EXPERIENCE WITH DETERMINATION OF WATER SATURATION FROM CORE IN THE COSSACK FIELD

1993 ◽  
Vol 33 (1) ◽  
pp. 39
Author(s):  
D. Lasserre & C.F. Choo
Keyword(s):  
Capillary Pressure ◽  
Water Saturation ◽  
Pressure Data ◽  
Reservoir Rocks ◽  
Saturation Parameter ◽  
The Core ◽  
Sandstone Reservoir

Water saturation measurements were made on core in two Cossack field appraisal wells to investigate the discrepancy between the water saturation calculated from logs and that observed from the capillary pressure data in the Cossack-1 discovery well. The core measurements resulted in a more accurate water saturation parameter which was then used to estimate the volume of hydrocarbons in place. The core measurements also provided valuable information about the wettability of the reservoir rocks. The results of this exercise also highlighted the uncertainty attached to the water saturation determination from logs in what was an apparently simple case of a thick, clean sandstone reservoir.

Gas-Water Capillary Pressure in Coal at Various Overburden Pressures

1976 ◽  
Vol 16 (05) ◽  
pp. 261-268 ◽  
Author(s):  
M.K. Dabbous ◽  
A.A. Reznik ◽  
B.G. Mody ◽  
P.F. Fulton ◽  
J.J. Taber
Keyword(s):  
Pore Structure ◽  
Pore Size ◽  
Capillary Pressure ◽  
Water Saturation ◽  
Petroleum Reservoir ◽  
Pressure Data ◽  
Overburden Pressure ◽  
Reservoir Rocks ◽  
Pore Compressibility ◽  
Different Types

Abstract Drainage air-water capillary-pressure curves were obtained for Pittsburgh and Pocahontas coals at various overburden pressures. Capillary-pressure data were used to investigate pore-size characteristics. Results were indicative of the complex pore structure of coal, consisting primarily of a network of macro- and microfractures. In most cases, however, displacement pressure and residual water saturation increased at higher overburden pressure. Reasonable agreement between measured relative permeabilities and those calculated from capillary-pressure data with Purcell's model was obtained for only a few samples. Fracture permeabilities computed from pore-size distribution were lower than permeabilities pore-size distribution were lower than permeabilities actually measured at the same overburden pressure. Helium porosity was considerably higher than porosity determined by water saturation, indicating porosity determined by water saturation, indicating inaccessible pore volume to water. Pore compressibility was determined under triaxial stress-loading conditions. Changes in porosity with overburden pressure were more significant at pressures below 1,500 psig. Above this pressure, pore compressibility appeared to approach a pressure, pore compressibility appeared to approach a constant value averaging about 0.5 × 10(−4) psi(−1) for the coal samples studied. Introduction Increased interest in underground coal gasification and coal-seam degasification for the purpose of producing clean energy stimulated fundamental producing clean energy stimulated fundamental research into the phenomena of multiphase fluid flow through coal. Two previous papers presented results of investigation of the air- and water-permeability and relative-permeability characteristics at various overburden pressures for two different types of coal. However, to understand the mechanisms of two-phase flow (usually gas and water) through a complex porous system such as coal, one needs a clear insight into the internal pore structure of coal and the interaction between pore structure of coal and the interaction between this structure and the associated fluids. Such knowledge of the make-up of the pore structure helps in modeling fluid flow through the system and in interpreting permeability and relative-permeability data. Interaction between the pore structure and fluids results in the capillary-pressure phenomena. Capillary-pressure data have been used extensively to determine the pore characteristics of many petroleum reservoir rocks and to relate these petroleum reservoir rocks and to relate these characteristics to the single- and two-phase flow behavior in the rock. It is also known that natural fracture systems are the principal source of flow capacity of many petroleum reservoir rocks and contribute materially petroleum reservoir rocks and contribute materially to the storage capacity of some. Changes in fracture capacity resulting from changes in net overburden pressure have an important influence on the flow pressure have an important influence on the flow properties of the rock, as reported by Jones. In our properties of the rock, as reported by Jones. In our previous work with coal, which is a naturally previous work with coal, which is a naturally fractured system, absolute and effective permeabilities were found to be highly sensitive to overburden pressure (pov). Thus, it would be expected that the pressure (pov). Thus, it would be expected that the effect of Pov on the fracture flow capacity, capillary pressure, and pore compressibility is more dramatic pressure, and pore compressibility is more dramatic for coal. The internal structure of coal has been studied by microscopic methods, gas sorption measurements, and by mercury porosimetry. Data on helium porosity of different types of coal also can be porosity of different types of coal also can be found in Ref. 5. However, we are not aware of any determinations of capillary pressure in coal at different overburden pressures. In this paper gas-liquid capillary-pressure relationships for coal at different overburden pressures are presented. pressures are presented. SPEJ P. 261

