Hydraulic fracturing is a commonly used stimulation technique for production optimization in various geological formations such as tight sandstone,shale,coal bed methane,and heat extraction in geothermal reservoirs.Br...Hydraulic fracturing is a commonly used stimulation technique for production optimization in various geological formations such as tight sandstone,shale,coal bed methane,and heat extraction in geothermal reservoirs.Breakdown pressure is a vital component in hydraulic fracture job design,which is affected by various parameters including rock strength and depth.Various methods including modelling and experimental approaches exist to quantify the breakdown pressure.There have been many strategies to reduce this pressure for efficient and economical hydraulic fracture jobs,especially when this pressure exceeds pump capacity.This study provides a detailed review of breakdown pressure in terms of fundamentals,influencing factors,and estimation approaches.In addition,different strategies are also presented to reduce the breakdown pressure along with cost analysis.Lastly,research gaps pertinent to this area are highlighted for emphasis in future research.Specifically,it has been found that high breakdown pressure is associated with challenges,but there are no comprehensive techniques and strategies to lower this pressure in formations with very high in situ stress profiles or complicated tectonic settings.Developing such methods is important to minimize operational failures,lower costs and reduce the environmental risks during reservoir exploitation.This study reviews the fundamentals,influencing factors,and estimation methods of breakdown pressure and provides a deep understanding of the strategies for its reduction.The study also presents the cost analyses,and highlights research gaps for future investigation.展开更多
The eutectic point is a critical parameter in the phase diagrams of solid–liquid equilibrium. In this study, high-pressure differential thermal analysis(HPDTA) was utilized to measure the melting temperatures of Fe–...The eutectic point is a critical parameter in the phase diagrams of solid–liquid equilibrium. In this study, high-pressure differential thermal analysis(HPDTA) was utilized to measure the melting temperatures of Fe–C alloy(3.4–4.2 wt.% C)under 5 GPa and to plot the liquidus temperature curves spanning from hypoeutectic to hypereutectic compositions. Our results indicate that under 5 GPa, the carbon content at the eutectic point of the Fe–C alloy decreases to 3.6–3.7 wt.%C, representing a reduction of approximately 0.6 wt.% C compared to the atmospheric pressure value(4.3 wt.% C). Concurrently, the eutectic temperature rises to 1195℃, showing an elevation of 48℃relative to the atmospheric pressure condition(1147℃). Microstructural analysis, x-ray diffraction(XRD), and hardness tests further corroborate these findings, demonstrating that high pressure significantly suppresses the solubility of carbon in γ-Fe, resulting in a decrease in the eutectic carbon content. Additionally, the hardness of the Fe–C alloy under 5 GPa is increased by more than 50% compared to that of the same type of Fe–C alloy under atmospheric pressure. This study provides essential experimental data for constructing high-pressure Fe–C phase diagrams and offers valuable insights for the design of high-performance Fe-based materials under extreme conditions.展开更多
This paper explores how dissolution and precipitation reactions are coupled in batch reactor experimental systems at elevated temperatures. This is the fifth paper in our series of ‘‘Coupled Alkali Feldspar Dissolut...This paper explores how dissolution and precipitation reactions are coupled in batch reactor experimental systems at elevated temperatures. This is the fifth paper in our series of ‘‘Coupled Alkali Feldspar Dissolution and Secondary Mineral Precipitation in Batch Systems.'' In the previous four papers we presented batch experiments of alkali-feldspar hydrolysis and explored the coupling of dissolution and precipitation reactions(Fu et al. in Chem Geol91:955–964, 2009; Zhu and Lu in Geochim Cosmochim Acta 73:3171–3200, 2009; Zhu et al.in Geochim Cosmochim Acta 74:3963–3983, 2010; Lu et al. in Appl Geochem30:75–90, 2013). Here, we present the results of additionalK-rich feldspar hydrolysis experiments at 150 °C. Our solution chemistry measurements have constrained feldspar dissolution rates, and our high resolution transmission electron microscopy work has identified boehmite precipitation. Reaction path modeling of K-feldspar dissolution and boehmite precipitation simulated the coupled reactions, but only with forced changes of boehmite rate law in the middle of experimental duration. The results which are reported in this article lend further support to our hypothesis that slow secondary mineral precipitation explains part of the wellknown apparent discrepancy between lab measured and field estimated feldspar dissolution rates(Zhu et al. in Water–rock interaction, 2004).展开更多
The characterization and enhanced oil recovery mechanisms of a nanosized polymeric cross-linked gel are presented herein.A negatively charged nanogel was synthesized using a typical free radical suspension polymerizat...The characterization and enhanced oil recovery mechanisms of a nanosized polymeric cross-linked gel are presented herein.A negatively charged nanogel was synthesized using a typical free radical suspension polymerization process by employing 2-acrylamido 2-methyl propane sulfonic acid monomer.The synthesized nanogel showed a narrow size distribution with one peak pointing to a predominant homogeneous droplet size.The charged nanogels were also able to adsorb at the oil-water interfaces to reduce interfacial tension and stabilize oil-in-water emulsions,which ultimately improved the recovered oil from hydrocarbon reservoirs.In addition,a fixed concentration of negatively charged surfactant(sodium dodecyl sulfate or SDS)was combined with different concentrations of the nanogel.The effect of the nanogels combined with surfactant on sandstone core plugs was examined by running a series of core flooding experiments using multiple flow patterns.The results show that combining nanogel and SDS was able to reduce the interfacial tension to a value of 6 Nm/m.The core flooding experiments suggest the ability of the nanogel,both alone and combined with SDS,to improve the oil recovery by a factor of 15%after initial seawater flooding.展开更多
We present an in-depth study of the failure phenomenon of solid expandable tubular (SET) due to large expansion ratio in open holes of deep and ultra-deep wells. By examining the post-expansion SET, lots of microcrack...We present an in-depth study of the failure phenomenon of solid expandable tubular (SET) due to large expansion ratio in open holes of deep and ultra-deep wells. By examining the post-expansion SET, lots of microcracks are found on the inner surface of SET. Their morphology and parameters such as length and depth are investigated by use of metallographic microscope and scanning electron microscope (SEM). In addition, the Voronoi cell technique is adopted to characterize the multi-phase material microstructure of the SET. By using the anisotropic elastoplastic material constitutive model and macro/microscopic multi-dimensional cross-scale coupled boundary conditions, a sophisticated and multi-scale finite element model (FEM) of the SET is built successfully to simulate the material microstructure damage for different expansion ratios. The microcrack initiation and growth is simulated, and the structural integrity of the SET is discussed. It is concluded that this multi-scale finite element modeling method could effectively predict the elastoplastic deformation and the microscopic damage initiation and evolution of the SET. It is of great significance as a theoretical analysis tool to optimize the selection of appropriate tubular materials and it could be also used to substantially reduce costly failures of expandable tubulars in the field. This numerical analysis is not only beneficial for understanding the damage process of tubular materials but also effectively guides the engineering application of the SET technology.展开更多
