Utility of fluid inclusion paleo-temperature in petroleum system modelling:A case study from western offshore,India

The paleo-temperature(Th)data from fluid inclusions are utilized for thermal history modelling using PetroMod software.Generally,bottom hole temperature(BHT)and vitrinite reflectance(Ro)measurements are widely used in petroleum system modelling(PSM)in the oil industry for calibration purposes.Th representing the minimum temperature of fluid entrapment estimated from fluid-inclusion study provides extra support to build the thermal models for PSM.Fluid inclusion parameters along with Rock-Eval pyrolysis analysis have been used to predict the maturity of oil in terms of API gravity as well as the maturity of source rocks respectively.Two exploratory wells RV-1(Mumbai Offshore Basin)and KK4C-A-1(Kerala-Konkan Offshore Basin),India were examined and the T_(h)from most of the fluid inclusions of wells RV-1 and KK4C-A-1 fell in the oil window range of 60-140℃suggesting thermal conditions favourable for oil generation in both of the wells.T_(h)of coeval aqueous inclusions along with the Hydrocarbon Fluid inclusions(HCFIs)was used to calibrate PSM.Vital parameters show that source rocks of well RV-1 are mature and that of well KK4C-A-1 are immature.Two sets of PSM are created in terms of generation and expulsion for the dry wells RV-1 and KK4C-A-1 and calibrated each well using fluid inclusion Th and BHT.From the fluid inclusion analysis method,it is evident that hydrocarbon generation happened in both wells and the paleo-temperature indicates that the formations of both wells were subjected to temperatures in the oil window range,even though it was designated as dry wells in the present scenario.The present study highlights the application of fluid inclusion paleo-temperature(Th)during calibration instead of commonly used methods.We could obtain desirable and accurate data output from PSM using T_(h) calibration.

Paleo-temperature Evolution and Water Soluble Gas in Sinian Reservoir, Anpingdian-Gaoshiti Structural Zone, Central Sichuan Basin

The paleo-temperature evolution of Sinian reservoir of Anping （安平） 1 well was rebuilt by taking the method of apatite fission track and Easy%Ro model. The result of apatite fission track determines the accurate burial history and overcomes the flaw that the vitrinite reflectance is taken as paleo-temperature indicator simply. The authors used the laser Raman technique to analyze the methane present in the calcite and quartz fluid inclusions of Sinian reservoir, finding that the methane is water soluble gas. The authors also simulated the paleo-pressure of fluid inclusion by using PVTsim software and finally worked out the methane solubility in water.

Clumped isotope analysis of lacustrine endogenic carbonates and implications for paleo-temperature reconstruction:A case study from Dali Lake

Carbonate clumped isotope(Δ47)is a new and reliable geothermometer.Endogenic carbonates in lake sediments are good archives to reconstruct lake water temperature using clumped isotope thermometry.However,applications of carbonate clumped isotope thermometry to lacustrine carbonates are still scarce because the existed organic and/or sulfur contaminants in such samples interfere with clumped isotope analysis and cause notable temperature biases.Therefore,exploring an effective way to remove contamination is a prerequisite to widely applying carbonate clumped isotope thermometry to lake sediments.By pretreating fine-grained endogenic carbonates from Dali lake sediments with hydrogen peroxide of different concentrations for different lengths of time,we conducted a series of conditional experiments to seek the optimal pretreatment condition for clumped isotope analysis.Δ47,Δ48 offset and 49 parameter were obtained from clumped isotope measurements to assess the effect of contamination removal.Results showed that untreated samples("0%-0")had a very high 49 parameter.After the treatment with hydrogen peroxide,the 49 parameter was significantly reduced while theΔ48 offset evidently increased.TheΔ47,Δ48 offset and 49 parameter of samples pretreated under different conditions showed significant variability,even though the measuredΔ47 temperatures changed within a relatively narrow range(i.e.,from 17.0±1.3 to 22.8±1.6°C).Among various treated samples,the sample"3%-8"yielded a smallerΔ48 offset and 49 parameter,and lowerΔ47 temperature of 17.0±1.3°C.Therefore,"reacting with 3%hydrogen peroxide for 8 h"was suggested to be the optimal condition for removing contaminants from lacustrine endogenic carbonates prior to clumped isotope analysis.At the time when the pretreatment condition was too intense(i.e.,H2O2 concentration>3%and/or reaction time>8 h),secondary contaminants might have been generated in the closed reaction system,whose ultimately transformed state may interfere with masses 47,48.Using the optimal pretreatment procedure,we obtained reasonableΔ47 temperature changes during the last deglaciation and found a temperature decrease of about 6°C in Northern China during the Younger Dryas period.Our study demonstrates a great potential of applying carbonate clumped isotope thermometry to lacustrine carbonates for paleo-temperature and paleo-elevation reconstructions in the future.