APPLICATION OF RESISTIVITY INVERSION MODELLING TO ENHANCE WATER SATURATION CALCULATIONS FROM WIRELINE LOGS

2000 ◽  
Vol 40 (1) ◽  
pp. 355
Author(s):  
C.J. Shield
Keyword(s):  
Capillary Pressure ◽  
Water Saturation ◽  
Strong Relationship ◽  
Data Set ◽  
Hydrocarbon Reservoir ◽  
The Core ◽  
Irreducible Water Saturation ◽  
Resistivity Logs ◽  
Resistivity Inversion ◽  
Induction Logs

Water saturation (Sw) values calculated from resistivity or induction logs are often higher than those measured from core-derived capillary pressure (Pc) measurements. The core-derived Sw measurements are commonly applied for reservoir simulation in preference to the log-derived Sw calculations. As it is economically and logistically impractical to core every hydrocarbon reservoir, a method of correlating the core-derived Sw to resistivity/induction logs is required. Two-dimensional resistivity modelling is applied to dual laterolog data to ascertain the applicability of this technique.The Griffin and Scindian/Chinook Fields, offshore Western Australia, have been producing hydrocarbons since 1994 from two early-to-middle Cretaceous reservoirs, the clean quartzose sandstones of the Zeepaard Formation and the overlying glauconitic, quartzose sandstones of the Birdrong Formation. Routine and special core analysis of cores recovered from wells intersecting these two reservoirs creates an excellent data set with which to correlate the good quality wireline log data.A strong relationship is noted between the modelled water saturation from resistivity logs, and the irreducible water saturation measured from core capillary pressure data. Correlation between the core-derived permeability and the invasion diameter calculated from the modelled laterolog data is shown to produce a locally applicable means of estimating permeability from the resistivity modelling results.The evaluation of these data from the Griffin and Scindian/Chinook Fields provides a method for reducing appraisal and development well analysis costs, through the closer integration of core and wireline log data at an earlier stage of the field appraisal phase.

A New Multiphysics Method for Simultaneous Assessment of Permeability and Saturation-Dependent Capillary Pressure in Hydrocarbon-Bearing Rocks

SPE Journal ◽  
2020 ◽  
pp. 1-17
Author(s):  
Artur Posenato Garcia ◽  
Zoya Heidari
Keyword(s):  
Pore Structure ◽  
Capillary Pressure ◽  
Size Distribution ◽  
Water Saturation ◽  
Rock Physics ◽  
Rock Fabric ◽  
The Core ◽  
Directional Permeability ◽  
Water Saturated ◽  
Pore Body

