Study on the Monitoring Malfunction of Water Pollution during Drought or Flood Period and Low-carbon and High-value Methodology--A Case Study of the Correlation Test of Water,Soil and Gas Pollution in Xiangxiang County

Based on the low-carbon and high-value methodology of chemical ecology and chemical informatics,combining theory and methods,taking saving,environmental protection,low carbon,high production,high value and circulation as values and aims,the relationship between human and land as a basis,ecosystem as a center,overall control as a goal and agricultural ecological engineering as a mean,environmental pollution detection,as one of bottlenecks for agricultural products and food security,should be solved firstly;through the field survey in dry years from 2009 to 2010 when drought and flood were frequent and the frequency of drought was higher than that of flood,plus the determination of surface water flow and water quantity in a small typical river basin,the correlation of local water,soil and gas in the county could be found,and the transfer of monitoring focus from water environment to atmospheric environment was possible and necessary.The study would promote the quantitative research on the correlation among water,soil and gas,and the results were in accordance with the conclusions of related studies.

Sources of high-temperature water and gas inrush during tunnel excavation:A case of Bangfu tunnel in Southwest China

Cases of simultaneous inrush of high-temperature water and harmful gases are infrequently reported in areas without geothermal anomalies,hydrocarbon source rock,or coal measures.For this,we investigated the origin,development,and formation of the high-temperature water and harmful gases that rushed into Bangfu tunnel,Southwest China.During excavation of the Bangfu tunnel through the F1-2 fault in sandstone,a significant incident occurred involving a sudden influx of high-temperature water(45.4℃)of NaeHCO_(3)type and harmful gases(CO_(2),H2S).An extensive geological examination uncovered a fault network extending from the crust to the mantle in the tunnel site area.The site features a substantial presence of both surface water and groundwater.Furthermore,within the middle crust at depths ranging from 19 km to 23 km,there are high-temperature ductile melts enriched with fluids and gases.Monitoring and experiments conducted on the harmful gases reveal that the primary source is identified in the crust,with the mantle source being secondary,followed by the atmospheric source being a minimal contribution.The hydrochemical and isotopic composition characteristics of the hightemperature rushed water indicate its evolution was formed through the infiltration of atmospheric precipitation from cold groundwater of the CaeHCO_(3)type.The mechanism underlying the formation of the inrush high-temperature water and harmful gases can be outlined as follows.The fault network,spanning from the crust to the mantle,serves as a migration pathway for the inflow substances.Mantlederived volatiles and high-temperature melts make heat energy facilitate the inrush activity,while groundwater contributes to heat transfer and acts as a medium for gas transport.As mantle-derived volatiles migrate towards the surface through the fault network,they mix with high-temperature melts and crust-derived gases,forming a crust-mantle mixed gas.Through processes such as deep hydrothermal circulation,shallow hydrothermal circulation,water/rock reaction,near-surface mixing,and dilution,CaeHCO_(3)type cold groundwater transforms into high-temperature water of NaeHCO_(3)type.The methodologies and findings of our research offer insights into the route selection,investigation,and construction of mountain tunneling projects under similar geological conditions.

Hydrate Prevention Strategies and the Associated Cost in the Gulf of Mexico

With the petroleum industry endeavoring to develop promising oil and gas in deeper water, gas hydrates prevention is a serious concern for oil and gas producing companies producing at conditions in the hydrate region. This paper details lessons learned from the successful field deployment of AA LDHI and proper implementation strategies used for 3 different practical fields as case studies in the Gulf of Mexico. From the 3 field experiences, the AA LDHI has been used to replace the conventional thermodynamic hydrate inhibitor due to its numerous benefits during steady state operations and transition operations where AA LDHI is injected prior to extended shut in and restart for fields producing at low water cut. However, the strategy to develop a cost effective chemical management of hydrates for fields producing at high water cut is by pumping methanol or diesel to push down the wellbore fluid below the mud line during planned and unplanned shut-ins to delay water production, it also secures the riser with non hydrate fluids. This illustrates how the AA LDHIs are used in conjunction with more conventional hydrate management approaches to reach an optimal cost effective field hydrate management solution. However, this shows that the key to overall success of hydrate prevention is a full integration of a good front end design, a comprehensive deployment and an effective down hole monitoring system.

Geochemical characteristics of produced fluids from CBM wells and their indicative significance for gas accumulation in Daning-Jixian block,Ordos Basin

The Daning-Jixian block,the eastern edge of the Ordos Basin,is one of the most potential areas for CO_(2)geological storage,enhanced coalbed methane recovery(ECBM)exploration and production in China in recent decades.The ionic composition and total dissolved solids(TDS)of the produced water,coal organic matter maturity,molecular composition and carbon isotope characteristics of the produced gas were utilized to analyze the hydrogeological condition,CBM generation and migration characteristics in this area.The CBM enrichment patterns and the geological impacts on gas well production characteristics were revealed.The optimal area for CBM development and CO_(2)geological storage in the study area were also proposed.Dominated by the Xueguan reverse fault zone,the hydraulic unit in this area can be divided into two parts(i.e.,the recharge-runoff zone in the east and the weak runoff-stagnation zone in the west).The thermogenic gas is dominating CBM genesis in this area.Secondary biogenic gas replenishment is only distributed in the eastern margin area,where theδ13C1 value is less than the thermal simulation results as an influence of hydrodynamic fractionation.Finally,two models of CBM formation and accumulation were proposed,1)thermogenic CBM migrated by hydrodynamic and resorbed for preservation at impermeable fault boundaries;2)thermogenic CBM trapped by fault and accumulated by hydrodynamic in slope zone.The gas production performance,generally increased from east to west,is mainly dominated by hydrogeological conditions.Generally,the west side of the fault zone is the enrichment and high-yield area for ECBM development and CO_(2)geological storage in the study area.

Simulation studies on optimizing oil productivity in oil rim reservoirs under gas cap blow down production strategy

Gas cap blow down strategy is normally deployed for Ultra-thin oil rim reservoirs with huge gas caps due to extremely high gas oil ratios from wells in such reservoirs.The current state leads to loss of production from the oil reserves due to high initial reservoir pressure thus,reducing its net present value.Data on important factors essential to the productivity of oil rim reservoirs are used to build a heterogeneous ultra-thin reservoir with a time step of 10,000 days using the Eclipse software and its embedded correlations.The reservoir is subjected to a gas cap blowdown via a gas well,then an oil well is initiated into the model at onset and after time periods of 2000 days,4000 days,6000 days and 8000 days to estimate the oil recovery.It is expected that due to the large nature of the gas cap,pressure decline will be drastic and leading to a low oil recovery,hence the injection of water and gas at different rates at the periods indicated.The results indicate an oil recovery of 4.3%during gas cap blow down and 10.34%at 6000 days.Peak oil recoveries of 12.64%and 10.80%are estimated under 30,000 Mscf/day at 4000 days and 1000 stb/day at 6000 days respectively.This shows an incremental oil recovery of 8.34%and 6.5%over that recorded during gas cap blow down.The results also indicate that the gas production at those periods was not greatly affected with an estimated increment of 257 Bscf recorded during 30,000 Mscf/day at 4000 days.All secondary injection schemes at the respective time steps had positive impact on the overall oil recoveries.It is recommended that extra production and injection wells be drilled,enhanced oil recovery options and injection patterns be considered to further increase oil recovery.