Permian Formation Research Articles

Early Permian sediment provenance and paleogeographic reconstructions in southeastern Gondwana using detrital zircon geochronology (Northern Perth Basin, Western Australia)

The Perth Basin (Western Australia) forms part of a north-trending belt of intracratonic rift basins that initiated in southeastern Gondwana in the Late Paleozoic. Existing provenance studies have highlighted the dominance of Proterozoic zircons derived from southerly terranes such as the Albany-Fraser Orogen, Leeuwin Complex, and more distant provinces in East Antarctica, with limited input from the adjacent Archean Western Australian Craton. New U-Pb geochronology data were acquired using a Sensitive High Resolution Ion Microprobe (SHRIMP II) on detrital zircons from Lower Permian formations exposed in the northeastern Perth Basin. In contrast to previous studies, Archean zircons, showing fine oscillatory zoning, dominate the age spectra with up to 90% grains ranging between 3.0 and 2.6Ga, indicating that granitic parent rocks of the adjacent craton were a major sediment source during the Early Permian. A minor Paleoproterozoic age population from the Gascoyne Complex of the Capricorn Orogen was likely transported southward and dispersed in the basin by a combination of longshore drift and tidal currents. Meso- and Neoproterozoic detritus became prominent only from the middle Artinskian, and may relate to the establishment of large northward-flowing river systems draining the Albany-Fraser province, the Prydz-Leeuwin Belt, and/or the Wilkes Land in East Antarctica. This study shows that integrating depositional processes and stratigraphic evolution of sedimentary formations with provenance analysis can enhance reconstruction of dispersal pathways to and within basins.

Lower permian reef-bank bodies’ characterization in the pre-caspian basin

Reef-bank reservoir is one of the targets for exploration of marine carbonate rocks in the Pre-Caspian Basin. Within this basin, the reef-bank bodies were primarily developed in the subsalt Devonian-Lower Permian formations, and are dominated by carbonate platform interior and margin reef-banks. The Lower Permian reef-bank present in the eastern part of the basin is considered prospective. This article provides a sequence and sedimentary facies study utilizing drilling and other data, as well as an analysis and identification of the Lower Permian reef-bank features along the eastern margin of the Pre-Caspian Basin using sub-volume coherence and seismic inversion techniques. The results indicate that the sub-volume coherence technique gives a better reflection of lateral distribution of reefs, and the seismic inversion impedance enables the identification of reef bodies’ development phases in the vertical direction, since AI (impedance) is petrophysically considered a tool for distinguishing the reef limestone and the clastic rocks within the formation (limestone exhibits a relatively high impedance than clastic rock). With this method, the existence of multiple phases of the Lower Permian reef-bank bodies along the eastern margin of the Pre-Caspian Basin has been confirmed. These reef-bank bodies are considered good subsalt exploration targets due to their lateral connectivity from south to north, large distribution range and large scale.

Возраст и состав верхней части верхневизейско-нижнепермского нефтегазоносного комплекса юга Косью-Роговской впадины

Возраст и состав верхней части верхневизейско-нижнепермского нефтегазоносного комплекса юга Косью-Роговской впадины

O-36 長門構造帯の三種類のペルム系 : 対比と問題点(4.地域地質・地域層序,口頭およびポスター発表,一般講演)

O-36 長門構造帯の三種類のペルム系 : 対比と問題点(4.地域地質・地域層序,口頭およびポスター発表,一般講演)

Lithostratigraphy of the Pietermaritzburg Formation (Ecca Group, Karoo Supergroup), South Africa

Abstract The Lower Permian Pietermaritzburg Formation is a mudrock-dominated, upward-coarsening stratigraphic unit in the lower Ecca Group (Karoo Supergroup) in the northeastern part of the main Karoo Basin of South Africa. The formation extends over most of the KwaZulu-Natal Province, and due to its lithology and the local climate, it is usually poorly exposed; hence the description is mainly based on borehole records. From a measured thickness of about 430 m south of the type area around Pietermaritzburg, the formation thins progressively northwards and pinches out against the Dwyka Group and pre-Karoo basement north of latitude 26° 30' S. This Lower Permian formation is considered a stratigraphic equivalent of the Prince Albert Formation in the southern part of the main Karoo Basin. The Pietermaritzburg Formation only preserves scattered, fragmentary plant fossil and invertebrate trace fossils, which are diagnostic of marine conditions (e.g. Helminthopsis). Based on its sedimentary facies characteristics and ichnofossil assemblages, the unit was probably deposited under low energy conditions on a northerly shallowing marine shelf that initially experienced deepening (during a major Artinskian transgression) and then shallowing in the early Kungurian.

