Burial dissolution of feldspar and carbonate minerals has been proposed to generate large volumes of secondary pores in subsurface reservoirs. Secondary porosity due to feldspar dissolution is ubiquitous in buried sandstones; however, extensive burial dissolution of carbonate minerals in subsurface sandstones is still debatable. In this paper, we first present four types of typical selective dissolution assemblages of feldspars and carbonate minerals developed in different sandstones. Under the constraints of porosity data, water–rock experiments, geochemical calculations of aggressive fluids, diagenetic mass transfer, and a review of publications on mineral dissolution in sandstone reservoirs, we argue that the hypothesis for the creation of significant volumes of secondary porosity by mesodiagenetic carbonate dissolution in subsurface sandstones is in conflict with the limited volume of aggressive fluids in rocks. In addition, no transfer mechanism supports removal of the dissolution products due to the small water volume in the subsurface reservoirs and the low mass concentration gradients in the pore water. Convincing petrographic evidence supports the view that the extensive dissolution of carbonate cements in sandstone rocks is usually associated with a high flux of deep hot fluids provided via fault systems or with meteoric freshwater during the eodiagenesis and telodiagenesis stages. The presumption of extensive mesogenetic dissolution of carbonate cements producing a significant net increase in secondary porosity should be used with careful consideration of the geological background in prediction of sandstone quality.
#1Guanghui Yuan(China University of Petroleum)H-Index: 12
#2Yingchang Cao(China University of Petroleum)H-Index: 20
Last. Fu-Lai Li(China University of Petroleum)H-Index: 2
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Abstract The feldspar group is one of the most common types of minerals in the earth's crust. Feldspar alteration (including the whole processes of feldspar dissolution, transfer of released solutes, and secondary mineral precipitation) is ubiquitous and important in fields including resources and environmental sciences. This paper provides a critical review of feldspar alteration and its geological significance in shallow aquifers to deep hydrocarbon reservoirs, as assessed from peer-reviewed p...
#1Guanghui Yuan(China University of Petroleum)H-Index: 12
#2Yingchang Cao(China University of Petroleum)H-Index: 20
Last. Zhenzhen Jia(China University of Petroleum)H-Index: 6
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Organic-inorganic interactions after oil charging are critical for determining the ongoing evolution of hydrocarbons and rock quality in water-wet siliciclastic reservoirs. It is the conceptual approach of this study to simulate and decipher these interactions by using quantitative analyses of the interrelated changes of minerals, water, hydrocarbons, gases, and organic acids in heated oil-water-rock systems. The experimental results show that organic-inorganic interactions occur between the org...
Abstract An example of diagenesis and reservoir quality of buried sandstones with ancient incursion of meteoric freshwater is presented in this study. The interpretation is based on information including porosity and permeability, petrography, stable isotopic composition of authigenic minerals, homogenization temperatures (T h ) of aqueous fluid inclusions (AFIs), and pore water chemistry. These sandstones, closely beneath or far from the regional unconformity formed during the late Paleogene pe...
Dawsonite is often associated with CO2-rich gas reservoirs, and it is regarded as a “trace mineral” for recording migration and accumulation of CO2. Following accepted petrological, mineralogical, and geochemical principles, we used several methods (described herein) to study the Cretaceous dawsonite-bearing sandstone reservoirs in the Songliao Basin, China. We used the ideas of “sequencing” and “timing” to verify the influx stages of CO2 and hydrocarbons, dividing their influx sequence pattern ...
Abstract Pore-throat size is a very crucial factor controlling the reservoir quality and oiliness of tight sandstones, which primarily affects rock-properties such as permeability and drainage capillary pressure. However, the wide range of size makes it difficult to understand their distribution characteristics as well as the specific controls on reservoir quality and oiliness. In order to better understand about pore-throat size distribution, petrographic, scanning electron microscopy (SEM), pr...
