton, algae, bacteria and other aquatic microorganisms. (3) The beginning time of the oil generation of the Chang 7 source rocks is at 165 Ma, and the peak oil generation occurred during 115–95 Ma. The cumulative amounts of oil generation are up to 4711 × 103 t/km2 and the ratios of peak generation amounts to cumulative generation amounts are >50%. The beginning timing and peak generation timing of the shales are earlier than those of the mudstones, respectively, and the cumulative oil generation amount of the shales is higher than that of the mudstones, indicating a better oil generation potential of the shales. (4) Due to the more remained oil possessed in the shales, the hydrocarbon expulsion threshold of the Chang 7 shales (2560 m) is deeper than that of the Chang 7 mudstones (2080 m). (5) The occurrences of the Chang 8–6 tight oils are predominantly controlled by the outer boundary of the Chang 7 source rocks distribution, while the transition areas between thickness, TOC, and RO high value centers are the accumulation and enrichment zones. The Chang 7 shales controlled the occurrence of the Chang 8 tight oil reservoirs and the Chang 7 mudstones controlled the occurrence of the Chang 7 and Chang 6 tight oil reservoirs.