assessment of the contribution of in situ combustion of coal to greenhouse gas emission based on a comparison of chinese mining information to previous remote sensing estimates greenhouse gas ghg emission from geological sources such as volcanic activity seabed gas hydrate release hydrocarbon seepage as well as uncontrolled combustion of fossil fuels is erratic and difficult to quantify in this paper we assess the ghg emission due to spontaneous combustion of in situ coal deposits coal fires this problem is aggravated by human intervention mining activities which on the other hand allows better constrained estimations and improved reduction strategies provided modern mining practices are employed in this study we present three case studies on coal fire related ghg emission quantification on provincial scale in china and we propose an integrated quantification aimed at the joint analyses of local knowledge geophysical data and remote sensing data with the objective to retrieve unbiased numbers as a first estimate we conclude that the emissions of ghgs from coal fires in china account for well less than 0 22 of all global fossil fuel related co2 emissions most likely even less than 0 1 this is much less than the previously estimated 2 3

geothermometry and geochemistry of aqueous and oil bearing fluid inclusions from fateh field dubai abstract the production of oil from fateh field dubai is principally from the cretaceous mishrif formation porosity in the reservoir facies is partly occluded by late coarse grained calcite cement this cement contains both aqueous and oil bearing fluid inclusions fluid inclusion geothermometry was used to determine the temperature of that cement precipitation and calculate its timing relative to basin burial history these data were related to source rock maturation and from that the timing of oil migration was inferred to be oligocene to mid miocene which is geologically contemporaneous with early petroleum generation r 0 0 5 0 6 in the khatiyah source rock the fluid inclusions were analyzed by a thermal decrepitation gas chromatography technique benzene and low molecular weight paraffins were present and a series of normal alkenes was tentatively identified in the aqueous inclusions fresh oil inclusions consisted of c 1 n c 25 compounds whose light hydrocarbon composition was consistent with derivation from an early mature source rock altered petroleum residues detected in many mishrif samples are contained either in inclusions or along crystal cleavages these materials are the subject of an ongoing geochemical study of fateh field

impact of underground coal fire on coal petrographic properties of high volatile bituminous coals a case study from coal fire zone no 3 2 in the wuda coalfield inner mongolia autonomous region north china abstract the wuda coalfield located in the inner mongolia autonomous region north china is known as one of china s major source of prime coking coals and a site of well researched and well documented underground coal fires the underground coal fire at the coal fire zone no 3 2 is situated in the active coal mine of suhai tu located in the north westerly part of the wuda coalfield the present paper investigates the impact of the underground coal fire on the coal seam no 10 by application of coal petrographic methods including detailed characteristic of macerals and other coal components maceral analysis microstructural analysis and vitrinite reflectances performed on 1 coal grains lacking impurities microfractures dark oxidation rims 2 on dark rimmed vitrinite as well as 3 on low temperature semi coke the investigated coal seam no 10 represents a high volatile a bituminous coal and is dominated by vitrinite followed by inertinite with minor amounts of liptinite and by non isotropic low temperature semi coke the microstructure of the oxidatively and thermally altered coals is represented by 1 extensive non tectonic microfissures and non tectonic microfractures i e shrinkage microfractures leading to defragmentation of coal grains 2 dark oxidation rims observed at grain margins non tectonic microfissures and microfractures and by 3 devolatilisation micropores random vitrinite reflectances measured in 1 coal grains lacking impurities microfractures and dark oxidation rims and in 2 dark rimmed vitrinite at non tectonic microfissures and fractures reveal significant lateral variations the presence of low temperature semi coke and its marked lower reflectance values are indicative of thermal alteration induced by the underground coal fire in the coal fire zone no 3 2 the results obtained from the performed analyses of organic matter point to both low temperature oxidation and low temperature pyrolysis processes the applied coal petrological approach revealed characteristic changes to the coal s microstructure its petrographic composition as well as to optical properties induced by the underground coal fire

petroleum accumulation in the deeply buried reservoirs in the northern dongying depression bohai bay basin china new insights from fluid inclusions natural gas geochemistry and 1 d basin modeling abstract the deeply buried reservoirs dbrs from the lijin shengtuo and minfeng areas in the northern dongying depression of the bohai bay basin china exhibit various petroleum types black oil gas condensates and pressure systems normal pressure overpressure with high reservoir temperatures 154 185 c the pressure volume temperature composition pvtx evolution of petroleum and the processes of petroleum accumulation were reconstructed using integrated data from fluid inclusions stable carbon isotope data of natural gas and one dimensional basin modeling to trace the petroleum accumulation histories the results suggest that 1 the gas condensates in the lijin area originated from the thermal cracking of highly mature kerogen in deeper formations two episodes of gas condensate charging which were evidenced by the trapping of non fluorescent gas condensate inclusions occurred between 29 25 5 ma and 8 6 5 0 ma with strong overpressure pressure coefficient pc 1 68 1 70 resulting in the greatest contribution to the present day gas condensate accumulation 2 the early yellow fluorescent oil charge was responsible for the present day black oil accumulation in well t764 while the late blue white oil charge together with the latest kerogen cracked gas injection resulted in the present day volatile oil accumulation in well t765 and 3 the various fluorescent colors yellow blue white and blue and the degree of bubble filling fv 2 3 72 5 of the oil inclusions in the minfeng area show a wide range of thermal maturity api gravity ranges from 30 to 50 representing the charging of black oil to gas condensates the presence of abundant blue white fluorescent oil inclusions with high grain obtaining oil inclusion goi values 35 8 usually 5 in oil reservoirs indicate that a paleo oil accumulation with an approximate api gravity of 39 40 could have occurred before 25 ma and gas from oil cracking in deeper formations was injected into the paleo oil reservoir from 2 8 ma to 0 ma resulting in the present day gas condensate oil accumulation this oil and gas accumulation model results in three oil and gas distribution zones 1 normal oil reservoirs at relatively shallow depth 2 gas condensate reservoirs that originated from the mixture of oil cracking gas with a paleo oil reservoir at intermediate depth and 3 oil cracked gas reservoirs at deeper depth the retardation of organic matter maturation and oil cracking by high overpressure could have played an important role in the distribution of different origins of gas condensate accumulations in the lijin and minfeng areas the application of oil and gas accumulation models in this study is not limited to the dongying depression and can be applied to other overpressured rift basins

