Simultaneous Experimental Analysis of Oil Content And Molecular Composition of Shale Fractions

The important research content and basis of exploration and development is to evaluate the reservoir property, oil bearing property, fluidity and compressibility of shale reservoir.The key of exploration and development is to evaluate the oil-bearing and fluidity of shale reservoir.In this paper, the "shale oil content and fine components synchronous experimental analysis device" is used. Five temperature ranges of 30 ℃-90 ℃, 90 ℃-150 ℃, 100 ℃- 200 ℃, 150 ℃-250 ℃ and 250 ℃-300 ℃ were adopted. The heating rate of each temperature segment was 25 ℃ / min, and the final temperature was kept constant for 5 min. The oil content of shale (pyrolysis S1) was cut into five fractions.Simultaneous determination of oil content and molecular composition of shale fractions,and the external standard method was used to evaluate the oil content and fluidity.The results show that the five fractions of shale are mainly composed of nC1-nC9 gas, nC10-nC15 gasoline, nC12-nC20 kerosene, nC15-nC22 diesel oil and nC18-nC26 heavy oil of the first member of Qingshangkou formation in Songliao basin.There are differences in the fractionation and oil content characteristics of samples with different maturity in different wells.The parent material, properties and quality of crude oil are reflected in shale. The higher the maturity of shale oil is, the more light components are, the larger the light / heavy ratio parameter value of (gasoline + kerosene + diesel) and heavy oil is, the better the fluidity is, and the easier to exploit effectively.

Investigation of the Enrichment and Accumulation of Normal Pressure Shale Gas in Anchang Syncline Outside of Sichuan Basin

Gas shales from the Wufeng-Longmaxi Formation in Anchang syncline in northern Guizhou area of Sichuan Basin are stable in distribution and can be classified as type I shale gas reservoir with great resource potential. The exploration and development of shale gas in Anchang syncline have achieved great progress. However, the enrichment rule and accumulation pattern of shale gas in Anchang syncline are still not clear at the present. Gas pressure in the Wufeng-Longmaxi Formations shales in Anchang syncline is normal. The maximum tested gas production in the field ranges from 18,000 to 58,000 m3/d. However, gas production of shale wells varies greatly even in the same platform. In order to understand the shale gas enrichment and accumulation and improve the effective development of shale gas in this area, comparative analyses on the geological characteristics and preservation conditions of gas reservoirs in several typical wells were carried out from the perspective of geology, petrophysics, geophysics, and well logging. Results show that shale gas in Anchang syncline has the characteristics of accumulating in both deep central position and gently wings. Tectonic preservation condition is the key factor to high gas production in Anchang area. The hydrological conditions, syncline structure, fault distribution, and cap rock quality comprehensively control the gas pressure and gas bearing capacity of shale reservoir. According to these factors, an accumulation model of shales with normal gas pressure is established: syncline controls the distribution of gas reservoir; fault controls the boundary of the reservoir; preservation conditions controls gas capacity. The results are benefit for the rolling exploration and development of shale gas in Anchang area, and are important for the development of normal pressure shale gas in northern Guizhou area.

Opening Shot

Yuan-tsung Chen writes her memoir in the midst of growing unrest when in 2019 the Communist rulers try to pass an extradition law in Hong Kong’s Legislative Council. To begin with, they set about “reforming” middle schoolers’ education— for instance, through the Orwellian rewriting of the history of the Cultural Revolution, from the ten-year-long “cataclysm” (Hao Jie—浩劫‎) to the ten years of “arduous exploration and development achievement.” Even according to the official death toll, 1.7 million people perished in the Cultural Revolution. The dead had families or relatives, friends or lovers, so how many more lives were ruined? Yuan-tsung simply cannot accept such a whitewashing without a guilty conscience. She is fully aware of the consequences of confronting the untruth. Nevertheless, she decides to write what she witnessed, saw, and understood as truth.

Enhancing subsalt imaging through advanced identification and suppression of interbed multiples and mode-converted reflections — Gulf of Mexico and Brazil case studies

In our case studies, the success of subsalt exploration and development wells depended heavily on the characterization of highly heterogeneous lacustrine microbial carbonates. Acoustic and elastic inversions have proved to be a good proxy for identification of reservoir quality variation for exploration and development well placements. However, qualitative and quantitative usage of subsalt seismic amplitudes requires proper illumination and good signal-to-noise ratio. If properly imaged, mode-converted reflections and interbed multiples can be complementary to the P-wave image. But, in conventional P-wave-oriented imaging, both types of events cannot be imaged correctly. They appear as coherent noise and negatively impact the overall exploration and development project outcomes, especially in areas with poor illumination. This paper consists of two parts: first, we investigate the potential problems resulting from converted waves and interbed multiples in data from two different basins — the Gulf of Mexico and the Campos Basin in offshore Brazil — and show our approach to attenuate them to reveal the true structures. The second part focuses on advanced identification of interbed multiples in modeling and migration methods. To facilitate the various strategies to attenuate interbed multiples, “interpretation” of the various events plays a significant role. Vertical seismic profile (VSP) data are excellent for the purpose; however, these data are only available at well locations, if they are recorded. As a result of many years of technology advancement, pseudo VSP data can be constructed effectively from standard streamer survey data. Two methods are highlighted in this paper for building pseudo VSP data in a full two-way sense, based on a typical Brazil-type salt model: Marchenko-based processing and full-wavefield migration. Major subsalt plays in the Gulf of Mexico and emerging plays in Brazil should benefit significantly from elimination of these kinds of coherent noise.

