Comprehensive Analysis of Connectivity and Permeability of a Pore-Fracture Structure in Low Permeability Seam of Huainan-Huaibei Coalfield.

The connectivity and permeability of the coal seam pore structures control the occurrence and migration of coalbed methane. Coal samples were used from Huainan-Huaibei to reconstruct three-dimensional models of the pores and an equivalent pore network model, Statistical pore structure characteristic parameters. The pore structure of the coal reservoir was analyzed from the direction of multidimensional and multiangle. It shows that based on quantitative analysis, the representative Elementary volume of 500 × 500 × 500 was the most suitable experimental volume. The Y-axis direction of the Renlou sample had poor pore connectivity compared to that of other samples. Large volume connected pores dominated their pore systems. In terms of coal sample pore connectivity, the coal samples from the Liuzhuang and Qidong regions had pore connectivity better than those from the other regions. The pore connectivity of the Liuzhuang coal samples was the best. In terms of coal permeability, the Liuzhuang sample had better permeability than the other three samples, and the permeability was the best in the Y-axis direction. For all the combinations of the different types of throats, the shorter the throat, the greater the equivalent radius and the better the permeability. Conversely, the worse the permeability. During gas injection production, the closer the gas injection area was to the gas injection well, the poorer the connectivity and the lower the permeability over time. Near the production area, where the CO2 did not reach the production area, the fracture porosity and effective connected porosity of the coal reservoir increased over time. When CO2 reached the production area, the change in its connected pore structure was consistent with the change in the connected pores in the gas injection area. With this study, the coal seam pore structure on a microscale was characterized. A comprehensive analysis of the coal reservoir pore connectivity and permeability was completed. The study results are significant for the exploration and development of coalbed methane in the Huainan-Huaibei coalfield.

Modeling of Supercritical CO2 Adsorption for Low-Permeability Coal Seam of Huainan-Huaibei Coalfield, China.

Investigating the coal adsorption behavior on supercritical CO2 (ScCO2) is crucial for long-term CO2 geological storage. In this paper, low-permeability coal samples from the Huainan-Huaibei coalfields in China were selected. The high-pressure isothermal adsorption of CO2 was carried out at 36, 42, and 48 °C. The results of adsorption experiments were analyzed by fitting 9 types of modified adsorption models, including three different adsorption theories. Considering that different adsorption mechanisms may exist for CO2 in coal, 14 mixed adsorption models were established. The accuracy of the coefficient of determination (R2) and root-mean-square error (RMSE) for ScCO2 excess adsorption capacity was analyzed, mainly focusing on the accuracy of the key model parameters such as the adsorption phase density and the theoretical adsorption capacity. These parameters were discussed, combined with the predicted adsorption phase density of CO2 based on the intercept method. The results indicate that among the 9 types of modified adsorption considered, based on the adsorption phase density screening, the deviation of the predicted adsorption capacity from the experimental value was then considered. The Dubinin-Radushkevich (DR) model can effectively fit the adsorption behavior of CO2 at low pressure (<7.5 MPa). The Langmuir (L), Langmuir-Freundlich (LF), Extended-Langmuir (EL), and TOTH models can effectively fit the adsorption behavior of CO2 at high pressure (7.5-20 MPa), while the multimolecular layer models were unsuitable for fitting ScCO2 adsorption. The model fitting results showed that only the monomolecular layer and micropore-filled adsorption models were suitable for fitting the ScCO2 adsorption capacity. The DR-LF model best fits the adsorption data based on its key parameters of adsorption phase density and theoretical adsorption capacity. The established mixed model DR-LF fitting results showed that the CO2 in coal was dominated by microporous filling adsorption. The higher the temperature, the greater the contribution of microporous filling adsorption to the total adsorption. There still exists deviation in the adsorption phase density and theoretical adsorption capacity. The contribution percentage of different adsorption mechanisms of CO2 in coal needs to be further investigated.

Effective Approach with Extra Desorption Time to Estimate the Gas Content of Deep-Buried Coalbed Methane Reservoirs: A Case Study from the Panji Deep Area in Huainan Coalfield, China.