It is a challenge to make thorough but efficient experimental designs for the coupled mineral dissolution and precipitation studies in a multi-mineral system, because it is difficult to speculate the best experimental...It is a challenge to make thorough but efficient experimental designs for the coupled mineral dissolution and precipitation studies in a multi-mineral system, because it is difficult to speculate the best experimental duration, optimal sampling schedule, effects of different experimental conditions, and how to maximize the experimental outputs prior to the actual experiments. Geochemical modeling is an efficient and effective tool to assist the experimental design by virtually running all scenarios of interest for the studied system and predicting the experimental outcomes. Here we demonstrated an example of geochemical modeling assisted experimental design of coupled labradorite dissolution and calcite and clayey mineral precipitation using multiple isotope tracers. In this study, labradorite(plagioclase) was chosen as the reactant because it is both a major component and one of the most reactive minerals in basalt. Following our isotope doping studies of single minerals in the last ten years, initial solutions in the simulations were doped withmultiple isotopes(e.g., Ca and Si). Geochemical modeling results show that the use of isotope tracers gives us orders of magnitude more sensitivity than the conventional method based on concentrations and allows us to decouple dissolution and precipitation reactions at near-equilibrium condition. The simulations suggest that the precise unidirectional dissolution rates can inform us which rate laws plagioclase dissolution has followed. Calcite precipitation occurred at near-equilibrium and the multiple isotope tracer experiments would provide near-equilibrium precipitation rates, which was a challenge for the conventional concentration-based experiments. In addition, whether the precipitation of clayey phases is the rate-limiting step in some multi-mineral systems will be revealed. Overall, the modeling results of multimineral reaction kinetics will improve the understanding of the coupled dissolution–precipitation in the multi-mineral systems and the quality of geochemical modeling prediction of CO_(2) removal and storage efficacy in the basalt systems.展开更多
Seismic data is commonly acquired sparsely and irregularly, which necessitates the regularization of seismic data with anti-aliasing and anti-leakage methods during seismic data processing. We propose a novel method o...Seismic data is commonly acquired sparsely and irregularly, which necessitates the regularization of seismic data with anti-aliasing and anti-leakage methods during seismic data processing. We propose a novel method of 4D anti-aliasing and anti-leakage Fourier transform using a cube-removal strategy to address the combination of irregular sampling and aliasing in high-dimensional seismic data. We compute a weighting function by stacking the spectrum along the radial lines, apply this function to suppress the aliasing energy, and then iteratively pick the dominant amplitude cube to construct the Fourier spectrum. The proposed method is very efficient due to a cube removal strategy for accelerating the convergence of Fourier reconstruction and a well-designed parallel architecture using CPU/GPU collaborative computing. To better fill the acquisition holes from 5D seismic data and meanwhile considering the GPU memory limitation, we developed the anti-aliasing and anti-leakage Fourier transform method in 4D with the remaining spatial dimension looped. The entire workflow is composed of three steps: data splitting, 4D regularization, and data merging. Numerical tests on both synthetic and field data examples demonstrate the high efficiency and effectiveness of our approach.展开更多
Black shales are usually interpreted to require anoxic bottom waters and deeper water sedimentation. There has long been a debate about whether the Devonian Cleveland Shale Member of the Ohio Shale (CSM) was deposited...Black shales are usually interpreted to require anoxic bottom waters and deeper water sedimentation. There has long been a debate about whether the Devonian Cleveland Shale Member of the Ohio Shale (CSM) was deposited in shallow- or deep-water depositional environments. This study looked at the CSM at 3 stratigraphic sections and 5 well cores in northeastern Ohio. The CSM mostly consists of sapropelite (interbedded carbonaceous black mudstones and gray calcareous claystones). The black and gray “shales” are rhythmically bedded at micro- (<1 cm thick), meso- (<10 cm thick) and macro-scales (10s of cm thick) and represent changes in organic matter content (ranging from 7% - 20% TOC). Three types of event layers are interbedded with the mudrocks: 1) tempestites, 2) proximal turbidites, and 3) hyperpycnites. Individual tempestites and turbidites are laterally continuous?≥35 km, while hyperpycnites are too thin (<1 cm) to trace laterally. Tempestites consist of hummocky stratified sandstones with groove casts and escape burrows overlain by planar laminated sandstones with wave ripples at the top. Tempestites average 13 cm thick, but can be amalgamated up to 45 cm thick, and are more common in the lower half of the unit. Turbidites are incomplete Bouma sequences that average 6 cm thick, show evidence of combined flow (“wave-modified turbidites”), and are more common toward the top of the unit. Hyperpycnites (density underflows from river discharge) consist of inverse-to-normal graded sandy or silty microlaminae that have been studied primarily by using petrography and SEM. Condensed sections in the CSM are probable firmgrounds with carbonate concretions, and indicate intervals of low sedimentation rates. The evidence shows that the CSM depositional environment was receiving siliciclastics from the northeast (e.g., Catskill delta), and that the coarser-grained clastic sediment was primarily transported as density underflows (turbidites and hyperpycnites). However, significant storm deposits (tempestites) within the CSM indicate erosion and redeposition occurred on a muddy clastic marine shelf at paleo-water depths less than storm-weather wave base (probably?≤50 m depth).展开更多