Phanerozoic oceanic and climatic perturbations in the context of Tethyan evolution

Climatic and environmental conditions play a pivotal role in the evolution of the biosphere,serving as the primary natural factors influencing biological evolution and the development of human civilization.The study of the evolution of Earth's habitability primarily revolves around the reconstruction of climatic and oceanic conditions in geohistorical periods,shedding light on their dynamic changes.This paper collates classic geological indicators and geochemical proxies associated with paleoclimatic and oceanic environmental conditions.The latest“big data”analyses and simulations made possible by the availability of previously unimagined massive datasets reveal several key findings:During the early Paleozoic,atmospheric oxygen levels were low,and widespread oceanic anoxia was prevalent;the Devonian era witnessed a greenhouse climate,followed by the Carboniferous ice age characterized by higher oceanic oxidation levels and alkalinity.The latest Paleozoic deglaciation occurred under high pCO_(2) conditions,extending into much of the Mesozoic and early Cenozoic,marked by multiple hyperthermal and anoxia expansion events,until the resurgence of global glaciation in the middle-late stages of the Cenozoic,ultimately bringing environmental and climatic conditions closer to modern levels.By correlating the aforementioned long-term trends with major geological events,we can delineate the co-evolution of paleoclimate and oceanic environments in tandem with the development of Tethys tectonics as follows.(1)During the Proto-Tethys stage,global paleo-elevations were relatively low,and atmospheric oxygen levels were also relatively modest.Despite the occurrence of significant tectonic movements that led to noticeable transgressive-regressive cycles,their effects on climate and oceanic environments were somewhat limited due to the relatively weak interactions.(2)The emergence of the Paleo-Tethys was a significant event that coincided with the formation of the supercontinent Pangaea.Intensive orogenic movements during this period increased the global land area and elevation.This,in turn,led to enhanced terrestrial weathering,which elevated sea surface productivity and resulted in massive nutrient input into the oceans.Consequently,this process contributed to the rise of oxygen levels in the atmosphere and a decrease in atmospheric pCO_(2).These changes are considered potential driving mechanisms for late Paleozoic glaciation and oceanic oxygenation.(3)The transition from the Paleo-Tethys to the Neo-Tethys was closely linked to the breakup of Pangaea.During this period,the terrestrial weathering processes were relatively weak due to decreased continental elevations.This resulted in a long-term greenhouse climate and intermittent global oceanic events,which were responses to the high atmospheric pCO_(2) levels during the Mesozoic and early Cenozoic eras.(4)The Neo-Tethys stage ended with the dramatic uplift of the Alps-Himalaya Mountain ranges due to the collision of India and Asia.This uplift had a profound global impact,significantly increasing continental elevations.As a result,weathering and carbon burial processes intensified,leading to a reduction in atmospheric pCO_(2).Concurrently,this uplift played a crucial role in the establishment of the East Asian monsoon and North Atlantic deep-water circulations,both of which played a part in triggering the late Cenozoic ice age.These models suggest that the teleconnections between land and sea(orogeny-terrestrial weathering-marine carbon burial)span over the whole Phanerozoic and might have played a key role in balancing the Earth surface system.Combined,the tectonic,volcanic,paleo-climatic,as well as paleoenvironmental events recorded in the Tethys oceans and adjunct continents represent valuable natural experiments and lessons for understanding the present and the future of Earth's habitability.

Numerical simulation of surface circulation of South China Sea during the last glaciation and its verification

In the glacial cycles, a marginal sea may display its 'amplifying effect' in environmental changes. An example is the South China Sea (SCS), where the glacial/interglacial contrast of winter sea surface temperature (SST) reaches 6—9℃, far exceeding that at similar latitudes in the Pacific. We speculated that such an 'amplifying effect' of SCS must be related to a radical, reorganization of the surface circulation during glacial period, but this is to be tested and verified. Numerical simulation is one way to test it.