Major controlling factors on hydrocarbon generation and leakage in South Atlantic conjugate margins: A comparative study of Colorado, Orange, Campos and Lower Congo basins

2013 ◽  
Vol 604 ◽  
pp. 172-190 ◽  
Author(s):  
Gabriela Marcano ◽  
Zahie Anka ◽  
Rolando di Primio
Keyword(s):  
Comparative Study ◽  
South Atlantic ◽  
Controlling Factors ◽  
Hydrocarbon Generation ◽  
Conjugate Margins

Pore characteristics and dominant controlling factors of overmature shales: A case study of the Wangyinpu and Guanyintang Formations in the Jiangxi Xiuwu Basin

2018 ◽  
Vol 6 (2) ◽  
pp. T393-T412 ◽  
Author(s):  
Fenglin Gao ◽  
Yan Song ◽  
Zhuo Li ◽  
Zhenxue Jiang ◽  
Zhiye Gao ◽  
...  
Keyword(s):  
Image Processing ◽  
Gas Adsorption ◽  
Controlling Factors ◽  
Mature Stage ◽  
Jiangxi Province ◽  
Type I ◽  
Hydrocarbon Generation ◽  
Pore Characteristics ◽  
Total Contribution ◽  
Main Controlling Factors

Because of the great potential for hydrocarbon generation, the Lower Cambrian Wangyinpu and Guanyintang Formations of the Jiangxi Xiuwu Basin have become the most important targets for shale-gas exploration in the Jiangxi province. We investigate the pore characteristics and main controlling factors of overmature shale using field emission-scanning electron microscopy, image-processing software (i.e., the Particles [Pores] and Crack Analysis System), X-ray diffraction, and gas-adsorption experiments. The results show that the shales have a high abundance of organic matter (OM), over maturity, and highly siliceous mineral content. The kerogen type is identified as type I. OM pores are the most developed, followed by interparticle (interP) pores and intraparticle (intraP) pores. We combine complementary image processing and gas-adsorption methods to reveal that micropores are mainly from OM pores; mesopores are from OM pores and interP pores; and macropores are from OM pores, interP pores, and intraP pores. Although the number of micropores is at a maximum, the total contribution of mesopores and macropores to the pore volume (PV) is larger than that of micropores. However, the specific surface area (SSA) is mainly from the micropores. OM content and maturity are the main controlling factors for the development of pore structures. Because of overmaturity, OM loses its potential for hydrocarbon generation and new pores cannot be produced. Gas loss leads to reservoir pressure drop, and the pores generated during the mature stage collapse and even disappear because they lack support. Therefore, PV, SSA, and porosity decrease when the OM content is more than 10%. When the OM content is less than 10%, most of the OM pores are preserved because they are protected by the skeleton particles.

A comparative study of endolithic microborings in basaltic lavas from a transitional subglacial–marine environment

2009 ◽  
Vol 8 (1) ◽  
pp. 37-49 ◽  
Author(s):  
Claire R. Cousins ◽  
John L. Smellie ◽  
Adrian P. Jones ◽  
Ian A. Crawford
Keyword(s):  
Comparative Study ◽  
Statistical Study ◽  
Controlling Factors ◽  
Basaltic Glass ◽  
Aqueous Alteration ◽  
The Past ◽  
Lower Elevation ◽  
Show Evidence ◽  
Freshwater Environments ◽  
Basaltic Lavas

AbstractSubglacially erupted Neogene basaltic hyaloclastites in lava-fed deltas in Antarctica were found to contain putative endolithic microborings preserved in fresh glass along hydrous alteration boundaries. The location and existence over the past 6 Ma of these lava deltas has exposed them to successive interglacials and subsequent percolation of the hyaloclastite with marine water. A statistical study of the hyaloclastites has found that endolithic microborings are distinctly more abundant within samples that show evidence for marine alteration, compared with those that have remained in a strictly freshwater (glacial) environment. Additionally, correlation between elevation and the abundance of microborings shows endolithic activity to be more prolific within lower elevation samples, where the hyaloclastites were influenced by marine fluids. Our study strongly suggests that endolithic microborings form more readily in marine-influenced, rather than freshwater environments. Indeed, marine fluids may be a necessary precondition for the microbial activity responsible. Thus, we suggest that the chemistry and origin of alteration fluids are controlling factors on the formation of endolithic microborings in basaltic glass. The study also contributes to the understanding of how endolithic microborings could be used as a biosignature on Mars, where basaltic lavas and aqueous alteration are known to have existed in the past.