record of late holocene debris avalanches and lahars at iliamna volcano alaska abstract iliamna volcano is a 3053 meter high glaciated stratovolcano in the southern cook inlet region of alaska and is one of seven volcanoes in this region that have erupted multiple times during the past 10 000 yr prior to our studies of iliamna volcano little was known about the frequency magnitude and character of holocene volcanic activity here we present geologic evidence of the most recent eruptive activity of the volcano and provide the first outline of late holocene debris avalanche and lahar formation iliamna has had no documented historical eruptions but our recent field investigations indicate that the volcano has erupted at least twice in the last 300 yr clay rich lahar deposits dated by radiocarbon to 1300 and 90 yr bp are present in two major valleys that head on the volcano these deposits indicate that at least two large possibly deep seated flank failures of the volcanic edifice have occurred in the last 1300 yr noncohesive lahar deposits likely associated with explosive pyroclastic eruptions date to 2400 1300 1500 300 and debris avalanche deposits from recent and historical small volume slope failures of the hydrothermally altered volcanic edifice cover most of the major glaciers on the volcano although these deposits consist almost entirely of hydrothermally altered rock debris and snow and ice none of the recently generated debris avalanches evolved to lahars a clay rich lahar deposit that formed

archaean oil migration in the witwatersrand basin of south africa abstract the late archaean witwatersrand supergroup of south africa hosts the largest known gold uranium pyrite ore deposits oil preserved in fluid inclusions in quartz grains in siliciclastic sedimentary rocks of that supergroup implies that hydrocarbon generation and migration occurred during the archaean and may have been involved in mineralization processes through reference to phanerozoic analogues oil bearing fluid inclusions entrapped in healed microfractures in detrital quartz grains and in early syntaxial quartz overgrowths imply that the onset of oil migration coincided with early to intermediate stages of burial while intra granular porosity was still preserved multiple generations of oil migration are indicated by i oil inclusions within early diagenetic cements at different levels in the stratigraphic succession ii more than one type of oil in entrapment sites iii oil entrapment in multiple stages of the quartz paragenetic sequence oil generation and migration are considered to have occurred throughout and for some considerable time after development of the witwatersrand basin consistent with progressive burial and kerogen maturation in more than one tectonic regime oil bearing fluid inclusions within detrital sandstone fragments suggest that oil migration also occurred in a sedimentary succession on the kaapvaal craton prior to 2 9 ga oil in the witwatersrand supergroup was most likely derived from multiple source areas with the principal source probably being shales within the lower witwatersrand supergroup the hydrocarbon migration history of the basin has important implications for understanding the textural relationship between gold bituminized oil and uraninite in the giant gold uranium pyrite ore deposits

aquifer protection during longwall mining of shallow coal seams a case study in the shendong coalfield of china large scale underground mining of shallow coal seams can have significant impacts on ground surface and potentially leads to incidental damage to the overlying aquifer with subsequent environmental hazards in order to deal with the apparent conflict between water protection and high production in underground mining an aquifer protection mining technique was trialed in panel 51201 in the shangwan colliery the shendong coalfield china overburden failure water level of the unconsolidated aquifer surface cracks and ground subsidence were monitored in a series of boreholes using borescope and also by observations in a nearby water well and by surface surveys monitoring results indicate that the aquifer protection mining technique can be successfully applied by modifying a few mining parameters such as mining height or advance rate under some suitable geological conditions the critical zone in the stratigraphy appears to be the weathered bedrock located immediately below the aquifer the weathered bedrock will remain impermeable after mining as long as its thickness is greater than the mining height the development of the mining induced overburden failure is affected by the key strata but ultimately controlled by the soft aquiclude such as the weathered zone it was observed respectively that the height of the caved zone was observed to be 5 to 6 times the mining height whilst the height of the fractured zone is about 10 to 11 times the mining height

field trials of aquifer protection in longwall mining of shallow coal seams in china the large scale mining of shallow coal seams has a significant impact on the overlying aquifers and surface ecological environment to protect the aquifers and maximize the coal resource recovery field trials were undertaken during the operation of the lw32201 in bulianta coal mine shendong china with a severely weathered rock swr layer and two key strata ks in the overlying strata aquifer protection in longwall mining aplm relies mainly on the rapid advance in some localized zones special measures should be taken to achieve the aplm including lowering mining height backfill and slurry injection to further understand the mechanism and applicable conditions of the aplm and validate the effectiveness of the aplm variation of the water table in the aquifer was observed as the longwall face passed through the zone this paper also discusses the mechanism and basic requirements of the aplm and the relationship between the fall of the water table and the surface subsidence the results of the field trials indicated that aplm in shallow coal seams could be successful under suitable conditions

analysis of developmental features and causes of the ground cracks induced by oversized working face mining in an aeolian sand area in order to satisfy the energy demand of china it is an effective way to exploit coal resources efficiently in western china when a coal seam with a shallow burial depth is mined on a large working face with width of 300 m in a semi desert aeolian sand area of western china the induced subsidence and damage of ground surface are remarkably different from those induced by a traditional mining condition by taking working face 12 406 of bulianta coalmine in shendong mining area as an example this paper based on actual measurement data analysed the developmental features and causes of ground surface racks research results showed that the shape of the static crack in the peripheral area on the working face was very similar to that contained in the actual measurement results of other areas specifically such static crack was arc shaped and the actually measured static crack angle was 84 5 however the dynamic crack above the working face took on uniqueness in two developmental cycles expansion to restoration this phenomenon is not available in other research areas starting from the structure of rock strata this paper analysed the two developmental cycles of dynamic cracks according to the periodic fracture theory of key stratum and verified the results of theoretical analysis by employing the similar material model

mining induced strata stress changes fractures and gas flow dynamics in multi seam longwall mining abstract this paper presents key findings from a recent comprehensive study of longwall mining induced strata movement stress changes fractures and gas flow dynamics in a deep underground coal mine in anhui china the study includes field monitoring of overburden displacement stress and water pressure changes at the longwall panel 1115 1 of the guqiao mine in addition 3d modelling of strata behaviour at the longwall panel using a 3d finite element code and goaf gas flow simulations with a cfd code are carried out this research has resulted in many new insights into the complex dynamic interaction between mining induced strata stress changes fractures and gas flow patterns based on the findings from the field monitoring and numerical modelling a three dimensional annular shaped overlying zone along the perimeter of the longwall panel is identified for optimal methane drainage during mining a practical method that helps define the geometry and boundary of this zone is proposed this study provides a new methodology and a set of engineering principles for the design of optimal co extraction of coal and methane

