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Journal of Petroleum Science & Engineering
Elsevier Science B.V.
Journal of Petroleum Science & Engineering

Elsevier Science B.V.

0920-4105

Journal of Petroleum Science & Engineering/Journal Journal of Petroleum Science & Engineering
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    Permeability reduction by gellan gum solutions

    Iskander GussenovSarkyt E.Kudaibergenov
    11页
    查看更多>>摘要：This paper summarizes the results of laboratory experiments with gellan gum.Gellan gum solutions demonstrated plugging in distilled water and brine saturated sand packs.Progressive plugging in distilled water saturated sand packs is explained by the presence of gel particles in the gellan gum solutions,whereas plugging in brine saturated sand packs is explained by the instantaneous gelation of gellan gum upon contact with brine.Gellan gum gel strength and its injectivity depend on brine salinity in the rage of 0-60 g-L-1.Gellan gum plugging behavior in porous media depends on polymer concentration,permeability,and temperature.However,in these tests internal pressure taps were not used,making conclusions impossible as to whether gellan gum solutions provide in-depth plugging in matrix rocks.Fracture models with an impermeable matrix and fractured sandstone cores were used in this study to compare gellan gum and hydrolyzed polyacrylamide gels.Alternating injection of gellan gum and brine demonstrated an effective way to plug 1-mm-height fractures.The plugging efficiency of polyacrylamide gel depends on the initial viscosity of the solution,if it is injected prior to gelation,and post flush salinity.Whereas in the case of gellan gum,these factors are not critical because the solution gels instantaneously upon contact with brine,with higher brine salinity improving gel strength.Although,maximal gel and post flush injection pressures were several times higher in the case of gellan gum,stabilized post flush injection pressure was higher in the case of hydrolyzed polyacrylamide gel placed as a mature gel in a sandstone fractured core.
      原文链接:
    • NSTL

    Nanoparticle-stabilized CO2 foam to improve conventional CO2 EOR process and recovery at Bati Raman oil field,Turkey

    S.Esra SafranMustafa Versan Kok
    8页
    查看更多>>摘要：(B.Raman),which is the largest oil field of Turkey's already existing CO2 injection system,does not produce at the desired efficiency due to the natural fracture characteristics.Therefore,this research is performed to control the CO2 mobility in the reservoir by creating nanoparticle stabilized CO2 foam using the property of nano-particles to be adsorbed at the gas-water interface permanently and to achieve additional oil recovery at the B.Raman oil field.In the initial stage of the research,dispersion stabilization and foamability of different nano-silicas are considered.The effects of nanoparticle concentration,salinity,temperature,and pH on foamability and dispersion stabilization were examined.Research results suggested that half hydrophobicity,salt addition,and increased concentration positively affect foamability,whereas the salinity value above 1% generated floc-culation.Also,although the foam with half hydrophobic nano-silica named H30 has better foamability,this foam could not be stabilized.The effects of pressure,phase ratio,and flow rate on foam formation were also studied.The better foam was observed at the observation cell when the CO2 to Nano dispersion phase ratio was 1.It was also found mat the pressure should be above 1100 psi where the CO2 was in the supercritical phase to create the foam with the current core flooding system.Then,the oil recovery test was conducted with suitable nano-particles,particularly the PEG and CC301.Before using nano-silica particles,CO2 injection and then WAG was applied to the core sample to express the B.Raman field case.The results indicate that foam application is successful if appropriate conditions exist.
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    • NSTL

    Semi-analytical modeling of rate transient for a multi-wing fractured vertical well with partially propped fractures considering different stress-sensitive systems

