INFLUENCE OF PORE GEOMETRY, PRESSURE AND PARTIAL WATER SATURATION TO ELECTRICAL PROPERTIES OF RESERVOIR ROCK: MODEL AND LABORATORY INVESTIGATION

Pressure and saturation are of two important parameters to be considered to evaluate the electrical properties of reservoir rock. As confining pressure can cause pore space of the rock to collapse and rock properties to change, it is necessary to examine in details how much the pressure and saturation changes affect the electrical properties. Investigations of electrical properties of sandstones and carbonates are the main focus in this work. The effects of pore geometries, confining pressure, and partial water saturation on electrical properties are investigated. The new electrical dispersion models from 0.1 Hz until 0.2 MHz for shaly sandstone are also developed. Petrographic image analysis is carried out to asses pore geometry of the media. Circularity, pore aspect ratio, pore size distribution and pore angle distribution are calculated to evaluate their effect on electrical dispersion. Confining pressure and water saturation observation are then evaluated to obtain their impact on pore structure and complex resistivity. The result of this work shows that surface conductivity plays as a dominant factor particularly in shaly media and it is indicated by electrical resistivity dispersion in low water saturation. When evaluating surface conductivity, the pore geometry has to be considered because large structure is easier to saturate rather than small structure. Moreover, the high water salinity can significantly reduce diffusive layer thickness and if the pore radii are very small, the diffusive layer thickness will touch each other and block the anion movement. In addition to these results, it is found that pore radius distribution provides more contribution to the electrical resistivity dispersion and becomes a basis to extract porosity from resistivity. Confining pressure only contributes small changes in pore geometry of media and the use of imaginary resistivity gives a better detection on it

INFLUENCE OF PORE GEOMETRY, PRESSURE AND PARTIAL WATER SATURATION TO ELECTRICAL PROPERTIES OF RESERVOIR ROCK: MODEL AND LABORATORY INVESTIGATION

Pressure and saturation are of two important parameters to be considered to evaluate the electrical properties of reservoir rock. As confining pressure can cause pore space of the rock to collapse and rock properties to change, it is necessary to examine in details how much the pressure and saturation changes affect the electrical properties. Investigations of electrical properties of sandstones and carbonates are the main focus in this work. The effects of pore geometries, confining pressure, and partial water saturation on electrical properties are investigated. The new electrical dispersion models from 0.1 Hz until 0.2 MHz for shaly sandstone are also developed. Petrographic image analysis is carried out to asses pore geometry of the media. Circularity, pore aspect ratio, pore size distribution and pore angle distribution are calculated to evaluate their effect on electrical dispersion. Confining pressure and water saturation observation are then evaluated to obtain their impact on pore structure and complex resistivity. The result of this work shows that surface conductivity plays as a dominant factor particularly in shaly media and it is indicated by electrical resistivity dispersion in low water saturation. When evaluating surface conductivity, the pore geometry has to be considered because large structure is easier to saturate rather than small structure. Moreover, the high water salinity can significantly reduce diffusive layer thickness and if the pore radii are very small, the diffusive layer thickness will touch each other and block the anion movement. In addition to these results, it is found that pore radius distribution provides more contribution to the electrical resistivity dispersion and becomes a basis to extract porosity from resistivity. Confining pressure only contributes small changes in pore geometry of media and the use of imaginary resistivity gives a better detection on it

INFLUENCE OF PORE GEOMETRY, PRESSURE AND PARTIAL WATER SATURATION TO ELECTRICAL PROPERTIES OF RESERVOIR ROCK: MODEL AND LABORATORY INVESTIGATION