chemical changes of fluid inclusion oil trapped during the evolution of an oil reservoir jabiru 1a case study timor sea australia abstract this study of the jabiru oil field timor sea australia shows how the variability of visual properties of fluid inclusions in palaeo oil zones can be mapped to identify internal structures that result from fluid interactions in the reservoir variability in the attributes of oil inclusion assemblages oias is greater within an inferred palaeo gas cap zone 1 and current residual zone zone 3 and less within the current oil zone zone 2 in zone 3 where water imbibed a higher proportion of oias with visual white fluorescing oil inclusions correlates with less mono aromatic compounds and a higher abundance of polar compounds determined on a bulk extract of inclusion oil using high performance liquid chromatography hplc the ch 2 ch 3 ratios and water contents determined by fourier transform infrared spectroscopy ft ir are higher in zone 1 where gas drained there is a higher proportion of oias with visual yellow fluorescing oil inclusions and these correlate with low hplc mono aromatic and moderate polar contents and low ft ir ch 2 ch 3 ratios and water contents interpretation of the grains with oil inclusions goi and pressure volume temperature composition pvtx fluid inclusion data suggests that a gas saturated blue fluorescing palaeo oil was present in the three zones at the same pressure temperature fluid inclusion forming event pt 1 lighter gas saturated blue fluorescing oil was present in zone 2 but was rarer in zones 1 and 3 at the later fluid inclusion forming event pt 2 the yellow and white inclusion oils trapped in zones 1 and 3 respectively are gas depleted and interpreted to result from the interaction between non movable residual oil around grains with the surrounding gas and water respectively comparison between the pvtx data and the published burial curve suggests that most of the fluid inclusions were trapped during two different hot fluid flow events the full oil column is interpreted to have been present during early mid tertiary the palaeo oil column was reduced during the late miocene by imbibition of water in the present residual zone and drainage of gas at the top of the reservoir

calibration of a 3d hydrodynamic meandering river model using fully spatially distributed 3d adcp velocity data abstractthis study used fully spatially distributed three dimensional 3d velocity data for the improved calibration of a 3d hydrodynamic model the conventional calibration methods do not account

assessing the maturity of oil trapped in fluid inclusions using molecular geochemistry data and visually determined fluorescence colours abstract the thermal maturity of oils extracted from inclusions and the fluorescence colours of oil bearing fluid inclusions have been measured in 36 sandstone samples from australasian oil fields the inclusion oils were analysed using an off line crushing technique followed by gc ms a maturity assessment was made for each inclusion oil using 25 molecular maturity ratios including a newly defined dimethyldibenzothiophene ratio dmdr each inclusion oil was placed in one of 4 maturity brackets approximately equivalent to early mid peak and post oil generation windows the fluorescence colours of oil inclusions were visually discriminated into blue white and yellow plus orange and their proportions estimated using point counting techniques sixteen samples have 85 of oil inclusions with blue fluorescence whilst other samples have more variable fluorescence colours one sample has 100 of oil inclusions with yellow plus orange fluorescence the results show that samples containing mainly blue fluorescing oil inclusions have thermal maturities anywhere within the oil window in particular the molecular geochemical data strongly suggests that oil inclusions with blue fluorescence can have relatively low maturities calculated reflectance

hydrocarbon generation in the permian irati organic rich shales under the influence of the early cretaceous parana large igneous province abstract the increasing global demand for natural gas and petroleum byproducts is turning organic rich shales into an important target for hydrocarbon exploration and production current understanding about hydrocarbon generation in unconventional plays such as oil shales and gas shales is still evolving especially in sedimentary basins where hydrocarbon generation is influenced by magmatism this is the case for the permian oil shales of the irati formation in the parana basin southern south america the irati shales are considered an atypical petroleum system due to thermal effects of the parana large igneous province lip emplaced during the early cretaceous in this context the focus of this study was to characterize the thermal conditions of hydrocarbon generation in the irati formation as well as the composition of related aqueous diagenetic fluids the kerogen from the irati organic rich shales has an aromaticity around 30 ar 30 as determined by carbon nuclear magnetic resonance 13c nmr and vitrinite reflectance ro of around 0 6 fluid inclusions in calcite and quartz veins present aqueous fluids with salinity of 0 5 wt of nacl equivalent and homogenization temperatures greater than 250 c hydrocarbon fluid inclusions were classified as black oil through their vapor fraction volumes fv 1 6 9 1 and homogenization temperatures th in the 60 80 c range methane ch4 or carbon dioxide co2 fluid inclusions were absent within the analyzed calcite and quartz veins the pvt model for trapped fluid inclusions suggests a shallow hydrocarbon petroleum system 2 5 km depth active during the early cretaceous synchronous with the parana lip

development law of air leakage fractures in shallow coal seams a case study in the shendong coalfield of china continuous air leakage from ground mining induced cracks is a significant cause of coal spontaneous combustion low oxygen at the working face and other disasters in shallow coal seams this paper studies mining induced cracks and air leakage caused by the repeated mining of shallow coal seams at the bulianta coal mine shendong coalfield china a similar simulation experiment was carried out in the laboratory and then the ground mining induced cracks were observed and the crack air leakage was detected the results showed that the surface air flowed into the composite goaf before the fractures redeveloped to the surface during the process of lower coal seam mining due to the different development processes of vertical fractures in various regions the width of the vertical fractures in the boundary area of the overlying goaf increases significantly after the repeated mining of coal seams while the vertical fractures in the central area of the overlying goaf experience almost no change the distribution of the surface air leakage cracks is in the shape of graben type cracks and half graben type cracks are surface air leakage cracks which are the focus of surface air leakage problems especially the half graben type cracks the results are important in engineering for reducing air leakage from surface mining induced cracks

