Areas Of Gas Accumulation Research Articles

The influence of pulsation ventilation on the removal and distribution of gas accumulation areas during gas leakage in industrial plants

A ventilation system with a constant velocity air supply might form airflow stagnant zones in industrial plants, making it challenging to dilute hazardous gas effectively. In this study, a novel ventilation mode called pulsating ventilation, which can potentially dilute the hazardous gas better, was applied in a ventilated room with nozzle air supply. Three different scenarios of gas accumulation were assumed, with the location of gas accumulation situated at the rear, near the floor, and in the corners of the room. Both the distribution of CO2 concentration and the efficiency of reducing the indoor CO2 concentration to the safety threshold were analyzed to evaluate the ventilation performance of pulsating ventilation. The results showed that pulsating ventilation outperformed constant velocity air supply in expeditiously eradicating gas accumulation areas for equivalent total air volumes. When the gas accumulation areas were located at the rear of the room, close to the floor, and in the corner of the room, pulsation ventilation reduced the time for the indoor CO2 concentration to drop to the safety threshold by 36.19%, 27.23%, and 36.25%, respectively. Holding the period constant, an increased amplitude correlated with a swifter decrease in peak pollutant concentration. Except for the case where the gas accumulation areas are close to the floor, when the amplitude is constant, the larger the period, the faster the peak concentration in the gas accumulation areas decreases.

Asymmetric development of overburden fracture and gas migration law for a goaf of entry formed by roof cutting

AbstractIn the study, a combined numerical simulation and on‐site monitoring method was used to analyze the asymmetric development characteristics of overlying rock fractures in a goaf under the condition of a goaf side entry formed by roof cutting and to explore the gas accumulation area in the goaf, achieving precise gas extraction from the goaf. The results demonstrates that a double‐balanced arch structure is formed under the condition of a goaf side entry formed by roof cutting, achieving safe retention of the roadway and showing the significance of the pressure relief effect of roof cutting. The collapse movement of the overlying rock on the roof‐cutting side is relatively advanced. The heights of the collapse zone on the roof‐cutting side and the uncut roof side are 28 and 24 m, respectively, and the development heights of the fracture zone are 37 and 42 m, respectively. The fault line on the roof‐cutting side gradually shifts toward the direction of the goaf, and the surface settlement and fracture development are relatively small. There is a clear asymmetric structure in terms of time effect, fault line, fracture zone height, and surface settlement compared to the uncut roof side. The gas is distributed throughout the entire goaf in the roof‐cutting and tunneling mode, and a high‐concentration gas accumulation area is formed near the open–off cut and working face on the high side of the fracture zone. Based on an actual situation, a method of drilling high and low positions in a fracture zone is proposed for extraction. Combined with on‐site monitoring, the goaf was no longer filled with gas during extraction, and the proportion of low‐concentration gas space considerably increased.