Pressure and saturation are of two important parameters to be considered to evaluate the electrical properties of reservoir rock. As confining pressure can cause pore space of the rock to collapse and rock properties to change, it is necessary to examine in details how much the pressure and saturation changes affect the electrical properties. Investigations of electrical properties of sandstones and carbonates are the main focus in this work. The effects of pore geometries, confining pressure, and partial water saturation on electrical properties are investigated. The new electrical dispersion models from 0.1 Hz until 0.2 MHz for shaly sandstone are also developed. Petrographic image analysis is carried out to asses pore geometry of the media. Circularity, pore aspect ratio, pore size distribution and pore angle distribution are calculated to evaluate their effect on electrical dispersion. Confining pressure and water saturation observation are then evaluated to obtain their impact on pore structure and complex resistivity. The result of this work shows that surface conductivity plays as a dominant factor particularly in shaly media and it is indicated by electrical resistivity dispersion in low water saturation. When evaluating surface conductivity, the pore geometry has to be considered because large structure is easier to saturate rather than small structure. Moreover, the high water salinity can significantly reduce diffusive layer thickness and if the pore radii are very small, the diffusive layer thickness will touch each other and block the anion movement. In addition to these results, it is found that pore radius distribution provides more contribution to the electrical resistivity dispersion and becomes a basis to extract porosity from resistivity. Confining pressure only contributes small changes in pore geometry of media and the use of imaginary resistivity gives a better detection on it. Modified D-model and Archie’s model are developed to calculate the dielectric viii permittivity and effective conductivity in high water salinity saturated-rock as a function of water saturation degree

Small-scale diagenetic facies heterogeneity controls porosity and permeability pattern in reservoir sandstones

The fluvial-aeolian Upper Rotliegend sandstones from the Bebertal outcrop (Flechtingen High, Germany) are the famous reservoir analog for the deeply buried Upper Rotliegend gas reservoirs of the Southern Permian Basin. While most diagenetic and reservoir quality investigations are conducted on a meter scale, there is an emerging consensus that significant reservoir heterogeneity is inherited from diagenetic complexity at smaller scales. In this study, we utilize information about diagenetic products and processes at the pore- and plug-scale and analyze their impact on the heterogeneity of porosity, permeability, and cement patterns. Eodiagenetic poikilitic calcite cements, illite/iron oxide grain coatings, and the amount of infiltrated clay are responsible for mm- to cm-scale reservoir heterogeneities in the Parchim formation of the Upper Rotliegend sandstones. Using the Petrel E&P software platform, spatial fluctuations and spatial variations of permeability, porosity, and calcite cements are modeled and compared, offering opportunities for predicting small-scale reservoir rock properties based on diagenetic constraints

Tipe, Lingkungan Dan Sejarah Diagenesis Batugamping Buliide Gorontalo Berdasarkan Analisis Petrografi

Penyebaran batugamping secara geologi yang berada di bagian tengah Cekungan Limboto menjadi daya tarik untuk penelitian mengenai tipe, lingkungan dan sejarah proses diagenesis batugamping. Penelitian difokuskan di Daerah Buliide Kota Gorontalo  yang berada di bagian selatan Danau Limboto. Penelitian ini menjadi menarik karena baru pertama kali dilakukan. Tujuan penelitian ini ada tiga yakni mengetahui tipe diagenesis, lingkungan diagenesis dan sejarah proses diagenesis batugamping Buliide. Ketiga tujuan penelitian tersebut akan dicapai melalui dua metode penelitian yakni survei lapangan berupa analisis petrologi dan analisis laboratorium berupa analisis petrografi. Hasil penelitian menunjukan nama batugamping Buliide adalah coralline floatstone. Tipe proses diagenesis yang terjadi ada lima yakni sementasi, pelarutan, penggantian, mikritisasi dan rekristalisasi. Lingkungan diagenesa batugamping Buliide terdiri dari zona marine phreatic, zona vadose dan zona freshwater  phreatic. Sejarah proses diagenesis batugamping Buliide dapat dibagi menjadi tiga tahapan yakni tahapan pertama terjadi di zona marine phreatic, tahapan kedua zona freshwater phreatic dan tahapan ketiga zona vadose dengan tipe diagenesis berbeda-beda

Fabrication of micro-/nanofluidic models and their applications for enhanced oil recovery mechanism study

