Papers by Bernhard Krooss
Abstract: Migration and Accumulation of Gas in OM rich Strata during Basin Evolution: A Model of dynamic Sorption
AAPG Bulletin, 2000
An Inter-laboratory Comparison of CO<sub>2</sub> Isotherms Measured on Argonne Premium Coal Samples
Energy & Fuels, Jul 1, 2004
Adsorption isotherms, which describe the coal's gas storage capacity, are important for estim... more Adsorption isotherms, which describe the coal's gas storage capacity, are important for estimating the carbon sequestration potential of coal seams. This study investigated the inter-laboratory reproducibility of carbon dioxide isotherm measurements on dry Argonne Premium Coal Samples (Pocahontas No. 3, Upper Freeport, Illinois No. 6, Wyodak-Anderson, and Beulah Zap). Four independent laboratories provided isotherm data for the five coal samples at temperatures of either 22 °C or 55 °C and pressures up to 7 MPa. The differences among the data sets in this study appeared to be rank-dependent in that the data among the laboratories agreed better for high-rank coal samples than for low-rank coal samples. A number of parameters such as sample size, equilibration time, and apparatus dimensions were examined to explain the rank effect, but no trend could be found that explained the differences. The variations among the data are attributed to different procedures for removing moisture to obtain the “dried” coal.
29th International Meeting on Organic Geochemistry, 2019
(X.M. Xie) had decreased by 81%, 56% and 84%, respectively, for all three samples, indicating tha... more (X.M. Xie) had decreased by 81%, 56% and 84%, respectively, for all three samples, indicating that the hydrocarbons were extracted to different extents during the flow-through tests. Additionally, the Rock-Eval S2 values decreased by 29%, 0.4%, and 16%, for the three samples, respectively, showing that the flow-through tests on two of the samples also extracted significant amounts of organic material commonly interpreted as "heavy-hydrocarbons". The free hydrocarbons in micro-fractures, especially fractures along the bedding, could be very important for shale oil mobilization and the intervals with well-developed laminae provide horizontal fracturing intervals that are most favorable.
Journal of radioanalytical chemistry, Mar 1, 1978
In order to clarify the influence of radiation degradation of DEHPA upon the extraction of lantha... more In order to clarify the influence of radiation degradation of DEHPA upon the extraction of lanthanides, the extraction of neodymium(liD was studied using DEHPA, MEHPA, 2-ethylhexanol and "r-ray irradiated DEHPA. The most significant effect of DEHPA radiolysis on the extraction was found to be the enhacement of extraction capability mainly due to the primary radiolysis product MEHPA. 2-Ethylbexanol, another radiolysis product, showed a depressant effect on DEHPA-Nd(llI) extraction. However, the mixture of MEHPA and 2-ethylhexanol improved the extraction. The mixed solvent DEHPA-MEHPA was found to be more effective than the individual components for lanthanide extraction.
Effective gas permeability of Tight Gas Sandstones as function of capillary pressure - a non-steady state approach
EGU General Assembly Conference Abstracts, May 1, 2014
Gas Slippage in Partially Saturated Tight Rocks and During Drainage
Stress-dependence of Porosity and Permeability of Upper Jurassic Bossier Shale: Implications for Gas in Place Calculations and Production
EGU General Assembly Conference Abstracts, Apr 1, 2015
石炭とマセラルは超高温開放系実験における動力学パラメータの確立と天然ガス形成過程予測に分けられる。【JST・京大機械翻訳】
Dixue Qianyuan, 2009
Laboratory Testing Procedure for CO2 Capillary Entry Pressures on Caprocks
CO 2-speicherung in kohleflözen: Sorptionskinetische untersuchungen im rahmen des EU-RECOPOL projektes
Abstract: A Comparison of Pyrolysis Products with Models for Gas Generation from Tarim Coal and Its Macerals and Geological Extrapolations
Reassessment of transient permeability measurement for tight rocks: The role of boundary and initial conditions
Journal of Natural Gas Science and Engineering, Nov 1, 2021
Abstract The pulse-decay method is one of the most widely used transient methods for permeability... more Abstract The pulse-decay method is one of the most widely used transient methods for permeability measurements. Though many modified pulse-decay methods with various experimental designs have been proposed, the theoretical analysis is still insufficient, especially from the perspective of the boundary and initial conditions. In terms of boundary conditions, the tests can be conducted with a reservoir of finite volume on one side of the sample and a reservoir of “zero”, finite, or “infinite” volume on the other side. Common initial conditions differ in terms of the pore pressure within the sample at the start of the test, which can be either equal to the downstream or the upstream reservoir pressure. For the first time, the method of separation of variables is used to obtain the analytical solutions of the pulse-decay methods and assess the specific effects of boundary and initial conditions. The results indicate that if the pressure difference between two ends of the sample is less than 10 %, the slope of the semi-logarithmic plot of pressure versus time is solely determined by the boundary conditions (pore volume/reservoir volume ratios), and the intercept depends on both the boundary and initial conditions. We show that the requirement that a new pressure pulse cannot be applied before the previous pulse subsides is unnecessary and the restriction on the pulse size can be relaxed to some extent. The duration of the pulse-decay tests is mainly determined by the boundary conditions, and the influence of initial conditions decreases as the reservoir volumes increase. The error in the permeability evaluation caused by the inaccuracy of pore and reservoir volume measurements is also discussed.