Nitrate treatments have been used for many years to control nuisance H2S smells from sewage works and similar organic-rich treatment plant which has been considered as biotechnology treatment.Recently,nitrate has also...Nitrate treatments have been used for many years to control nuisance H2S smells from sewage works and similar organic-rich treatment plant which has been considered as biotechnology treatment.Recently,nitrate has also been used in field wide applications to oilfield systems for SRB(sulfate reducing bacteria)and sulfide control,including application to injection water,reservoirs and produced water treatment plant the primary objective of the work was to recommend appropriate nitrate treatment strategies that will cost-effectively control problems caused by bacterial growth in the water injection system.The implementation of the technology resulted in significant reduction in chemical and operating costs.Moreover,the treatment proved effective controlling sulfide even in the challenging operational conditions of flowing significantly less than the specified flow rate of 1 m/s.展开更多
Nitrate application in oil field water systems is a maturing technology.The treatment has been widely implemented around the world.In seawater applications,the technology has proven to effectively control SRB(sulfate ...Nitrate application in oil field water systems is a maturing technology.The treatment has been widely implemented around the world.In seawater applications,the technology has proven to effectively control SRB(sulfate reducing bacteria)activity and the associated generation of H2S(hydrogen sulfide);however,in produced water applications,a number of concerns have been raised,ranging from the effect of stimulated biomass growth on formations and equipment to elevated corrosion rates and increased downtime.Nitrate treatment has been implemented for approximately three years at a Central Arabia oil field.This paper discusses the mechanisms of nitrate application in controlling biological generation of sulfide and tested sulfate and nitrate respiration using wild SRB enrichment culture.The results indicated that SRB thriving in oil field environment includes species that are able to respire nitrate,i.e.,they can switch readily from sulfate reduction to a nitrate reduction pathway.The addition of nitrate was effective in controlling the biogenic sulfide.The study also evaluated a panel of PCR(polymerase chain reaction)primers targeting 16S RNA gene or some specific genes for characterization of the general microbial community and the SRB community.It is found that PCR primers targeting the genes encoding sulfate reduction activity,the gene encoding NiFe-hydrogenase,and the 16S rRNA gene could be used efficiently to monitor the diversity of SRB in oil fields.展开更多
One Field has been eternally acknowledged as a sweet arena without the presence of any souring phenomena.On the other hand,the Sulfate Reducing Bacteria(SRB)growth which has been lately observed in the field Water Inj...One Field has been eternally acknowledged as a sweet arena without the presence of any souring phenomena.On the other hand,the Sulfate Reducing Bacteria(SRB)growth which has been lately observed in the field Water Injection System played a major role in increasing the H2S concentrations in particular A fields.The objective of this study is to mitigate the SRB growth in the A Water Injection System and manage the risk of the Hydrogen Sulfide(H2S).In order to reduce the H2S concentrations and the return the Fields back to their original states.Thereafter,Biocide Treatment usage;based on the thorough evaluation performed in both the Lab and Fields by collecting more than 100 samples from designated wellheads and identified sampling points in the field Water Injection System network.Biocide field trial for one year was conducted with a persistent monitoring program.It appealed that the Biocide Treatment is influential,efficient and functional,carving deeper in the SRB mitigation and H2S risk management,the averaged H2S concentrations and trends in the Fields are being controlled and minimized in both the oil and gas phases.展开更多
Surfactants play a critical role in enhanced oil recovery(EOR) applications;however,their performance is often compromised in harsh reservoir conditions,such as high temperature and high salinity,due to precipitation ...Surfactants play a critical role in enhanced oil recovery(EOR) applications;however,their performance is often compromised in harsh reservoir conditions,such as high temperature and high salinity,due to precipitation caused by interactions with multivalent metal ions.Chelating agents were introduced into oilfields for various purposes due to their ability to sequester metal ions.In this work,we conducted a comprehensive investigation about chelating agent-surfactant(CS) flooding for carbonate reservoirs,as an alternative to the well-established alkaline surfactant(AS) flooding used in sandstone.The tested surfactants include sodium dodecyl sulfate(anionic)(SDS),dodecyltrimethylammonium bromide(cationic)(DTAB),Triton X100(nonionic),and a locally synthesized zwitterionic surfactant.The tested chelating agents include diethylenetriaminepentaacetic acid(DTPA),ethylenediaminetetraacetic acid,and glutamic acid N,N-diacetic acid.pH and temperature,as dominant factors in chelating agent solubility and brine stability,were modified to test chelating agent solutions of different concentrations and their mixtures with surfactants.Interfacial tension reduction by chelating agents alone,surfactants alone,and their mixtures were measured.Wettability alteration brought by chelating agents and surfactants on carbonate rock surfaces was evaluated using the static contact angle method.Based on the obtained results,chelating agents can be applied as low-cost additives for surfactant stabilization in high salinity conditions.The addition of chelating agents significantly improved the stability of SDS and DTAB in salt solutions and seawater.At a relatively low concentration(0.25 wt%),DTPA was able to stabilize DTAB of 1.00 wt% in seawater at high temperature(90℃).DTPA,among the tested three chelating agents,exhibited a stronger stabilization effect on surfactants of different ion types.When chelating agents are to be applied in brine,an optimal applicable pH range of 5-9 is recommended so not to induce solubility issue of chelating agents or stability issues of metal ions.In this range,IFT reduction is more significant at high pH,while wettability alteration is more significant at low pH.The combination of a cationic surfactant with a chelating agent forms a low adsorption wettability modifier which can change strongly oil-wet rock to water-wet conditions,thus significantly increasing the residual oil recovery from oil-wet carbonate formations.Zwitterionic and nonionic surfactants are also applicable to combine with a chelating agent for EOR purposes.Anionic surfactant SDS,however,showed a growing inhibition on the wettability alteration effect induced by EDTA as the concentration of SDS increased.展开更多
