RELIABLE QUANTIFICATION OF PORE GEOMETRY IN CARBONATE ROCKS USING NMR AND ELECTRICAL RESISTIVITY MEASUREMENTS FOR ENHANCED ASSESSMENT OF PERMEABILITY AND CAPILLARY PRESSURE

2021 ◽  
Author(s):  
Zulkuf Azizoglu ◽  
◽  
Artur Posenato Garcia ◽  
Zoya Heidari ◽  
◽  
...  
Keyword(s):  
Pore Size Distribution ◽  
Pore Size ◽  
Capillary Pressure ◽  
Size Distribution ◽  
Pore Geometry ◽  
Pore Throat ◽  
Permeability Model ◽  
Resistivity Measurements ◽  
Constriction Factor ◽  
Directional Permeability

Reliable and real-time assessment of directional permeability and saturation-dependent capillary pressure are utterly important because they significantly affect the exploitation strategies. Conventional well-log-based methods (e.g., NMR-based, saturation-height analysis, resistivity-based, correlation-based) are either highly dependent on calibration efforts or rely on model parameters which are difficult to obtain in real-time and make them dependent on core measurements. Moreover, most conventional methods for assessment of directional permeability and saturation-dependent capillary pressure fail in the presence of multi-modal pore-size distribution. Recent publications suggested that integration of transverse Nuclear Magnetic Resonance (T2 NMR) and resistivity measurements enables assessment of pore-throat-size distribution as well as permeability and capillary pressure. However, the reliability of these methods is questionable in rocks with complex/multi-modal pore geometry. The objectives of this paper include (a) reliably estimating a variable constriction factor (a geometric parameter which relates the pore- and throat-size) in rocks with complex pore geometry to accurately quantify pore geometry, which is the main contribution of this work, (b) developing a new rock physics workflow for integrating NMR and electrical conductivity for assessment of permeability and capillary pressure that takes into account a variable constriction factor, and (c) verifying the reliability of the introduced workflow using core scale measurements. The proposed workflow starts with calculating pore-body-size distribution from NMR T2 distribution. Then, we combine electrical resistivity and pore-size distribution to estimate the distribution of constriction factor in the pore structure. Next, we determine pore- throat-size distribution using the estimated variable constriction factor. We then introduce a new permeability model which takes variable constriction factor into account. The inputs to the permeability model include throat-size distribution, tortuosity, and porosity. Finally, we calculate saturation-dependent capillary pressure using the estimated throat-size distribution. We successfully verified the reliability of the introduced workflow in the core-scale domain in carbonate rock samples with complex pore structure. The permeability estimates obtained by the new workflow yielded less than 7% average relative error when compared against core measurements. We also observed a good agreement between the throat-size distribution and capillary pressure estimated from the new workflow and the ones acquired from MICP (mercury injection capillary pressure) measurements. Results also confirmed that integration of a variable constriction factor improves directional permeability estimates compared to cases where an effective constriction factor was used to quantify pore-throat size distribution in rocks with multi-modal pore-size distribution.

Trapping patterns during capillary displacements in disordered media

2022 ◽  
Vol 933 ◽  
Author(s):  
Fanli Liu ◽  
Moran Wang
Keyword(s):  
Numerical Simulations ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Disordered Media ◽  
Pore Geometry ◽  
Control Parameters ◽  
Pore Throat ◽  
The Impact ◽  
Theoretical Analyses

We investigate the impact of wettability distribution, pore size distribution and pore geometry on the statistical behaviour of trapping in pore-throat networks during capillary displacement. Through theoretical analyses and numerical simulations, we propose and prove that the trapping patterns, defined as the percentage and distribution of trapped elements, are determined by four dimensionless control parameters. The range of all possible trapping patterns and how the patterns are dependent on the four parameters are obtained. The results help us to understand the impact of wettability and structure on trapping behaviour in disordered media.