Experimental determination of porosity and methane sorption capacity of organic-rich shales as a function of effective stress: Implications for gas storage capacity
AAPG Bulletin, Feb 1, 2021
Gas storage capacity estimates of shales are routinely assessed using laboratory data from unconf... more Gas storage capacity estimates of shales are routinely assessed using laboratory data from unconfined methane sorption and porosity measurements. In this study, the stress dependence of the methane excess sorption capacity and specific pore volume are investigated simultaneously. Experiments were performed on dry core plugs (Cambrian–Ordovician Alum, Jurassic Bossier, Late Cretaceous Eagle Ford, and Jurassic Kimmeridge shales) at 30°C under controlled confining stress up to 40 MPa and gas pressures up to 20 MPa. Increasing overburden stress results in a significant decrease of both specific pore volume and excess sorption capacity. The stress sensitivity of the specific pore volume was most prominent for the total organic carbon (TOC)–rich Kimmeridge sample (45% TOC) and further decreased in the order of Bossier, Eagle Ford, and Alum. Stress dependence of the methane excess sorption capacity, expressed as percentage reduction at 40-MPa overburden as compared to unconfined conditions, decreases in the order Eagle Ford (∼56%), Bossier (∼30%), Kimmeridge (∼14%), and Alum (∼5%). Although the decrease of specific pore volume is definitely caused by poroelastic compression, the mechanism(s) leading to the reduction of excess sorption capacity with stress require further investigation. Gas storage calculations show that routine methods based on unconfined data may grossly overestimate the total storage capacity. In this scenario, at 2500-m depth, the total gas storage capacity will be overestimated by 5% for the Alum, 28% for the Bossier, 18% for the Eagle Ford, and 28% for the Kimmeridge if the stress dependent reduction of volume and sorptive storage capacity is not considered.
Marine and Petroleum Geology, Dec 1, 2020
Pore structure and gas transport properties of fourteen samples from the Jurassic Sargelu and the... more Pore structure and gas transport properties of fourteen samples from the Jurassic Sargelu and the Cretaceous Garau formations in Lurestan province, southwest Iran, were studied under the aspect of shale gas exploration and production. Porosity was determined by helium pycnometry and water saturation (Archimedes principle). Low-pressure adsorption of N 2 was used to determine total pore volumes, specific surface areas and microporosity. Highpressure mercury intrusion porosimetry (MIP) was applied to assess pore-size distributions. Permeability measurements were performed with helium and methane at confining pressures of 40 to 10 MPa using steady state and non-steady state methods. Permeability and porosity values determined by the different methods are in a good agreement. For lowpermeable samples (less than 1 microdarcy ~ 10 − 18 m 2) the "constant downstream pressure" technique is the most efficient method for slip flow evaluation (Klinkenberg plot), yielding apparent permeability coefficients over a wide range of reciprocal mean pressures (1/p mean) in one single run. A positive correlation was found between TOC content, porosity and permeability coefficients. Samples displaying clear signs of recrystallization tend to exhibit higher permeability. None of the parameters determined in this study, however, showed a correlation with mineralogy. The relationship between Klinkenberg-corrected permeability coefficients and confining pressure could be expressed by an exponential decay function. Stress sensitivity was typically higher for low-permeable samples. Samples containing highly recrystallized carbonates exhibited lower stress sensitivity, indicating an increase in rigidity due to recrystallization. No correlation was found between methane/helium permeability ratios, sorption capacity, and TOC contents. Thus, gas transport properties of this sample set were not affected by sorption and/or swelling of organic matter.
Geofluids, Oct 16, 2015
, +49 (0)241 / 80 92152) Single-and two-phase (gas/water) fluid transport in tight sandstones has... more , +49 (0)241 / 80 92152) Single-and two-phase (gas/water) fluid transport in tight sandstones has been studied by conducting series of permeability tests on core plugs of nine tight sandstones of the Southern North Sea. Experiments comprised 1) steady state single-phase gas permeability tests, yielding absolute (Klinkenberg-corrected) permeability coefficients between 1E-17 and 1E-19 mˆ2, 2) steady state permeability tests with water yielding absolute permeability coefficients from 1E-16 to 1E-19 mˆ2 3) dynamic gas breakthrough (drainage and imbibition) experiments yielding effective gas permeability coefficients between 1E-17 and 1E-22 mˆ2. Petrophysical standard methods (He-pycnometry, Archimedes method, NMR, Hg-injection porosimetry) were used to assess the porosity and characterize the pore structure of the samples.
