scholarly journals Feldspar Dissolution and Its Influence on Reservoirs: A Case Study of the Lower Triassic Baikouquan Formation in the Northwest Margin of the Junggar Basin, China

Geofluids ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-19 ◽  
Author(s):  
Meng Xiao ◽  
Xuanjun Yuan ◽  
Dawei Cheng ◽  
Songtao Wu ◽  
Zhenglin Cao ◽  
...  
Keyword(s):  
Clay Minerals ◽  
Physical Property ◽  
Junggar Basin ◽  
Sedimentary Facies ◽  
Lower Triassic ◽  
Depositional Environments ◽  
Source Rocks ◽  
Reservoir Quality ◽  
Delta Plain ◽  
Feldspar Dissolution

Feldspar dissolution is a common feature in clastic rock reservoirs of petroliferous basins and has an important influence on reservoir quality. However, the effect of feldspar dissolution on reservoir quality varies under different depositional environments and diagenetic systems. The study area in this paper is located in the Baikouquan Formation in the northwestern margin of the Junggar Basin, which is significantly influenced by feldspar dissolution. Based on the analyses of core and thin section observations, QEMSEM, XRD, SEM, CL, fluorescence, and image analysis software combined with logging and physical property data, this study shows that feldspar dissolution in the subaqueous distributary channel of a fan delta plain, which has good original physical properties and low mud contents, significantly improves the properties of the reservoir. The main reasons for this are as follows: (1) the sedimentary facies with good original properties and low mud content is a relatively open system in the burial stage. The acidic fluids needed for feldspar dissolution are mostly derived from organic acids associated with the source rocks and migrate to the good-permeability area of the reservoir; (2) the by-products of feldspar dissolution, such as authigenic clay minerals and authigenic quartz, are transported by pore water in a relatively open diagenetic system and then precipitated in a relatively closed diagenetic system; and (3) the clay minerals produced by feldspar dissolution in different diagenetic environments and diagenetic stages have different effects on the reservoir. When the kaolinite content is less than 3%, the illite content is less than 4%, and the chlorite content is less than 12%, the clay minerals have a positive effect on the porosity. These clay minerals can reduce porosity and block pore throats when their contents are larger than these values.

The Lower Triassic Caley Member: depositional facies, reservoir quality and seismic expression

2018 ◽  
Vol 58 (2) ◽  
pp. 878 ◽  
Author(s):  
Jack Woodward ◽  
Jon Minken ◽  
Melissa Thompson ◽  
Margarita Kongawoin ◽  
Laurence Hansen ◽  
...  
Keyword(s):  
Seismic Data ◽  
Lower Triassic ◽  
Source Rocks ◽  
Geochemical Data ◽  
Reservoir Quality ◽  
Depositional Facies ◽  
Efficient System ◽  
Delta Plain ◽  
Porosity And Permeability ◽  
Thin Reservoir

Recent exploration success in the Lower Keraudren Formation of the Bedout sub-basin has resulted in the emergence of the Caley Member reservoirs (Thompson et al. 2018). The interplay of several unique characteristics at this stratigraphic level are favourable for the generation, trapping and deliverability of hydrocarbons. These unique characteristics include, the preservation of porosity and permeability at depths greater than 4000 m, an organic-rich delta-plain lagoon mudstone source rock interbedded with the reservoir and the presence of a thick hemi-pelagic shale. This proximity of the mature source rocks and reservoir quality units combined with a thick overlying shale has created a highly efficient system for trapping hydrocarbons. Seismic data is a key tool to help unlock this play. Seismic imaging of a relatively thin reservoir at a depth below 4000 m has proved challenging. Quadrant has undertaken several stages of reprocessing and conducted multiple seismic inversions to better image and predict the reservoir. Integration and interpretation of geophysical, geological and geochemical data of this recently discovered reservoir has increased Quadrant’s understanding of the potential of the under-explored Bedout sub-basin.