Identification of overpressures resulting from undercompaction and hydrocarbon generation in shale dominated settings using well log data

Based on the concepts of organic geochemistry and well log characteristics, we discuss the differences between undercompaction overpressure (UCOP) and hydro-carbon-generating pressurization (HGP) from well logs in the Chang 7 Shale, Ordos Basin. The results revealed that shales have better hydrocarbon generation potential than mudstones. We found the UCOP is characterized by significant changes of acoustic traveltime (AC), compensation neutron (CNL), density (DEN) and resistivity (RT) on the well logs. Whereas the HGP causes obvious changes in the AC and RT logs, minor deviations are generally revealed in the CNL and DEN logs. Further stud-ies revealed that while UCOP occurs primarily in thick shale layers of the sedimentary center, HGP is predominant in the thin shales of the sedimentary edge. The reason for the above difference may be attributed to the ubiquity of the shales associated with HGP, with the variation in Well logs caused by the HGP concealed by the abnormal variation of UCOP. These findings thus revealed the distribution and well log features of abnormal overpressure for the different generating mechanisms, thus providing significant guidance for further exploration and development of the overpressured formations.

Research Progress of High Temperature Resistant Fracturing Fluid System

China has made significant progress in the efficient exploration and development of deep-seated oil and gas wells. Reservoir reformation, as the core tool of high-temperature deep-seated exploration and development, puts forward a strong demand for fracturing fluids. The ultra-high temperature fracturing fluid system developed in my country is mainly divided into two types: ultra-high temperature guar gum fracturing fluid and ultra-high temperature synthetic polyacrylamide fracturing fluid. The high temperature resistant fracturing fluid system is mainly composed of high temperature resistant thickener, high temperature resistant crosslinking agent and temperature stabilizing additives and other additives. Based on indoor research and a large amount of literature, this article summarizes the research and application of high temperature resistant fracturing fluid system, high temperature resistant thickener, high temperature resistant crosslinking agent and temperature stabilizing additives in my country in recent years, and pointed out the shortcomings and limitations of the high-temperature fracturing fluid, the technical direction of the development of high-temperature resistant fracturing fluid technology is proposed.

Role Played by Oil Emplacement in Controlling Pore Network Evolution of Tight Sandstones

Whether oil emplacement and diagenetic sequences provoke, deteriorate, or have no effect on pore network evolution, as implied by recent tests and theoretical analysis, are critical factors in forecasting hydrocarbon exploration and development potentials. Therefore, a systematic investigation on the effect of oil emplacement of tight sandstones is conducted to study the importance of this behavior on the pore evolution path. This study evaluated the role played by oil emplacement and diagenesis in the pore network evolution of Upper Triassic tight sandstones in the Ordos Basin. To help provide a comprehensive understanding, we have used a multidisciplinary method including physical properties, casting thin section, scanning electron microscope, X-ray diffraction, fluorometric, and inclusion analysis. The results demonstrate that the sandstones could be divided into four groups based on new criteria: calcareous sandstone, high soft component sandstone, low soft component sandstone with continual oil emplacement, and low soft component sandstone with intermittent oil emplacement. The physical properties of those types of sandstones were gradually reduced. Quartz cement captured hydrocarbon, carbonate captured hydrocarbon, free hydrocarbon, and adsorbed hydrocarbon were the four main kinds of hydrocarbons. The maturity of those sandstones was decreased progressively, indicating that the formation time of those hydrocarbons was favorable to maturity. Four stages of oil emplacement happened, and large-scale emplacement mainly occurred in the late Jurassic and early Craterous. The evidence demonstrated that tight sandstones’ high porosity could be attributed to positive diagenetic contributions with a complex interplay of chemical compaction, early formed clays, and large-scale oil emplacement. This work would provide new sights for a better understanding of the tight oil accumulation modes, and the findings could be applied in the hydrocarbon exploration and development field.

Multiple Influences of Paleogeography, Sequence Stratigraphy, and Fold Structure on Coalbed Methane Accumulation in the Lopingian (Late Permian) of Junlian Coalfield, SW China

Junlian coalfield is one of the main targets for coalbed methane (CBM) exploration and development in the southwest China. Based on field geological survey, core observation, gas content statistics, coal maceral composition, vitrinite reflectance ( R O ), proximate analysis and trace element test, lithological types, lithofacies, sedimentary environment, and structural analysis, this research established the sequence stratigraphy frame, revealed the plane distribution characteristics of sedimentary facies, and defined CBM accumulation mode. The results show that six rock types were identified and further subdivided into twenty lithofacies types. Four types of sedimentary systems such as alluvial plains, delta, lagoon-tidal flat, and carbonate platform were summarized according to their combination characteristics. Additionally, 12-14 fourth-order sequences and three third-order sequences CSI, CSII, and CSIII were divided, and a sequence stratigraphic framework of the Lopingian coal-bearing series was established. Among them, the features of third-order sequence CSIII paleogeography from west to east are alluvial plains, deltas, lagoon-tidal flats, and limited carbonate platforms. Thick coal seams are mainly developed in the sedimentary environment of tidal flats, delta plains, and floodplains behind banks. Closely related to coal seam thickness, gas contents of Lopingian coal seams are generally higher than 8 m3/t, except the low level in northwest and partial denudation areas. CBM accumulation is significantly controlled by the fold structure, and the hydraulic plugging effect makes the syncline core favorable for CBM accumulation. Furthermore, favorable geostress conditions enable the secondary anticline to become a favorable area for CBM accumulation when the sealing conditions are better. This research will provide a theoretical guide for the exploration and development of CBM in the study area.