#1Jian Wang(China University of Petroleum)H-Index: 8
#2Yingchang Cao(China University of Petroleum)H-Index: 20
Last. Qisong Xu(China University of Petroleum)H-Index: 2
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The compositions, distribution and its interaction with rocks of the evolving pore fluids controls the distribution of carbonate cements and reservoir storage spaces. The reservoir quality of the red-bed sandstone reservoirs in the Dongying Depression was investigated by an integrated and systematic analysis including carbonate cement petrology, mineralogy, carbon and oxygen isotope ratios and fluid inclusions. The investigation was also facilitated by probing the mineral origins, precipitation ...
Feldspar dissolution and precipitation of clays and quartz cements are important diagenetic reactions affecting reservoir quality evolution in sandstones with detrital feldspars. We examined two sets of sandstone reservoirs to determine whether the sandstone diagenetic systems were open or closed to the mass transfer of products from feldspar dissolution and its impact on reservoir quality. One of the reservoirs is the Eocene fan delta sandstone buried 2.5–4.0 km (1.5–2.5 mi) below sea level (BS...
Abstract To investigate CO 2 Capture, Utilization, and Storage (CCUS) in sandstones, we performed three 150 °C flow-through experiments on K-feldspar-rich cores from the Eau Claire formation. By characterizing fluid and solid samples from these experiments using a suite of analytical techniques, we explored the coupled evolution of fluid chemistry, mineral reaction rates, and hydrogeochemical properties during CO 2 sequestration in feldspar-rich sandstone. Overall, our results confirm prediction...
Last. Li Xiaoyan(China University of Petroleum)H-Index: 3
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Abstract The Eocene sandstones in the northern Dongying Sag, Bohai Bay Basin, China, are reservoirs for large accumulations of hydrocarbons. The sandstones are mainly lithic arkoses and feldspathic litharenites, texturally and compositionally immature. These sandstones have a wide range of porosity (0.4–37%) and permeability (0.004–6969 mD) and show an overall decrease in reservoir quality from 1500 m to 5000 m below sea level. The reduction in reservoir quality is a product of several digenetic...
#2Yingchang Cao(China University of Petroleum)H-Index: 20
Last. Kelai Xi(China University of Petroleum)H-Index: 12
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Abstract Carbonates are suggested to dissolve rapidly than feldspars by laboratory experiments. Petrography texture of selective dissolution of feldspars in the presence of carbonates, however, is widespread in buried sandstones and even shales, inspiring a revisit to the chemistry of burial secondary pores. Feldspar dissolution, precipitation of secondary minerals (quartz, clays), and carbonate cementation are common chemical reactions in the Eocene sandstones in the northern Dongying Sag. Petr...
Water inrush from coal seam floors is one major geological obstacle hindering safe and efficient production activities in mines. Determining the source of water inrush can facilitate its prediction and guide decisions regarding measures for prevention and control. The process of identifying the location of hidden hydraulic contact points in different confined aquifers forms the basis of hydrogeological explorations. It is also the basis for categorizing mine areas prone to water inrush and makin...
Abstract Large Carboniferous petroleum systems exist in the Central Asian Orogenic Belt (CAOB), including the South Caspian and Junggar basins. In this study, we investigated one such petroleum system in the range belt by analyzing hydrocarbons in vein cements in the Daerbute fault zone that cuts Carboniferous strata in West Junggar, northwest China. Our multiple analytical methods included conventional petrographic descriptions, fourier transform infrared (FTIR) spectroscopy, and time-of-flight...
Abstract Calcite cement is a typical product of fluid–rock interaction in petroleum reservoirs, and its migration has a major impact on reservoir heterogeneity. A case study of a closed diagenetic system was carried out on the Upper Triassic Yanchang Formation of Ordos Basin, China—the most successful exploration region for tight sandstone oil in China. The investigated sandstones are mainly lithic arkoses (Q31F42L27). Three occurrences of calcite cement are the most important diagenetic mineral...