Geological characteristics and main controlling factors of Permian lacustrine tight oil in the eastern part of the Junggar Basin

The Junggar basin is rich in oil and gas resources, and recently, unconventional oil and gas reservoirs have become important targets. Significant amounts of oil and gas are located in Permian formations in the Shazhang–Dajing area, however, fewer studies have focused on unconventional oil and gas reservoirs, particularly on the factors controlling the distribution of unconventional reservoirs. In this study, a sequence stratigraphic framework of the study area was developed based on cores, well logs and seismic data. Source rock samples were analyzed, including tests of kerogen, vitrinite reflectance, chloroform bitumen, organic carbon and group composition. The physical properties and pore characteristics of reservoir samples were also analyzed using scanning electron microscope and high resolution electron microscope. The Permian Pingdiquan Formation comprises three thirdorder sequences in which individual sequence can be divided into a low-stand system tract (LST), a transgression system tract (TST), an early high-stand system tract (E-HST), and a late high-stand system tract (L-HST). Several source rock lithologies have high total organic carbon (TOC), and are matured, having excellent hydrocarbon generation potential. Clastic and dolomitic rocks are the main reservoirs, and nanometer-scale pores are the main reservoir space in the tight reservoirs. The distribution of tight oil is controlled by the sequence stratigraphy, palaeogeomorphic units, and sedimentary facies. The fine sediments, which were generally deposited near the initial flooding surface (FFS) and the maximum flooding surface (MFS), are favorable zones for tight oil. The distributions of the hydrocarbon source rocks are controlled by the depositional environment, depending on the palaeogeomorphic units; the deep depression in the Huoshaoshan area and the moderately-deep depression in the Shishugou area are two distinct hydrocarbon generating centers. The distribution of tight oil is clearly controlled by the sedimentary facies; the tight oil is mainly located in the fan delta front and lacustrine depositional environments. The distribution of tight oil in this area is summarized, and favorable areas of tight oil are proposed.

Identification of Rocks and Their Quartz Content in Gua Musang Goldfield Using Advanced Spaceborne Thermal Emission and Reflection Radiometer Imagery

Quartz is an important mineral element and the most abundant rock-forming mineral that controls the mineralogy of a reservoir. At the surface, quartz is more stable than most other rock minerals because it is made up of interlocking silica that makes it quite resistant to mechanical weathering. Quartz abundance is an indication of mineralization in many metal deposits; therefore, identification and mapping of quartz in rocks are of great value for exploration and resource potential assessments. In this study, thermal infrared (TIR) bands of the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) imagery were used to identify quartz contained rocks in Gua Musang. First, the image was corrected for atmospheric effect and the study area subset for further processing. Thereafter, spectral transformation (principal component analysis (PCA)) was implemented on the TIR bands and the resulting principal component (PC) images were analysed. The three optimal PCs were selected using the strength of spectral interaction and the eigenvalues of each band. To discriminate between quartz-rich and quartz-poor rocks, RGB false colour composite and greyscale image of one of the PCs were analysed. The result shows that volcanogenic igneous rock and carbonate sedimentary rocks of Permian formation are quartz-poor while Triassic sedimentary rock made up of organic particles and sandstone is quartz-rich. On the contrary, the quartz content in the metamorphic rock varies across the area but is richer in quartz content than the igneous and carbonate rocks. Classification of the composite image classified using maximum likelihood (ML) supervised classification method produced overall accuracy and Kappa coefficient of 96.53%, and 0.95, respectively.

