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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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    Effect of the internal plastic deformation of salt structures on the lithologic succession of evaporites:A case study on the Palaeogene Kumugeliemuqun formation,Kelasu Thrust Belt,Kuqa depression,Tarim Basin

    Peng QinDakang ZhongChen Su
    17页
    查看更多>>摘要:For a normal saline lake sequence,as long as the oppositional setting is the same,the sediments thickness and saline lake sequence are comparable across an area.However,in the Palaeogene Kumugeliemuqun Formation,in wells from similar depositional settings and the same member,the saline lake succession varies greatly.Member 1 of the Kumugeliemuqun Formation,depending on the combination of halite,gypsum,and dolomite(limestone),is divided into four types of saline lake successions:type A,type B,type C,and type D.In the same depositional setting,the saline lake succession and sediment thickness among adjacent areas differ.In member 2 of the Kumugeliemuqun Formation,depending on the association of mudstone and halite,ten different saline lake successions were identified as sequences 1 to 10.Even within the same depositional setting,the saline lake succession and sediment thickness can differ.To explain this phenomenon,we present evidence that includes the sediment thickness,a single cycle of saline lake succession,and an ancient landform,and a salt structure to analyze the role of tectonic deformation in members 1 and 2 of the Kumugeliemuqun Formation.Moreover,waveform indication inversion was used to describe tectonic deformation patterns.The results reveal that saline succession types C and D were the result of tectonic deformation in member 1,while saline lake succession sequence types A and B were not affected by tectonic deformation in member 1.Additionally,the ten diverse saline lake succession sequences in member 2 are all the result of intense tectonic deformation.The inversion results reveal that the inclined dirust,recumbent,and sheath folding are the principal deformation styles in member 2,while flow and hook folds are the main internal deformation styles in member 1.Finally,based on these observations,we conclude that tectonic compression created the plastic flow of rock salt,which induced folding and faulting deformation.The faults produced repetition in the lithologic succession,and the folds resulted in the inversion of the lithologic succession.Therefore,due to the effects of the faults and folds,even within the same depositional setting,the lithologic succession and sediment tiiicknesses differ from one another.

    Reservoir zonation in the framework of sequence stratigraphy:A case study from Sarvak Formation,Abadan Plain,SW Iran

    Arad KianiMohammad Hossein SaberiBahman ZareNezhad
    19页
    查看更多>>摘要:Located in the northeast of the Arabian Plate,Zagros Basin hosts some of the most significant hydrocarbon reservoirs in Iran,including the Sarvak Formation.It has been dated back to the Middle Cretaceous and exhibits a dominantly carbonate lithology.In this study,petrographic and petrophysical data of the Sarvak Formation were analyzed.The results of the petrographic study showed that the formation was deposited in a homoclinal carbonate-ramp depositional environment and exposed to diagenetic processes in three depositional environments:marine,meteoric,and deeply buried environments.The stratigraphic modified Lorenz plot(SMLP)method was used to distinguish between the reservoir and non-reservoir zones.By integrating the petrographic and petrophysical findings,stratigraphic relationships among the identified zones were assessed.Accordingly,three third-order sedimentary sequences were identified on the Middle Cenomanian-to-Middle Turanian section within the studied formation.Two disconformities were detected in the Upper Sarvak,namely Cenomanian-Turonian disconformity(CTD)and Middle Turonian disconformity(MTD).The highest-quality reservoir zones were related to the CTD.The porosity resulted from the karstification,meteoric diagenesis,and significant dissolution beneath the CTD was found to have greatly increased the reservoir quality.Later on,however,the sediments were overmatured under the impact of the MTD,which is known to take a long time to occur,with their porosity largely decreased,ending up with a much lower reservoir quality.In general,the sedimentary fades were found to be the most important factors controlling the distribution of the reservoir zones across the Sarvak Formation,followed by the diagenetic processes.The findings provided an insight into the factors controlling the reservoir quality in the Sarvak Formation within the study area and the Arabian Plate.

    Petrographic,mineralogical and geochemical constraints on the fluid origin and multistage karstification of the Middle-Lower Ordovician carbonate reservoir,NW Tarim Basin,China

