Characterization of Fluid Drainage Mechanism at Core and Pore Scales: an NMR Capillary Pressure–Based Saturation Exponent Prediction

2021 ◽  
Author(s):  
Abubakar Isah ◽  
Abdulrauf Rasheed Adebayo ◽  
Mohamed Mahmoud ◽  
Lamidi O. Babalola ◽  
Ammar El-Husseiny
Keyword(s):  
Electrical Resistivity ◽  
Capillary Pressure ◽  
Oil Recovery ◽  
Gas Storage ◽  
Pressure Curve ◽  
Pore Scale ◽  
Resistivity Index ◽  
Capillary Pressure Curve ◽  
In Series ◽  
Saturation Exponent

Abstract Capillary pressure (Pc) and electrical resistivity index (RI) curves are used in many reservoir engineering applications. Drainage capillary pressure curve represents a scenario where a non-wetting phase displaces a wetting phase such as (i) during gas injection (ii) gas storage in reservoirs (e.g. aquifer or depleted hydrocarbon reservoirs). The gas used for injection is typically natural gas, N2, or CO2. Gas storage principally used to meet requirement variations, and water injection into oil-wet reservoirs are drainage processes. Resistivity index (RI) curve which is used to evaluate the potential of oil recovery from a reservoir, is also an important tool used in log calibration and reservoir fluid typing. The pore drainage mechanism in a multimodal pore system is important for effective recovery of hydrocarbon reserves; enhance oil recovery (EOR) planning and underground gas storage. The understanding of pore structure and drainage mechanism within a multimodal pore system during petrophysical analysis is of paramount importance to reservoir engineers. Therefore, it becomes inherent to study and establish a way to relate these special core analyses laboratory (SCAL) methods with quick measurements such as the nuclear magnetic resonance (NMR) to reduce the time requirement for analysis. This research employed the use of nuclear magnetic resonance (NMR) to estimate saturation exponent (n) of rocks using nitrogen as the displacing fluid. Different rock types were used in this study that cover carbonates, sandstones, and dolomites. We developed an analytical workflow to separate the capillary pressure curve into capillary pressure curve for macropores and a capillary pressure curve for the micropores, and then used these pore scale Pc curves to estimate an NMR - capillary pressure - based electrical resistivity index - saturation (NMR-RI-Sw) curve for the rocks. We predicted the saturation exponent (n) for the rock samples from the NMR-RI-Sw curve. The NMR-based saturation exponent estimation method requires the transverse (T2) relaxation distribution of the rock - fluid system at various saturations. To verify the reliability of the new workflow, we performed porous plate capillary pressure and electrical resistivity measurements on the rock samples. The reliability of the results for the resistivity index curve and the saturation exponent was verified using the experimental data obtained from the SCAL method. The pore scale Pc curve was used to ascertain the drainage pattern and fluid contribution of the different pore subsystems. For bimodal rock system, the drainage mechanism can be in series, in parallel, or in series - parallel depending on the rock pore structure.

New Methods for Measuring Imbibition Capillary Pressure and Electrical Resistivity Curves by Centrifuge

1974 ◽  
Vol 14 (03) ◽  
pp. 243-252 ◽  
Author(s):  
Miklos T. Szabo
Keyword(s):  
Electrical Resistivity ◽  
Gravitational Field ◽  
Capillary Pressure ◽  
Water Reservoir ◽  
Pressure Curve ◽  
Resistivity Index ◽  
Rotary Axis ◽  
New Methods ◽  
Capillary Pressure Curve ◽  
Filter Disc

