Reduction and prediction of sandstone reservoir potential, Jurassic , North Sea

1985 ◽  
Vol 315 (1531) ◽  
pp. 187-202 ◽  
Keyword(s):  
North Sea ◽  
Burial Depth ◽  
Pore Waters ◽  
Secondary Porosity ◽  
Depth Data ◽  
General Decline ◽  
Mineral Compositions ◽  
The Difference ◽  
Detrital Mineral ◽  
Reservoir Potential

Porosity, permeability, mineralogical and depth data for two North Sea Jurassic sandstone sequences were analysed. Both sequences show statistically significant negative correlations between present burial depth and porosity. The influence of secondary porosity creation is subordinate to that of the general decline in porosity. For a given burial depth , sequence A is, on average, a little more porous (about 3%) than B. However, for a given porosity sequence A displays a permeability 1—3 orders of magnitude greater than B. The large permeability difference between A and B is a function of authigenic mineralogy. The only significant cement within the reservoir intervals of sequence A is quartz . Sequence B contains authigenic clays, quartz and subordinate carbonate. The abundant authigenic clay in B severely reduced permeability. In both instances, the cements are products of burial and were precipitated from pore waters expelled from shales during compaction. The expelled pore waters were both acidic and rich in solutes; a product of reactions between maturing organic matter, clays and iron oxides. The difference in authigenic mineralogy between the sequences was caused by the reaction between pore waters and sandstones with different detrital mineral compositions. Thus the present reservoir quality is a product of burial and of the reactions between evolving pore fluids and minerals in the sandstone.

Dissolution of apatite in North Sea Jurassic sandstones: implications for the generation of secondary porosity

Clay Minerals ◽  
1986 ◽  
Vol 21 (4) ◽  
pp. 711-733 ◽  
Author(s):  
A. C. Morton
Keyword(s):  
High Temperature ◽  
North Sea ◽  
Sedimentary Basins ◽  
Mineral Dissolution ◽  
Heavy Mineral ◽  
Heavy Minerals ◽  
Burial Depth ◽  
Pore Fluids ◽  
Secondary Porosity ◽  
Deep Burial

AbstractHeavy-mineral studies on Jurassic sandstones from the central and northern North Sea areas and from the Lossiemouth Borehole (onshore NE Scotland) show that the dissolution of apatite is a function of depositional environment rather than burial depth. In the shallow marine Upper Jurassic sands of the Claymore, Clyde and Tartan Fields, and in the deeper-water Magnus sands, apatite is ubiquitous, even where burial depths exceed 3800 m. Conversely, the fluvio-deltaic sands of the Beatrice, Heather, Ninian and Murchison Fields, and of the Lossiemouth Borehole, have suffered apatite dissolution, although burial depths range from very shallow (Lossiemouth Borehole) to about 3300 m. This clearly indicates that apatite dissolution has taken place through penetration of low-pH meteoric groundwaters at a very early stage in diagenesis, and that high-temperature fluids circulating in deep burial have had little or no effect. This is in accord with patterns of mineral dissolution observed in other sedimentary basins and in the North Sea Palaeocene. Although dissolution of heavy minerals is unlikely to generate significant secondary porosity, the process is nevertheless caused by the same pore-fluids that dissolve major framework constituents. Patterns of heavy-mineral dissolution therefore provide clues to the nature of these pore-fluids. Here, the relative stability of apatite is particularly significant. The order of stability apatite > garnet > kyanite, which characterizes deep burial of North Sea sandstones, has previously been simulated experimentally using fluids of pH 8 at room temperature. This suggests that high-temperature acidic pore-fluids may not have played a significant role in the development of secondary porosity in North Sea sandstones.

Inversion of Reservoir Parameters by Ultra-High Temperature and High Pressure CO2 Gas Reservoirs with Nuclear Logging

2021 ◽  
Author(s):  
Hengrong Zhang ◽  
Lizhi Xiao ◽  
Wensheng Wu ◽  
Xinyue Fu ◽  
Shenglin He
Keyword(s):  
Joint Inversion ◽  
Simulation Method ◽  
Inversion Method ◽  
Burial Depth ◽  
Gas Reservoirs ◽  
Co2 Gas ◽  
Carbonate Cement ◽  
Response Equation ◽  
Temperature And Pressure ◽  
The Difference