Summary Cost-effective exploitation of heterogeneous/anisotropic reservoirs (e.g., carbonate formations) relies on accurate description of pore structure, dynamic petrophysical properties (e.g., directional permeability, saturation-dependent capillary pressure), and fluid distribution. However, techniques for reliable quantification of permeability still rely on model calibration using core measurements. Furthermore, the assessment of saturation-dependent capillary pressure has been limited to experimental measurements, such as mercury injection capillary pressure (MICP). The objectives of this paper include developing a new multiphysics workflow to quantify rock-fabric features (e.g., porosity, tortuosity, and effective throat size) from integrated interpretation of nuclear magnetic resonance (NMR) and electric measurements; introducing rock-physics models that incorporate the quantified rock fabric and partial water/hydrocarbon saturation for assessment of directional permeability and saturation-dependent capillary pressure; and validating the reliability of the new workflow in the core-scale domain. To achieve these objectives, we introduce a new multiphysics workflow integrating NMR and electric measurements, honoring rock fabric, and minimizing calibration efforts. We estimate water saturation from the interpretation of dielectric measurements. Next, we develop a fluid-substitution algorithm to estimate the T2 distribution corresponding to fully water-saturated rocks from the interpretation of NMR measurements. We use the estimated T2 distribution for assessment of porosity, pore-body-size distribution, and effective pore-body size. Then, we develop a new physically meaningful resistivity model and apply it to obtain the constriction factor and, consequently, throat-size distribution from the interpretation of resistivity measurements. We estimate tortuosity from the interpretation of dielectric-permittivity measurements at 960 MHz by applying the concept of capacitive formation factor. Finally, throat-size distribution, porosity, and tortuosity are used to calculate directional permeability and saturation-dependent capillary pressure. We test the reliability of the new multiphysics workflow in the core-scale domain on rock samples at different water-saturation levels. The introduced multiphysics workflow provides accurate description of the pore structure in partially water-saturated formations with complex pore structure. Moreover, this new method enables real-time well-log-based assessment of saturation-dependent capillary pressure and directional permeability (in presence of directional electrical measurements) in reservoir conditions, which was not possible before. Quantification of capillary pressure has been limited to measurements in laboratory conditions, where the differences in stress field reduce the accuracy of the estimates. We verified that the estimates of permeability, saturation-dependent capillary pressure, and throat-size distribution obtained from the application of the new workflow agreed with those experimentally determined from core samples. We selected core samples from four different rock types, namely Edwards Yellow Limestone, Lueders Limestone, Berea Sandstone, and Texas Cream Limestone. Finally, because the new workflow relies on fundamental rock-physics principles, permeability and saturation-dependent capillary pressure can be estimated from well logs with minimum calibration efforts, which is another unique contribution of this work.

scholarly journals Analysis of the efficiency of models of transition zones to determine oil-saturation factors and position of contact of hydrocarbons with water

2020 ◽  
pp. 67-76
Author(s):  
G. E. Stroyanetskaya
Keyword(s):  
Capillary Pressure ◽  
Transition Zone ◽  
Water Saturation ◽  
Residual Water ◽  
Oil Saturation ◽  
Transition Zones ◽  
The Core ◽  
Geophysical Parameter ◽  
Saturation Factor ◽  
Geophysical Information

The article is devoted to the usage of models of transition zones in the interpretation of geological and geophysical information. These models are graphs of the dependences of oil-saturation factors of the collectors on their height above the level with zero capillary pressure, taking into account the geological and geophysical parameter. These models are not recommended for estimating oilsaturation factors of collectors in the transition zone. The height of occurrence of the collector above the level of zero capillary pressure can be estimated from model of the transition zone that take into account the values of the coefficients of residual water saturation factor of the collectors, but only when the model of the transition zone is confirmed by data capillarimetry studies on the core.

Interpretation of Differential Pressure in Laboratory Surfactant/Polymer Displacements

1983 ◽  
Vol 23 (05) ◽  
pp. 791-803 ◽  
Author(s):  
C. Stanley McCool ◽  
Ravi Parmeswar ◽  
G. Paul Willhite
Keyword(s):  
Crude Oil ◽  
Capillary Pressure ◽  
Differential Pressure ◽  
Mobility Control ◽  
Pressure Effects ◽  
Rock Surface ◽  
Pressure Measurements ◽  
Pressure Data ◽  
The Core ◽  
Oil Water