Petrophysical Characterization of Gondwana Shales of South Karanpura Coal Field, Jharkhand, India

Sedimentary rocks such as shales are the most abundant sedimentary rocks in the earth’s crust. Shales are characterized by preferred particle orientations of platy clay minerals, strong laminations and presence of fissility. In petroleum geology, organic shales behave as both source rocks as well as seal rocks that trap oil and gas. In seismic exploration, shales interface with other rocks to form good reflectors. As a result, seismic and petrophysical properties of shales and the relationships among these properties are important for both exploration and reservoir management. The Gondwana shale of South Karanpura coalfield, Eastern India of Barakar (lower Permian) and Barren-Measures (Middle Permian) formation, majorly characterized by non-marine sedimentary fill and narrow graben structures, are used for petrophysical characterization. Because of thermal maturity and high content of organic matter in shale rock, South Karanpura coalfield is considered as one of the potential shale gas field in Damodar Valley Basin and it is a part of the “Gondwana” basins of Eastern India. This paper discusses various experimental techniques that are applied to shales to obtain velocity, elastic properties structure, minerals composition, texture/fabric and pore types. These techniques include ultrasonic acoustic measurements, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The frequency values used for acoustic measurements are 54 KHz (P-wave) and 250 KHz (S-wave). The resolution of these imaging techniques varies from micrometres to angstroms and the resulting images generally reflect the composition, topography, or combination of both. The estimated P-wave velocity for Barren-Measures and Barakar formation varies from 1463–1890m/s and 2110–3947m/s, respectively while the Shear-wave velocity varies from 898m/s–1232m/s to 1306m/s–2515m/s respectively which suggest that formation is hard and compact in the latter case. XRD and SEM analysis reveals the presence of clay minerals and other minerals, organic matter, texture/topography and pore types in the shale rock sample. The clay minerals identified consist of Kaolinite, Illite while Quartz, Siderite, Muscovite, Orthoclase and Rutile comprises of non-clay minerals in the sample.

High-resolution shear-wave seismic reflection as a tool to image near-surface subrosion structures – a case study in Bad Frankenhausen, Germany

Abstract. Subrosion is the subsurface leaching of soluble rocks that results in the formation of depression and collapse structures. This global phenomenon is a geohazard in urban areas. To study near-surface subrosion structures, four shear-wave seismic reflection profiles, with a total length of ca. 332 m, were carried out around the famous leaning church tower of Bad Frankenhausen in northern Thuringia, Germany, which shows an inclination of 4.93° from the vertical. Most of the geological underground of Thuringia is characterized by soluble Permian deposits, and the Kyffhäuser Southern Margin Fault is assumed to be a main pathway for water to leach the evaporite. The seismic profiles were acquired with the horizontal micro-vibrator ELVIS, developed at Leibniz Institute for Applied Geophysics (LIAG), and a 72 m long landstreamer equipped with 72 horizontal geophones. The high-resolution seismic sections show subrosion-induced structures to a depth of ca. 100 m and reveal five features associated with the leaching of Permian deposits: (1) lateral and vertical varying reflection patterns caused by strongly heterogeneous strata, (2) discontinuous reflectors, small offsets, and faults, which show the underground is heavily fractured, (3) formation of depression structures in the near-surface, (4) diffractions in the unmigrated seismic sections that indicate increased scattering of the seismic waves, and (5) varying seismic velocities and low-velocity zones that are presumably caused by fractures and upward-migrating cavities. A previously undiscovered southward-dipping listric normal fault was also found, to the north of the church. It probably serves as a pathway for water to leach the Permian formations below the church and causes the tilting of the church tower. This case study shows the potential of horizontal shear-wave seismic reflection to image near-surface subrosion structures in an urban environment with a horizontal resolution of less than 1 m in the uppermost 10–15 m.

