Compositional Analysis of Mineralogy

2014 ◽  
Author(s):  
John H. Doveton
Keyword(s):  
Pore Space ◽  
Compositional Analysis ◽  
Petrophysical Properties ◽  
Rock Composition ◽  
Multiple Components ◽  
West Texas ◽  
Geological Models ◽  
Porosity Logs ◽  
Complex Formations ◽  
Porosity Estimation

Formation lithologies that are composed of several minerals require multiple porosity logs to be run in combination in order to evaluate volumetric porosity. In the most simple solution model, the proportions of multiple components together with porosity can be estimated from a set of simultaneous equations for the measured log responses. These equations can be written in matrix algebra form as: . . . CV = L . . . where C is a matrix of the component petrophysical properties, V is a vector of the component unknown proportions, and L is a vector of the log responses of the evaluated zone. The equation set describes a linear model that links the log measurements with the component mineral properties. Although porosity represents the proportion of voids within the rock, the pore space is filled with a fluid whose physical properties make it a “mineral” component. If the minerals, their petrophysical properties, and their proportions are either known or hypothesized, then log responses can be computed. In this case, the procedure is one of forward-modeling and is useful in situations of highly complex formations, where geological models are used to generate alternative log-response scenarios that can be matched with actual logging measurements in a search for the best reconciliation between composition and logs. However, more commonly, the set of equations is solved as an “inverse problem,” in which the rock composition is deduced from the logging measurements. Probably the earliest application of the compositional analysis of a formation by the inverse procedure applied to logs was by petrophysicists working in Permian carbonates of West Texas, who were frustrated by complex mineralogy in their attempts to obtain reliable porosity estimates from logs, as described by Savre (1963). Up to that time, porosities had been commonly evaluated from neutron logs, but the values were excessively high in zones that contained gypsum, caused by the hydrogen within the water of crystallization. The substitution of the density log for the porosity estimation was compromised by the occurrence of anhydrite as well as gypsum.

scholarly journals Structure-texture peculiarities influence on petrophysical properties of Neftekumsk carbonate sediments

2020 ◽  
Vol 164 ◽  
pp. 01007
Author(s):  
Natalia Yeriomina ◽  
Vladimir Gridin ◽  
Zinaida Sterlenko ◽  
Yelena Tumanova ◽  
Katerina Chernenko
Keyword(s):  
Pore Space ◽  
Three Dimensional ◽  
Carbonate Sediments ◽  
Petrophysical Properties ◽  
Petrophysical Parameters ◽  
The Core ◽  
Geological Models ◽  
Dimensional Distribution

The analysis of structure-texture peculiarities of carbonate sediments of Neftekumsk’ reservoir within the limits of Zimne-Stavkinsko- Pravoberezhny field was realized in the field of massive bioherm buildups and interreef lowerings in accordance with data of the core analyses. The existing pore space was divided into structure-texture classes. The correlations between petrofabrics and petrophysical parameters were determined. The received data can be used for describing of the three- dimensional distribution of petrophysical properties with the aim to increase the quality of three-dimensional (3-D) geological models.

scholarly journals Multifractal Analysis of Pore Structure and Evaluation of Deep-Buried Cambrian Dolomite Reservoir with Image Processing: A Case from Tarim Basin, NW China

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-18
Author(s):  
Xiaojun Zhang ◽  
Haodong Han ◽  
Jun Peng ◽  
Yingchun Gou
Keyword(s):  
Pore Structure ◽  
Thin Section ◽  
Tarim Basin ◽  
Clustering Analysis ◽  
Multifractal Analysis ◽  
Pore Space ◽  
Tectonic Activity ◽  
Petrophysical Properties ◽  
Nw China ◽  
Crystalline Dolomite

Reservoir pore space assessment is of great significance for petroleum exploration and production. However, it is difficult to describe the pore characteristics of deep-buried dolomite reservoirs with the traditional linear method because these rocks have undergone strong modification by tectonic activity and diagenesis and show significant pore space heterogeneity. In this study, 38 dolostone samples from 4 Cambrian formations of Tarim Basin in NW China were collected and 135 thin section images were analyzed. Multifractal theory was used for evaluation of pore space heterogeneity in deep-buried dolostone based on thin section image analysis. The physical parameters, pore structure parameters, and multifractal characteristic parameters were obtained from the digital images. Then, the relationships between lithology and these parameters were discussed. In addition, the pore structure was classified into four categories using K-means clustering analysis based on multifractal parameters. The results show that the multifractal phenomenon generally exists in the pore space of deep-buried dolomite and that multifractal analysis can be used to characterize the heterogeneity of pore space in deep-buried dolomite. For these samples, multifractal parameters, such as αmin, αmax, ΔαL, ΔαR, Δf, and AI, correlate strongly with porosity but only slightly with permeability. However, the parameter Δα, which is usually used to reveal heterogeneity, does not show an obvious link with petrophysical properties. Of dolomites with different fabrics, fine crystalline dolomite and medium crystalline dolomite show the best petrophysical properties and show significant differences in multifractal parameters compared to other dolomites. More accurate porosity estimations were obtained with the multifractal generalized fractal dimension, which provides a new method for porosity prediction. The various categories derived from the K-means clustering analysis of multifractal parameters show distinct differences in petrophysical properties. This proves that reservoir evaluation and pore structure classification can be accurately performed with the K-means clustering analysis method based on multifractal parameters of pore space in deep-buried dolomite reservoirs.