scholarly journals Sedimentology, petrography, and reservoir quality of the Zarga and Ghazal formations in the Keyi oilfield, Muglad Basin, Sudan

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yousif M. Makeen ◽  
Xuanlong Shan ◽  
Habeeb A. Ayinla ◽  
Ekundayo Joseph Adepehin ◽  
Ndip Edwin Ayuk ◽  
...  
Keyword(s):  
Thin Section ◽  
Sedimentary Facies ◽  
Depositional Environments ◽  
Coarse Grained ◽  
Reservoir Quality ◽  
Research Attention ◽  
Sequence Composition ◽  
Exploration And Production ◽  
Authigenic Mineral ◽  
Thin Section Analysis

AbstractThe Zarga and Ghazal formations constitute important reservoirs across the Muglad Basin, Sudan. Nevertheless, the sedimentology and diagenesis of these reservoir intervals have hitherto received insignificant research attention. Detailed understanding of sedimentary facies and diagenesis could enhance geological and geophysical data for better exploration and production and minimize risks. In this study, subsurface reservoir cores representing the Zarga formation (1114.70–1118.50 m and 1118.50–1125.30 m), and the Ghazal formation (91,403.30–1406.83 m) were subjected to sedimentological (lithofacies and grain size), petrographic/mineralogic (thin section, XRD, SEM), and petrophysical (porosity and permeability) analyses to describe their reservoir quality, provenance, and depositional environments. Eight (8) different lithofacies, texturally characterized as moderately to well-sorted, and medium to coarse-grained, sub-feldspathic to feldspathic arenite were distinguished in the cored intervals. Mono-crystalline quartz (19.3–26.2%) predominated over polycrystalline quartz (2.6–13.8%), feldspar (6.6–10.3%), and mica (1.4–7.6%) being the most prominent constituent of the reservoir rocks. Provenance plot indicated the sediments were from a transitional continental provenance setting. The overall vertical sequence, composition, and internal sedimentary structures of the lithofacies suggest a fluvial-to-deltaic depositional environment for the Ghazal formation, while the Zarga formation indicated a dominant deltaic setting. Kaolinite occurs mainly as authigenic mineral, while carbonates quantitatively fluctuate with an insignificant amount of quartz overgrowths in most of the analyzed cores. Integration of XRD, SEM, and thin section analysis highlights that kaolinite, chlorite, illite, and smectite are present as authigenic minerals. Pore-destroying diagenetic processes (e.g. precipitation, cementation, and compaction etc.) generally prevailed over pore-enhancing processes (e.g. dissolution). Point-counted datasets indicate a better reservoir quality for the Ghazal formation (ɸ = 27.7% to 30.7%; K = 9.65 mD to 1196.71 mD) than the Zarga formation (17.9% to 24.5%; K = 1051.09 mD to 1090.45 mD).

scholarly journals Authigenic clay minerals and calcite dissolution influence reservoir quality in tight sandstones: Insights from the central Junggar Basin, NW China

2020 ◽  
Vol 1 (1-2) ◽  
pp. 8-19
Author(s):  
Dongdong Hong ◽  
Jian Cao ◽  
Tao Wu ◽  
Sisi Dang ◽  
Wenxuan Hu ◽  
...  
Keyword(s):  
Clay Minerals ◽  
Junggar Basin ◽  
Reservoir Quality ◽  
Calcite Dissolution ◽  
Nw China

Oil Sands Forming Model of the Northwest Edge of the Junggar Basin, China

2015 ◽  
Vol 1092-1093 ◽  
pp. 1430-1435
Author(s):  
Qun Zhao ◽  
Hong Yan Wang ◽  
De Xun Liu ◽  
Shen Yang ◽  
Dong Mei Luo
Keyword(s):  
Oil Sands ◽  
Junggar Basin ◽  
Sedimentary Facies ◽  
Source Rocks ◽  
Alluvial Fans ◽  
Tectonic Movement ◽  
Oil Sand ◽  
Oil Viscosity ◽  
Multi Phase ◽  
Abundance And Distribution