Stress-dependence of porosity and permeability of the Upper Jurassic Bossier shale: an experimental study
Geological Society, London, Special Publications, 2017
In order to characterize the stress-dependence of porosity and permeability of Bossier shale, a s... more In order to characterize the stress-dependence of porosity and permeability of Bossier shale, a series of measurements was conducted on three dry, horizontally orientated samples using various gases under controlled stress conditions.The Klinkenberg-corrected permeability and gas slippage factors varied by more than two orders of magnitude (0.21–86 µD) and by one order of magnitude (0.09–0.89 MPa), respectively. Porosity values measured under in situ stress conditions were lower by up to 30% than those measured at ambient conditions. Therefore, disregarding the stress-dependence of porosity may lead to a substantial overestimation of the free gas storage capacity.The stress sensitivity of Klinkenberg-corrected permeability coefficients (−0.012–−0.063MPa−1) is much larger than the stress sensitivity of porosity (−0.0014–−0.0033 MPa−1). Particularly for pore systems dominated by microfractures or slit-shaped pores, the permeability is highly sensitive to effective stress changes. While conventional pore models use porosity stress-sensitivity exponents (m) ranging between 3 and 5, we measured values of up to 27. Strongly stress-sensitive permeability behaviour is a result of effective stress preferentially reducing the volume and effective cross-section of transport pathways. In contrast, stress-dependent permeability of a less stress-sensitive sample is instead controlled by the redistribution of flow.
Organic Geochemistry, Aug 1, 2007
Anhydrous non-isothermal heating experiments were conducted under controlled compressive stress o... more Anhydrous non-isothermal heating experiments were conducted under controlled compressive stress on cylindrical plugs of six oil shales from Permian through Eocene age. The objective of this study was to compare the distribution of acyclic paraffins in initial, residual and expelled organic matter and to highlight causes of compositional differences resulting from expulsion. Pristane generation from kerogen is highest in the Eocene Messel shale and affects the pristane / phytane (pr / ph) ratio commonly used as a redox proxy. The isoprenoid to n-alkane ratios (pr / n-C 17 , ph/ n-C 18) decrease during generation and are lowest in the residual bitumen due to preferential generation and retention of n-alkanes. The n-alkane distribution shows that only lacustrine shales produce high wax oils. Evaporative fractionation leads to loss of n-alkanes up to n-C 20 with boiling points below 350°C. This demonstrates that lacustrine and marine shales may lead to accumulation of low wax oils due to evaporative fractionation after expulsion.
Fuel, Jul 1, 2017
h i g h l i g h t s Experimental measurements of apparent gas permeability on gas shales. Pitfall... more h i g h l i g h t s Experimental measurements of apparent gas permeability on gas shales. Pitfalls in the evaluation of high pressure apparent gas permeability data. Terzaghi's principle is not valid for permeability of gas shales. A permeability minimum occurs in the P p range from 2 to 10 MPa. Poro-elastic and fluid-dynamic effects are superposed (0 to >20 MPa P p).
Competitive sorption of CH4, CO2 and H2O on natural coals of different rank
International Journal of Coal Geology, Oct 1, 2015
Abstract Competitive sorption of CH 4 and CO 2 from a two-component gas mixture has been studied ... more Abstract Competitive sorption of CH 4 and CO 2 from a two-component gas mixture has been studied on three coals of different rank (subbituminous coal, high-volatile bituminous coal and anthracite). On each coal, binary excess sorption isotherms were measured in the dry state and after moisture-equilibration at 53% and 97% relative humidity (RH), to investigate the effect of pre-adsorbed water on the CH 4 and CO 2 sorption and selectivity at 318 K. Excess sorption isotherms were determined using a manometric setup and CH 4 /CO 2 feed gas mixtures containing between 70 and 85% of CH 4 . The total gas (CH 4 + CO 2 ) excess sorption capacity is reduced by pre-adsorbed moisture, which is most pronounced for the subbituminous coal. A large decrease in excess sorption capacity was observed for the 53% RH moisture equilibrated samples, whereas only a small further decrease was observed upon moisturization to 97% RH. The anthracite had the highest sorption capacity by far, regardless of the amount of pre-adsorbed water. All measurements show a preferential sorption of CO 2 at all three moisture states. The CO 2 selectivity over CH 4 tends to decrease with increasing maturity and moisture content. The mean CO 2 selectivity for the three investigated coals varies between 6 and 9. The extended Langmuir model for adsorption of gas mixtures is shown to be an acceptable first order approximation of the measured competitive sorption isotherm.
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Papers by Bernhard Krooss