inducing mode analysis of rock burst in fault affected zone with a hard thick stratum occurrence study of movement characteristics of a hard thick stratum hts affected by a fault in a coalmine is significant to predict the dynamic hazards i e rock bursts and shock bumps because of the particular structural and mechanical properties of the hts and the fault hence using udec numerical simulation the movement characteristic of hts and fault slipping law with different mining directions towards the fault were studied then two different inducing modes and corresponding mechanisms of rock burst were obtained the results show that the structure of overlying strata on two fault walls is different because of fault cutting and fault dip it results in the hts of two fault walls presenting different movement stage characteristics from analysis of fault plane stress and fault slipping we obtain that footwall mining has higher risk of rock burst than hanging wall mining finally summarizing two different inducing modes of rock burst affected by the hts and the fault one that mainly resulted from the strain energy release caused by the hts obvious bending and failure i e hanging wall mining and one that notably affected by fault slipping and hts failure subsidence i e footwall mining a field case regarding microseismic monitoring is used to verify the numerical simulation results study results can serve as a reference for predicting of rock bursts and their classification into hazardous areas under similar conditions

hydrocarbon charging and accumulation history in the niudong buried hill field in the baxian depression eastern china abstract the niudong buried hill field which lies in the baxian depression of the bohai bay basin is the deepest oil gas accumulation in eastern china its precambrian dolomite reservoir occurs at burial depths of 5860 m 6027 m this paper attempts to document the hydrocarbon charging and accumulation history in this field which could greatly enhance the understanding of the mechanisms for the formation of deep hydrocarbon accumulations our previous study of oil trapped in fluid inclusions has demonstrated that the ratio parameters of the fluorescence spectral intensities at 425 nm and 433 nm q 425 433 ratio and at 419 nm and 429 nm q 419 429 ratio can be more effective for revealing hydrocarbon charging history than the previously used fluorescence parameters such as lambda max and red green quotient as well as fluorescence colors the hydrocarbon charging and accumulation history in the niudong buried hill field was studied with an integrated approach involving the application of these two spectral parameters of petroleum inclusion fluorescence as well as utilization of other data including homogenization temperatures of aqueous inclusions coeval with petroleum inclusions and cross cutting relationships of cements and oil veins in pores and fractures the results indicate that the dolomite reservoir in the niudong buried hill field experienced three episodes of hydrocarbon charging in the first two episodes between 38 5ma and 25ma the low mature and mature oils which were derived from source rocks in the sha 4 member of the eocene shahejie formation migrated into the reservoir but part of them leaked out due to normal faulting at the updip margin of the buried hill these early charged oils were preserved mainly in small pores in micritic dolomites by oil wettability and capillary pressure in the neogene the basin subsided as a whole and local faults at the updip margin became inactive and played a sealing role by approximately 13ma the source rocks became highly mature and the generated hydrocarbons then migrated into the reservoir and accumulated therefore the last charging is the most important for hydrocarbon accumulation in the niudong buried hill field

diagenesis and burial history of great oolite limestone southern england oil is produced from the middle jurassic great oolite limestone in the western wealden basin england additional production was discovered 150 stbopd 42 api in 1986 at the conoco 1 storrington well the storrington discovery is of note because the porosity in reservoir grainstones and packstones is largely primary and averages 19 4 the highest value yet found for the great oolite secondary porosity is of little significance for all wells studied porosity in great oolite grainstones and packstones ranges between 3 and 20 and there is no relation between porosity and lithology locally porosity may be largely occluded by coarse calcite spar which fluid inclusion studies show precipitated in the deep burial environment exploration in the great oolite the efore must seek diagenetic fairways wherein primary porosity has been preserved limestones in the producing interval of the great oolite at 1 storrington contain zoned syntaxial cements are generally high in magnesium content and have stable isotope compositions that indicate the involvement of marine waters relatively heavy dgr18o our interpretation is that the limestones were stabilized early in a mixing zone between freshwater and marine phreatic environments coarse calcite spar in the great oolite contains aqueous and oil inclusions the results of geothermometry studies show that the precipitation of calcite cements occurred at depth near maximum burial and at certain locations was synchronous with oil migration inversion of the basin was a later event the construction of burial history diagrams that incorporate fluid inclusion and maturation data shows that oil migration was during the late cretaceous a distribution pattern for oil inclusions in the great oolite indicates migration was mainly in the western part of the basin and initially into pre late cretaceous traps

depositional diagenetic thermal and maturation histories of cretaceous mishrif formation fateh field dubai rudist reef associated limestones comprising the cretaceous mishrif formation are the major reservoirs in fateh field a giant oil field in offshore dubai in this study mishrif cores from four wells on the western flank of the field were examined to gain insights into the depositional diagenetic thermal and maturation histories of the mishrif formation in this area the wells lowest on the west flank contain relatively deep water lower fore reef facies bounded by two erosional unconformities the upper unconformity marks the laffan mishrif contact and extends over fateh field throughout the region in fateh field the lower intra mishrif unconformity has been identified only on the western flank but is probably present in other locations low on the fateh structure the identification of the lower unconformity indicates two cycles of mishrif sedimentation the cycles are related to deep seated salt movement and epeiric sea level changes fluid inclusion data maturation calculations and burial history modeling indicate that the timing of cementation by blocky calcite spar and oil migration were approximately synchronous and occurred during the oligocene to miocene

simulating mining induced strata permeability changes abstract mining processes fracture the surrounding strata and may modify the flow of groundwater by inducing new fractures or changing the permeability of existing defects the result of mining induced permeability changes can be disturbance to aquifers or other surface or sub surface water bodies traditional methods for predicting mining induced fracture connectivity and enhanced permeability based on empirical strain based criteria may not satisfy modern regulatory demands nor adequately reflect local geological geotechnical and hydrogeological conditions standard continuum numerical methods may indirectly estimate permeability enhancement from plastic strains however they are not able to track aperture on flow paths or predict fracture connectivity this paper presents a numerical approach that is demonstrated to be capable of representing longwall mining induced fracturing in sedimentary rock masses by initiating and propagating fractures determining connectivity and calculating aperture in a piecewise manner on flow paths we have estimated permeability enhancement from first principles fracture intensity and porosity metrics are calculated and identify the height of the enhanced permeability fractured zone above a longwall goaf permeability within the overburden is estimated from the kozeny carman permeability porosity equation at a mine site studied in detail in this paper a permeability increase from the in situ state is predicted to range from approximately eight orders of magnitude in the caved zone to one to two orders of magnitude in the strata above the fractured zone realistically simulating cracking fracturing and crushing of rock strata remains numerically intensive and challenging at the scale of a longwall panel it is demonstrated in this paper and provides valuable insights into the rockmass response to mining