The Junggar Basin has the basic conditions for giant oil-sand mine to form and it is the hot point for exploration and development of oil sands. Multi-layer source rocks deposited in the Manas Lake Depression have produced abundant hydrocarbon in the course of multi-phase tectonic movement and they were the source of oil sands. Many unconformities formed also in the course of multi-phase tectonic movement were the main pathway of lateral movement of hydrocarbon and the well-developed abnormal faults were the main vertical pathway. The sands bodies of fluvial facies in alluvial fans in front of the Zhair Mountain offered a very favorable reservoirs for oil-sand mine. Hard biodegradation make the viscosity of hydrocarbon heavier and heavier. The hydrocarbon seized on the surface of sands, and then oil sands were formed. The peculiar characters of the northwest edge of the Junggar Basin make the oil sands occur at the compressive side of the basin. And the lateral distribution of oil sands mine is bigger and the scale is smaller relatively. The fault’ openness, fossil landscape, sedimentary facies, oil viscosity have controlled the abundance and distribution of oil sands.

scholarly journals The Jurassic of East Greenland: a sedimentary record of thermal subsidence, onset and culmination of rifting

2003 ◽  
Vol 1 ◽  
pp. 657-722 ◽  
Author(s):  
Finn Surlyk
Keyword(s):  
North Sea ◽  
Middle Jurassic ◽  
Sedimentary Facies ◽  
Lower Triassic ◽  
Depositional Environments ◽  
The Arctic ◽  
Time Interval ◽  
East Greenland ◽  
Thermal Subsidence

The Late Palaeozoic – Mesozoic extensional basin complex of East Greenland contains a record of deposition during a period of Rhaetian – Early Bajocian thermal subsidence, the onset of rifting in the Late Bajocian, its growth during the Bathonian–Kimmeridgian, culmination of rifting in the Volgian – Early Ryazanian, and waning in the Late Ryazanian – Hauterivian. The area was centred over a palaeolatitude of about 45°N in the Rhaetian and drifted northwards to about 50°N in the Hauterivian. A major climate change from arid to humid subtropical conditions took place at the Norian–Rhaetian transition. Deposition was in addition governed by a long-term sea-level rise with highstands in the Toarcian–Aalenian, latest Callovian and Kimmeridgian, and lowstands in the latest Bajocian – earliest Bathonian, Middle Oxfordian and Volgian. The Rhaetian – Lower Bajocian succession is considered the upper part of a megasequence, termed J1, with its base in the upper Lower Triassic, whereas the Upper Bajocian – Hauterivian succession forms a complete, syn-rift megasequence, termed J2. The southern part of the basin complex in Jameson Land contains a relatively complete Rhaetian–Ryazanian succession and underwent only minor tilting during Middle Jurassic – earliest Cretaceous rifting. Rhaetian – Lower Jurassic deposits are absent north of Jameson Land and this region was fragmented into strongly tilted fault blocks during the protracted rift event. The syn-rift successions of the two areas accordingly show different long-term trends in sedimentary facies. In the southern area, the J2 syn-rift megasequence forms a symmetrical regressive–transgressive–regressive cycle, whereas the J2 megasequence in the northern area shows an asymmetrical, stepwise deepening trend. A total of eight tectonostratigraphic sequences are recognised in the Rhaetian–Hauterivian interval. They reflect major changes in basin configuration, drainage systems, sediment transport and distribution patterns, and in facies and depositional environments. The sequences are bounded by regional unconformities or flooding surfaces and have average durations in the order of 10 Ma. They are subdivided into conventional unconformity-bounded depositional sequences with durations ranging from tens of thousands of years, in the Milankovitch frequency band, up to several million years. Deposition was alluvial and lacustrine in the Rhaetian–Sinemurian, but almost exclusively marine during the Pliensbachian–Hauterivian time interval when a marine strait, up to 500 km wide and more than 2000 km long, developed between Greenland and Norway, connecting the Arctic Sea and the North Sea. Coal-bearing fluvial and paralic deposits occur, however, at the base of the onlapping Middle Jurassic succession in the central and northern part of the basin complex. The sedimentary development is similar to that in the Northern North Sea and on the Norwegian shelf, and East Greenland offers important onshore analogues for virtually all of the types of deeply buried Jurassic depositional systems of these areas and especially their hydrocarbon reservoirs.