”Micro-/nanofluidic model, as a potential powerful tool, has been used for decades for investigating fluid flow at pore-scale in energy field. It is still increasingly imperative nowadays to use different micromodels to direct observe pore-level fluid flow and analyze mechanisms of different enhanced oil recovery methods. In this work, three main tasks including three dimensional micromodels (1D,2D,3D) are proposed to fabricate and use for investigating different mechanisms of different enhanced oil recovery methods. For 1D capillary tube micromodel, we fabricate and use it to investigate the dynamics of a trapped oil droplet under seismic vibration. Seismic stimulation is a promising technology aimed to mobilize the entrapped non-wetting fluids in the subsurface. The applications include enhanced oil recovery or CO2 sequestration. For 2D micromodel, we fabricate to mimic unconventional dual-porosity shale-like tight porous media and investigate the fluid flow behavior under such conditions. Unconventional oil reservoirs have become significant sources of petroleum production and have even better potential in the future. Many shale oil systems consist of nanoscale pores and micro-scale fractures that are significantly smaller than those from conventional reservoirs. Therefore, it is increasingly important to investigate fluid flow behaviors in nanoscale channels. For 3D micromodel, we packed and sintered glass beads into quartz tubes to mimic 3D porous media. Because of difficulties for direct visualization, almost all the micromodels available are two-dimensional models which cannot represent real interconnected pore network of a real reservoir porous media. Thus, we build fully transparent 3D models to direct visualize and investigate the in-situ emulsification mechanism for nanogel flooding”--Abstract, page iv

Structural and diagenetic controls on reservoir quality in tight siliciclastic and carbonate rocks

Upper Carboniferous (Westphalian C/D) fluvial sandstones and Zechstein Ca2 (Stassfurt, second cycle) carbonates represent two important hydrocarbon reservoir units in NW Europe. A better understanding of reservoir quality variations and their spatial variability is crucial to develop successful exploration strategies. In fluvial Westphalian C/D sandstones and Ca2 carbonate reservoirs, the reservoir properties are controlled by diagenetic alterations and intense fracturing

Holistic correlation of physical and mechanical properties of selected natural stones for assessing durability and weathering in the natural environment.

The main purpose of this study is to understand influences of bulk structure of materials on strength behavior as well as water storage and transfer in order to assess durability and weathering. Therefore, a selection of different methods are applied and compared to optimize the understanding of material structure and physico-mechanical behavior. Optical microscopy (Digital Image Analysis) and scanning electron microscopy as well as water vapor permeability, biaxial flexural strength and ultrasonic velocity are measured on different natural materials: sandstones with clayey, silicious or calcareous binder, oolithic and micritic magnesian limestones and a thermally aged Proconnesian marble. Microstructurales and macrostructurales properties of these materials are studied before and after artificial weathering (freeze-thaw cycles). First, and in order to validate the efficiency of the digital image analysis to characterize porosity and structure, traditional porosity measurements as water ad- and absorption and mercury porosimetry are crosschecked with the result obtained from digital image analysis. Limits of each methods are also defined. Then, validations of non-destructive and semi-destructive methods are also pursued to evaluate their potential value to replace and complement standardized methods. By analysis of linear correlations, some essential mechanisms should be underlined, which may connect the macrostructure to the microstructure of the material. A systematic method of analysis should clearly appear and emphasize the role of the structure (grain size, grain contact and pore shape) on physical and mechanical behavior. The main parameters leading to weathering should then be identified and models of correlations drawn. Correlations between the various physico-mechanical properties could ameliorate the possibilities to assess durability and weathering in the natural environment

Visual Methods of Monitoring the Effect of Wettability on Fines Migration in Sandstones