Abstract The Yinggehai basin is located in the western part of the South China Sea, the burial depth of the Huangliu and Meishan formations in the target layer is close to 4000 meters, the formation temperature is close to 200 degrees Celsius, and the formation pressure is up to 100 MPa. The reservoir is characterized by low porosity-ultra-low permeability, heavy carbonate cement, complex CO2 content, this leads to complex neutron and density logging effects. The solubility of CO2 Above CH4, the solubility change with temperature and pressure is different from CH4, which makes it difficult to identify the CO2 gas layer. In this paper, based on the difference in the physical characteristics of CO2 and CH4, the Boltzmann equation combined with MCNP software was used to simulate the neutron and density logging responses under different CO2 saturations. Environmental factors such as temperature and pressure, carbonate cement, mud content and pores were studied To measure the effect of logging response, the LM inversion method is used to jointly invert CO2 saturation of density and neutron logs. The purpose of the inversion is to reduce the non-uniqueness of the evaluation of porosity and CO2 saturation. By introducing the Levenberg-Marquardt (LM) method, the neutron logging response equation of the porosity, argillaceous content, CO2, CH4 in the rock and the corresponding temperature and pressure is solved, and also the response equation of above parameters to density logging, where porosity and CO2 content are the key parameters, and the calculation results prove the effectiveness of the method by comparing the sampling data. The results show that the accuracy of the estimated CO2 saturation is increased by 10% compared with the conventional interpretation method, and the new simulation method improves the calculation speed several times compared to the MCNP software. The joint inversion method has been successfully applied to field data, which has greatly improved the saturation evaluation results of traditional logging interpretation methods, can be extended to other fields of nuclear logging simulation and inversion.

Mineralogical Study of Huashan Granite-Type Uranium Ore Deposit in Northeast of Guangxi

2012 ◽  
Vol 621 ◽  
pp. 17-22 ◽  
Author(s):  
Zhi Qiang Kang ◽  
Zuo Hai Feng ◽  
Yong Gao Huang ◽  
Hong Yi Chen ◽  
Wei Fu ◽  
...  
Keyword(s):  
Uranium Mineral ◽  
Ore Deposit ◽  
Granite Pluton ◽  
Uranium Ore ◽  
Mineralogical Characteristics ◽  
Granite Type ◽  
Mineralogical Study ◽  
Mineral Compositions ◽  
The Difference ◽  
Main Component

Huashan granite-type uranium ore deposit is originated within the Huashan granite pluton in northeast of Guangxi, the mineral (mineralization) occurrences already found include Changchong, Baishijiao and Caomiping. Previous studies are relatively weak, especially in mineralogical characteristics, in this paper, a detailed study of minerals has been carried out through EPMA and EDS, the results show that the uranium mineral compositions of the three mineral (mineralization) occurrences are significantly different, but all of them are of secondary uranium minerals, among them, the main component of Changchong mineral (mineralization) occurrence is (meta-) autunite, of Baijiaoshi mineral (mineralization) occurrence is kasolite, and of Caomiping mineral (mineralization) occurrence is torbernite and zeunerite, which reflect the difference of their minerals sources.

Analysis of Ground Massif Temperatures with Slinky Horizontal Heat Exchanger

2015 ◽  
Vol 752-753 ◽  
pp. 1035-1039 ◽  
Author(s):  
Michaela Šeďová ◽  
Pavel Neuberger ◽  
Radomír Adamovský
Keyword(s):  
Heat Exchanger ◽  
Heat Source ◽  
Heat Pump ◽  
Cold Water ◽  
Heat Energy ◽  
Burial Depth ◽  
Heating Season ◽  
Energy Potential ◽  
The Difference ◽  
Subsurface Temperatures

The article is describing a ground massif with a Slinky heat exchanger as a heat source for a heat pump, which is used for cold water warming and a heating of an administration building. The object of the research is to analyse the influence of the heat exchanger on the ground massif temperature while extracting heat energy at the beginning and during the heating season 2012 - 2013, as well as beyond it. Based on executed measurements the process of the ground massif temperatures near the exchanger is described. Also described is temperature process of the ground massif on a reference lot in a burial depth of the heat exchanger, and also subsurface temperatures in a depth of 0.2 m. The energy potential of the ground massif was evaluated using the difference of temperatures of the ground massif in the area of the Slinky heat exchanger at the beginning and at the end of the heating season.