    Lanpu ChenHeng ZhangZhongxian Cai
    17页
    查看更多>>摘要:The Middle-Lower Ordovician carbonate formation is the most important hydrocarbon-bearing unit in the Tarim Basin,China.Previous studies have predominately attributed the fracture-cave carbonate reservoirs to epigene karstification,and few involved polygenic karstification.Until now,mechanism and evolution model of the fracture-cave reservoirs has not been very robust.Based on detailed petrographic,mineralogical,karstological and geochemical analysis at the outcrop,this research provides new insights into the characteristics of the karst reservoir,origin of diagenetic fluids and multistage karstification in the Middle-Lower Ordovician.The results indicate that matrix porosity and permeability of the reservoir rock are low,ranging from 0.03% to 1.35%(mean 0.46%)and from 0.000864 mD to 9.15 mD(mean 0.33 mD),respectively,and that karst cave and fracture systems account for the dominant secondary reservoir porosity in the Middle-Lower Ordovician.Meteoric water and hydrothermal fluids are the two most important diagenetic fluids in the Middle-Lower Ordovician,and two stages of dissolution are responsible for the development of the fracture-cave reservoirs in the region.Extensive dissolution by meteoric water resulted in the formation of large volumes of fracture-cave reservoirs during the Middle Caledonian.Hydrothermal dissolution induced by the hydrothermal event during the Early Permian formed additional fracture-cave reservoirs in the Middle-Lower Ordovician carbonate as well.The meteoric dissolution is primarily controlled by the karst unconformity,and the fracture-cave system resulting from meteoric dissolution has a stratiform distribution below the unconformity.The fracture-cave system formed by hydrothermal fluids is mainly controlled by the deep-seated faults and the previous permeable layers,which determine that its distribution is closely related to faults.Moreover,hydrothermal dissolution may occur at high temperature and at great depths,while mineral precipitation may be the dominate process at relatively low temperature and at shallow depths.In this study,a reservoir development model of multistage karstification was established that could further enhance the knowledge of karstification process and assist in petroleum exploration in deep carbonate strata.

    A molecular insight into the effect of key ions on the detachment of crude oil from calcite surface:Implication for low salinity water flooding in carbonate reservoirs

    Songqi LiYuetian LiuLiang Xue
    13页
    查看更多>>摘要:The detachment of crude oil from calcite surface plays an important role in oil recovery and wettability alteration during low salinity water flooding in carbonate reservoirs.The effects of brine salinities and key ions on the dynamic detachment process have been much of debate in the past decades in theories and experiments due to complex mechanisms behind the crude oil-calcite interactions.Herein,molecular dynamic simulation was used to study the influence of brine salinities and ion concentrations on the detachment mechanism of crude oil from calcite surface by establishing 20 brine-crude oil-calcite molecular models varying salinities and key ion concentrations in brine.Molecular configurations,concentration distribution profiles,interaction energies,H-bond numbers and center of mass(COM)distances were carefully analyzed to characterize the dynamic crude oil detachment performance.The results reveal that reducing the brine salinities and ion concentrations can significantly weaken the interaction intensity between oil and calcite and accelerate the detachment process.Therefore,the oil detachment is induced and the effect of low salinity on oil detachment process is significantly time-dependent.The concentration distribution profiles shows that the strong polar oil molecules,for example acetic acid molecules,can't be detached from calcite surface by tuning the brine salinity and key ions.The present of Mg~(2+)and Na~+ is able to delay the detachment process of oil molecules and as a consequence,result in the impeded oil detachment process according to time-dependent dynamic molecular configurations,interaction energies and COM distances analysis.Furthermore,the present of Ca~(2+)is able to strengtiien the interaction between oil and calcite and in consequence,hinder the detachment of oil molecules from the calcite surface according to the interaction energy,the molecular configuration and COM distances.This study should provide the molecular-scale insights into wettability alteration and enhanced oil recovery by low salinity water flooding in carbonate reservoirs.

    Effects of surfactant on the molecules of different polarity of solubilization:Based on the study of micellar microscopic morphology mechanism

    Chun FengLinghui SunWeidong Liu
    9页
    查看更多>>摘要:Determining the macro-solubilization capacities and micro-mechanism of surfactant micelles with low concentration is significant for the optimization of the medium of displacement and the further enhanced oil recovery.In this study,the solubilization capacities and interaction of polar anisole,nonpolar white oil and kerosene(polar and nonpolar)in SDBS and industrial betaine were compared from microscopic to macroscopic point of view with cryogenic transmission electron microscopy,dynamic light scattering and UV-Vis's spectroscopy.The study finds that the solubilization capacities were positively correlated with the concentration of micelles and the polar of molecules.Considering the importance of morphology of micelles to the solubilization capacities,and the morphology of micelles gradually changed from spherical to vesicle with increasing concentration.And the size of micelles was determined,and size were roughly in common with the concentration below 1 wt% or else the size of betaine was bigger than that of SDBS,which indicated that betaine might be larger and more likely to form vesicles than SDBS at the same concentration.Moreover,anisole is localized in the surface of micelles and size of solubilizing anisole was the biggest,which indicates the solubilization maxima was positively correlated with the volume of swelling micelle.These results imply that the concentration,morphology and solubilization | location of micelles appear to important factors affecting the solubilization performance of surfactant.

