Geochemical modeling to aid experimental design for multiple isotope tracer studies of coupled dissolution and precipitation reaction kinetics

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.

基于CFD-DEM算法的压裂支撑剂缝内铺砂规律

为优化页岩气支撑剂的输送性能,采用计算流体力学-离散元(CFD-DEM)耦合方法对中等矩形裂缝进行数值模拟,考虑了重力、浮力以及颗粒-颗粒、颗粒-流体、颗粒-壁面之间的相互作用,采用单一因素控制变量法对支撑剂密度、携砂液流速、支撑剂质量分数以及压裂液黏度4个影响因素进行评价。研究结果表明:降低支撑剂与压裂液之间的质量分数差,可以提高86%的输送距离,确保支撑剂运移至裂缝深处;较高的携砂液流速会增大支撑剂的流化度,在距离入口较远处沉降;由于液体对颗粒的曳力作用,一定程度地提高压裂液的黏度会使支撑剂填充层的液体体积分数增加23%;增大支撑剂的砂比可以提前达到支撑剂的“平衡高度”,但在入口处有堆积,容易产生卡泵现象,可以采取变速加砂和梯度混砂的方式提高支撑剂的输送效果。研究结果可为现场压裂作业提供参考。

Coupled alkali feldspar dissolution and secondary mineral precipitation in batch systems: 5. Results of K-feldspar hydrolysis experiments

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).

Characterization and oil recovery enhancement by a polymeric nanogel combined with surfactant for sandstone reservoirs

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.

水力振荡器数值计算研究

目前尚未开展水力振荡器在改变特定参数和参数间在某种最优配合条件下能否得以优化的研究,制约了该工具的进一步完善。针对该问题,利用SolidWorks软件对水力振荡器的各部分结构进行三维建模,在ICEM CFD中进行网格划分,将网格导入ANSYS CFX进行数值计算与分析。研究结果表明:当流体通过水力振荡器时,旋转部件的运动使得流体动能增加,在流动过程中流体的动能重新转换为压能,使得该工具沿轴向正方向产生持续轴向力推动钻头做功;动静干涉作用和交界面速度变化所造成的流体震荡使得静止域产生剧烈的轴向和径向周期振动;大流量工况下轴向推力均值更大,轴向和径向振动也更为剧烈;在持续轴向推力和大幅度轴向振动推动下,该工具对钻柱施加周期性轴向振动和钻压并稳定推进。研究成果可为提高水力振荡器优化设计与敏感性分析水平提供相应的理论支撑。

Multi-scale elastoplastic mechanical model and microstructure damage analysis of solid expandable tubular

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.

Shallow-Water Origin of a Devonian Black Shale, Cleveland Shale Member (Ohio Shale), Northeastern Ohio, USA

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).

Nitrate Biotechnology for Oil Industry and Gas Application

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.

Nitrate Application in Mitigation of SRB Activity and Biogenic Sulfide Production

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.

Production Well Microbial Mitigation and H2S Risk Management

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.

Integrate intere-well connectivity data with static reservoir models based on Bayesian formalism

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.

Polymeric microsphere injection in large pore-size porous media

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.

An artificial-neural-network-based surrogate modeling workflow for reactive transport modeling

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.

Propagation of surfactant and polymer flow in natural carbonate cores

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.

Core-scale modeling of surfactant-assisted spontaneous water imbibition in carbonates

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.

Making True Amplitude Angle Domain Common Image Gathers Using Invertible Radon Transform

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.