PROMISING OIL AND GAS COMPLEXES OF PREDVERKHOYANSKАYА OIL AND GAS AREA

This article provides information on the main most common and most promising sediment complexes: Riphean, Vendian-Lower Paleozoic and Upper Paleozoic-Mesozoic.
 Riphean deposits within the area under consideration have now been uncovered on the northwestern side of the Vilyui syneclise. Within the southern slope of the Anabar anteclise, the Tankhai and Sokhsolokha structural-formation zones are distinguished.
 Permian deposits are most widely distributed within the Predverkhoyanskiy trough. They were opened by deep drilling wells in the northern part of the Anabar-Lena branch, in the central region (the Kyutingdinsky graben) and in the Aldan branch of the trough.
 The Permian and Lower Triassic deposits adjacent to large gas generation zones of deflections and depressions are characterized by the most favorable conditions for the placement of large oil and gas accumulation zones. In the regional assessment of the conditions for the placement and preservation of large oil and gas accumulation zones, the most favorable conditions are associated with the second hydrogeological floor.
 Seven oil and gas accumulation zones have been identified within the Predverkhoyanskiy pericratonic trough: the Hapchagai-Tomporuk and Loglor-Linden oil and gas accumulation zones are zones with proven industrial gas content. All deposits of the Khapchagai megaval fall into the Vilyuisk zone, due to the presence of horizons with relatively high filtration and capacitance properties in the near-axial part of the hemisyneclise.
 The Predverkhoyanskаyа oil and gas accumulation area combines linear pre-thrust structural traps formed parallel to the face of the structures of the Verkhoyansk folded region advancing on the Mesozoic cover of the platform. Typical traps are pre-thrust and especially sub-thrust anticlines, to a lesser extent closed kinks of layers in the hanging wings of shaft-like up-thrust structures.
 The Kyutingda possible oil and gas accumulation zone is one of the most promising sites for setting up regional exploration. The capacity of sedimentary discharge in the left-bank near-platform part of the Kyutingdinsky graben is estimated at about 5 km. This significantly increases the prospects of oil and gas potential in the north of the Predverkhoyanskiy trough.
 The Prialdanskaya and Prilenskaya possible zones of oil and gas accumulation are located along the platform side of the latitudinal and meridional branches of the Predverkhoyanskiy pericratonic trough, respectively. The prospects for the oil and gas potential of these zones are due, on the one hand, to the development of basal sandstones of the Upper Paleozoic, in which lithologically and stratigraphically shielded traps may be present. On the other hand, numerous bitumen manifestations indicate the intermediate, transit nature of this territory with respect to the migration of hydrocarbons. The terrigenous section of the Upper Paleozoic-Mesozoic deposits of the Prialdanskaya and Prilenskaya is favorable for the accumulation and formation of hydrocarbon traps.

Discussion on technical countermeasure of improving development effect of low permeability reservoir

Low PERMEABILITY RESERVOIR IS AN IMPORTANT MATERIAL FOUNDATION FOR STABLE PRODUCTION IN OLD AREAS, BUT DUE TO THE limitations OF reservoir physical properties, exploitation methods and other factors, the late production effect is poor, therefore, from the reservoir and development approach, the technical measures to improve oil recovery in low permeability reservoir are discussed. Based on the analysis of the factors influencing the development effect of double low reservoir and the geological characteristics of reservoir, from the viewpoint of seepage mechanics, this paper systematically classifies five indexes, such as main pipe radius, flow percentage, starting pressure gradient, clay mineral content and crude oil viscosity. The five-element combination evaluation method is used to optimize the low permeability point reservoir, and on this basis, favorable oil and gas accumulation areas are found. According TO THE DEVELOPMENT status of low permeability reservoir, reasonable injection-production network and well type are demonstrated to break the bottleneck of conventional low permeability water injection and improve the development benefit of low permeability reservoir.

Simulation Study of Gas Explosion Propagation Law in Coal Mining Face With Different Ventilation Modes

In ventilation working face, different ventilation way is one of the important factors affecting the propagation of gas explosion shock wave. In order to study the gas explosion shock wave propagation laws in coal mining faces with different ventilation methods, using Fluent simulation software, combined with pipeline gas explosion experiments and the actual situation of gas accumulation area explosion in the corner of 415 coal face in Chenjiashan coal mine, Shaanxi Province, and on the basis of building a three-dimensional mathematical and physical model, the gas explosion simulations under Y-type and W-type ventilation methods were carried out, respectively. The results are described as follows: (1) The attenuation trend of overpressure peak value of inlet roadway 1 and working face with Y-type ventilation conforms to the power function form. Intake airway 2 and return airway have the same peak overpressure attenuation trend, but the peak value of overpressure in return airway is generally 10.6% higher than that in intake airway 2, and its attenuation rate is a process from low to high and then to low. (2) The peak attenuation trend of overpressure in intake airways 1 and 2 with W-type ventilation conforms to the form of power function, and the peak attenuation trend of overpressure in return airway conforms to the form of exponential function. The peak value of overpressure decreases with the increase in the distance from the explosion source, and its attenuation rate decreases gradually. The research results have important theoretical significance for improving the prevention of gas explosion in coal mining face with different ventilation modes.