Effets de la texture petrographique sur les proprietes petrophysiques d'un calcaire en zone de diagenese meteorique (calcaire oligocene d'Aquitaine, France)

2000 ◽  
Vol 171 (4) ◽  
pp. 419-430 ◽  
Author(s):  
Adrian Cerepi ◽  
Louis Humbert ◽  
Rene Burlot
Keyword(s):  
Porous Medium ◽  
Specific Surface ◽  
Pore Space ◽  
Space Complexity ◽  
Petrophysical Properties ◽  
Chemical Analyses ◽  
Reservoir Properties

Abstract 120 samples of three quarries of the Oligocene Aquitaine limestone were subjected to petrographic, petrophysical and chemical analyses. Strong variations of depositional and diagenetic textures were observed. Four main depositional textures characterize this limestone: mudstone-wackestone, packstone, packstone-grainstone and grainstone. The diagenetic transformations recognized and specially meteoric leaching increases the heterogeneity of porous medium. The "Pierre de Bordeaux" shows a high variation of porosity (12,8 % to 42,51%), permeability (4,27 to 4755 mD), specific surface (0,78 to 3,73 m 2 /g) and distribution of pore throats (from monomodal to three modal distribution). Petrophysical properties depend strongly on depositional and diagenetic patterns. Textures with two and three modal distribution of porous medium, packstone-grainstone and grainstone have the best reservoir properties. The meteoric dissolution associated to microfracturing improves strongly both the macroporosity, permeability in mudstone-wackestone and packstone and increases the pore space complexity in all textures.

scholarly journals Formation and Accumulation of Pore Methane Hydrates in Permafrost: Experimental Modeling

Geosciences ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 467 ◽  
Author(s):  
Evgeny Chuvilin ◽  
Dinara Davletshina
Keyword(s):  
Gas Hydrates ◽  
Gas Hydrate ◽  
Pore Space ◽  
Hydrate Formation ◽  
Methane Hydrates ◽  
Frozen Soils ◽  
Geological Models ◽  
Negative Temperatures ◽  
Thermobaric Conditions ◽  
Ice Content

Favorable thermobaric conditions of hydrate formation and the significant accumulation of methane, ice, and actual data on the presence of gas hydrates in permafrost suggest the possibility of their formation in the pore space of frozen soils at negative temperatures. In addition, today there are several geological models that involve the formation of gas hydrate accumulations in permafrost. To confirm the literature data, the formation of gas hydrates in permafrost saturated with methane has been studied experimentally using natural artificially frozen in the laboratory sand and silt samples, on a specially designed system at temperatures from 0 to −8 °C. The experimental results confirm that pore methane hydrates can form in gas-bearing frozen soils. The kinetics of gas hydrate accumulation in frozen soils was investigated in terms of dependence on the temperature, excess pressure, initial ice content, salinity, and type of soil. The process of hydrate formation in soil samples in time with falling temperature from +2 °C to −8 °C slows down. The fraction of pore ice converted to hydrate increased as the gas pressure exceeded the equilibrium. The optimal ice saturation values (45−65%) at which hydrate accumulation in the porous media is highest were found. The hydrate accumulation is slower in finer-grained sediments and saline soils. The several geological models are presented to substantiate the processes of natural hydrate formation in permafrost at negative temperatures.

Oil and Gas Reef Facies Reservoir 3D Geological Modeling

2018 ◽  
Vol 785 ◽  
pp. 118-124
Author(s):  
Vadim Aleksandrov ◽  
Marsel Kadyrov ◽  
Zinaida Ufelman ◽  
Vadim Golozubenko ◽  
Vladimir Kopyrin
Keyword(s):  
Oil And Gas ◽  
Three Dimensional ◽  
Geological Modeling ◽  
Reef Facies ◽  
3D Geological Modeling ◽  
Natural Reservoir ◽  
Reef Structure ◽  
Geological Models ◽  
Complex Formations

The paper presents a technique of three-dimensional geological modeling of one of the most complex formations, reef deposits. The research objective is an investigation of how the reef structure genesis influences the three-dimensional geological grid of reef mass. Using the paleogeographic and paleofacies methods of investigation, the conceptual and three-dimensional geological models of a natural reservoir have been constructed.