    Yongzheng CuiRuizhong JiangYihua Gao
    13页
    查看更多>>摘要：Multi-fracture wings can be generated around vertical well after hydraulic fracturing,and damage usually occurs in far from wellbore fracture due to poor proppant transport.The existing rate transient models ignore the different stress-sensitive behaviors in propped and un-propped fractures.For tight reservoir characterization and production prediction,in this paper,a semi-analytical Blasingame decline analysis model of a multi-wing fractured vertical well(MFVW)is formulated with partially propped fractures under different stress-sensitive effects.Compared to propped section,lower initial conductivity and larger stress sensitivity are considered in un-propped section.Employing Laplace transformation,numerical inversion,node analysis,and an iteration method,the production rate is obtained and then verified.Afterward systematic sensitivity analyses are carried out.The influences of parameters such as un-propped section length and different stress-sensitive behavior on production rate are studied in detail.A big difference is observed between type curves of the uniform and nonuniform stress-sensitive models.The properties of propped fracture section mainly put an impact on the early time production rate.The stress-sensitive un-propped fracture section makes production rate reduction at the middle time,and such an influence is enhanced with a longer un-propped section.Sharper decline rate and smaller minimum conductivity both would enhance the production reduction caused by stress-sensitivity.For the first time,the flow flux and pressure along the partially propped fracture of MFVW are analyzed.It has been found that the max flux rate would not appear in the first near wellbore segment with smaller 0 in MWFV.And flow flux in un-propped section is lower by order of magnitude than that of the propped section at early time,the majority of the total production at early time is contributed by the near wellbore propped fracture section.The model can help for better understand of the flow mechanism and achieve more realistically fracture flow simulation.It has practical significance for better development of tight resources.
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    • NSTL

    Spearman rank correlations analysis of the elemental,mineral concentrations,and mechanical parameters of the Lower Cambrian Niutitang shale:A case study in the Fenggang block,Northeast Guizhou Province,South China

    Gang ZhaoWenlong DingJing Tian
    14页
    查看更多>>摘要：The increasing complexity of reservoirs,particularly shale reservoirs,demands accurate information on the formation composition,mineralogy,and mechanical parameters for effective exploitation.The development of geochemical and geophysical logging technology allows the investigation of the correlations between the elemental,mineral contents,and the mechanical parameters of shale.Taking the Lower Cambrian Niutitang Formadon shale in the Fenggang block in nordieastern Guizhou as an example,889 data sets of the main elemental(Si,Ca,Fe,S,Ti,Gd,K,Mg,and S)concentrations and minerals(carbonate,pyrite,clay,quartz,feldspar,and mica)from Elemental Capture Spectroscopy logging and rock mechanics parameters(dynamic Young's modulus,dynamic Poisson's ratio,shear modulus,bulk modulus,and brittleness index)determined via Sonic Scanner logging data in the target zone of the study area are collected.We investigated the relationships between the mechanical parameters and the elemental,and mineral concentrations by Spearman rank correlation analysis.The influence of different Si concentrations on the mechanical parameters of the rock(positive/negative,and significance)is discussed based on the mineral contents determined via X-ray diffraction of 24 experimental samples.When 22.1%<DWSi(dry weight fraction of the silicon content as a percent)<28.40% and 28.40%<DWSi<34.20%,the static Young's modulus,shear modulus,bulk modulus,and brittleness index exhibit a highly positive/negative correlation that is significant with the increase/decrease in DWSi,WCLA(dry weight fraction of clay),and WQFM(dry weight fraction of quartz,feldspar,and mica)contents,respectively.DWSi = 28.4% is suggested as the turning point for the correlation change(positive/negative,significance).Thus,there exists uncertainty in the determination of the mechanical parameters of rock within certain elemental content ranges.More mathematical models and factors need to be considered to adequately characterize the mechanical parameters of rock.
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    • NSTL

    Analysis of dolomite reservoir characteristics of Lower Permian Maokou Formation and dolomite origins in Chuanzhong Area

    Zubing LiChangbing HuangFei Yang
    8页
    查看更多>>摘要：Dolomite of Lower Permian Maokou Formation has a strong heterogeneous formation in-plane and vertical in Chuanzhong Area.Its formation mechanism is not yet fully understood.Thus,this study focuses on the Maokou Formadon core and conducts thin section analysis,isotope analysis,cathodoluminescence,and data analysis of fluid inclusion using a combination of geological and chemical analysis methods to summarize the characteristics of dolomite reservoir layer of Maokou Formation and its formation mechanism.The Maokou Formation is believed to be the result of a deformity of dolostones,medium-fine grained dolomite,and a few gray dolomites,with the exception of gypsum layer.In the reservoir space of dolostones,pore type occupies the first layer,and dissolved seam and particle-dissolved pores are in the second layer.The dolomite value of δ~(13)C was distributed in the range of 1.78‰-3.95‰(PDB),and the value of δ~(18)O was distributed in the range of-7.39%o to-3.8%o(PDB)with above 120 salinity.Thus,the dolomite reservoir was formed in a normal marine environment.Inclusions show that dolomite in the study area have a multi-phase fluid filling and a homogenized temperature of the maximum value of above 160 ℃,which is not within the value that the normal temperature gradient can reach.Thus,buried dolomitization,seepage flow,Penesyndiagenesis,and Sabha genetic model are ruled out from the study area of Maokou Formation.The fault development that connected the basal layer with the stratum of Maokou Formadon was distributed in the G3 well area,which provides a channel for the upper channeling of the basal hydrothermal fluid.In the Chuanzhong Area,the dolomite of the Lower Permian Maokou Formation is considered to be mainly of tectonic-hydrothermal origin.
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    • NSTL