Reconstruction Method of Old Well Logging Curves Based on BI-LSTM Model—Taking Feixianguan Formation in East Sichuan as an Example

In order to define a favorable oil and gas accumulation area, this study focused on reservoir recognition which is based on logging data of old wells. The Gaofengchang structure in eastern Sichuan is used as a test area to discuss the necessity and feasibility of curve construction by combining new and old wells. Analysis of the reasons for the inaccuracy of the traditional curve reconstruction method is also provided. Given the interdependence of the well log in the depth domain sample sequence, a new intelligent construction method (BI-LSTM) based on the cyclic neural network is proposed. A discussion on the effect of data increments on prediction accuracy is also provided. The following four conclusions were achieved through curve reconstruction experiments: a high-precision CNL pseudo-curve was obtained; an underdetermined equation in optimization logging interpretation method needed to be extended to a positive definite equation; the quantitative processing of the complex lithologic reservoir parameters for the old wells was realized; and the processing result of the lithology physical property were basically consistent with the core data. Therefore, the BI-LSTM proposed in this paper could improve the accuracy of logging curve construction and has a good promotion significance for the old well review.

Reasonable Arrangement of High-Level Orientation Extraction Boreholes of Pressure Relief Gas in Overlying Strata under High-Strength Fully Mechanized Mining in Low-Gas-Thick-Coal Seam

In order to solve the problem of pressure relief gas control under high-strength fully mechanized top-coal caving in low-gas-thick-coal seams, this paper studies the evolution of overburden structures and the distribution characteristics of fissure fields during the initial and stable period of working face by physical simulation and numerical analysis. The mathematical model of coupling between mining fracture field and pressure relief gas field is established. The results reveal the distribution characteristics of pressure relief gas field that considers mining-induced fissure field. According to the distribution of mining gas accumulation area, the high directional long boreholes have been put forward to control the pressure relief gas in goafs, and the effect has been tested. The results show that the initial pressure and three periodic pressures occurred from the cutting hole to 135 m in the initial mining period of the working face. The height of collapse zone developed to 22 m, and fracture height developed to 75 m. The development height of caving zone is stable at 25∼27 m, and the development height of fissure zone is stable at 75∼95 m. The process and distribution of pressure relief gas flow in goaf are obtained by solving the numerical model of pressure relief gas flow in mining fissure field. The gas accumulation area is located within 25∼55 m from return laneway and 25∼50 m from the roof of coal seam. After the implementation of high directional long drilling gas drainage technology in the initial mining period and the stable mining period, good results have been obtained in the gas control, where the average concentration of gas extraction is 5.8%, the average gas flow rate is 0.71 m3/min, and the gas concentration in upper corner and return air is less than 0.8%. The results can provide a reference for pressure relief gas control under similar conditions.

Analysis of accumulation models of Middle Permian in Northwest Sichuan Basin

Great progress has been made in middle Permian exploration in Northwest Sichuan in recent years, but there are still many questions in understanding the hydrocarbon accumulation conditions. Due to the abundance of source rocks and the multi-term tectonic movements in this area, the hydrocarbon accumulation model is relatively complex, which has become the main problem to be solved urgently in oil and gas exploration. Based on the different tectonic backgrounds of the middle Permian in northwest Sichuan Basin, the thrust nappe belt, the hidden front belt, and the depression belt are taken as the research units to comb and compare the geologic conditions of the middle Permian reservoir. The evaluation of source rocks and the comparison of hydrocarbon sources suggest that the middle Permian hydrocarbon mainly comes from the bottom of the lower Cambrian and middle Permian, and the foreland orogeny promoted the thermal evolution of Paleozoic source rocks in northwest Sichuan to high maturity and over maturity stage. Based on a large number of reservoir physical properties data, the middle Permian reservoir has the characteristics of low porosity and low permeability, among which the thrust nappe belt and the hidden front belt have relatively high porosity and relatively developed fractures. The thick mudstone of Longtan formation constitutes the regional caprock in the study area and the preservation condition is good as a whole. However, the thrusting faults destroyed the sealing ability of the caprock in the nappe thrust belt. Typical reservoir profiles revealed that the trap types were different in the study area. The thrust fault traps are mainly developed in the thrust nappe belt, while the fault anticline traps are developed in the hidden front belt, and the structural lithological traps are developed in the depression belt. The different structural belts in northwest Sichuan have different oil and gas accumulation models, this paper built three hydrocarbon accumulation models by the analysis of reservoir formation conditions. The comprehensive analysis supposed the hidden front belt is close to the lower Cambrian source rock, and the reservoir heterogeneity is weak, faults connected source rock is developed, so it is a favorable oil and gas accumulation area in the middle Permian.