THE CHARACTERISTICS OF PORE SPACE IN LOWER TRIASSIC SANDSTONES OF THE WARSAW REGION

2019 ◽  
Vol 474 (474) ◽  
pp. 73-84
Author(s):  
Marta KUBERSKA ◽  
Anna BECKER ◽  
Aleksandra KOZŁOWSKA
Keyword(s):  
Carbon Dioxide ◽  
Image Analysis ◽  
Pore Space ◽  
Carbon Dioxide Sequestration ◽  
Lower Triassic ◽  
Underground Storage ◽  
Petrophysical Properties ◽  
Secondary Porosity ◽  
Diagenetic Alteration ◽  
Diagenetic Processes

Reservoir and sealing properties of Lower Triassic sandstones from seven boreholes of the central part of the Koszalin-Zamość Synclinorium were investigated in terms of potential levels for underground storage of carbon dioxide. Extensive petrographic studies, image analysis, and investigations of petrophysical properties of rocks and pore space were carried out. The research shows that diagenetic processes both variously affected the intensity of alteration and variously shaped the pore space. Not only primary but also secondary porosity, resulting from diagenetic alteration and dissolution, is observed in the rocks. Microscopic observations revealed that the pore space in studied samples is dominated by macropores. The results obtained indicate a poor suitability of the Lower Triassic deposits for the purpose of carbon dioxide sequestration.

An Innovative Approach to Integrated Fluid Typing in Depleted Reservoirs

2021 ◽  
Author(s):  
Asari Ramli ◽  
Ayham Ashqar ◽  
M. Azan Karim
Keyword(s):  
Economic Value ◽  
Fluid Phase ◽  
Cost Effective ◽  
Integrated Approach ◽  
Petrophysical Properties ◽  
Fluid Type ◽  
Confidence Factor ◽  
Production History ◽  
Fluid Properties ◽  
Porosity Logs

Abstract The economic value of completing a reservoir is strongly influenced by the fluid type. Wells drilled in developed brown field penetrate reservoirs with significant pressure loss due to offset production. A major challenge in evaluating mature reservoirs is the uncertainty introduced by pore fluids with unknown or varying petrophysical properties, such as change hydrocarbon gravity, diminishing pore pressures, and low to absent gas level indication. These are prone to error and uncertainty. Accurate understanding of reservoir fluid properties is therefore a key requirement for successful reservoir management. This manuscript illustrates a successful integrated workflow to ascertain. An integration between LWD triple combo data, near/far neutron, mud logs, pressure measurement, and production history of neighbouring wells, are critical to confirm fluid type within the drilled reservoirs. Cross plots, ratios and confidence analysis are required to ascertain the confidence level. Acquired data was ranked according to uncertainty associated with the acquisition technique, rate of penetration, lag time, mud type, and pre-test drawdown. Mobility was used as an indicator of fluid type or phase change in absence of any major rock type changes. Gas data were verified for any mud contamination and analysed using ratios to verify Hydrocarbon wetness. Data was ranked based on confidence factor determined through data precision and reservoir propertied. We also highlight the uncertainty in measurements. The fluid typing workflow used successfully identified the correct fluid typing, and reduced the reliance on single conventional method, or the need to run pre-test measurements. Data in intervals dominated with residual oil saturation showed misleading fluid type, same applies in high permeability sand, corrected gas data analysis gave a good indication of fluid type and mapped the change in fluid phase when combined with log data, while near/ far neutron aided to correlate the different sands, however due to its relationship with porosity, there is no one correlation could be derived. This paper illustrates that standard petrophysical techniques, such as analysis of density and neutron porosity logs, near/far neutrons, pretest can give misleading results if used in solo without consideration to the uncertainty associated with the measurement. The integration of fundamentally different data has resulted in identifying the fluid typing and its distribution in the reservoir and without integrating other measurements. A fluid typing systematic was developed to ensure the best and cost-effective model to assure the correct fluid type is identified. In this paper, a methodology is proposed which uses the geodesic transform, and integrate various source fundamentally different data, which is routinely acquired, then develop a systematic reasoning of confidence on data precision and accuracy. The system followed ensured the correct mapping of fluid typing in various reservoirs with different petrophysical properties. It is the first time such workflow is followed, and an integrated approach is consistently used in different sandstone reservoirs.

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