High water-cut has become a worldwide challenge for oil production.It requires extensive efforts to process and dispose.This entails expanding water handling facilities and incurring high power consumption costs.Polym...High water-cut has become a worldwide challenge for oil production.It requires extensive efforts to process and dispose.This entails expanding water handling facilities and incurring high power consumption costs.Polymeric microsphere injection is a cost-effective way to deal with excessive water production from subterranean formations.This study reports a laboratory investigation on polymeric microsphere injection in a large volume to identify its in-depth fluid diversion capacity in a porous media with large pore/particle size ratio.The performance of polymeric microsphere injection was evaluated using etched glass micromodels based on the pore network of a natural carbonate rock,which were treated as water-wet or oil-wet micromodels.Waterflooding was conducted to displace oil at reservoir temperature of 95°C,followed by one pore volume of polymeric microsphere injection.Three polymeric microsphere samples with median particle size of 0.05,0.3,and 20μm were used to investigate the impact of particle size of the polymeric microspheres on incremental oil production capacity.Although the polymeric microspheres were much smaller than the pores,additional oil production was observed.The incremental oil production increased with increasing polymeric microsphere concentration and particle size.As a comparison,polymeric microsphere solutions were injected into oil-wet and water-wet micromodels after waterflooding.It was observed that the oil production in oil-wet micromodel was much higher than that in water-wet micromodel.The wettability of micromodels affected the distribution patterns of the remaining oil after waterflooding and further dominated the performance of the microsphere injection.The study supports the applicability of microsphere injection in oil-wet heterogeneous carbonates.展开更多
The inter-well connectivity calculated from reservoir dynamic production data reflects formation heterogeneity quantitatively.Currently,the calculated inter-well connectivity between pair wells is mainly used as a too...The inter-well connectivity calculated from reservoir dynamic production data reflects formation heterogeneity quantitatively.Currently,the calculated inter-well connectivity between pair wells is mainly used as a tool for water flood management but not for quantitative reservoir characterization.This study proposes an innovative,dynamic data integration workflow that can integrate inter-well connectivity with a static reservoir model.In the workflow,the first step is calculating the inter-well connectivity vectors from the reservoir pairwise injector and producer wells.The second step covers interpolation in the domain of interest.The third step is to update the permeability model based on the Bayesian updating method.The result of this study shows that integrating the calculated inter-well connectivity with the static models enhances model reliability and it also provides an insight to deeper geological understanding reflected from dynamic data integration in reservoir modeling.展开更多
Process-based reactive transport modeling(RTM)integrates thermodynamic and kinetically controlled fluid-rock interactions with fluid flow through porous media in the subsurface and surface environment.RTM is usually c...Process-based reactive transport modeling(RTM)integrates thermodynamic and kinetically controlled fluid-rock interactions with fluid flow through porous media in the subsurface and surface environment.RTM is usually conducted through numerical programs based on the first principle of physical processes.However,the calculation for complex chemical reactions in most available programs is an iterative process,where each iteration is in general computationally intensive.A workflow of neural networkbased surrogate model as a proxy for process-based reactive transport simulation is established in this study.The workflow includes(1)base case RTM design,(2)development of training experiments,(3)surrogate model construction based on machine learning,(4)surrogate model validation,and(5)prediction with the calibrated model.The training experiments for surrogate modeling are generated and run prior to the predictions using RTM.The results show that the predictions from the surrogate model agree well with those from processes-based RTM but with a significantly reduced computational time.The well-trained surrogate model is especially useful when a large number of realizations are required,such as the sensitivity analysis or model calibration,which can significantly reduce the computational time compared to that required by RTM.The benefits are(1)it automatizes the experimental design during the sensitivity analysis to get sufficient numbers and coverage of the training cases;(2)it parallelizes the calculations of RTM training cases during the sensitivity analysis to reduce the simulation time;(3)it uses the neural network algorithm to rank the sensitivity of the parameters and to search the optimal solution for model calibration.展开更多
This work numerically investigates surfactant effects on spontaneous water imbibition in oil-wet carbonates.An open boundary core-scale imbibition model with 9×9×10 gridblocks was used in UTCHEM to simulate ...This work numerically investigates surfactant effects on spontaneous water imbibition in oil-wet carbonates.An open boundary core-scale imbibition model with 9×9×10 gridblocks was used in UTCHEM to simulate carbonate core plug exposure to a vast water body.The simulation models were developed based on surfactant-assisted imbibition tests that were conducted in secondary and tertiary oil production modes using Amott cells at 75℃.Capillary and gravity forces were captured by history matching the experiments.Through history matching,the inputs for surfactant adsorption and diffusion,capillary pressure and relative permeability were calibrated.In tertiary mode,the surfactants-assisted imbibition process presents the performance in mixed-wet state rather than oil-wet state,which is governed by wettability alteration.A simulation model for surfactant-assisted imbibition in secondary mode was used to investigate the effects of various factors including interfacial tension(IFT)reduction,wettability alteration,adsorption,volume of surrounding water and capillary force.The simulation results suggest that surfactant-assisted water imbibition in secondary mode is gravity dominant,which is facilitated by both IFT reduction and wettability alteration caused by addition of proper surfactants.Different from water imbibition in water-wet core,it presents vertically dominant oil flow with a hemispherical oil-rich area and uneven remaining oil saturation.It is obvious that sufficient surfactant supply in vast water is required to make effective imbibition,in consideration of surfactant consumption and changes in concentration gradients.This core-scale modeling provides insights of surfactant-assisted imbibition in initially oil-wet carbonates and helps scale up the application in a cost-effective way.展开更多
This paper presents an experimental and analytical study of comprehensive effects of surfactant and polymer in aqueous solutions on the propagation in carbonates.Single-phase flow tests of surfactant,polymer and surfa...This paper presents an experimental and analytical study of comprehensive effects of surfactant and polymer in aqueous solutions on the propagation in carbonates.Single-phase flow tests of surfactant,polymer and surfactant-polymer mixture were respectively conducted on natural carbonate core plugs at high temperature and high salinity reservoir conditions.The effect of different factors on chemical propagation was taken into account by use of a convection-dispersion model.The dynamic adsorptions of two amphoteric surfactants at 2000 mg/L concentration onto the carbonate rocks were 0.21 and 0.17 mg/g-rock,respectively.The dynamic adsorptions of a sulfonated polymer at 2000 and 5000 mg/L were 0.11 and 0.17 mg/g-rock,respectively.Surfactant-polymer mixtures in aqueous solutions were coinjected to evaluate their competitive adsorption,showing the surfactant adsorption was reduced by approximately 50%.The dispersion coefficient of the chemicals in the carbonate cores was in the magnitude of 10^(-3) cm^(2)/s.Caused by dispersion and adsorption,chemical concentration reduction occurred obviously during the propagation in carbonate porous media.Chromatographic separation took place in the surfactant-polymer co-injection scheme,which was estimated by modeling as well.展开更多