Reservoir forming conditions and exploration potential of Lower Paleozoic carbonate rocks in Gucheng area, Tarim Basin

The Gucheng region is oil and gas accumulation area of Tarim Basin，dominated by beach controlled lithologic oil and gas reservoirs，which has superior oil and gas accumulation conditions and broad exploration prospects. The lower Paleozoic strata in the Gucheng region are the Carboniferous, Ordovician, and Cambrian systems from top to bottom. The Silurian, Devonian, and Permian systems are missing. The lower Ordovician – Cambrian are the main exploration target layers in the area. There are four reservoirs: the Ordovician group, the Yingshan group, the Penglaiba group and the Cambrian group in The Gucheng region, The upper part of the Yijianfang formation and Yingshan formation are limestone reservoir, which is a set of potential reservoir. The lower part of the Yingshan formation, the Penglaiba formation, and the Cambrian formation developed three sets of dolomite reservoirs. The distribution of oil and gas in Gucheng region was mainly found in Yijianfang formation, Yingshan formation, Penglaiba formation and Cambrian of the Ordovician. The Yingshan group and the Hanwu group were the main exploration target layers. Yingshan formation and Cambrian are the main exploration targets, and Yijianfang formation and Penglaiba formation of Ordovician can be used as the concurrent exploration targets. Gucheng region can form two major realistic exploration areas: dolomite reservoir of Ordovician and reef beach of Cambrian. The Ordovician dolomite reservoirs are mainly searched for the inner shoal of the platform edge high-energy facies belt, and the Cambrian system is mainly search for the high-energy reef beach far away from the platform edge facies belt in the north of cherchen fault.

Areas of oil and gas accumulation in the Pripyat-Dnieper-Donetsk oil and gas province and the possibility of their study by remote methods

In connection with the need to increase the energy resources of Ukraine, it is essential to expand the areas and depths of prospecting, as well as to improve the methodology and technology of oil and gas exploration. The most promising area for the search for new oil and gas fields in Ukraine remains the Pripyat-Dneprovsko-Donetsk oil and gas province. Increasing the depth of new energy sources because of the increasing cost of exploration and deep drilling requires more accurate and efficient predictions, which should be based on a more rigorous scientific substantiation of new directions of work and the application of new efficient technologies. The article develops the concept of deep degassing of the Earth, which is of great importance for the development of modern ideas about the formation and geological history of the Pripyat-Dnieper-Donetsk oil and gas province. The authors considered the nature of oil and gas accumulation areas and their relationship with the “pipes” of deep degassing of the Earth, as well as the possibilities of structural-tectonic, lithological-geochemical and remote sensing methods in identifying new oil and gas fields in the Pripyat-Dnieper-Donetsk oil and gas province and signs of their connection with «pipes» hydrocarbon deep degassing of the Earth. To implement new methodology and technology of prospecting, exploration of oil and gas fields, the article proposes to make wider use of the modern capabilities of satellite methods, which make it possible to quickly cover large areas with multiple surveys, increase the efficiency of solving geological problems, and also significantly reduce the cost of oil and gas exploration.