different bedding loaded coal mechanics properties and acoustic emission using taw 2000kn electro hydraulic servo rock press machines and the american physical acoustics company s sh ii acoustic emission systems experimental studies began to address the mechanical properties in different beddings of loaded coal and the related acoustic emission characteristics established based on the acoustic emission damage model and verify the model the results show that the mechanical properties of different coal sample beddings are distinctive with maximum uniaxial compressive strength and elastic modulus of vertical stratification of coal samples and the minimum poisson s ratio thus the minimum uniaxial compressive strength and elastic modulus of oblique bedding coal samples along with the maximum poisson s ratio in the processes of loading result in different bedding coal samples having different stress strain curves especially when different bedding coal samples experience the stages of fissure compression elastic deformation plastic deformation and instability and destruction in addition the displacement proportions of each stage of the loading process have relatively obvious differences the loading times of vertical parallel and oblique bedding coal are 495 382 and 331 s respectively and their acoustic emission mutation points of peak stress are approximately 60 41 and 33 respectively thus we can use the mutation point as precursor information to estimate the damage intensity in different bedding seams the theoretical and experimental stress strain curves obtained by the coal damage model are basically identical verifying the reliability of the model and reflecting the feasibility of acoustic emission technology in the study of coal damage the results can effectively forecast coal and gas outburst hazard in coal mines especially highly gassy and outburst mines it can also make comprehensive predictions for flooding accidents roof fall accidents and other disasters and provide valuable evacuation time for underground coal mine workers the results are of great scientific significance in safeguarding the safety of coal mines

soil and water conservation in mining area based on ground surface subsidence control development of a high water swelling material and its application in backfilling mining it has always been a crucial issue in the mining industry that the surface subsidence induced by underground coal mining can lead to the severe deterioration or loss of soil and water resources in mining area backfilling has become one of the most frequently used mining method to solve this puzzle as it can effectively control the movement of overlying strata and therefore soil and water resources will not be destroyed by mining activities a new type of high water swelling material hwsm was developed to address the key issues of current backfilling materials used in collieries such as the high cost inadequate strength and low expansion rate based on the principle that the strength of backfilling body satisfies the requirement a critical ratio of water to solid material a mixture of fly ash which was used as an aggregate lime anhydrite cement and additive ingredients was determined which varied from 0 8 1 to 0 9 1 meanwhile the mass ratio of fly ash anhydrite lime cement and additives was determined to be 24 6 0 8 5 1 1 8 1 laboratory tests showed that strength of samples that met the required setting time for practical use could reach 5 39 5 52 mpa after 63 days the expansion rate after 3 h varied between 9 9 and 10 8 and the bleeding rate ranged from 0 3 to 0 33 industrial application has been conducted in wangtaipu colliery and results showed that the proposed hwsm had an outstanding mechanical performance with good expansion rates and fluidity these properties indicate that the developed material is suitable for use as a good backfilling material in mining so as to effectively reduce the ground surface subsidence and to conserve the soil and water

fluid inclusion petrography and tectonic burial history of the al ali no 2 well evidence for the timing of diagenesis and oil migration northern oman foredeep cores cut in shallow marine lower and middle cretaceous carbonates in the al ali no 2 well umm al qaiwain united arab emirates display a five stage sequence of calcite cementation fracturing and stylolitization these stages are correlated with the tectonic history of the northern oman orogeny occurrence of fluorescent hydrocarbon fluid inclusions is restricted to stage 2 and stage 3 fracture filling calcites that are crosscut by stylolites stylolite formation during rapid burial beneath abyssal campanian foredeep sediments restricts hydrocarbon migration to post mid cenomanian and pre mid campanian time

diagenesis and reservoir quality evolution of palaeocene deep water marine sandstones the shetland faroes basin british continental shelf abstract the palaeocene deep water marine sandstones recovered from six wells in the shetland faroes basin represent lowstand transgressive and highstand systems tract turbiditic sediments mineralogic petrographic and geochemical analyses of these siliciclastics are used to decipher and discuss the diagenetic alterations and subsequent reservoir quality evolution the middle upper palaeocene sandstones subarkoses to arkoses from the shetland faroes basin british continental shelf are submarine turbiditic deposits that are cemented predominantly by carbonates quartz and clay minerals carbonate cements intergranular and grain replacive calcite siderite ferroan dolomite and ankerite are of eogenetic and mesogenetic origins the eogenetic alterations have been mediated by marine meteoric and mixed marine meteoric porewaters and resulted mainly in the precipitation of calcite 18 o v pdb 10 9 and 3 8 trace amounts of non ferroan dolomite siderite 18 o v pdb 14 4 to 0 6 as well as smectite and kaolinite in the lowstand systems tract lst and highstand systems tract hst turbiditic sandstone below the sequence boundary minor eogenetic siderite has precipitated between expanded and kaolinitized micas primarily biotite the mesogenetic alterations are interpreted to have been mediated by evolved marine porewaters and resulted in the precipitation of calcite 18 o v pdb 12 9 to 7 8 and fe dolomite ankerite 18 o v pdb 12 1 to 6 3 at temperatures of 50 140 and 60 140 c respectively quartz overgrowths and outgrowth which post and pre date the mesogenetic carbonate cements is more common in the lst and tst of distal turbiditic sandstone discrete quartz cement which is closely associated with illite and chlorite is the final diagenetic phase the clay minerals include intergranular and grain replacive eogenetic kaolinite smectite and mesogenetic illite and chlorite kaolinite has been subjected to mesogenetic replacement by dickite the k feldspar and plagioclase grains have been albitized dissolution of calcite cement and of framework grain feldspar volcanic fragments and mud intraclasts has resulted in a considerable enhancement of reservoir quality

reply to comment by oxtoby on assessing the maturity of oil trapped in fluid inclusions using molecular geochemistry data and visually determined fluorescence colours the authors welcome the opportunity to respond to some of the comments of oxtoby 2002 regarding their recent paper george et al 2001 we will respond to the two main topics that have been raised by oxtoby 2002 firstly the petrological procedures used and secondly the possible causes for the wide maturity range of blue fluorescing oil inclusions the issue of the relationship of fluorescence colour and api gravity raised by oxtoby 2002 was not discussed in the paper