Converting subsurface offset domain common image gathers(ODCIGs)to angle domain common image gathers(ADCIGs)through a Radon Transform(RT)in either the spatial or wavenumber domain is efficient and valid except for the...Converting subsurface offset domain common image gathers(ODCIGs)to angle domain common image gathers(ADCIGs)through a Radon Transform(RT)in either the spatial or wavenumber domain is efficient and valid except for the distortion of both frequency spectrum and amplitude versus angle(AVA)effect.This paper presents two modifications to the existing method to keep the frequency spectrum of the resultant ADCIGs the same as the input data and to preserve the relative amplitudes.The spectrum invariance is achieved by replacing the conventional RT or slant slack by an invertible RT.Amplitude preservation is obtained by applying an amplitude correction factor in the angle domain.Tests on both synthetic and field datasets validate the accuracy of these modifications.展开更多
文摘Hydraulic fracturing is a commonly used stimulation technique for production optimization in various geological formations such as tight sandstone,shale,coal bed methane,and heat extraction in geothermal reservoirs.Breakdown pressure is a vital component in hydraulic fracture job design,which is affected by various parameters including rock strength and depth.Various methods including modelling and experimental approaches exist to quantify the breakdown pressure.There have been many strategies to reduce this pressure for efficient and economical hydraulic fracture jobs,especially when this pressure exceeds pump capacity.This study provides a detailed review of breakdown pressure in terms of fundamentals,influencing factors,and estimation approaches.In addition,different strategies are also presented to reduce the breakdown pressure along with cost analysis.Lastly,research gaps pertinent to this area are highlighted for emphasis in future research.Specifically,it has been found that high breakdown pressure is associated with challenges,but there are no comprehensive techniques and strategies to lower this pressure in formations with very high in situ stress profiles or complicated tectonic settings.Developing such methods is important to minimize operational failures,lower costs and reduce the environmental risks during reservoir exploitation.This study reviews the fundamentals,influencing factors,and estimation methods of breakdown pressure and provides a deep understanding of the strategies for its reduction.The study also presents the cost analyses,and highlights research gaps for future investigation.
基金Project supported by the National Key Research and Development Program of China (Grant No. 2023YFA1406200)。
文摘The eutectic point is a critical parameter in the phase diagrams of solid–liquid equilibrium. In this study, high-pressure differential thermal analysis(HPDTA) was utilized to measure the melting temperatures of Fe–C alloy(3.4–4.2 wt.% C)under 5 GPa and to plot the liquidus temperature curves spanning from hypoeutectic to hypereutectic compositions. Our results indicate that under 5 GPa, the carbon content at the eutectic point of the Fe–C alloy decreases to 3.6–3.7 wt.%C, representing a reduction of approximately 0.6 wt.% C compared to the atmospheric pressure value(4.3 wt.% C). Concurrently, the eutectic temperature rises to 1195℃, showing an elevation of 48℃relative to the atmospheric pressure condition(1147℃). Microstructural analysis, x-ray diffraction(XRD), and hardness tests further corroborate these findings, demonstrating that high pressure significantly suppresses the solubility of carbon in γ-Fe, resulting in a decrease in the eutectic carbon content. Additionally, the hardness of the Fe–C alloy under 5 GPa is increased by more than 50% compared to that of the same type of Fe–C alloy under atmospheric pressure. This study provides essential experimental data for constructing high-pressure Fe–C phase diagrams and offers valuable insights for the design of high-performance Fe-based materials under extreme conditions.
基金grant from the State Key Laboratory of Ore Deposits at the Institute of Geochemistry, Chinese Academy of Sciences
文摘This paper explores how dissolution and precipitation reactions are coupled in batch reactor experimental systems at elevated temperatures. This is the fifth paper in our series of ‘‘Coupled Alkali Feldspar Dissolution and Secondary Mineral Precipitation in Batch Systems.'' In the previous four papers we presented batch experiments of alkali-feldspar hydrolysis and explored the coupling of dissolution and precipitation reactions(Fu et al. in Chem Geol91:955–964, 2009; Zhu and Lu in Geochim Cosmochim Acta 73:3171–3200, 2009; Zhu et al.in Geochim Cosmochim Acta 74:3963–3983, 2010; Lu et al. in Appl Geochem30:75–90, 2013). Here, we present the results of additionalK-rich feldspar hydrolysis experiments at 150 °C. Our solution chemistry measurements have constrained feldspar dissolution rates, and our high resolution transmission electron microscopy work has identified boehmite precipitation. Reaction path modeling of K-feldspar dissolution and boehmite precipitation simulated the coupled reactions, but only with forced changes of boehmite rate law in the middle of experimental duration. The results which are reported in this article lend further support to our hypothesis that slow secondary mineral precipitation explains part of the wellknown apparent discrepancy between lab measured and field estimated feldspar dissolution rates(Zhu et al. in Water–rock interaction, 2004).
文摘The characterization and enhanced oil recovery mechanisms of a nanosized polymeric cross-linked gel are presented herein.A negatively charged nanogel was synthesized using a typical free radical suspension polymerization process by employing 2-acrylamido 2-methyl propane sulfonic acid monomer.The synthesized nanogel showed a narrow size distribution with one peak pointing to a predominant homogeneous droplet size.The charged nanogels were also able to adsorb at the oil-water interfaces to reduce interfacial tension and stabilize oil-in-water emulsions,which ultimately improved the recovered oil from hydrocarbon reservoirs.In addition,a fixed concentration of negatively charged surfactant(sodium dodecyl sulfate or SDS)was combined with different concentrations of the nanogel.The effect of the nanogels combined with surfactant on sandstone core plugs was examined by running a series of core flooding experiments using multiple flow patterns.The results show that combining nanogel and SDS was able to reduce the interfacial tension to a value of 6 Nm/m.The core flooding experiments suggest the ability of the nanogel,both alone and combined with SDS,to improve the oil recovery by a factor of 15%after initial seawater flooding.