Global energy demands are changing, with focus on replacement of hydrocarbons with renewables. However, the reliance on hydrocarbons cannot be removed in the short term, so any methods to improve the efficiency and environmental profile of hydrocarbon extraction are needed. Hydrocarbon extraction rate may be reduced if the formation becomes damaged during the extraction process. This damage may be particularly problematic during low salinity enhanced oil recovery (EOR) and although there are many mechanisms by which this may happen, the mechanism which is of particular interest in this work is that of fines migration, especially in combination with variation of wettability. This work considers a variety of different methods to investigate the ways in which fine mineral particles move when encountering surfaces with variable wettability, and new test methods to rapidly assess the fines migration potential of a sandstone. Throughout this work, 3D printing is used to assist in these investigations, and hence firstly a comprehensive study of the wettability of commonly used 3D printing materials was undertaken which showed good agreement with the literature. Contributions to the wettability of aspects of the printing process resulting in variation of roughness was also evaluated but did not correlate at the length scales studied. Secondly, a study of the likelihood of removal of fines from sandstones by ultrasonic treatment in various salinity brines was performed, finding increased removal in low salinity brines and giving general agreement to those previously reported in the literature. Finally, several conceptual experiments looking at methods to monitor the movement of fine particles over surfaces of variable wettability, including drop spread and flow through 3D printed flow cells with individual particle tracking, were carried out. The results were compared to flow simulations and showed good agreement between particle tracking and simulated flow

Pore-scale Visualisation and Geochemical Modelling of Low Salinity Water Flooding as an Enhanced Oil Recovery Method

Low salinity water (LSW) injection is a promising technique for improving oil recovery from reservoirs. The salinity ranges from 1000 to 2000 ppm which is significantly less than the salinity of the formation brine. However, the mechanisms underlying the Low Salinity Effect (LSE) are not well understood. To investigate the dynamics of displacement, clean and clay coated micromodels were fabricated and used where the wettability was set to both water-wet and oil-wet. This allows the visualisation of pore-scale displacement mechanisms in the presence and absence of kaolinite and illite. It is observed that in water-wet systems, in the absence and presence of clays, LSW hinders “snap-off,” perhaps due to the development of a viscoelastic water/oil interface. There was a transition from snap-off to piston-like displacement in much of the volume of each pore and the amount of trapped oil was decreased by almost 10%. The wettability alteration toward water-wetness is also visualised for oil-wet systems which resulted in 15% improved recovery in oil-wet porous medium. Throughout LSW injection microfluidic experiments after the long-term aging period with oil, fines migration was insignificant. In another set of experiments, when the systems were flushed with LS brine without any delay, fines migration was significant. These observations suggest that the aging time and crude oil composition are contributing factors to fines release. Also analysed is the impact of type of clay mineral and nature of cations on LSE, using geochemical modelling complemented with visualisation experiments. The models are developed to provide the charge density and electrostatic potential profiles (the ζ-potential) at the brine/mineral interface of illite as a basal-charged clay against an edge-charge dominated kaolinite. Based on the observations and simulation results, it was concluded that since kaolinite has higher density of acid/base reaction sites on its surface (edges) than does illite, the charge development under differing ionic strength and pH was significant. As a result, kaolinite responded well to LSW injection, whereas illite did not. This could elucidate the unlike sensitivities of clays to LSW, such as their extent of being prone to wettability alteration. The SCM results agree well with the microfluidic results when DLE is considered the mechanism behind LSE. The extent of the ζ-potential calculated by SCMs shows the degree of electrostatic repulsion between adjacent, similarly charged surfaces, that is, the brine− oil and brine−clay interfaces, so the enhanced repulsion forces weakened the oil and clay pinning points. As a result, wettability altered toward more water-wetness, which is confirmed by contact angle measurements. Once the attraction forces were low enough, the oil was released from the clay surface and replaced by water, as observed in microfluidic experiments. If the chemical composition of connate water and the content of clay minerals in a particular reservoir can be determined to a degree, the findings of this study will determine the concentration of ions and pH of the injecting water that maximise LSE (wettability alteration) and the resulting oil recovery.Thesis (Ph.D.) -- University of Adelaide, Australian School of Petroleum, 201