Abstract Experimental data were obtained for two surfactant/polymer systems in which fluid mobilities and mobility control were studied through the analysis of differential pressure measurements. One system used nonane as the hydrocarbon phase, while the other system used crude oil from the Madison field, Greenwood County, KS. During the experimental studies, capillary-pressure effects were observed in differential pressure data when floods were conducted at reservoir rates and small port spacing. Capillary-pressure effects interfered with the measurement of the "true" or viscous pressure drop in oil/water banks and the transition region between the oil/water bank and surfactant slug. Pressure ports were designed to permit injection of small quantities of fluid at the rock surface during permit injection of small quantities of fluid at the rock surface during displacements to verify and to eliminate capillary-pressure effects. Movement of fluid regions through the core was inferred from the differential pressure measurements along the core. Similar pressure perturbations at the ports were extrapolated to the end of the core and perturbations at the ports were extrapolated to the end of the core and correlated with effluent fractions. In the nonane system, the microemulsion surfactant slug changed to a more mobile macroemulsion within the first half of the displacement. This macroemulsion moved through the last half of the core as a stabilized, constant velocity bank indicating good mobility control even though the apparent viscosity of the macroemulsion was less than that of the stabilized oil/water bank. In the crude-oil surfactant system, pressure data collected along the core indicated capillary-pressure effects at the leading edge of the oil bank and the formation of a viscous, less mobile region resulting from mixing of the microemulsion slug with resident fluids. Phase-behavior studies indicated the formation of a viscous lower phase as the microemulsion was diluted with brine. The formation and propagation of this viscous region during displacement leads to favorable mobility control illustrated by the pressure/mobility curves as well as by good oil recoveries (80 to 95%). pressure/mobility curves as well as by good oil recoveries (80 to 95%). Introduction Mobility control is a necessary requirement for an effective surfactant flood. Mobility control is achieved when the displacing fluids' mobilities are less than or equal to the displaced fluids' mobilities. In a typical surfactant/polymer flood, the mobility of the stabilized oil/water bank must be greater than the surfactant slug's mobility, which in turn must be greater than the mobility of the trailing polymer bank. When these criteria are met, mixing between the different fluid banks will be minimized. This allows the surfactant slug to move as a stabilized bank, contacting a larger percentage of the reservoir. A procedure for selecting the mobility for the surfactant slug and polymer bank was presented by Gogarty et al. They obtain a design mobility polymer bank was presented by Gogarty et al. They obtain a design mobility of the stabilized oil/water bank generated ahead of a surfactant slug from one of the following two methods. 1. Total relative mobilities as a function of water saturations are calculated from relative-permeability curves. The minimum total mobility is selected as a safe value of the design mobility. Chang et al., pointed out that decreasing water-saturation (drainage for water-wet rocks) curves should be used. SPEJ p. 791

Imaging of ribosomal RNA-protein interactions by dark-field STEM

1989 ◽  
Vol 47 ◽  
pp. 250-251
Author(s):  
M. Boublik ◽  
V. Mandiyan ◽  
S. Tumminia ◽  
J.F. Hainfeld ◽  
J.S. Wall
Keyword(s):  
Nucleic Acid ◽  
16S Rrna ◽  
Dark Field ◽  
Radius Of Gyration ◽  
Central Domain ◽  
The Core ◽  
16S Rna ◽  
30S Subunit ◽  
Core Particles

Success in protein-free deposition of native nucleic acid molecules from solutions of selected ionic conditions prompted attempts for high resolution imaging of nucleic acid interactions with proteins, not attainable by conventional EM. Since the nucleic acid molecules can be visualized in the dark-field STEM mode without contrasting by heavy atoms, the established linearity between scattering cross-section and molecular weight can be applied to the determination of their molecular mass (M) linear density (M/L), mass distribution and radius of gyration (RG). Determination of these parameters promotes electron microscopic imaging of biological macromolecules by STEM to a quantitative analytical level. This technique is applied to study the mechanism of 16S rRNA folding during the assembly process of the 30S ribosomal subunit of E. coli. The sequential addition of protein S4 which binds to the 5'end of the 16S rRNA and S8 and S15 which bind to the central domain of the molecule leads to a corresponding increase of mass and increased coiling of the 16S rRNA in the core particles. This increased compactness is evident from the decrease in RG values from 114Å to 91Å (in “ribosomal” buffer consisting of 10 mM Hepes pH 7.6, 60 mM KCl, 2 m Mg(OAc)2, 1 mM DTT). The binding of S20, S17 and S7 which interact with the 5'domain, the central domain and the 3'domain, respectively, continues the trend of mass increase. However, the RG values of the core particles exhibit a reverse trend, an increase to 108Å. In addition, the binding of S7 leads to the formation of a globular mass cluster with a diameter of about 115Å and a mass of ∽300 kDa. The rest of the mass, about 330 kDa, remains loosely coiled giving the particle a “medusa-like” appearance. These results provide direct evidence that 16S RNA undergoes significant structural reorganization during the 30S subunit assembly and show that its interactions with the six primary binding proteins are not sufficient for 16S rRNA coiling into particles resembling the native 30S subunit, contrary to what has been reported in the literature.

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