基金Project supported by the National Major Science & Technology Project of China (Grant No. 2016ZX05020-003).
文摘We present an in-depth study of the failure phenomenon of solid expandable tubular (SET) due to large expansion ratio in open holes of deep and ultra-deep wells. By examining the post-expansion SET, lots of microcracks are found on the inner surface of SET. Their morphology and parameters such as length and depth are investigated by use of metallographic microscope and scanning electron microscope (SEM). In addition, the Voronoi cell technique is adopted to characterize the multi-phase material microstructure of the SET. By using the anisotropic elastoplastic material constitutive model and macro/microscopic multi-dimensional cross-scale coupled boundary conditions, a sophisticated and multi-scale finite element model (FEM) of the SET is built successfully to simulate the material microstructure damage for different expansion ratios. The microcrack initiation and growth is simulated, and the structural integrity of the SET is discussed. It is concluded that this multi-scale finite element modeling method could effectively predict the elastoplastic deformation and the microscopic damage initiation and evolution of the SET. It is of great significance as a theoretical analysis tool to optimize the selection of appropriate tubular materials and it could be also used to substantially reduce costly failures of expandable tubulars in the field. This numerical analysis is not only beneficial for understanding the damage process of tubular materials but also effectively guides the engineering application of the SET technology.
基金partially supported by U.S. National Science Foundation grants EAR-2221907partly sponsored by agencies of the United States Government。
文摘It is a challenge to make thorough but efficient experimental designs for the coupled mineral dissolution and precipitation studies in a multi-mineral system, because it is difficult to speculate the best experimental duration, optimal sampling schedule, effects of different experimental conditions, and how to maximize the experimental outputs prior to the actual experiments. Geochemical modeling is an efficient and effective tool to assist the experimental design by virtually running all scenarios of interest for the studied system and predicting the experimental outcomes. Here we demonstrated an example of geochemical modeling assisted experimental design of coupled labradorite dissolution and calcite and clayey mineral precipitation using multiple isotope tracers. In this study, labradorite(plagioclase) was chosen as the reactant because it is both a major component and one of the most reactive minerals in basalt. Following our isotope doping studies of single minerals in the last ten years, initial solutions in the simulations were doped withmultiple isotopes(e.g., Ca and Si). Geochemical modeling results show that the use of isotope tracers gives us orders of magnitude more sensitivity than the conventional method based on concentrations and allows us to decouple dissolution and precipitation reactions at near-equilibrium condition. The simulations suggest that the precise unidirectional dissolution rates can inform us which rate laws plagioclase dissolution has followed. Calcite precipitation occurred at near-equilibrium and the multiple isotope tracer experiments would provide near-equilibrium precipitation rates, which was a challenge for the conventional concentration-based experiments. In addition, whether the precipitation of clayey phases is the rate-limiting step in some multi-mineral systems will be revealed. Overall, the modeling results of multimineral reaction kinetics will improve the understanding of the coupled dissolution–precipitation in the multi-mineral systems and the quality of geochemical modeling prediction of CO_(2) removal and storage efficacy in the basalt systems.
文摘Seismic data is commonly acquired sparsely and irregularly, which necessitates the regularization of seismic data with anti-aliasing and anti-leakage methods during seismic data processing. We propose a novel method of 4D anti-aliasing and anti-leakage Fourier transform using a cube-removal strategy to address the combination of irregular sampling and aliasing in high-dimensional seismic data. We compute a weighting function by stacking the spectrum along the radial lines, apply this function to suppress the aliasing energy, and then iteratively pick the dominant amplitude cube to construct the Fourier spectrum. The proposed method is very efficient due to a cube removal strategy for accelerating the convergence of Fourier reconstruction and a well-designed parallel architecture using CPU/GPU collaborative computing. To better fill the acquisition holes from 5D seismic data and meanwhile considering the GPU memory limitation, we developed the anti-aliasing and anti-leakage Fourier transform method in 4D with the remaining spatial dimension looped. The entire workflow is composed of three steps: data splitting, 4D regularization, and data merging. Numerical tests on both synthetic and field data examples demonstrate the high efficiency and effectiveness of our approach.
文摘Black shales are usually interpreted to require anoxic bottom waters and deeper water sedimentation. There has long been a debate about whether the Devonian Cleveland Shale Member of the Ohio Shale (CSM) was deposited in shallow- or deep-water depositional environments. This study looked at the CSM at 3 stratigraphic sections and 5 well cores in northeastern Ohio. The CSM mostly consists of sapropelite (interbedded carbonaceous black mudstones and gray calcareous claystones). The black and gray “shales” are rhythmically bedded at micro- (<1 cm thick), meso- (<10 cm thick) and macro-scales (10s of cm thick) and represent changes in organic matter content (ranging from 7% - 20% TOC). Three types of event layers are interbedded with the mudrocks: 1) tempestites, 2) proximal turbidites, and 3) hyperpycnites. Individual tempestites and turbidites are laterally continuous?≥35 km, while hyperpycnites are too thin (<1 cm) to trace laterally. Tempestites consist of hummocky stratified sandstones with groove casts and escape burrows overlain by planar laminated sandstones with wave ripples at the top. Tempestites average 13 cm thick, but can be amalgamated up to 45 cm thick, and are more common in the lower half of the unit. Turbidites are incomplete Bouma sequences that average 6 cm thick, show evidence of combined flow (“wave-modified turbidites”), and are more common toward the top of the unit. Hyperpycnites (density underflows from river discharge) consist of inverse-to-normal graded sandy or silty microlaminae that have been studied primarily by using petrography and SEM. Condensed sections in the CSM are probable firmgrounds with carbonate concretions, and indicate intervals of low sedimentation rates. The evidence shows that the CSM depositional environment was receiving siliciclastics from the northeast (e.g., Catskill delta), and that the coarser-grained clastic sediment was primarily transported as density underflows (turbidites and hyperpycnites). However, significant storm deposits (tempestites) within the CSM indicate erosion and redeposition occurred on a muddy clastic marine shelf at paleo-water depths less than storm-weather wave base (probably?≤50 m depth).