Hotspot origin for asymmetrical conjugate volcanic margins of the austral South Atlantic Ocean as imaged on deeply penetrating seismic reflection lines

2019 ◽  
Vol 7 (4) ◽  
pp. SH71-SH97 ◽  
Author(s):  
Kyle Reuber ◽  
Paul Mann ◽  
Jim Pindell
Keyword(s):  
Oceanic Crust ◽  
Seismic Reflection ◽  
Seismic Refraction ◽  
South Atlantic ◽  
Plate Motion ◽  
Basin Evolution ◽  
Spreading Ridge ◽  
The South ◽  
Volcanic Material ◽  
Conjugate Margins

We have interpreted 27,550 km of deep-penetrating, 2D-seismic reflection profiles across the South Atlantic conjugate margins of Uruguay/Southern Brazil and Namibia. These reflection profiles reveal in unprecedented detail the lateral and cross-sectional, asymmetrical distribution of voluminous, postrift volcanic material erupted during the Barremian-Aptian (129–125 Ma) period of early seafloor spreading in the southernmost South Atlantic. Using this seismic grid, we mapped the 10–200 km wide, continental margin-parallel limits of seaward-dipping reflector (SDR) complexes — that are coincident with interpretations from previous workers using seismic refraction data from the South American and West African conjugate margins. Subaerially emplaced and tabular SDRs have rotated downward 20° in the direction of the mid-Atlantic spreading ridge and are up to 22 km thick near the limit of continental crust. The SDR package is wedge shaped and thins abruptly basinward toward the limit of oceanic crust where it transitions to normal, 6–8 km thick oceanic crust. We have developed a model for the conjugate rifted margins that combine diverging tectonic plates and northwesterly plate motion relative to a fixed mantle position of the mantle plume. Our model explains an approximately 30% higher volume of SDRs/igneous crust on the trailing Namibian margin than on the leading Brazilian margin during the syn- and postrift phases. Our model for volcanic margin asymmetry in the South Atlantic does not require a simple shear mechanism to produce the asymmetrical volcanic material distribution observed from our data and from previously published seismic refraction studies. Determining the basinward extent of the extended continental basement is crucial for understanding basin evolution and for hydrocarbon exploration. Although these conjugate margins have evolved asymmetrically, their proximity during the early postrift stage suggests a near-equivalent, early basin evolution and similar hydrocarbon potential. Understanding the tectonic and magnetic processes that produce these observed asymmetries is critical for understanding volcanic passive margin evolution.

scholarly journals Physical modeling of salt structures in the middle south Atlantic marginal basins and their controlling factors

2021 ◽  
Vol 48 (1) ◽  
pp. 136-145
Author(s):  
Yixin YU ◽  
Chongzhi TAO ◽  
Shuaiyu SHI ◽  
Jinyin YIN ◽  
Changwu WU ◽  
...  
Keyword(s):  
Physical Modeling ◽  
South Atlantic ◽  
Controlling Factors

scholarly journals The Genetic Mechanism and Evolution Process of Overpressure in the Upper Ordovician–Lower Silurian Black Shale Formation in the Southern Sichuan Basin

Minerals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 238
Author(s):  
Xiaoqi Wang ◽  
Yanming Zhu
Keyword(s):  
Shale Gas ◽  
Southern China ◽  
Pressure Coefficient ◽  
Fluid Pressure ◽  
Initial Pressure ◽  
Gas Production ◽  
Controlling Factors ◽  
Formation Mechanisms ◽  
Hydrocarbon Generation ◽  
Upper Ordovician

The overpressure phenomenon is a widespread occurrence in unconventional shale gas reservoirs. Multiple overpressure shale gas fields were discovered in southern China, and there is no doubt that the gas production per well increases with increasing pressure coefficient (the ratio of the reservoir fluid pressure to the corresponding normal hydrostatic pressure). Thus, successful evaluation and production strategies of organic-rich shale deposits require an understanding of the evolution of the pressure coefficient and its controlling factors in these deposits. In this paper, drilling engineering data of a typical well were collected, and clay mineral tests and overburden diffusion coefficient experiments were conducted. Based on multiphysics simulations, this paper analyzes the overpressure characteristics and formation mechanisms of overpressure in the Longmaxi Formation shale, as well as its geological evolution and controlling factors. The results show that the large amount of shale gas is the cause of overpressure formation rather than disequilibrium compaction. The simulation results show that pressure coefficients of the typical well range from 0.84 to 1.49. The current pressure coefficient increases with increasing pressure coefficient after the last hydrocarbon generation. A large initial pressure coefficient (>1.9), short lifting time (<100 Ma) and small lifting amplitude (<4000 m) are favorable for the preservation of shale gas.

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