Prediction of coal seam details and mining safety using multicomponent seismic data: A case history from China

With the increasing mining depth of coal mines, geologic hazards have become the main source of accidents. For this reason, coal seam prediction requires more assessment parameters, such as the degree of anisotropy, [Formula: see text] value, and elastic modulus. These parameters are difficult to determine using only the PP-wave. We have inverted and interpreted multicomponent seismic data acquired from a [Formula: see text] area in the Guqiao mine located on the southern margin of the North China plate, under the constraints of drill, log, and rock-physics test data. The production coal seam 11-2 of the mine, located in the Permian Formation, was our focus of this study, and our objective was to determine the structure, fracture development, thickness, surrounding rock lithology, roof stability, and mining safety of the seam. To achieve this, we first performed an analysis of S-wave splitting and joint PP- and PS-wave inversions. The inversion results were then combined to derive additional parameters, such as the [Formula: see text] value and dynamic Young’s modulus. Finally, we established a safety coefficient for assessing the safety of coal mining. The coefficient was based on the degree of anisotropy, coal bed thickness, Young’s modulus, and [Formula: see text] value of the coal-bearing strata. The geologic data for two mining tunnels in the 11-2 coal bed, provided by Huainan Coal Mining Group, were used to verify the known structure and lithology predictions. In addition, the known structural interpretations based on the PP- and PS-wave sections were obviously superior to the results of a previous survey based on the PP-wave only. The predicted thickness of coal seam 11-2 was accurate, as confirmed by comparison with that determined from drill data. Our joint PP- and PS-wave inversion and interpretation provides more information for coal seam prediction, creating a new application for coal seismic survey.

Provenance of middle to late Palaeozoic sediments in the northeastern Colombian Andes: implications for Pangea reconstruction

ABSTRACTGlobal-scale Palaeozoic plate tectonic reconstructions have suggested that Laurentia was obliquely approaching against the northwestern margin of Gondwana until the final agglutination of Pangea. In this contribution integrated petrographic analysis, heavy mineral analysis, and tourmaline geochemistry were done, and U–Pb detrital zircon geochronology was obtained, in late Palaeozoic sedimentary and meta-sedimentary units from the Floresta and Santander Massifs in the Eastern Colombian Andes in order to constrain their provenance and related it with the magmatic, sedimentary, and deformational record of the Gondwana–Laurentia convergence until the late Carboniferous to Permian formation of Pangea. Late Devonian to early Carboniferous sandstones from the Floresta Massif changed from sublithoarenites to lithoarenites, tracking the progressive uplift and unroofing of sedimentary and metamorphic rocks, with associated volcanic activity. The U–Pb detrital zircon geochronology from the sedimentary and metasedimentary of Floresta and Santander documents Mesoproterozoic and Palaeoproterozoic sources, and younger Ordovician to Silurian age populations, that can be related to the early to middle Palaeozoic plutonic rocks and the Amazon Craton. The limited Silurian to Early Devonian detrital ages that contrast with the more significant Middle to Late Devonian zircons that document the erosion of contemporaneous magmatic sources formed after a late Silurian to Early Devonian reduction on the magmatic activity along the proto-Andean margin. These rocks were apparently deformed and metamorphosed between the late Carboniferous and the early Permian. It is suggested that the filling and deformation record of these rocks documented the changes in plate convergence obliquity at the western margin of Gondwana associated with the migration of Laurentia until its final position in Pangea. Between the late Carboniferous and the early Permian, peri-Gondwanan continental terranes also collided with the continental margin. Over-imposed Mesozoic tectonics have contributed to the final redistribution of these terranes to their current position.Abbreviations:LA: laser ablation inductively couple mass spectrometer; CL: cathodoluminiscence

Литогенез пермских толщ Аян-Юряхского антиклинория Яно-Колымской складчатой области

Литогенез пермских толщ Аян-Юряхского антиклинория Яно-Колымской складчатой области

Application of 1D paleo‐fluvial process modelling at a basin scale to augment sparse borehole data: example of a Permian formation in the Galilee Basin, Australia