    Crossflow effects on low salinity displacement in stratified heterogeneity

    Lekan LadipoMartin J.BluntPeter R.King
    26页
    查看更多>>摘要:Crossflow is a major factor affecting recovery efficiency in heterogeneous permeable media.In typical water-oil displacements,viscous-dominated crossflow improves oil recovery efficiency relative to no-crossflow depending on the shock-front and/or the mobility ratio across the displacement front.Its impact is not yet fully understood for augmented or engineered waterfloods such as controlled/low salinity waterflooding(LSWF).This is critical in such a flood with two distinct displacement shock-fronts-unlike a standard waterflood-that are potentially influenced by mixing of the brines which further complicates the crossflow behaviour.This paper presents a comprehensive treatment of crossflow effects on recovery or displacement efficiency along stratified media of contrasting properties during LSWF considering physical dispersion.We define dimensionless numbers to characterize no-crossflow,viscous-and gravity-dominated crossflow regimes for different mobility-ratios.In two-dimensional numerical simulations,we explore the influence of property contrasts and mobility-ratios across the two distinct shock-fronts on the viscous crossflow behaviour in a LSWF.The sensitivity of viscous crossflow recovery and(low-salinity)engineered-water sweep efficiency to mobility-ratios is evaluated at different performance times relative to no-crossflow displacement.Viscous crossflow(VC)is found to be relevant in water-oil displacements for permeability contrasts less than or equal to 1000,but less important for EOR low-salinity displacement once the permeability contrast exceeds 50.For the mobility-ratio cases considered,VC is unidirectional-from the fast to slow layer-only when the mobility-ratios across the two distinct shock-fronts are both favourable.Unlike a typical water-oil displacement,the weak dependency of late-time recovery efficiency on VC is observed to be a function of the mobility-ratio and dispersion in LSWF.An unfavourable mobility-ratio case is identified for viscous-dominated crossflow effects that is specific to low-salinity displacements.Ways to improve the flood design to ensure favourable displacement are presented.The findings of this study can help for better understanding of crossflow behaviour and regimes in reservoir settings,to mitigate any potential unfavourable impact on recovery or displacement efficiency with engineered or low-salinity water injection.

    Agglomerative clustering to improve the resolution of pseudo well stochastic seismic inversion:A case study

    Ashok YadavSoumya Ranjan NayakSamit Mondal
    12页
    查看更多>>摘要:The Monte Carlo rejection and Monte Carlo Markov Chain methods are two common sampling techniques in Bayesian seismic inversion.Conventional methods of pseudo well stochastic seismic inversion for reservoir properties uses Monte Carlo rejection sampling of pseudo-wells to select those that best match seismic traces.The selected pseudo-wells do not influence the selection/rejection of subsequent pseudo-wells.The process requires a very large number of prior pseudo-wells to draw a reasonable outcome,which consumes a major part of the computation time.In conventional methods,the best-matched pseudo-wells often have dissimilarly shaped volume of shale logs,which can degrade the resolution of the outcome.Though Agglomerative clustering is well-known but the idea of grouping pseudo-wells based on similarly shaped volume of shale logs in pseudo well stochastic seismic inversion is unique.We propose an agglomerative clustering technique to group the prior pseudo-wells according to the shape of their volume of shale logs,before matching to seismic.The centroids of the pseudo-well clusters summarize the large number of prior pseudo-wells.The best-matched pseudo-well cluster centroid with seismic gives the most likely outcome while the two next best-matched cluster centroids give alternative results.The alternative results are useful to understand the uncertainty in the outcome.It has been observed that,the proposed method has reduced computation time(50-55% less than conventional pseudo well stochastic inversion).Meanwhile,the quantification of sand volume from the proposed method shows improvement over the conventional method.A comparison between the proposed and the conventional method has been shown on a synthetic wedge model and real seismic.In the wedge model(volume of sand is 0.65),the resultant volume of sand predicted in the modified method(0.7)is better than that predicted using the conventional method(0.8).The modified pseudo-well stochastic seismic inversion method has been applied on seismic data from deepwater Krishna-Godavari basin.The result shows an improvement in the characterization of thin shale layers within the reservoir.