Large-scale gas accumulation mechanisms and reservoir-forming geological effects in sandstones of Central and Western China

Large-scale gas accumulation areas in large oil-gas basins in central and Western China have multiple special accumulation mechanisms and different accumulation effects. Based on the geological theory and method of natural gas reservoir formation, this study examined the regional geological and structural background, formation burial evolution, basic characteristics of gas reservoirs, and fluid geology and geochemistry of typical petroliferous basins. The results show that the geological processes such as structural pumping, mudstone water absorption, water-soluble gas degasification and fluid sequestration caused by uplift and denudation since Himalayan stage all can form large-scale gas accumulation and different geological effects of gas accumulation. For example, the large-scale structural pumping effect and fluid sequestration effect are conducive to the occurrence of regional ultra-high pressure fluid and the formation of large-scale ultra-high pressure gas field; mudstone water absorption effect in the formation with low thickness ratio of sandstone to formation is conducive to the development of regional low-pressure and water free gas reservoir; the water-soluble gas degasification effect in large-scale thick sandstone can not only form large-scale natural gas accumulation; moreover, the degasification of water-soluble gas produced by the lateral migration of formation water will produce regional and regular isotopic fractionation effect of natural gas, that is, the farther the migration distance of water-soluble gas is, the heavier the carbon isotopic composition of methane formed by the accumulation.

Effect and mechanism of geological structures on coal seam gas occurrence in Changping minefield

AbstractThe main factor affecting the gas content in a coal seam is the geological structure, and different types of geological structure have different effects on the gas content in a coal seam. To explore the main controlling factors of gas content in coal seam No. 3 in the Changping minefield, and the effect of different geological structures on gas control in a coal seam, this study analyzes the types and quantities of geological structures in the Changping minefield. Further, geological boreholes are used to sample and analyze coal seams near different geological structures and at different burial depths. The results show that the main controlling factor of gas content in a coal seam is the burial depth of the coal seam, and the gas content tends to increase with the increasing depth. A geological structure has an effect on the occurrence of coal seam gas in a local area, and the gas content in the coal seam near a fault is 1.6 times that in the normal areas at the same depth. The gas content in the upper wall of a normal fault is 21.6% higher than that in the lower wall. The syncline and anticline axes are prone to form gas accumulation areas, where the gas content is 30%‐60% higher than the normal level. Gas accumulation is prone to occur around a collapse column, and the gas content there is 2.47 times higher than that in a normal area at the same burial depth. Combining the formation mechanism and structural characteristics of different geological structures, this study analyzes the effect of geological structures on coal seam gas quantitatively and provides a theoretical basis for the prevention and control of gas disasters in the Changping minefield.

Numerical investigation of two-phase flow characteristics in multiphase pump with split vane impellers

Multiphase pump is a cost-effective option for subsea oil and gas field development. The ability to handle different inlet gas volume fractions (GVFs) especially high inlet GVF is critical to the development of pump performance. In this study, the two-phase flow characteristics in normal impeller and split vane impeller at different inlet GVFs were investigated by steady numerical simulations. The gas distribution on blade-to-blade plane and meridional flow channel at different inlet GVFs were analyzed and compared. Gas accumulation area and movement characteristics of the gas-liquid flow in impeller flow passage were also pointed out by unsteady simulations. Experimental results of the pump differential pressure were compared with the numerical simulation results, to validate the accuracy of numerical simulation method. The flow characteristics in pump with modified impeller and its performance at different inlet GVFs were both compared with that of the normal impeller. The steady simulation results of normal impeller in different inlet GVFs show that gas concentrating area in the flow passage increases as inlet GVF grows. The unsteady simulation results indicate that gas pocket firstly occurs on the pressure side of impeller, then moves to the suction side in the middle area of blade and finally transfers to outlet of impeller and disappears. The errors between numerical simulation results and experiment data are below 10 %, which validated the feasibility of the numerical simulation method. Simulation results on the split vane impeller demonstrate that the gas accumulation area in flow passage of the modified impeller is dramatically decreased compared to that of the normal impeller. The performance of the modified impeller is generally better than the normal impeller especially in high inlet GVF conditions.