文摘Nitrate treatments have been used for many years to control nuisance H2S smells from sewage works and similar organic-rich treatment plant which has been considered as biotechnology treatment.Recently,nitrate has also been used in field wide applications to oilfield systems for SRB(sulfate reducing bacteria)and sulfide control,including application to injection water,reservoirs and produced water treatment plant the primary objective of the work was to recommend appropriate nitrate treatment strategies that will cost-effectively control problems caused by bacterial growth in the water injection system.The implementation of the technology resulted in significant reduction in chemical and operating costs.Moreover,the treatment proved effective controlling sulfide even in the challenging operational conditions of flowing significantly less than the specified flow rate of 1 m/s.
文摘Nitrate application in oil field water systems is a maturing technology.The treatment has been widely implemented around the world.In seawater applications,the technology has proven to effectively control SRB(sulfate reducing bacteria)activity and the associated generation of H2S(hydrogen sulfide);however,in produced water applications,a number of concerns have been raised,ranging from the effect of stimulated biomass growth on formations and equipment to elevated corrosion rates and increased downtime.Nitrate treatment has been implemented for approximately three years at a Central Arabia oil field.This paper discusses the mechanisms of nitrate application in controlling biological generation of sulfide and tested sulfate and nitrate respiration using wild SRB enrichment culture.The results indicated that SRB thriving in oil field environment includes species that are able to respire nitrate,i.e.,they can switch readily from sulfate reduction to a nitrate reduction pathway.The addition of nitrate was effective in controlling the biogenic sulfide.The study also evaluated a panel of PCR(polymerase chain reaction)primers targeting 16S RNA gene or some specific genes for characterization of the general microbial community and the SRB community.It is found that PCR primers targeting the genes encoding sulfate reduction activity,the gene encoding NiFe-hydrogenase,and the 16S rRNA gene could be used efficiently to monitor the diversity of SRB in oil fields.
文摘One Field has been eternally acknowledged as a sweet arena without the presence of any souring phenomena.On the other hand,the Sulfate Reducing Bacteria(SRB)growth which has been lately observed in the field Water Injection System played a major role in increasing the H2S concentrations in particular A fields.The objective of this study is to mitigate the SRB growth in the A Water Injection System and manage the risk of the Hydrogen Sulfide(H2S).In order to reduce the H2S concentrations and the return the Fields back to their original states.Thereafter,Biocide Treatment usage;based on the thorough evaluation performed in both the Lab and Fields by collecting more than 100 samples from designated wellheads and identified sampling points in the field Water Injection System network.Biocide field trial for one year was conducted with a persistent monitoring program.It appealed that the Biocide Treatment is influential,efficient and functional,carving deeper in the SRB mitigation and H2S risk management,the averaged H2S concentrations and trends in the Fields are being controlled and minimized in both the oil and gas phases.
基金supported by the College of Petroleum Engineering&Geoscience (CPG) at King Fahd University of Petroleum and Minerals (KFUPM)。
文摘Surfactants play a critical role in enhanced oil recovery(EOR) applications;however,their performance is often compromised in harsh reservoir conditions,such as high temperature and high salinity,due to precipitation caused by interactions with multivalent metal ions.Chelating agents were introduced into oilfields for various purposes due to their ability to sequester metal ions.In this work,we conducted a comprehensive investigation about chelating agent-surfactant(CS) flooding for carbonate reservoirs,as an alternative to the well-established alkaline surfactant(AS) flooding used in sandstone.The tested surfactants include sodium dodecyl sulfate(anionic)(SDS),dodecyltrimethylammonium bromide(cationic)(DTAB),Triton X100(nonionic),and a locally synthesized zwitterionic surfactant.The tested chelating agents include diethylenetriaminepentaacetic acid(DTPA),ethylenediaminetetraacetic acid,and glutamic acid N,N-diacetic acid.pH and temperature,as dominant factors in chelating agent solubility and brine stability,were modified to test chelating agent solutions of different concentrations and their mixtures with surfactants.Interfacial tension reduction by chelating agents alone,surfactants alone,and their mixtures were measured.Wettability alteration brought by chelating agents and surfactants on carbonate rock surfaces was evaluated using the static contact angle method.Based on the obtained results,chelating agents can be applied as low-cost additives for surfactant stabilization in high salinity conditions.The addition of chelating agents significantly improved the stability of SDS and DTAB in salt solutions and seawater.At a relatively low concentration(0.25 wt%),DTPA was able to stabilize DTAB of 1.00 wt% in seawater at high temperature(90℃).DTPA,among the tested three chelating agents,exhibited a stronger stabilization effect on surfactants of different ion types.When chelating agents are to be applied in brine,an optimal applicable pH range of 5-9 is recommended so not to induce solubility issue of chelating agents or stability issues of metal ions.In this range,IFT reduction is more significant at high pH,while wettability alteration is more significant at low pH.The combination of a cationic surfactant with a chelating agent forms a low adsorption wettability modifier which can change strongly oil-wet rock to water-wet conditions,thus significantly increasing the residual oil recovery from oil-wet carbonate formations.Zwitterionic and nonionic surfactants are also applicable to combine with a chelating agent for EOR purposes.Anionic surfactant SDS,however,showed a growing inhibition on the wettability alteration effect induced by EDTA as the concentration of SDS increased.