Statistical Based Estimation of Biporous Evaporator Dryout

2013 ◽  
Author(s):  
Sean Reilly ◽  
Ivan Catton
Keyword(s):  
Pressure Drop ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Capillary Pressure ◽  
Size Distribution ◽  
Numerical Estimate ◽  
Effective Means ◽  
Electronics Cooling ◽  
Vapor Permeability ◽  
Dry Out

Biporous wicks are an effective means for facilitating evaporation in heat pipes used for electronics cooling. They facilitate boiling within the wick by having two distinct size distributions of pores; the smaller pores provide high capillary pressure to pump liquid to the surface while the larger pores maintain high vapor permeability. The wicks investigated in this study were sintered copper biporous material. The authors previously presented a validated statistical model, based on work by Kovalev, which could predict the performance of biporous wicks tested at UCLA with reasonable accuracy [1]. Using this model, the author was able to gain new insight into the effect that the numerical estimate of liquid saturation of the wick has on dry out. The pore size distribution allows the determination of the capillary pressure available inside the wick and the Kovalev model provides the required pressure drop to supply liquid water to the heater surface. This led to a method of predicting dry out by comparing the capillary pressure in the wick to the required pressure drop from the model to estimate when the wick was dried out. When the required pressure drop determined by code exceeds the peak effective capillary pressure provided by the wick, the large pores of the wick are considered to be dry. These values are correlated to the input heat flux to determine what at what input power the wick begins to dry out. While the wick will not fail in this mode, the overall heat transfer coefficient will have peaked. In this work, this method of determining dry out will be validated against wicks tested at UCLA by comparing the input powers at which this dry out phenomenon occurs. Accurate predictions of dry out and the role of the pore size distribution are critical in developing methods to delay dry out of biporous wicks. By comparing the relative dry out points of various wick geometries to each other, augmented wick geometries can be suggested for future work. This modeling tool can lay the foundation for future tailoring of biporous evaporator wicks to specific tasks.

Calculating Pore Size Distribution by Using Capillary Pressure

2014 ◽  
Author(s):  
Kegang Ling ◽  
Guoqing Han ◽  
Zheng Shen ◽  
Ali Ghalambor ◽  
Jun He ◽  
...  
Keyword(s):  
Pore Size Distribution ◽  
Pore Size ◽  
Capillary Pressure ◽  
Size Distribution

scholarly journals An integrated pore size distribution measurement method of small angle neutron scattering and mercury intrusion capillary pressure

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Rui Shen ◽  
Xiaoyi Zhang ◽  
Yubin Ke ◽  
Wei Xiong ◽  
Hekun Guo ◽  
...  
Keyword(s):  
Neutron Scattering ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Capillary Pressure ◽  
Size Distribution ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Measurement Method ◽  
Full Scale ◽  
Mercury Intrusion

AbstractSmall-angle neutron scattering and high-pressure mercury intrusion capillary pressure testing are integrated to analyze the pore size distribution of the broad sense shale oil reservoir samples of the Permian Lucaogou Formation in the Jimsar Sag, Junggar Basin, China. The results show that, compared with the measurement method integrating gas adsorption and mercury intrusion, combination of small-angle neutron scattering and mercury intrusion can more accurately characterize full-scale pore size distribution. The full-scale pore size distribution curve of the rock samples in the study area includes two types: the declining type and submicron pore-dominated type. The declining type is mainly found with silty mudstone and dolomitic mudstone, and most of its pores are smaller than 80 nm. Silt-fine sandstones and dolarenite are mostly of the submicron pores-dominated type, with most pores smaller than 500 nm. They also present large specific pore volumes and average pore diameters of macropores and are the favorable lithogenous facies for development of high-quality reservoirs.

A New Approach for Building Composite Cores for Corefloods in Complex Carbonate Rocks

2021 ◽  
Author(s):  
Yildiray Cinar ◽  
Ahmed Zayer ◽  
Naseem Dawood ◽  
Dimitris Krinis
Keyword(s):  
Pore Size Distribution ◽  
Pore Size ◽  
Capillary Pressure ◽  
Size Distribution ◽  
Carbonate Reservoir ◽  
Reservoir Rock ◽  
Rock Types ◽  
Pore Structures ◽  
Irreducible Water Saturation ◽  
Wide Range