sliding instability characteristics and re stabilization mechanism of key stratum in thin topsoil scs mining a computer aided case study from the niushan coal mine china roof step subsidence and support crushing accidents caused by the sliding instability of fractured single key stratum often occur in shallow coal seam scs for this reason the exploration of fracture displacement laws and control mechanism of key stratum in thin topsoil scs is of great significance for both roof control and safety production from this perspective in this study numerical simulation and theoretical analysis were conducted to establish a mechanical model of the key stratum structure after sliding instability in thin topsoil scs moreover its instability characteristics and re stabilization control mechanism were analyzed the results revealed that the fractured key stratum block could reach re stabilization without any support crushing after sliding instability in thin topsoil scs depending on the significant unloading effect of the topsoil the mechanical model of the key stratum structure after sliding instability was also analyzed to obtain the criterion for the re stabilization of the sliding instable rock block the computational analysis corroborated that increasing the support intensity could promote the re stabilization of fractured key stratum block after sliding instability and the required support working resistance could be obtained for preventing support crushing incidents

surface stepped subsidence related to top coal caving longwall mining of extremely thick coal seam under shallow cover the surface stepped subsidence had badly affected the public infrastructure safety the formation mechanism of the surface stepped subsidence case was explained the surface subsidence profile after the sequent mining activity was predicted the possible controls of the stepped subsidence were lastly proposed

a fluid inclusion study of cement and vein minerals from the celtic sea basins offshore ireland abstract fluid inclusion petrography and microthermometry have been carried out on jurassic sandstone cements quartz calcite and dolomite and later fracture filling calcite quartz veins from the north celtic sea and the fastnet basins fluid inclusions in the sandstone cements are small 1 8 m monophase liquid only or liquid rich two phase liquid vapour aqueous inclusions all display irregular to elliptical morphologies the two phase aqueous inclusions homogenise to the liquid phase between 60 122 c and have salinities ranging from 7 0 16 0 wt nacl equivalent indicating precipitation of the cements by moderate salinity waters in contrast the veins host both aqueous and petroleum inclusions the aqueous inclusions are liquid rich two phase liquid vapour inclusions 2 30 m long that are typically primary and show irregular and negative crystal shape morphologies their homogenisation temperatures to liquid range from 50 145 c and salinities from 6 20 wt nacl equivalent indicating broadly similar salinities coupled with a wider range of minimum trapping temperatures to those recorded from the cements yellow brown two phase liquid vapour petroleum inclusions are hosted by vein calcite from several wells in the central north celtic sea basin some of these inclusions appear to be primary and all are spatially associated with the aqueous inclusions the two phase liquid vapour petroleum inclusions homogenise mostly to the liquid between 50 130 c petroleum inclusions in the vein calcites indicate that petroleum was transported via fractures at a late stage through the jurassic and cretaceous strata of the celtic sea basins and apparently not through the sandstone matrix

coal fires revisited the wuda coal field in the aftermath of extensive coal fire research and accelerating extinguishing activities abstract the wuda coal mining area in inner mongolia autonomous region china is one of the largest coal fire areas world wide at the same time it is also one of the most extensively researched ones the sub surface coal fires raging in the underground coal seams of the syncline are located directly west of the town of wuda the fires have been mapped in situ based on remote sensing data as well as based on geo physical survey all throughout the years 2001 to 2005 numerous publications depict the situation during that time in the present study we assess the current situation in wuda coal field five years after the last field campaigns under nowadays on going and accelerating extinguishing activities we present the results of coal fire dynamics assessment based on in situ mappings between 2004 and 2010 the analyses of changes in mining infrastructure between 2005 and 2012 as well as land cover change in the area from 2005 to 2012 newest high resolution multispectral and panchromatic quickbird data as well as time series of quickbird data supported this endeavor we furthermore present the result of semi structured interviews undertaken with members of the local mine directorate of the wuda syncline all jointly analyzed data indicate that the wuda coal fires tend to move eastwards within the syncline meaning that they move along the dip of the coal seams to greater depths furthermore mining related infrastructure is clearly moving from the west to the east as well despite large funds spent on fire extinguishing only few fires remain permanently extinct while other fire areas increase in size the former land cover structure in the arid syncline does not exist anymore extinguishing activities have led to a complete turn over of all material in the region the coal fire problem in wuda area remains a pressing one

separation and fracturing in overlying strata disturbed by longwall mining in a mineral deposit seam abstract mining induced fractures influence the stability of overburden and may provide pathways for transferring heat and mass in underground environment a novel approach was proposed to quantify the separation and fracture evolution in the undermined overburden consisting of 1 theoretical distribution models of the void ratios of fractures vrfs based on analytical evaluation of key strata subsidence and 2 numerical modeling using the universal distinct element code and a sequence of image post processing procedures for a longwall mining panel both theoretical calculations and numerical simulations indicated that vrf first increased rapidly then gradually decreased and finally stabilized to a minimum from the surrounding edges of disturbed strata to their centers and gradually decreased from deep to shallow strata the fractures exhibited a fracture rich arch distribution type along a vertical section numerous fractures occurred around the arch feet near the perimeters of mined out area and or arch crown near the center of disturbed strata the distributions of vrfs show the heights shapes and damage intensities of fractured zones and can also be used as porosity parameters to determine the permeabilities of mining disturbed overburdens therefore the vrf models can be used as a quantitative parameter to assess the extent of possible risk zones e g for water inflow into the mine or escape of hazardous fluids to the surface

fractural structure of thick hard roof stratum using long beam theory and numerical modeling the thick hard rock thr roof of the long wall mining face is prone to the large sized cantilever roof and its sudden fracture will cause serious rock dynamic disasters such as coal and gas outburst and rockburst in this study based on the long beam theory the initial fracture mechanical model for thr was established and the first weighting characteristics and extreme fracture step distance were calculated this study introduced a new technology called deep hole pre splitting blasting dpb which could break the thr by drilling holes with different depths and angles at different levels of roof rock and then blasting it field measurement analysis indicated that the immediate roof and lower thick hard strata were fully collapsed to fill the goaf and the upper thick hard stratum was effectively cut off the results showed that mechanical model and drilling holes method and dpb technique were so notably that would lead to a foundation for large scale popularization and application in a chinese mine