AbstractThe heterogeneous hydraulic conductivity (K) in water‐bearing formations controls subsurface flow and solute transport processes. Geostatistical techniques are often employed to characterize the K distribution in space based on the correlation between K measurements. However, at the basin scale, there are often insufficient measurements for inferring the spatial correlation. This is a widespread problem that we address in this study using the example of the Betts Creek Beds (BCB) in the Galilee Basin, Australia. To address the lack of data, we use a 1D stochastic fluvial process‐based model (SFPM) to quantify the total sediment thickness, Z(x), and the sandstone proportion over the total thickness, Ps(x), in the BCB. The semivariograms of Z(x) and Ps(x) are then extracted and used in sequential Gaussian simulation to construct the 2D spatial distribution of Z(x) and Ps(x). Ps(x) can be converted to a K distribution based on classical averaging methods. The results demonstrate that the combination of SFPM and geostatistical simulation allows for the evaluation of upscaled K distribution with a limited number of K measurements. Copyright © 2015 John Wiley & Sons, Ltd.

Discussion on Palaeozoic discontinuities in the Kuh-e Surmeh area (Zagros, Iran)

Evidence of several major unconformities in the Lower Palaeozoic succession in Iran lead to question the role of tectonic/eustatism/climate in terms of their formation. The studied Palaeozoic succession in the Kuh-e Surmeh Anticline is characterized by the preservation of two thin Ordovician and Lower Permian Formations separated by a large hiatus encompassing the Upper Ordovician up to the lowermost Permian. The Ordovician sequences were deposited in shallow shoreface to lower offshore environments and the Lower Permian corresponds to a wave-dominated estuarine system evolving to a delta system. These mainly clastic successions represent good reservoirs in the regional Palaeozoic petroleum system of the Iranian plate separated by a major unconformity. The local erosion of the Zakeen Fm., observed in the neighbouring areas close to the Kuh-e Surmeh anticline, can be used to specify the role of the different controlling factors. We show that the influence of regional tectonics (Hercynian Orogeny/extensional deformation) and climate (Hirnantian and Carboniferous glaciations) related to the late Ordovician and Late Carboniferous/Early Permian succession cannot be ruled out from the possible candidates participating in erosion, but local diapir doming seems to better explain part of this local intense erosion.

Upbeat Natural Gas Producers Show Value of Low Expectations

Conference Review - HIS Energy CERAWeek in Houston, Texas, April 20-24, 2015 The price declines for oil and natural gas are equally brutal, with roughly a 50% decline for both fuels. But the mood of those working in the gas sector was upbeat at the recent IHS CERAWeek conference compared with those in oil. The difference can be credited to the differing expectations. On the oil side, USD 100/bbl crude looked like a sure thing going forward until the price slid to around USD 50/bbl. Those on the gas side experienced a move within a low price range they have been living with for years. That range roughly runs from a high of USD 5 to a low of USD 2 per MMBtu, which is near the recent price of about USD 2.50, said Dave Pursell, managing director, head of securities at Tudor, Pickering, Holt & Co. “For the last 5 years, gas prices have been down,” said Steven Mueller, chairman and chief executive officer (CEO) of Southwestern Energy. While he said he would like to see prices rise, “we designed our company around low gas prices.” The group has hammered down the cost of profitably producing gas and maximized output by targeting the best reservoir rock, most of which is in the Marcellus Shale. The same can be said of the other companies working in formations that mostly produce dry gas. “Production has not only increased, it has accelerated,” Mueller said. He described the combination of ingredients that led to the surge as a “power function.” The fortunes of oil and gas diverged in fall 2008. Initially, both oil and gas exploration plunged after the financial crisis led to a recession. While oil recovered in late 2009, setting the stage for the booms in the Bakken, Eagle Ford, and Permian formations, gas prices stayed low. Both oil and gas drilling reached nearly the same peak when measured by the number of drilling rigs working. The top week for gas was 1,606 working rigs in mid-September 2008, while oil reached 1,601 in September 2014, according to the Baker Hughes weekly rig count totals. Since they hit their peaks, the number of rigs drilling for gas has sunk to 225 in late April while oil has fallen to 701.