Optimization of shale gas reservoir evaluation and assessment of shale gas resources in the Oriente Basin in Ecuador

The petroleum geological features of hydrocarbon source rocks in the Oriente Basin in Ecuador are studied in detail to determine the potential of shale gas resources in the basin. The favorable shale gas layer in the vertical direction is optimized by combining logging identification and comprehensive geological analysis. The thickness in this layer is obtained by logging interpretation in the basin. The favorable shale gas accumulation area is selected by referring to thickness and depth data. Furthermore, the shale gas resource amount of the layer in the favorable area is calculated using the analogy method. Results show that among the five potential hydrocarbon source rocks, the lower Napo Formation is the most likely shale gas layer. The west and northwest zones, which are in the deep-sea slope and shelf sedimentary environments, respectively, are the favorable areas for shale gas accumulation. The favorable sedimentary environment formed thick black shale that is rich in organic matter. The black shale generated hydrocarbon, which migrated laterally to the eastern shallow water shelf to form numerous oil fields. The result of the shale gas resource in the two favorable areas, as calculated by the analogy method, is 55,500 × 108 m3. This finding shows the high exploration and development potential of shale gas in the basin.

Investigation on propagation mechanism of large scale mine gas explosions

This work presented an investigation into the gas explosions that occur in coal mines. The propagation of the explosion waves was studied by using large eddy simulation (LES) coupled with weighted essentially non-oscillatory (WENO) finite difference scheme. The results showed that the destructive effects of gas explosions were mainly caused by the high-speed airflow, and the high pressure of the shockwave. The comparison between the numerical and experimental results confirmed that the overpressure and airflow velocity initially increased, and then decreased slightly after the explosion has occurred in the coal mine, and their maximum values increased with the increase of the gas accumulation zone. The flame length was found to be far greater than the length of the original gas accumulation area, and the ratio of them is 5–7 which is related to the gas accumulation area.

Experimental investigations on a common centrifugal pump operating under gas entrainment conditions

This paper presents an experimental study on the effects of additional gas entrainment in centrifugal pumps designed for conveying liquid phases only. The pump performance has been evaluated for several gas entrainment conditions, and for various operational settings of the pump, such as its alignment and the rotational speed of the impeller. As a main performance indicator the impact of entrained gas on the hydraulic power of the pump has been analyzed using experimental data. Additionally, high-resolution gamma-ray computed tomography (HireCT) operated in time-averaged rotation-synchronized scanning mode has been applied to quantify local phase fraction distributions inside the rapidly rotating pump impeller. Based on these quantitative tomographic measurements, gas holdup profiles along selected streamlines have been calculated and gas accumulation areas inside the impeller chambers have been visualized. Thus, various internally accumulated gas holdup patterns have been identified and, eventually, associated with characteristic pump performance behaviors. Moreover, the tomographic measuring method allowed an enhanced gas holdup analysis in specified pump compartments. As a result, the related specific gas and liquid phase holdup profiles have been evaluated.

Critical geological characteristics and gas-bearing controlling factors in Longmaxi shales in southeastern Chongqing, China

The southeastern Chongqing area, one of the highest potential shale gas accumulation areas in China, experienced strong tectonic movements. Due to the tectonic uplift in Himalayan period, the target shale formation is characterized by shallow burial depth and abundant fractures. The Lower Silurian Longmaxi shale was deposited under deep and shallow continental shelf environments with abundant pyrites and graptolite fossils. The lithology of the formation includes black carbonaceous shale, calcareous shale, and siliceous shale. The thickness of the shale varies greatly from 40 to 200 m from southeast to northwest with obvious zonation. Total organic carbon (TOC) content ranges from 1.0 to 4.0% and decreases upward in the formation owing to the change of sedimentary facies. The organic matter reaches dry gas zone. Porosity ranges from 0.5 to 7.9%, and the permeability is measured in the microdarcy to nanodarcy range. Abundant fragile minerals exist in the shales which benefit the hydraulic stimulation. Isothermal adsorption tests show that the sorption gas content in place of the Longmaxi shale ranges from 1.0 to 4.5 m3/t and the gas content in place reaches the standard of commercial exploitation. Factors impacting gas-bearing characteristics were analyzed using a mathematical statistic method, which demonstrates that TOC is the most important factor, especially to the sorption gas content. Meanwhile, clay content, thermal maturity, porosity, and mineral components are also significant factors regarding shale gas-bearing characteristics.