In this study, 11 core coal samples were collected from deep-buried coalbed methane (CBM) reservoirs with burial depth intervals of 900-1500 m for gas estimation content by a direct method. In desorption experiments, the cumulative gas desorption data were recorded within 2 h in the field on the basis of the China National Standard method. For accuracy, two improved methods were proposed. The results show that the gas contents of deep-buried coal samples based on the China National Standard and mud methods are 3.58-9.89 m3/t (average of 6.03 m3/t) and 3.74-10.05 m3/t (average of 6.20 m3/t), respectively. The proposed Langmuir equation and logarithmic equation methods exhibited nonlinear relationships between the cumulative desorption volume and desorption time, which yield values of 6.33-13.34 m3/t (average of 9.36 m3/t) and 6.15-13.86 m3/t (average of 10.37 m3/t), respectively. In addition, the two proposed methods combine the raw data within 2 h by the China National Standard method and additional desorption points during extra time, which are helpful for the ability of the hypothetical methods to calculate the gas content. The Langmuir equation method is a relatively more accurate method to estimate the gas content in comparison with the proposed logarithmic method, which is based on the relative error and comparison plots of actual data and simulated results. From the perspective of numerical value, the Langmuir equation method gives values 1.06-3.39 times (average of 1.86 times) those of the China National Standard method. These analyses show that the proposed Langmuir equation method with extra desorption points is an effective method to determine the gas content of deep-buried CBM reservoirs.

Methodology for Lost Gas Determination from Exploratory Coal Cores and Comparative Evaluation of the Accuracy of the Direct Method.

In the coal exploration of China, the commonly used direct method within 120 min has potential errors in lost gas calculation of deep coal seam for its complex geological conditions. The exploration of deep coal resources by drilling holes in Huainan of Eastern China offered an opportunity to starting research into developing a new method. A developed method with error analysis was constructed to estimate the lost gas using the total desorption process obtained from exploratory coal cores. The accuracy of the direct method was also evaluated comparatively. The result shows that the desorption curve of tested coal samples matches the fitted curve equation. Desorption temperature and the tectonic coal with associated pore characteristics significantly affect the variation of the adsorption characteristics and the estimation of lost gas. The direct method obviously underestimates the lost gas, and methodology using a new lost gas estimation procedure with additional residual gas allows for achieving relatively accurate results of the determination of gas content in coal seams. The calculated result of the new method is about 1.00-1.41 times that of the direct method. The error analysis of desorption results allowed us to determine the dependence between the time (retrieval time and desorption time) and determination method. The time used for desorption in the tank is allowed to extend to less than 400 min or more than 1000 min, which is very potentially important to accurately get the coalbed gas content for coring samples, especially deep exploratory cores for field application.

Preliminary Assessment of the Resource and Exploitation Potential of Lower Permian Marine-Continent Transitional Facies Shale Gas in the Huainan Basin, Eastern China, Based on a Comprehensive Understanding of Geological Conditions.

The Huainan Basin in eastern China contains abundant shale gas resources; the Lower Permian is an exploration horizon with a high potential for shale gas in marine-continent transitional facies. However, few detailed analyses have investigated shale gas in this area. In this paper, a comprehensive investigation of the geochemical characteristics, physical properties, and gas-bearing capacities of shale reservoirs was conducted, and the resource and exploitation potential were evaluated. The results show that the cumulative thicknesses of the Shanxi Formation (P1s) and lower Shihezi Formation (P2xs) are mostly greater than 35 and 65 m, respectively. The TOC contents of the P1s and P2xs shale vary from 0.11 to 8.87% and from 0.22 to 14.63%, respectively; the kerogens predominantly belong to type II with minor amounts of type I or type III kerogens; average R o values range between 0.83 and 0.94% and between 0.82 and 1.02% in P1s and P2xs, respectively; the shale samples are primarily at a low maturity, while some shale samples have entered the high-maturity stage. The shale reservoirs have low permeability and porosity in P1s and P2xs, respectively. The pores of the P1s shale reservoir are characterized by well-developed micropores and transition pores and poorly developed mesopores, while the pores in the P2xs shale reservoir are all characterized by well-developed micropores and transition pores and some well-developed macropores; the different pore types in the shale reservoirs developed in the organic matter, clay minerals, and pyrite, while a few endogenous fractures developed in the organic matter and structural fractures developed in the minerals. The total shale gas contents in P1s and P2xs are 2.85 and 2.96 m3 t-1, respectively. The P2xs shale reservoir has a higher hydrocarbon generation potential than P1s and has a lower gas generation potential. The total shale gas amounts in P1s and P2xs are 3602.29-4083.04 × 108 and 2811.04-3450.77 × 108 m3, respectively. Further research on shale gas exploration and exploitation for these formations needs to be performed.

Supercritical-CO2 Adsorption Quantification and Modeling for a Deep Coalbed Methane Reservoir in the Southern Qinshui Basin, China.