Abstract Three new techniques have been developed for measuring the imbibition capillary pressure curve of small porous samples by centrifuge. The paper shows the capillary pressure and saturation distributions in the cores subjected to different speeds of rotation by each of the techniques. Combination of these methods with measurements of electrical resistivity also makes it possible to obtain numerous resistivity-index/saturation curves or capillary-pressure/resistivity-index curves relatively quickly in either the drainage direction or the imbibition direction of saturation change. INTRODUCTION TO THE CAPILLARY PRESSURE MEASUREMENTS It has been known for more than 2 decades how to obtain the drainage capillary pressure curve by means of a centrifuge. Recently others have attempted to explain the mechanism of the gravity drainage of porous samples in the gravity field of a centrifuge by demonstrating the saturation distributions along the samples at different speeds of rotation. These works have led to both new methods and new evaluation techniques. However, there is still no method known by which the centrifuge can be used to obtain the capillary pressure curve in the imbibition direction. pressure curve in the imbibition direction. This paper reports the technical and theoretical considerations for thus obtaining such a curve. SHORT, SINGLE-CORE METHOD Both in this and in the following methods a system had to be chosen that would permit the quantity of fluid entering the sample to be controlled and regulated. A system in which the sample is simply surrounded by water could be neglected unless the sample is intermediately wet or oil wet; however, only in the negative capillary pressure interval could it be used. The applicability of this system to the case of water-wet samples may be explained very simply. From a partially oil-saturated sample the oil will be displaced by water, and subjecting this system to a multiplied gravitational field will only accelerate this displacement process. Therefore, there is no chance to regulate the degree of imbibition. A theoretical solution cannot be considered when the side of a sample farthest from the rotary axis is in contact with water or with a water-saturated porous disc because the imbibition occurs against the centrifugal force. Although it is true that imbibition will take place, the rate of imbibition will be slower than would be expected in the disc method in the earth gravitational field. Consequently, a method had to be chosen in which the direction of phase exchange occurs as a result of the natural fluid differences. That is, the water must enter the sample moving off the rotary axis and the quantity of imbibed water must be controllable. Fig. 1 illustrates a test cell that meets the requirements noted above. The cell can be used to obtain both imbibition and drainage data. For imbibition tests the sample is placed in contact with the filter nearest the rotary axis as shown. A fine porous filter paper is placed between the sample and the filter disc to provide good capillary contact. The water reservoir above the filter disc is partially filled. JPT P. 243

scholarly journals Effects of Foam Microbubbles on Electrical Resistivity and Capillary Pressure of Partially Saturated Porous Media

Molecules ◽  
2020 ◽  
Vol 25 (15) ◽  
pp. 3385 ◽  
Author(s):  
Abdulrauf R. Adebayo ◽  
Abubakar Isah ◽  
Mohamed Mahmoud ◽  
Dhafer Al-Shehri
Keyword(s):  
Porous Media ◽  
Electrical Resistivity ◽  
Capillary Pressure ◽  
Oil Recovery ◽  
Water Saturation ◽  
Porous Plate ◽  
Fluid Distribution ◽  
Cross Sectional ◽  
Injection Process ◽  
Saturation Exponent

Laboratory measurements of capillary pressure (Pc) and the electrical resistivity index (RI) of reservoir rocks are used to calibrate well logging tools and to determine reservoir fluid distribution. Significant studies on the methods and factors affecting these measurements in rocks containing oil, gas, and water are adequately reported in the literature. However, with the advent of chemical enhanced oil recovery (EOR) methods, surfactants are mixed with injection fluids to generate foam to enhance the gas injection process. Foam is a complex and non-Newtonian fluid whose behavior in porous media is different from conventional reservoir fluids. As a result, the effect of foam on Pc and the reliability of using known rock models such as the Archie equation to fit experimental resistivity data in rocks containing foam are yet to be ascertained. In this study, we investigated the effect of foam on the behavior of both Pc and RI curves in sandstone and carbonate rocks using both porous plate and two-pole resistivity methods at ambient temperature. Our results consistently showed that for a given water saturation (Sw), the RI of a rock increases in the presence of foam than without foam. We found that, below a critical Sw, the resistivity of a rock containing foam continues to rise rapidly. We argue, based on knowledge of foam behavior in porous media, that this critical Sw represents the regime where the foam texture begins to become finer, and it is dependent on the properties of the rock and the foam. Nonetheless, the Archie model fits the experimental data of the rocks but with resulting saturation exponents that are higher than conventional gas–water rock systems. The degree of variation in the saturation exponents between the two fluid systems also depends on the rock and fluid properties. A theory is presented to explain this phenomenon. We also found that foam affects the saturation exponent in a similar way as oil-wet rocks in the sense that they decrease the cross-sectional area of water available in the pores for current flow. Foam appears to have competing and opposite effects caused by the presence of clay, micropores, and conducting minerals, which tend to lower the saturation exponent at low Sw. Finally, the Pc curve is consistently lower in foam than without foam for the same Sw.