Abstract Carbonate reservoir rocks are composed of complex pore structures and networks, forming a wide range of sedimentary facies. Considering this complexity, we present a novel approach for a better selection of coreflood composites. In this approach, reservoir plugs undergo a thorough filtration process by completing several lab tests before they get classified into reservoir rock types. Those tests include conventional core analysis (CCA), liquid permeability, plug computed tomography (CT), nuclear magnetic resonance (NMR), end-trim mercury injection capillary pressure (MICP), X-ray diffraction (XRD), thin-section analysis (TS), scanning electron microscopy (SEM), and drainage capillary pressure (Pc). We recommend starting with a large pool of plugs and narrowing down the selection as they complete different stages of the screening process. The CT scans help to exclude plugs exhibiting composite-like behavior or containing vugs and fractures that potentially influence coreflood results. After that, the plugs are categorized into separate groups representing the available reservoir rock types. Then, we look into each rock type and determine whether the selected plugs share similar pore-structures, rock texture, and mineral content. The end-trim MICP is usually helpful in clustering plugs having similar pore-throat size distributions. Nevertheless, it also poses a challenge because it may not represent the whole plug, especially for heterogeneous carbonates. In such a case, we recommend harnessing the NMR capabilities to verify the pore-size distribution. After pore-size distribution verification, plugs are further screened for textural and mineral similarity using the petrographic data (XRD, TS, and SEM). Finally, we evaluate the similarity of brine permeability (Kb), irreducible water saturation (Swir) from Pc, and effective oil permeability data at Swir (Koe, after wettability restoration for unpreserved plugs) before finalizing the composite selection. The paper demonstrates significant aspects of applying the proposed approach to carbonate reservoir rock samples. It integrates geology, petrophysics, and reservoir engineering elements when deciding the best possible composite for coreflood experiments. By practicing this workflow, we also observe considerable differences in rock types depending on the data source, suggesting that careful use of end-trim data for carbonates is advisable compared to more representative full-plug MICP and NMR test results. In addition, we generally observe that Kb and Koe are usually lower than the Klinkenberg permeability with a varying degree that is plug-specific, highlighting the benefit of incorporating these measurements as additional criteria in coreflood composite selection for carbonate reservoirs.

Effect of Pore-Size Distribution on Phase Transition of Hydrocarbon Mixtures in Nanoporous Media

SPE Journal ◽  
2016 ◽  
Vol 21 (06) ◽  
pp. 1981-1995 ◽  
Author(s):  
Lei Wang ◽  
Xiaolong Yin ◽  
Keith B. Neeves ◽  
Erdal Ozkan
Keyword(s):  
Phase Transition ◽  
Phase Change ◽  
Pore Size Distribution ◽  
Phase Behavior ◽  
Pore Size ◽  
Capillary Pressure ◽  
Size Distribution ◽  
Hydrocarbon Mixtures ◽  
Nanoporous Media ◽  
Light Oil

Summary Pore sizes of many shale-oil and tight gas reservoirs are in the range of nanometers. In these pores, capillary pressure and surface forces can make the phase behavior of hydrocarbon mixtures different from that characterized in pressure/volume/temperature (PVT) cells. Many existing phase-behavior models use a single pore size to describe the effect of confinement on phase behavior. To follow up with our earlier theoretical studies and experimental observations, this research investigates the effect of pore-size distribution. By use of a vapor/liquid equilibrium model that considers the effect of capillary pressure, we present a procedure to simulate the sequence of phase changes in a porous medium caused by a pore-size distribution. This procedure is used to simulate depressurizations of a light oil and a retrograde gas confined inside nanoporous media, the pore-size distributions of which are characteristic of tight reservoirs. The fluid compositions are representative of typical reservoir fluids. Predictions of the model show that phase transition in nanoporous medium with pore-size distribution is not described by a single phase boundary. The initial phase change in the large pores alters the composition of the remaining fluid, and, in turn, suppresses the next phase change. For the two cases studied, models with and without capillary pressure gave similar predictions. For light oil, capillary pressure still noticeably increased the level of supersaturation, and the critical gas saturation had a strong influence on the properties of produced fluids. For retrograde gas, the effect of capillary pressure was insignificant because of the low interfacial tension (IFT). Despite the choice of fluids, calculations indicate that the smallest pores are probably always occupied by hydrocarbon liquid during depressurization.

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