theoretical analysis of the secondary development of mining induced surface cracks in the ordos region prior studies have indicated that mining induced surface dynamic cracks in eastern china only undergo one expanding closure development cycle however field measurements from the bulianta mines of northwestern china demonstrated that ground dynamic cracks in the ordos region went through two expanding closure cycle using in situ measurement data and theoretical analysis we find that the strata control theory cannot reasonably explain this special phenomenon in this paper we propose a novel explanation from the perspective of soil mechanics a comparison of two field examples in eastern and northwestern china demonstrates that our theoretical explanation is in agreement with in situ observations and therefore is a reasonable interpretation for the secondary development of ground dynamic cracks in the bulianta mines this study provides a theoretical basis for the mechanism of mining induced ground dynamic cracks

formation of fractured zones in overburden due to longwall mining the fractured zones caused by mining were studied in the overburden of the torezko snezhnyanskaya area ukraine through the change in natural gas emission from these zones during longwall coal excavation zones of interconnected fractures and separate horizontal fractures were studied with vertical wells drilled from the ground surface down to active underground workings the maximum heights of the zone of interconnected fractures and separate horizontal fractures may reach 19 41 and 53 92 times the thickness of the coal seam respectively it was found that the ratio between the maximum height of the zone of interconnected fractures and the thickness of the extracted coal seam increases with the increasing number of rock layer interfaces and decreases with the increasing stiffness of immediate roof it is shown that the growth of the zone of interconnected fractures occurred during 17 39 days at an average rate of 0 94 1 97 m day 1 and it was accompanied by increasing methane emission from overburden observation shows that the formation of separate horizontal fractures began only 11 49 5 days after the height of the zone of interconnected fractures reached its maximum value formation of separate horizontal fractures in overburden over the longwall excavation occurred as a stepped process from lower to upper sandstone sandy shale layer interfaces in the direction of the ground surface

hydrocarbon inclusions in late calcite cements migration indicators in the great oolite group weald basin s england abstract the fluorescence responses of hydrocarbon inclusions in calcite and dolomite cements are used to indicate the timing and longevity of oil migration in great oolite reservoirs of the weald basin of southern england oil migration and late stage calcite cementation were penecontemporaneous processes the gravity of the included hydrocarbons increases towards the basin depocentre through the range of 20 to 40 api reflecting the maturity of the source rocks reservoirs with a spread in the gravity of oil within inclusions were charged throughout source rock maturation those reservoirs with oil inclusions of a single gravity were charged in a discrete event

adcp measurements of gravity currents in the chicago river illinois a unique set of observations of stratified flow phenomena in the chicago river was made using an upward looking acoustic doppler current profiler adcp during the period november 20 2003 to february 1 2004 water density differences between the chicago river and its north branch nb seem to be responsible for the development of gravity currents with the objective of characterizing the occurrence frequency and evolution of such currents the adcp was configured to continuously collect high resolution water velocity and echo intensity profiles in the chicago river at columbus drive during the observation period 28 gravity current events were identified lasting a total of 77 of the time sixteen of these events were generated by underflows from the nb and 12 of these events were generated by overflows from the nb on average the duration of the underflow and overflow events was 52 3 and 42 1 h respectively a detailed analysis of one underflow event which started on january 7 2004 and lasted

evolution mechanism of water flowing zones and control technology for longwall mining in shallow coal seams beneath gully topography the height and evolution mechanism of fractured water flowing zones are of great importance for prevention of water inrush disasters and protection of immediate environments particularly in ecological vulnerable areas in this paper comparative approaches including empirical formula calculation physical simulation numerical simulation and protem transient electromagnetic analysis are employed to identify the development of the fracture zones caused by water flowing so as to ensure mining safety and protection of groundwater in shallow coal seams beneath gully topography an empirical formula was used to calculate the height of the water flowing fracture zone and an experimental study utilizing a model based on a similar material was adopted to analyze the movement and fracture development of the overlying strata results provide a reasonable basis from which a rational mining height may be determined the protem transient electromagnetic apparatus was employed to detect the water flowing structure conductivity of the overlying strata induced by mining beneath gully topography in the field the water flowing fracture of the overlying strata can be estimated according to comprehensive analysis of the apparent resistivity changes of the field gully surface crack development and aquifer water level accordingly the control technologies in the field were implemented and discussed regarding preventing gully water from rushing into underground mining spaces through water flowing fracture zones results indicate that safe and efficient mining of shallow seams beneath gully topography can be achieved by prevention of gully accidents and protecting the surface water resources of the ecological environment

history of hydrocarbon charge on the atlantic margin evidence from fluid inclusion studies west of shetland fluid inclusions in jurassic reservoir sandstones help us to understand the history of hydrocarbon charge in the west of shetland region the sandstones contain both hydrocarbon and aqueous fluid inclusions hydrocarbons are present in trails of secondary inclusions through detrital grains and as primary inclusions in quartz overgrowths this is direct evidence for at least two episodes of hydrocarbon charge before the present oil entered the rock consistent with indirect evidence from burial history modeling and organic geochemistry fluorescence colors indicate that the two oils are of distinct composition the first oil was degraded reflecting an episode of uplift and exposure to near surface fluids before reburial and migration of a second live oil oils comparable to these two paleocharges were mixed to produce the oils that are encountered in the current reservoir pores showing that they were preserved despite repeated tectonic events at the atlantic margin

estimating suspended solids concentrations from backscatter intensity measured by acoustic doppler current profiler in san francisco bay california abstract the estimation of mass concentration of suspended solids is one of the properties needed to understand the characteristics of sediment transport in bays and estuaries however useful measurements or estimates of this property are often problematic when employing the usual methods of determination from collected water samples or optical sensors analysis of water samples tends to undersample the highly variable character of suspended solids and optical sensors often become useless from biological fouling in highly productive regions acoustic sensors such as acoustic doppler current profilers that are now routinely used to measure water velocity have been shown to hold promise as a means of quantitatively estimating suspended solids from acoustic backscatter intensity a parameter used in velocity measurement to further evaluate application of this technique using commercially available instruments profiles of suspended solids concentrations are estimated from acoustic backscatter intensity recorded by 1200 and 2400 khz broadband acoustic doppler current profilers located at two sites in san francisco bay california adcp backscatter intensity is calibrated using optical backscatterance data from an instrument located at a depth close to the adcp transducers in addition to losses from spherical spreading and water absorption calculations of acoustic transmission losses account for attenuation from suspended sediment and correction for nonspherical spreading in the near field of the acoustic transducer acoustic estimates of suspended solids consisting of cohesive and noncohesive sediments are found to agree within about 8 10 of the total range of concentration to those values estimated by a second optical backscatterance sensor located at a depth further from the adcp transducers the success of this approach using commercially available doppler profilers provides promise that this technique might be appropriate and useful under certain conditions in spite of some theoretical limitations of the method