    How petrophysical heterogeneity controls the saturation calculations in carbonates,the Barremian-Aptian of the central Persian Gulf

    Vahid TavakoliDanial HassaniHossain Rahimpour-Bonab
    12页
    查看更多>>摘要:Water saturation calculations are among the most important aspects of reservoir characterization.Despite this importance,the effects of these calculations on the resulted oil in place remain unclear.Extreme heterogeneity in most of the carbonate reservoirs strongly affects the coefficients of the Archie equation and resulted water saturation.Therefore,a practical method to evaluate and manage the heterogeneity of such reservoirs,greatly improves the reliability of the final results.In this study,porosity,permeability,thin sections data,well logs and saturation tests of Barremian-Aptian carbonate Dariyan Formation in the central Persian Gulf have been used.Both core and reservoir scale techniques including flow zone indicator,Winland R35,electrofacies and strati-graphically modified Lorenz plot were used to evaluate the heterogeneity.Archie coefficients were arranged in different rock types.Results show that flow zone indicator is the most accurate technique to manage the heterogeneity of the reservoir with higher R2 value between porosity and permeability.The cementation factor was measured for each unit and the amounts of water saturation was calculated using deterministic analysis.Water saturation also calculated with the constant coefficients,which are routinely used in formation evaluation.The average Sw amount for constant Archie coefficients method was determined as 0.62,whereas it is 0.73,0.80,0.70,and 0.77 in flow zone indicator method,Winland R35 technique,stratigraphically modified Lorenz plot and electrofacies determination,respectively.The results demonstrate that calculating water saturation with constant Archie coefficients leads to slightly lower water saturation values,resulting in higher oil saturations and overestimating the oil in place.

    Emulsified acid systems for oil well stimulation:A review

    Ahmad A.AdewunmiTheis SoilingAbdullah S.Sultan
    12页
    查看更多>>摘要:This review discusses the application of emulsified acids for oil well stimulation.Types of oil,aqueous solutions,and emulsifiers are discussed in detail along with the solid agents and inhibitors that are utilized for emulsified acid formation.It has been found that there are at least nineteen(19)proposed ways of combining the chemicals that potentially can be employed operationally.The impact of heat and viscosity on the efficiency of the acid emulsions and the carbonate-decomposition kinetics are also in focus.Pumping emulsified acids through pipelines constitutes enormous flow challenges and this review shows that it is where the main obstacle lies.High-level understanding of emulsification is paramount for smooth pumping and transport of emulsions through pipes and here we show that several mechanisms are in play and that need to be considered for a smooth operation that involves an emulsified acid.Again,pipeline design and specifications must be properly handled,as various emulsions possess unique and distinct flow patterns.Core flooding constitutes a mode of investigation that guides how to achieve the optimal emulsified acid volume during injection and field trials;such studies are highlighted.More importantly,part of the objectives herein is to present some of the rheological approaches that will assist in the assessment of drag of a specific emulsion system which is very valuable when it comes to an assessment of how various additives impacts the drag.Further,this review shows that there is still room for improvement when it comes to the formulation of smart acid emulsions with an emphasis on quick pumping into the oil well without extreme pressure build-up or pressure drop.Functionalized polymers,either organic or inorganic(here primarily organoclays),that are soluble in either water or oil and stable in strong acid can mitigate some of the challenges while pumping acid emulsions.Novel nanomaterials with a high surface area in combination with thermal and acid resilience have also recently gained traction when it comes to the formation of new classes of emulsions that would prove valuable in oilfield stimulation.Overall,the application of emulsified acid systems provides a route to better controlled and more efficient acid stimulation jobs with the drag being the remaining challenge that should be properly managed.

    Evaluation of excessive wellhead motions:Reliability assessment and wellhead integrity index(Part II)

    Marcelo Anunciagao JaculliJose Ricardo Pelaquim MendesDanilo Colombo
    13页
    查看更多>>摘要:As discussed in part I of this work,the wellhead is an important component in the context of well integrity and operational safety,as it serves as a link between well and riser in offshore oil wells.The wellhead must sustain loads from the casings(soil reaction),which are hung into it through the casing hangers,as well as sustain loads from the riser(waves,current),which is connected at the top of the BOP(right above the wellhead)through the lower flex joint.In Part I of this work,we proposed a deterministic methodology to evaluate excessive wellhead motions,considering a mechanical system that couples the vessel,the riser,the wellhead itself,the conductor and surface casings,and their interaction with the soil.Now,in Part II,we move onto a stochastic analysis,which allows us to calculate the wellhead reliability.The simulation of this system provides the motions experienced by the wellhead;then,criteria such as maximum allowable lateral deflection and maximum allowable rotation are applied to verify if they will cause wellhead failure.Several interesting results have been observed:modern 5-phase wells with cemented conductor confer higher integrity to the wellhead compared to old 4-phase wells with jetted conductors;current speed/profile is the variable that affects the most the wellhead reliability;and heavier inner fluids reduce the reliability,posing a problem for later drilling phases.Finally,an integrity index for the wellhead throughout the well life cycle is suggested,aggregating the literature related to wellhead fatigue failure.The wellhead integrity index can then be combined with other indexes from other barrier elements to evaluate the overall integrity of barrier envelopes.