Formation of subsurface shallow gas accumulations in Amurskiy Bay (Peter the Great Bay, Sea of Japan) as a result of postglacial sea-level change, paleoceanographic conditions and hydrological activity

We present new data on the study of subsurface gas accumulations in the sediments of Amurskiy Bay (the Sea of Japan). Geophysical research (single-channel continuous seismic profiling with airguns and high-resolution acoustic investigations with a high-frequency GeoPulse profiler) shows that the bay depression is filled by Pre-Quaternary sediments that are at least 0.8s (TWT) thick and overlaying Late Pleistocene–Holocene sediments that are up to 30m thick. The Pre-Quaternary deposits are possibly represented by coal-containing Mesozoic and Cenozoic rocks. Gas-related acoustic anomalies were found in the Late Pleistocene–Holocene silty sediments in the northern part of the bay. These gas-related anomalies have been divided into blanket column, turbidity and pillar anomalies. A single pockmark was also observed in the bottom relief of the bay. The gas accumulation area in the sediments is 19km long and 12km wide. The degassing of the Pre-Quaternary coal-containing deposits is assumed to be the major cause of gas. The formation of most of the gas anomalies in the Late Pleistocene–Holocene sediments and the trigger mechanism of gas migration may be associated with sea-level changes, paleoceanographic conditions, sedimentation features and the hydrodynamic regime in the bay. Increases in the number of diatoms and the presence of aberrant forms of some silicoflagellates have been observed in areas with high gas contents. Areas with numerous small underwater elevations or mounds were distinguished in the bay. In the northern part of the bay, the mounds correspond to ostraceous reefs or other local shellfish colonies. In the southern part of the bay, the elevations could be related to methane-derived authigenic carbonates, which formed pavements for the fixation of shellfish colonies and construction of reefs.

Experimental study on the goaf flow field of the “U+I” type ventilation system for a comprehensive mechanized mining face

“U” and “U+I” type ventilation experiments were performed on a three-dimensional fully mechanized caving face simulation experimental platform. The distribution laws of the pressure field and gas field in the mine goaf were obtained. Results show that the flow field in the goaf is generally asymmetric; the location of the gas accumulation area changes with ventilation parameters and can be used as an evaluation indicator to study the air leakage extent in the goaf. Hence, drainage pipes buried in the goaf to intensively extract gas can be designed in such gas areas, which can give considerations in both improving gas drainage efficiency and reducing air leakage. By comparing the gas extraction effect of model experiments with that of on-site underground practices, the basic laws are commonly consistent according to comparative analysis. Thus the experimental results can be used to guide the application of underground gas prevention and control.

Seismic Sedimentology of Changling Gas Field, Northeast China

Sedimentary facies plane features of Changling No.1 gas field is analyzed with multiattribute analysis. In Changling area, the signal to noise ratio of the seismic data is low and the sand body distribution in lateral lithologic reservoir changes fast. In this condition, research of seismic sedimentology is launched. Through the seismic stratigraphic classification, the target stratum, Denglouku group is divided into four sand groups. On the basis of the calibration of synthetic seismograms and interpretation of horizon, accurate corresponding relation between the seismic reflection and geological horizon is established. By means of multiple attribute extraction technology, relatively independent attributes related to oil and gas are selected, and afterwards the analysis of the petrophysical characteristics and the optimization of the seismic attribute are achieved. Finally, through the seismic attributes analysis technology and the horizon slice technology, combined with the result of sedimentary facies analysis, the favorable areas of gas accumulation are predicted.