Accurate depiction of the adsorption capacity of supercritical CO2 (ScCO2) by existing adsorption models is an important focus for deep coal seams in CO2-enhanced coalbed methane (CO2-ECBM) recovery. To investigate the applicability of different adsorption models for the adsorption isotherms of ScCO2, the validities of 10 different adsorption models were analyzed, based on analyses of the adsorption characteristics of ScCO2 from deep coal seams of the Southern Qinshui Basin, China. These models include the Langmuir (L) model, two-parameter Langmuir (TL) model, Toth (T) model, Langmuir-Freundlich (LF) model, extended Langmuir (EL) model, double parameter Brunauer-Emmett Teller model, three-parameter BET (TBET) model, Dubinin-Radushkevich (D-R) model, Dubinin-Astakhov (D-A) model, and Ono-Kondo lattice (OK) model. These models were tested for both the excess and absolute adsorption capacities of ScCO2 under various temperatures and pressures. The simulation accuracy of the different adsorption models was analyzed. The optimal models for the adsorption of ScCO2 in deep coal seams were selected based on a comprehensive analysis of the simulation parameters, standard error, and residual sum of squares. There were obvious differences in the validity of the different adsorption models in terms of the excess adsorption capacity and absolute adsorption capacity of ScCO2. The D-A and D-R models are the optimal adsorption models for the adsorption isotherms of the excess adsorption of ScCO2 for the whole tested pressure range. The T, TL, and D-R models are the optimal adsorption models in simulation of the excess adsorption capacity of ScCO2 for the selected adsorption models when the equilibrium pressure is divided into two sections at the point of 8.13 MPa. In simulation of the absolute adsorption capacity of ScCO2, the TBET and LF models are the optimal adsorption models among the selected models when the equilibrium pressure is less than or equal to 8.13 MPa. The linear, exponential, logarithmic, power function, and polynomial adsorption simulation all have good precision in the simulation of the absolute adsorption capacity of ScCO2 when the pressure is beyond 8.13 MPa.

[Applying Team Resource Management to the Reduction of Ventilator-Associated Pneumonia in the Intensive Care Unit].

BACKGROUND & PROBLEMS: Ventilator-associated pneumonia (VAP) is a common healthcare-associated infection in the intensive care unit. The average VAP rate was .128% in our unit during 2011. Therefore, we designed a project to identify relevant problems, including: inadequate knowledge about VAP care, incorrect techniques for sputum suction, patient head elevation < 30~45 degrees, ventilator humidifier installed with water equipment designed without water-resistant barriers, failure to change the resuscitator and small-volume nebulizer regularly, and possible cross-contamination between respiratory-care devices. PURPOSE: We targeted a VAP rate decrease from the current .128% to less than .1%. RESOLUTION: The improvement measures implemented included team resource management (TRM) with VAP education, promotion, a written reminder regarding sputum accumulation sites, instruction to elevate the head of patients to an appropriate height, introduction of an auto-stop water adding system, and regular changes of related devices at assigned positions. RESULTS: The VAP rate decreased from .128% to .065%. CONCLUSIONS: The risk identification and associated TRM project improved teamwork and the quality of care in the ICU.

Study on the law of heavy metal leaching in municipal solid waste landfill.

Comparative leaching experiments were carried out using leaching medium with different pH to municipal solid waste in the landfill columns in order to investigate the mobility of heavy metals. The leachate pH and oxidation-reduction potential were measured by oxidation-reduction potential analyzer; the contents of heavy metals were measured by inductively coupled plasma mass spectrometry. It is very different in leaching concentrations of heavy metals; the dynamic leaching of heavy metals decreased with the rise of the leaching amount on the whole. Acid leaching medium had definite influence on the leaching of heavy metals in the early landfill, but it had the obvious inhibition effect on the leaching in the middle and late period of landfill; the neutral and alkaline leaching medium are more beneficial to the leaching of heavy metals. Due to the influence of the environment of landfill, the differences of the results in cumulative leaching amount, leaching rate, and leaching intensity of heavy metals are very big. The calculation results of the release rates of heavy metals prove that the orders of the release rates are not identical under different leaching conditions. Acid rain made heavy metals migrate from municipal solid waste to soil and detain in soil more easily; approached neutral and alkaline leaching mediums are more beneficial to leaching of heavy metals in the municipal solid waste and soil with leachate. The field verification of experimental data showed that the law of heavy metal leaching in municipal solid waste revealed by the experiment has a good consistency with the data obtained by municipal solid waste landfill.