    Hierarchical reservoir lithofacies and acoustic impedance simulation:Application to an oil field in SW of Iran

    Mehdi SadeghiNasser MadaniReza Falahat
    16页
    查看更多>>摘要：In this study,a hierarchical simulation algorithm was implemented to produce 3D models of lithofacies and acoustic impedance(AI)in an oil field in southwestern Iran.Hierarchical simulation is a powerful method that takes into account the spatial distribution and hard contact relationships of continuous variables within the categorical variables in reservoir characterization.To implement the hierarchical simulation algorithm in this study,pluri-Gaussian simulation was used to construct the layouts of one categorical variable(lithofacies domains)and turning bands simulation was used to produce one continuous variable(AI models)within each simulated domain.The dataset that is available to test the proposed method includes the lithofacies and AI logs of seven wells.For validation of the proposed model,one of wells was excluded from the initial dataset to check the accuracy of results.The algorithm was implemented on a gridded model to produce 50 realizations of 3D lithofacies and AI models.The statistical analyses of the produced models verified the capabilities of hierarchical simulation in reproducing the lithofacies domains and AI values related to each domain.The simulated AI models were compared with the seismic inversion model to corroborate the reliability of the results.In addition,to show the superiority of the hierarchical approach,the results were compared to the results of direct AI modeling in which the AI models were generated without considering any lithofacies data.The comparisons in the blind well indicated a high correlation between the modeled values and the true AI.The correlation coefficient between average AI models of the hierarchical approach and the true AI was 0.85.Whereas,this value was 0.75 for the average of directly simulated AI models and 0.74 for the seismic inversion,respectively.Histogram analysis also verified the capability of the hierarchical modeling in reproducing the statistical properties of the original data.The resulting AI model obtained using the method proposed in this study also showed a high compatibility with the deterministic seismic inversion cube.
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    • NSTL

    Geochemical characteristics and the constraints on paleoenvironment,provenance,and tectonic setting of Precambrian Xifangshan Formation in the northwestern Tarim Basin,NW China

    Jian LiJingchun TianXiang Zhang
    15页
    查看更多>>摘要：Combining geochemistry and petrology to clarify paleoenvironment,provenance and tectonic setting is the most reliable approach.Few studies have been conducted on the Xifangshan Formation,a set of turbidite deposits from the Precambrian in the northwestern Tarim Basin,NW China.The tectonic setting during this period is not clear.This study reports the petrological characteristics and geochemical data of the Xifangshan sandstones,aiming to constrain the paleoclimate,paleoredox conditions,paleoweathering,provenance,and finally establish the tectonic development pattern of this period.Xifangshan Formation is mainly composed of litharenite and feld-spathic litharenite.Most of the trace elements(Rb,Sr,Pb,U,Y,Sc,V,Cr,Cu,Co,Ni,Zn)are depleted relative to the upper continental crust.And,the rare earth elements show a slight negative Eu anomaly.The sandstones were first-cycle,displaying immaturity of composition and structure.The major element composition and low chemical index of alteration indicate that the sandstones have experienced weak weathering during transportation.Multiple geochemical indicators show that the Xifangshan Formation was deposited in an oxic-suboxic marine environment with moderate salinity and semiarid climate.Based on the geochemical and petrographic characteristics of the rock fragments,the source of the Xifangshan Formation has a felsic provenance,and the parent rock is predominantly acidic magmatic rocks,with a small amount of intermediate magmatic rocks.Influenced by the subduction of the ancient oceanic plate,the blueschist-bearing Aksu Group and the continental margin magmatic arc were formed.This magmatic arc provided the source for the Xifangshan Formation sandstones.
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    • NSTL

    Fast and effective observations of the pore structure of tight sandstones at the same location by utilizing AFM and CF-SEM