The origin of the Avram Iancu U–Ni–Co–Bi–As mineralization, Băiţa (Bihor) metallogenic district, Bihor Mts., Romania

The Băiţa metallogenic district in the Bihor Mountains is a historically important mining area in Romania. Uranium mining took place between 1952 and 1998 from various deposits, but very little is known about the geology and mineralogy of these deposits. In this paper, we describe geology and mineralogy of uranium mineralization of the Avram Iancu uranium mine from waste dump samples collected before complete remediation of the site. Texturally and mineralogically complex assemblages of nickeline, cobaltite–gersdorffite solid solution, native Bi, Bi-sulfosalts, molybdenite, and pyrite–chalcopyrite–sphalerite occur with uraninite, “pitchblende,” and brannerite in most of the ore samples. The association of nickel, cobalt, and arsenic with uranium is reminiscent of five-element association of vein type U–Ni–Co–Bi–As deposits; however, the Avram Iancu ores appear to be more replacement-type stratiform/stratabound. Avram Iancu ore samples contain multistage complex, skarn, uranium sulfide, arsenide assemblages that can be interpreted to have been formed in the retrograde cooling stages of the skarn hydrothermal system. This mineralizing system may have built-up along Upper Cretaceous–Paleogene “Banatite” intrusions of diorite-to-granite composition. The intrusions crosscut the underlying uraniferous Permian formations in the stacked NW-verging Biharia Nappe System. The mineralization forms stacked, multilayer replacement horizons, along carbonate-rich lithologies within the metavolcanic (tuffaceous) Muncel Series. Mineral paragenesis and some mineral chemistry suggest moderate-to-high <450, i.e., 350–310 °C, formation temperatures for the uranium sulfide stage along stratigraphically controlled replacement zones and minor veins. Uranium minerals formed abundantly in this early stage and include botryoidal, sooty and euhedral uraninite, brannerite, and coffinite. Later and/or lower-temperature mineral assemblages include heterogeneous, complexly zoned arsenide–sulfarsenide solid solutions associated with minute but abundant uranium minerals. Within the later arsenide–sulfarsenide mineral assemblage, there is great variation in Ni, Co, and S content with generally increasing arsenic content. Uranium minerals in this late-stage assemblage include very fine euhedral uraninite and brannerite inclusions in arsenide–sulfarsenide minerals. Native bismuth and Bi-sulfosalt krupkaite are observed in this As–S-rich assemblage strongly associated with cobaltite.

Paleogeographic Peculiarities of Potassium and Potassium-Magnesium Salt Generation in the Southeast of the Russian Plate

Permian salt-bearing formation covers a substantial area of the Russian Plate.In some places,it is up to several kilometers thick.The salt-bearing formation contains unique accumulations of potassium and magnesium salts,

Evaluation of uncertainty in mineral prospectivity mapping due to missing evidence: A case study with skarn-type Fe deposits in Southwestern Fujian Province, China

In this paper, the southwestern Fujian metallogenic belt, one of the important Fe polymetallic belts in southern China, was chosen as a case study area to evaluate the uncertainty due to missing evidence in mineral prospectivity mapping. Four geological features were considered important for mineral prospectivity mapping based on the geological model for skarn deposits in the belt: (1) the Yanshanian granitic intrusions, because they provided energy, fluids, and part of the metal budget; (2) faults, because they served as pathways for hydrothermal fluids; (3) the Carboniferous–Permian carbonate sequences, because they supplied part of the metal budget and served as host rocks for ore deposition; and (4) geochemical anomalies, because they indicate presence of skarn-type alteration and mineralization. Four separate predictive evidence layers depicting each the above geological features were extracted from relevant geoscience data and were integrated using a modified fuzzy weights-of-evidence model, which retains the advantages of both fuzzy weights-of-evidence and logistic regression modeling. The results show that most of the known Fe deposits occur in or near, and thus have strong correlation with, areas of high posterior probabilities, as indicated by the delineated prospective areas that occupy only 4.6% of the studied region but contain 88.5% of the total number of known Fe deposits. Different combinations of predictive evidence layers were used to examine prediction uncertainty related to missing evidence. Plots of accumulative number of Fe deposits versus accumulative prospective areas show that the order of the most to the least important evidence of mineral prospectivity in the studied region is: favorable rock types>geochemical anomalies>intrusive rocks>faults. Results of blind testing the prospectivity models indicate that the geological model of Fe mineralization in the belt is suitable for predicting exploration target areas for skarn-type Fe deposits, and suggest that the highest risk in follow-up exploration is related to sequences of carbonates in the Carboniferous–Permian formations that were likely either not mapped or not represented at the present regional scale of mapping.