constraining the oil charge history of the south pepper oilfield from the analysis of oil bearing fluid inclusions abstract the south pepper oilfield located in the barrow sub basin on the nw margin of the australian continent has experienced a multi phase charge history abundant oil bearing fluid inclusions are present in samples from within the current gas cap suggesting that an oil column existed prior to gas this palaeo oil gas leg fi oil has ts tm and c29 c30 hopane ratios of 1 and the c35 homohopanes are a significant proportion of the extended homohopanes it has lower pr ph and diasterane sterane ratios than the currently reservoired live oil and contains gammacerane a series of peaks tentatively identified as c30 to c34 17 h 30 norhopanes and a large amount of 2 methylhopanes collectively geochemical analysis of the gas leg fi oil suggests that it was generated from a less mature more calcareous source rock deposited under more reducing conditions than the upper jurassic dingo claystone the main source of the live oil in addition the presence of c30 dinosteranes in the gas leg fi oil provides a triassic or younger age constraint this makes palaeozoic carbonates an unlikely source possible source intervals for the gas leg fi oil are thin lower jurassic limestones and marls which occur at the base of the lower dingo claystone or a thin limestone unit the cunaloo member at the base of the triassic locker shale samples from within the present oil leg also contain abundant oil inclusions consistent with high oil saturations at the present day however these oil inclusions exhibit different fluorescence colours suggesting they represent a second oil charge geochemically the oil leg fi oil has an intermediate composition between the live oil and the gas leg fi oil suggesting that gas charge displaced the first oil charge samples of which were preserved as fluid inclusions in the oil leg sample biodegradation of the first oil charge indicated by the presence of 17 h 25 norhopanes in the currently reservoired live oils can be attributed to the ingress of meteoric waters probably during sub aerial exposure of the basin margin during miocene wrenching changing environmental conditions curtailed bacterial activity and allowed unaltered oil sourced from the dingo claystone to accumulate below the gas cap and mix with the biodegraded residues of the first oil charge to achieve the live oil composition the biodegradation event must have preceded the second charge as the live oil contains compounds such as n alkanes which would have been removed had alteration occurred after the second charge complex charge histories are common and the analysis of palaeo oils trapped within fluid inclusions provides the opportunity to achieve a more comprehensive assessment of hydrocarbon charge

the application of fluid inclusions to migration of oil and diagenesis in petroleum reservoirs abstract fluid inclusions can be used to interpret thermal history and petroleum maturation and migration relative to burial history temperature pressure and composition data collected from fluid inclusions are used to determine the environment of diagenesis and the timing of cementation and migration cements in petroleum reservoirs contain both oil and aqueous fluid inclusions fluorescence spectroscopy is used to identify oil inclusions and to determine the maturity of entrapped oil the lifetime of fluorescence induced by a pulsed laser is related to the api gravity of entrapped oil interpretation of fluid inclusion data depends on knowing the origin of fluid inclusions and the probability that they survive in the burial environment those aspects of fluid inclusion study are investigated by synthesizing oil and aqueous inclusions in calcite crystals in laboratory experiments examples of how fluid inclusions are used to determine the physico chemical environments of diagenesis in petroleum reservoirs and the timing of cementation and migration are given for the wealden basin england the mishrif formation dubai the smackover formation gulf coast u s a and jurassic sandstones offshore norway in the wealden basin temperature data from fluid inclusions are used to determine that oil migration occurred in the cretaceous and that the reservoir rocks have been uplifted to varying degrees at a time after migration distribution of oil inclusions indicates that generation and migration of oil was principally in the western part of the basin the geochemistry of oil inclusions in calcite cements from the mishrif formation dubai are used to determine the type and maturity of entrapped oil temperature data from oil and water inclusions are used to relate reservoir diagenesis to burial history and the migration of oil in deep smackover reservoirs oil contains h 2 s the origin of the h 2 s is examined by study of fluid inclusions containing h 2 s in jurassic sandstones offshore norway fluid inclusion studies show that silica cementation is related to burial depth whereas a later calcite cementation originated from invasion of a hot fluid

petroleum charge history in the baiyun depression and panyu lower uplift in the pearl river mouth basin northern south china sea constraints from integration of organic geochemical and fluid inclusion data the source thermal maturity and charge history of oil and gas condensate in the baiyun depression and the panyu lower uplift were determined using organic geochemical and fluid inclusion data nearly all the gas condensates and oil in the study area originated from eocene enping formation source rocks whereas the condensate fluids in the eastern area originated from the enping and zhuhai formations the condensate fluids have a relatively low thermal maturity with a calculated vitrinite reflectance equivalent that typically ranges from 0 8 to 1 0 based on the c29 sterane isomerization ratios and aromatic hydrocarbon maturity parameters four types of oil inclusions with various fluorescence colors yellow blue and api gravities 25 44 were recognized in the oligocene and lower miocene reservoir units which suggest multiple oil charging events the homogenization temperatures of the fluid inclusions recorded the oil charge events accompanying large scale hot fluid movement which was most likely caused by the charging of high temperature natural gas from the deeper wenchang formation the trapping pressures of the oil inclusions and the reconstructed burial histories were used to determine the timing of oil charge the main oil charge occurred from 16 7 ma throughout the baiyun depression and panyu lower uplift whereas the panyu lower uplift experienced an additional oil charge from 5 0 ma the natural gas charge occurred during the main oil charging period and may continue to the present day multiple physical processes such as gas injection without gas exsolution gas washing with gas exsolution and migration fractionation have played important roles in gas condensate formation and controlling the petroleum distribution in the baiyun depression and panyu lower uplift