scholarly journals Sedimentary Characteristics Analysis and Sedimentary Facies Prediction of Jurassic Strata in the Northwest Margin of Junggar Basin—Covering the W105 Well Region in the Wuerhe Area

Minerals ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 68
Author(s):  
Shiqi Liu ◽  
Yuyang Liu
Keyword(s):  
Cross Sections ◽  
Oil And Gas ◽  
Junggar Basin ◽  
Sedimentary Facies ◽  
Delta Front ◽  
Delta Plain ◽  
Fan Delta ◽  
Single Well ◽  
Northwest Region ◽  
Sand Bodies

As the northwestern area of the Junggar Basin is a key area for oil and gas exploration, the sedimentary facies of the Jurassic formations in the Wuerhe area has long been a focus of research. The target strata are Jurassic strata, including five formations: the Lower Jurassic Badaowan and Sangonghe, the Middle Jurassic Xishanyao and Toutunhe and the Upper Jurassic Qigu. Disputes over the are sedimentary facies division exist in this area. Considering the W105 well region in this area as an example, the overall sedimentary facies of single-well logging facies is analyzed and then expanded to two cross-sections and characterized. Based on previous studies, a detailed overview of the regional stratigraphy is obtained by well logs and other data. Then, two cross-sections are selected and analyzed. The single-well and continuous-well facies of 10 wells in the sections are analyzed to grasp the sand bodies’ spatial distribution. Finally, a planar contour map of the net to gross ratio is mapped to analyze the sources and the distribution of the sand bodies in each period. The sedimentary facies map is also mapped to predict the sedimentary evolution. The results show that the sedimentary facies of the Badaowan Formation in the study area was an underwater distributary channel of the fan-delta front, and the sand body spread continuously from northwest to southeast. The Sangonghe Formation entered a lake transgression period with a rising water level, at which time shore–shallow lacustrine deposits were widespread throughout the region. The period of the Xishanyao Formation entered a regression period, the northwest region was tectonically uplifted, and the central and southeastern regions facies were dominated by the fan-delta front and shallow lacustrine. During the Toutunhe Formation period, the northwest region continued to uplift and was dominated by delta plain facies. During the period of the Qigu Formation, the thickness of stratigraphic erosion reached its maximum, and the non-erosion area of the study area was mainly deposited by the fan-delta plain. Overall, the Jurassic system in the W105 well area is a fan delta–lacustrine–fan delta sedimentary system.

Clay mineralogy and geochemistry of early Jurassic sedimentary rocks from the Moezian Platform, northern Bulgaria

Clay Minerals ◽  
2002 ◽  
Vol 37 (3) ◽  
pp. 413-428 ◽  
Author(s):  
E. Hrischeva ◽  
S. Gier
Keyword(s):  
Clay Minerals ◽  
Clay Mineral ◽  
Sedimentary Rocks ◽  
Depositional Environments ◽  
Early Jurassic ◽  
Source Rocks ◽  
Shallow Marine ◽  
Fine Grained ◽  
Depositional Processes ◽  
Mineral Assemblages