Experimental Validation of a Pore-Scale-Derived Dimensionless Capillary Pressure Function for Imbibition Under Mixed-Wet Conditions

SPE Journal ◽  
2017 ◽  
Vol 22 (05) ◽  
pp. 1338-1348 ◽  
Author(s):  
Y.. Zhou ◽  
J. O. Helland ◽  
D. G. Hatzignatiou ◽  
R.. Ahsan ◽  
A.. Hiorth
Keyword(s):  
Capillary Pressure ◽  
Reservoir Simulation ◽  
Simulation Models ◽  
Pressure Curve ◽  
Pore Scale ◽  
Pressure Function ◽  
Capillary Pressure Curve ◽  
Mixed Wettability ◽  
Dimensionless Function ◽  
Capillary Pressure Curves

Summary We validate experimentally a dimensionless capillary pressure function for imbibition at mixed-wet conditions that we developed recently on the basis of pore-scale modeling in rock images. The difference from Leverett's traditional J-function is that our dimensionless function accounts for wettability and initial water saturation after primary drainage through area-averaged, effective contact angles that depend on the wetting property and distribution of oil- and water-wet grain surfaces. In the present work, we adopt the dimensionless function to scale imbibition capillary pressure data measured on mixed-wet sandstone and chalk cores. The measured data practically collapse to a unique curve when subjected to the dimensionless capillary pressure function. For each rock material, we use the average dimensionless curve to reproduce the measured capillary pressure curves and obtain excellent agreement. We also demonstrate two approaches to generate different capillary pressure curves at other mixed-wettability states than that available from the data used to generate the dimensionless curve. The first approach changes the shape of the spontaneous- and forced-imbibition segments of the capillary pressure curve whereas the saturation at zero capillary pressure is constant. The second approach shifts the vertical level of the entire capillary pressure curve, such that the Amott wetting index (and the saturation at zero capillary pressure) changes accordingly. Thus, integrating these two approaches with the dimensionless function yields increased flexibility to account for different mixed-wettability states. The validated dimensionless function scales mixed-wet capillary pressure curves from core samples accurately, which demonstrates its applicability to describe variations of wettability and permeability with capillary pressure in reservoir-simulation models. This allows for improved use of core experiments in predicting reservoir performance. Reservoir-simulation models can also use the dimensionless function together with existing capillary pressure correlations.

Fractal Capillary Pressure Curve Models

Fractals ◽  
2017 ◽  
pp. 29-54
Author(s):  
Behzad Ghanbarian ◽  
Humberto Millán
Keyword(s):  
Capillary Pressure ◽  
Pressure Curve ◽  
Capillary Pressure Curve

scholarly journals A New Method for Predicting the Permeability of Sandstone in Deep Reservoirs

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Feisheng Feng ◽  
Pan Wang ◽  
Zhen Wei ◽  
Guanghui Jiang ◽  
Dongjing Xu ◽  
...  
Keyword(s):  
Support Vector Regression ◽  
Capillary Pressure ◽  
Prediction Models ◽  
Reservoir Rock ◽  
Support Vector ◽  
Pressure Curve ◽  
Pore Throat ◽  
Capillary Pressure Curve ◽  
Mercury Injection ◽  
Mercury Injection Capillary Pressure

Capillary pressure curve data measured through the mercury injection method can accurately reflect the pore throat characteristics of reservoir rock; in this study, a new methodology is proposed to solve the aforementioned problem by virtue of the support vector regression tool and two improved models according to Swanson and capillary parachor parameters. Based on previous research data on the mercury injection capillary pressure (MICP) for two groups of core plugs excised, several permeability prediction models, including Swanson, improved Swanson, capillary parachor, improved capillary parachor, and support vector regression (SVR) models, are established to estimate the permeability. The results show that the SVR models are applicable in both high and relatively low porosity-permeability sandstone reservoirs; it can provide a higher degree of precision, and it is recognized as a helpful tool aimed at estimating the permeability in sandstone formations, particularly in situations where it is crucial to obtain a precise estimation value.

scholarly journals Pore-scale X-ray imaging with measurement of relative permeability, capillary pressure and oil recovery in a mixed-wet micro-porous carbonate reservoir rock

Fuel ◽  
2020 ◽  
Vol 268 ◽  
pp. 117018 ◽  
Author(s):  
Amer M. Alhammadi ◽  
Ying Gao ◽  
Takashi Akai ◽  
Martin J. Blunt ◽  
Branko Bijeljic
Keyword(s):  
Capillary Pressure ◽  
Relative Permeability ◽  
Oil Recovery ◽  
Carbonate Reservoir ◽  
Reservoir Rock ◽  
Pore Scale ◽  
X Ray ◽  
X Ray Imaging
Sign in / Sign up

Export Citation Format

Share Document