Modelling CO2-brine-rock interactions in the Upper Paleozoic formations of Ordos Basin used for CO2 sequestration

Subsurface immobilization and conversion of CO2 into solid mineral phases in deep siliciclastic saline formations containing silicate minerals, commonly known as “mineral trapping”, is gaining research attention as a significant option to reduce CO2 emissions in the atmosphere. Although mineral trapping of CO2 is a long-term process, a combination of short-term results from both laboratory experiments and numerical simulations can lead to some general understanding of the required long-term CO2 sequestration mechanisms. This is a 100 year preliminary batch simulation study of four sandstone samples, under CO2 saturated water at 75 °C from the Upper Permian formations in the Ordos Basin, using the TOUGHREACT/ECO2N module to simulate the CO2-brine-rock interaction processes in deep siliciclastic multilayered saline aquifers. The samples approximately correspond to the four target saline formations selected by the Shenhua Group for a CO2 sequestration field demonstration project in the Ordos Basin, PR China. Preliminary simulation results show that the initial salinity of formation brine plays a significant role in determining the amount of CO2 that will be sequestered by solubility or mineral trapping in a deep saline aquifer. Minimal differences between experimental results and numerical calculation occur in low salinity waters, and significantly larger differences in high salinity waters, which is still under the maximum acceptable difference between experimental and computed data (10 %). The upper Liujiagou formation, with the highest level of salinity (ca. 88.7 g/L TDS) and lowest level of CO2 solubility, offers the highest mineral trapping capacity, with a maximum carbonate mineral storage of ca. 0.7 kg/m3 of bulk rock over a 100 year period. Regardless of the initial acidity or alkalinity of the aquifer brine, injection of CO2 will inflict a sudden drop in pH of the brine to acidity levels in a range of 3.0–4.6. The subsequent amount of dissolved and precipitated minerals, arising from the CO2-brine-rock interaction, is site specific and mainly dependent on initial aquifer mineralogy and brine composition.

U–Pb zircon geochronology of basal granite by LA-ICP-MS in Yitong Basin, Northeast China: Implications for origin of limestone

Massive deposits of limestone were encountered for the first time by wells drilled into the bedrocks of Yitong Basin, Northeast China. U–Pb zircon dating analyses with LA-ICP-MS were then employed to determine the geological ages of the deposits and analyze the impact of a later magmatic intrusion upon the hydrocarbon generation and preservation environment in the deposits. Analyses of 6 granite samples taking from the limestone shows that the basement of the Yitong Basin contains numerous zircons of magmatic origin and these zircons are characterized in CL images as light color, clear oscillatory zoning and intact crystalline form, In terms of REE (rare earth elements) content and its distributive pattern, the zircons are shown with mild loss of Eu, high Th/U ratio and left-slanting distributive curves. Concordia plots based on U–Pb dating of 61 zircons of magmatic origin showed concentrated data points along the Concordia line, indicating no obvious Pb loss. The crystallization ages of 6 granite samples were dated as 220 Ma, 192 Ma, 261 Ma, 185 Ma, 270 Ma and 273 Ma, respectively. Based on the understanding, we inferred that the limestone of sedimentary genesis imbedded with the Permian formations of the basin was formed during deposition in the Permian era. The magma activity was the most active during the Jurassic. Magmatic intrusion was thought to be originated from deeper parent rocks below the Permian layers. It cut through the Permian limestone from the bottom up and released great amount of heat to bake the limestone. This accelerated hydrocarbon generation in the limestone and increased its KTG (kerogen to gas) rate to 0.9 or more during 190 Ma and 185 Ma. Early hydrocarbon generation and poor preservation are the two hydrocarbon-related features of the limestone. In terms of reservoir lithology, the limestone went through thermal contact metamorphism with the heat and volatile components from magmatic activities. It is also observed that contact metamorphism of the limestone was the most active near the eruption points of magma.