AbstractClay minerals in early Jurassic sequences of shales, siltstones and sandstones deposited in non-marine, transitional and shallow marine environments have been examined by X-ray diffraction, electron microscopy and chemical analysis to study the relationship between clay minerals, their environment of deposition and subsequent diagenetic modifications.The inherited clay mineral composition of the fine-grained sediments reflects the influence of climate, relief, source rocks and depositional processes. Inhomogeneous clay mineral assemblages, comprising abundant kaolinite and varying proportions of illite, I-S, chlorite and vermiculite, characterize fine-grained sediments from the non-marine and transitional environments. In shallow marine depositional environments clay mineral assemblages are more uniform, dominated by illite+I-S with minor kaolinite and chlorite.The principal diagenetic process affecting fine-grained sedimentary rocks is the smectite–illite transformation. In sandstones, the authigenic formation of kaolinite, chlorite and illite appears to have been primarily determined by the environment of deposition.

Controls on reservoir quality in fan-deltaic conglomerates: Insight from the Lower Triassic Baikouquan Formation, Junggar Basin, China

2019 ◽  
Vol 103 ◽  
pp. 55-75 ◽  
Author(s):  
Xun Kang ◽  
Wenxuan Hu ◽  
Jian Cao ◽  
Haiguang Wu ◽  
Baoli Xiang ◽  
...  
Keyword(s):  
Junggar Basin ◽  
Lower Triassic ◽  
Reservoir Quality

scholarly journals Origin and Sources of Minerals and Their Impact on the Hydrocarbon Reservoir Quality of the PaleogeneLulehe Formation in the Eboliang Area, Northern Qaidam Basin, China

Minerals ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 436 ◽  
Author(s):  
Bo Chen ◽  
Feng Wang ◽  
Jian Shi ◽  
Fenjun Chen ◽  
Haixin Shi
Keyword(s):  
Clay Minerals ◽  
Large Scale ◽  
Qaidam Basin ◽  
Hydrocarbon Exploration ◽  
Integrated Analysis ◽  
Reservoir Quality ◽  
Stability Field ◽  
Hydrocarbon Reservoir ◽  
Quartz Cement ◽  
Feldspar Dissolution

The Lulehe sandstone in the Eboliang area is a major target for hydrocarbon exploration in the northern Qaidam Basin. Based on an integrated analysis including thin section analysis, scanning electron microscopy, X-ray diffraction, cathodoluminescence investigation, backscattered electron images, carbon and oxygen stable isotope analysis and fluid inclusion analysis, the diagenetic processes mainly include compaction, cementation by carbonate and quartz, formation of authigenic clay minerals (i.e., chlorite, kaolinite, illite-smectite and illite) and dissolution of unstable materials. Compaction is the main factor for the deterioration of reservoir quality; in addition, calcitecement and clay minerals are present, including kaolinite, pore-filling chlorite, illite-smectite and illite, which also account for reservoir quality reduction. Integration of petrographic studies and isotope geochemistry reveals the carbonate cements might have originated from mixed sources of bioclast- and organic-derived CO2 during burial. The quartz cement probably formed by feldspar dissolution, illitization of smectite and kaolinite, as well as pressure solution of quartz grains. Smectite, commonly derived from alteration of volcanic rock fragments, may have been the primary clay mineral precursor of chlorite. In addition, authigenic kaolinite is closely associated with feldspar dissolution, suggesting that alteration of detrital feldspar grains was the most probable source for authigenic kaolinite. With the increase in temperature and consumption of organic acids, the ratio of K+/H+ increases and the stability field of kaolinite is greatly reduced, thereby transforming kaolinite into mixed layer illite/smectite and illite. Within the study area, porosity increases with chlorite content up to approximately 3% volume and then decreases slightly, indicating that chlorite coatings are beneficial at an optimum volume of 3%. A benefit of the dissolution of unstable minerals and feldspar grains is the occurrence of secondary porosity, which may enhance porosity to some extent. However, the solutes cannot be transported over a large scale in the deep burial environment, and simultaneous precipitation of byproducts of feldspar dissolution such as authigenic kaolinite and quartz cement will occur in situ or in adjacent pores, resulting in heterogeneity of the reservoirs.

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