    Wentong ZhangZhengfu NingShaohua Gai
    8页
    查看更多>>摘要：Atomic force microscopy(AFM),which allows 3D construction,nondestructive,and has a high resolution has been used to describe the pore structure of unconventional reservoirs.Due to its scalability,convenience,and flexibility,scanning electron microscopy(SEM)is widely conducted to describe the surface morphology of unconventional reservoirs.However,the two technologies are rarely combined to achieve fast and effective observations of the pore structure of unconventional reservoirs at the same location of the same sample(SLSS).In this study,nanoindentation technology is introduced to create a marked district(MD).Afterward,fast and effective observations of the pore structure of tight sandstones at the SLSS can be realized by searching this identifiable district with AFM and cold-field scanning electron microscopy(CF-SEM).The results demonstrate that AFM and CF-SEM rapidly capture observations of the surface morphology of tight sandstones at the SLSS.The method used in this study accomplishes the goal of fast and effective scanning at the SLSS(only a few minutes),while exhibiting the high potential of combining AFM and CF-SEM for comprehensively investigating the pore structure of reservoirs ranging from nanoscale to microscale.The most unique component of the presented method is that it is especially for the in situ observation of variations in the surface properties(morphology,electric,mechanical,surface force,and roughness)and pore size of all heterogeneous materials subjected to various external stimuli because the applied experimental technologies(nanoindentation,AFM,and CF-SEM)are all exhibit nondestructive properties.
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    • NSTL

    Effects of cleaning process using toluene and acetone on water-wet-quartz/CO2 and oil-wet-quartz/CO2 wettability

    Ahmed Al-YaseriGhazanfer Raza AbbasiNurudeen Yekeen
    10页
    查看更多>>摘要：Acetone,toluene,and heptane have been perceived as the conventional cleaning agents for the preservation of original water-wet rock reservoir wettability,and for restoration of oil-wet core to its initial wetting condition,prior to measurement of contact angles of CO2-brine-rock systems.However,these organic solvents could be adsorbed on rock surfaces,which modifies the wettability of the reservoir rock and thus triggers uncertainties of the CO2 containment estimation.Presently,there is scarcity of data in literature on the impact of cleaning agents on the wettability of rock/CO2/brine/systems and its attendant effect on CO2 storage capacities.To provide insights on the impact of cleaning agents on CO2 wettability of sandstone,water-wet and oil-wet quartz substrates were aged in acetone,toluene,and heptane,respectively.Advancing and receding contact angles of CO2-brine-quartz systems were measured at a constant temperature(323 K)and varying pressures(5-20 MPa).Impact of cleaning the minerals surfaces with air plasma,N2 and oven after cleaning with either toluene or acetone on CO2 wettability was also assessed and compared.The results show that chemicals that are used quite often to clean mineral surfaces can alter the rock wettability.Significant alterations in wetting conditions were observed when oil wet-rock was cleaned with toluene and water-wet rock was cleaned with acetone.Our results suggest that to preserve the original wettability,we will need to use toluene to clean the water-wet rock and acetone to clean the oil-wet rock.Heptane is only suitable for wettability modification of the oil-wet cores and not for restoration of oil-wet core to its original reservoir wettability.The results confirm that air plasma is the only way to remove surface contamination and organic carbon from the quartz substrates.Cleaning minerals surfaces or rock samples by toluene,acetone and heptane without air plasma will lead to incorrect contact angle and bias wettability measuments.
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    • NSTL

    Petroleum system analysis of the Paleozoic series in the Fars Platform of Iran

    Majid AlipourBahrain AlizadehShohreh Mirzaie
    10页
    查看更多>>摘要：The Paleozoic petroleum system of the Fars Platform of Iran is analyzed using ID petroleum system models of 17 deep wells drilled in the study area.The main aim was to investigate the hitherto undocumented influence of salt tectonics on the essential elements and processes of this petroleum system.For the first time,a better understanding about the geohistory evolution of this prolific petroleum system is provided over the Fars Platform.Modeling results indicate that hydrocarbon generation from the Silurian source rock was associated with salt withdrawal synclines.Salt tectonics further controlled the entrapment styles and the geometric distribution of carrier/reservoir rocks and their overlying evaporitic seals.Our findings provide new insights for identifying the remaining exploration potential in the Paleozoic petroleum system of the Fars Platform and suggest that the role of salt tectonics should be considered in the future basin and petroleum system modeling studies in this area.
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    • NSTL