Diagenesis of the shallow marine Fulmar Formation in the Central North Sea

Clay Minerals ◽  
1986 ◽  
Vol 21 (4) ◽  
pp. 537-564 ◽  
Author(s):  
D. J. Stewart
Keyword(s):  
Clay Mineral ◽  
North Sea ◽  
Large Scale ◽  
Shear Zones ◽  
Upper Jurassic ◽  
Burial Diagenesis ◽  
Secondary Porosity ◽  
Shallow Marine ◽  
History Of ◽  
Central North Sea

AbstractThe diagenetic history of the Upper Jurassic Fulmar Formation of the Central North Sea is described with emphasis on the Fulmar Field. The Fulmar Formation was deposited on a variably subsiding shallow-marine shelf under the influence of halokinetic and fault movements. The sediments are extensively bio-destratified although large-scale cross-bedding is locally preserved. The dominant mechanism of deposition is thought to have been storm-generated currents. Soft-sediment deformation structures are common and are attributed to syn- and post-depositional dewatering of the sandstones. The dewatering was associated with fractures and shear zones which reflect tectonic instability resulting from periodic salt withdrawal and/or graben fault movements. The dewatering may have been initiated by repacking of the sediments during earth movements or by the gradual build-up and sudden release of overpressures due to compaction and/or clay mineral dehydration during rapid burial at the end of the Cretaceous. The formation is composed of arkosic sandstone of similar composition to Triassic sandstones from which it was probably derived. The sandstones also contain limited amounts of marine biogenic debris including sponge solenasters, bivalve shells, rare ammonites and belemnites. Initial diagenesis began with an environment-related phase during which quartz and feldspar overgrowths and chalcedony and calcite cements were precipitated. These cements appear to form concretions adjacent to local concentrations of sponge debris and shell debris, respectively, and were disturbed after their formation by fracturing and dewatering. This was followed by an early burial stage of diagenesis which resulted in extensive dolomite cementation and minor clay mineral authigenesis (illite and chlorite). The last phase of mineral growth was probably pyrite. During early burial diagenesis, secondary porosity after feldspar and/or carbonate was produced, although the exact timing is not clear. The lack of both stylolitic developments and extensive illitization indicates that the late burial diagenesis stage was never reached, although sufficient clay diagenesis occurred to destroy all traces of mixed-layer illite-smectite (present in some shallower wells). The main control on reservoir behaviour is primary depositional fabric. Diagenesis only overprints these controls. Locally-cemented fracture sets act as baffles to fluid flow, but they are not extensive and the reservoir acts as one unit.

POROSITY GENERATION AND RESERVOIR POTENTIAL OF OULDBURRA FORMATION CARBONATES, OFFICER BASIN, SOUTH AUSTRALIA

1995 ◽  
Vol 35 (1) ◽  
pp. 106 ◽  
Author(s):  
M.R. Kamali ◽  
N.M. Lemon ◽  
S.N. Apak
Keyword(s):  
Oil And Gas ◽  
South Australia ◽  
Gas Production ◽  
Burial Diagenesis ◽  
Secondary Porosity ◽  
Oil And Gas Production ◽  
Shallow Marine ◽  
Subaerial Exposure ◽  
The Usa ◽  
Reservoir Potential

Porosity generation and reservoir potential of the early Cambrian Ouldburra Formation in the eastern Officer Basin is delineated by combining petrographical, petrophysical and sedimentological studies. The shallow marine Ouldburra Formation consists of carbonates, mixed carbonates and clastics, clastics and evaporites. Detailed analysis of more than 100 samples shows that dolomitisation resulted in substantial secondary porosity development within the carbonates. Secondary porosity has also been generated within the mixed siliciclastic-carbonate zone by carbonate matrix and grain dissolution as well as by dolomitisation. Prospective reservoir units correspond to highstand shallow marine facies where short periods of subaerial exposure resulted in diagenetic changes.Sedimentary facies and rock character indicate that sabkha and brine reflux models are applied to dolomitisation within the Ouldburra Formation. Dolomite mainly occurs in two stages: common anhedral dolomites formed early by replacement of pre-existing limestone, and saddle dolomite and coarse crystalline dolomite formed during the late stages of burial diagenesis, associated with hydrocarbon shows. The dolomite reservoirs identified are ranked on the basis of their porosity distribution and texture into groups I to IV. Dolomites with rank I and II exhibit excellent to good reservoir characteristics respectively.The Ouldburra Formation shows many depositional and diagenetic similarities to the Richfield Member of the Lucas Formation in the Michigan Basin of the USA. Substantial oil and gas production from middle Devonian shallow water to sabkha dolomites makes the Richfield Member an attractive reservoir analogue to the Ouldburra Formation.

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