文摘High water-cut has become a worldwide challenge for oil production.It requires extensive efforts to process and dispose.This entails expanding water handling facilities and incurring high power consumption costs.Polymeric microsphere injection is a cost-effective way to deal with excessive water production from subterranean formations.This study reports a laboratory investigation on polymeric microsphere injection in a large volume to identify its in-depth fluid diversion capacity in a porous media with large pore/particle size ratio.The performance of polymeric microsphere injection was evaluated using etched glass micromodels based on the pore network of a natural carbonate rock,which were treated as water-wet or oil-wet micromodels.Waterflooding was conducted to displace oil at reservoir temperature of 95°C,followed by one pore volume of polymeric microsphere injection.Three polymeric microsphere samples with median particle size of 0.05,0.3,and 20μm were used to investigate the impact of particle size of the polymeric microspheres on incremental oil production capacity.Although the polymeric microspheres were much smaller than the pores,additional oil production was observed.The incremental oil production increased with increasing polymeric microsphere concentration and particle size.As a comparison,polymeric microsphere solutions were injected into oil-wet and water-wet micromodels after waterflooding.It was observed that the oil production in oil-wet micromodel was much higher than that in water-wet micromodel.The wettability of micromodels affected the distribution patterns of the remaining oil after waterflooding and further dominated the performance of the microsphere injection.The study supports the applicability of microsphere injection in oil-wet heterogeneous carbonates.
文摘The inter-well connectivity calculated from reservoir dynamic production data reflects formation heterogeneity quantitatively.Currently,the calculated inter-well connectivity between pair wells is mainly used as a tool for water flood management but not for quantitative reservoir characterization.This study proposes an innovative,dynamic data integration workflow that can integrate inter-well connectivity with a static reservoir model.In the workflow,the first step is calculating the inter-well connectivity vectors from the reservoir pairwise injector and producer wells.The second step covers interpolation in the domain of interest.The third step is to update the permeability model based on the Bayesian updating method.The result of this study shows that integrating the calculated inter-well connectivity with the static models enhances model reliability and it also provides an insight to deeper geological understanding reflected from dynamic data integration in reservoir modeling.
文摘Process-based reactive transport modeling(RTM)integrates thermodynamic and kinetically controlled fluid-rock interactions with fluid flow through porous media in the subsurface and surface environment.RTM is usually conducted through numerical programs based on the first principle of physical processes.However,the calculation for complex chemical reactions in most available programs is an iterative process,where each iteration is in general computationally intensive.A workflow of neural networkbased surrogate model as a proxy for process-based reactive transport simulation is established in this study.The workflow includes(1)base case RTM design,(2)development of training experiments,(3)surrogate model construction based on machine learning,(4)surrogate model validation,and(5)prediction with the calibrated model.The training experiments for surrogate modeling are generated and run prior to the predictions using RTM.The results show that the predictions from the surrogate model agree well with those from processes-based RTM but with a significantly reduced computational time.The well-trained surrogate model is especially useful when a large number of realizations are required,such as the sensitivity analysis or model calibration,which can significantly reduce the computational time compared to that required by RTM.The benefits are(1)it automatizes the experimental design during the sensitivity analysis to get sufficient numbers and coverage of the training cases;(2)it parallelizes the calculations of RTM training cases during the sensitivity analysis to reduce the simulation time;(3)it uses the neural network algorithm to rank the sensitivity of the parameters and to search the optimal solution for model calibration.
文摘This work numerically investigates surfactant effects on spontaneous water imbibition in oil-wet carbonates.An open boundary core-scale imbibition model with 9×9×10 gridblocks was used in UTCHEM to simulate carbonate core plug exposure to a vast water body.The simulation models were developed based on surfactant-assisted imbibition tests that were conducted in secondary and tertiary oil production modes using Amott cells at 75℃.Capillary and gravity forces were captured by history matching the experiments.Through history matching,the inputs for surfactant adsorption and diffusion,capillary pressure and relative permeability were calibrated.In tertiary mode,the surfactants-assisted imbibition process presents the performance in mixed-wet state rather than oil-wet state,which is governed by wettability alteration.A simulation model for surfactant-assisted imbibition in secondary mode was used to investigate the effects of various factors including interfacial tension(IFT)reduction,wettability alteration,adsorption,volume of surrounding water and capillary force.The simulation results suggest that surfactant-assisted water imbibition in secondary mode is gravity dominant,which is facilitated by both IFT reduction and wettability alteration caused by addition of proper surfactants.Different from water imbibition in water-wet core,it presents vertically dominant oil flow with a hemispherical oil-rich area and uneven remaining oil saturation.It is obvious that sufficient surfactant supply in vast water is required to make effective imbibition,in consideration of surfactant consumption and changes in concentration gradients.This core-scale modeling provides insights of surfactant-assisted imbibition in initially oil-wet carbonates and helps scale up the application in a cost-effective way.
文摘This paper presents an experimental and analytical study of comprehensive effects of surfactant and polymer in aqueous solutions on the propagation in carbonates.Single-phase flow tests of surfactant,polymer and surfactant-polymer mixture were respectively conducted on natural carbonate core plugs at high temperature and high salinity reservoir conditions.The effect of different factors on chemical propagation was taken into account by use of a convection-dispersion model.The dynamic adsorptions of two amphoteric surfactants at 2000 mg/L concentration onto the carbonate rocks were 0.21 and 0.17 mg/g-rock,respectively.The dynamic adsorptions of a sulfonated polymer at 2000 and 5000 mg/L were 0.11 and 0.17 mg/g-rock,respectively.Surfactant-polymer mixtures in aqueous solutions were coinjected to evaluate their competitive adsorption,showing the surfactant adsorption was reduced by approximately 50%.The dispersion coefficient of the chemicals in the carbonate cores was in the magnitude of 10^(-3) cm^(2)/s.Caused by dispersion and adsorption,chemical concentration reduction occurred obviously during the propagation in carbonate porous media.Chromatographic separation took place in the surfactant-polymer co-injection scheme,which was estimated by modeling as well.
文摘Converting subsurface offset domain common image gathers(ODCIGs)to angle domain common image gathers(ADCIGs)through a Radon Transform(RT)in either the spatial or wavenumber domain is efficient and valid except for the distortion of both frequency spectrum and amplitude versus angle(AVA)effect.This paper presents two modifications to the existing method to keep the frequency spectrum of the resultant ADCIGs the same as the input data and to preserve the relative amplitudes.The spectrum invariance is achieved by replacing the conventional RT or slant slack by an invertible RT.Amplitude preservation is obtained by applying an amplitude correction factor in the angle domain.Tests on both synthetic and field datasets validate the accuracy of these modifications.
