CO_2-triggered gelation for mobility control and channeling blocking during CO_2 flooding processes

CO_2 flooding is regarded as an important method for enhanced oil recovery(EOR) and greenhouse gas control.However,the heterogeneity prevalently distributed in reservoirs inhibits the performance of this technology.The sweep efficiency can be significantly reduced especially in the presence of thief zones.Hence.gas channeling blocking and mobility control are important technical issues for the success of CO_2 injection.Normally.crosslinked gels have the potential to block gas channels,but the gelation time control poses challenges to this method.In this study,a new method for selectively blocking CO_2 channeling is proposed,which is based on a type of CO_2-sensilive gel system(modified polyacrylamide-methenamine-resorcinol gel system) to form gel in situ.A CO_2-sensitive gel system is when gelation or solidification will be triggered by CO_2 in the reservoir to block gas channels.The CO_2-sensitivity of the gel system was demonstrated in parallel bottle tests of gel in N_2 and CO_2 atmospheres.Sand pack flow experiments were conducted to investigate the shutoff capacity of the gel system under different conditions.The injectivity of the gel system was studied via viscosity measurements.The results indicate that this gel system was sensitive to CO_2 and had good performance of channeling blocking in porous media.Advantageous viscosity-temperature characteristics were achieved in this work.The effectiveness for EOR in heterogeneous formations based on this gel system was demonstrated using displacement tests conducted in double sand packs.The experimental results can provide guidelines for the deployment of the CO_2-sensitive gel system for field applications.     

A quick evaluation model for CO<Subscript>2</Subscript> flooding and sequestration

CO₂ flooding not only triggers an increase in oil production, but also reduces the amount of CO₂ released to the atmosphere (by storing it permanently in the formations). It is one of the best ways to use and store CO₂. This paper firstly selects the key factors after analyzing the factors influencing the CO₂ storage potential in the formations and oil recovery, and then introduces a series of dimensionless variables to describe reservoir characteristics. All influencing factors with varying values are calculated through a Box-Behnken experimental design. The results are interpreted by a response surface method, and then a quick screening model is obtained to evaluate the oil recovery and CO₂ storage potential for an oil reservoir. Based on the evaluation model, sensitivity analysis of each factor is carried out. Finally, research on CO₂ sequestration and flooding in a typical reservoir indicates that the evaluation model fits well with the numerical simulation, which proves that the evaluation model can provide criteria for screening attractive candidate reservoirs for CO₂ sequestration and flooding.     

Effect of CO<Subscript>2</Subscript> on the oxidation of cyclohexene by H<Subscript>2</Subscript>O<Subscript>2</Subscript> using Co<Subscript>1.5</Subscript>PW<Subscript>12</Subscript>O<Subscript>40</Subscript> catalyst

Oxidation of cyclohexene by cheap and environmentally friendly oxidants, namely H₂O₂ and CO₂ has been catalyzed by Co_1.5PW₁₂O₄₀. It has been found that the main products of the oxidation are 2-cyclohexen-l-one (enone), 2-cyclohexen-l-ol (enol) and 1, 2-cyclohexanediol (diol) with the enone as the major product. Oxidation by CO₂ along with H₂O₂ remarkably increased the conversion compared to that by CO₂ and H₂O₂ separately. This might be due to the fact that CO₂ increases the percarbonate species (HCO₄ ^?) responsible of the oxidation by oxygen transfer, which indicated that the CO₂/H₂O₂ mixture is a useful reagent system. The decrease of both the selectivity of the enone and epoxide in favor of that of diol at higher conversions indicated that the diol was formed from the epoxide by consecutive reaction and/or directly from cyclohexene.     

Characteristics of CO<Subscript>2</Subscript> sequestration in saline aquifers

Storage of CO2 in saline aquifers is a viable option for reducing the amount of CO2 released to the atmosphere. This paper provides an overall review of CO2 sequestration in saline aquifers. First,the principles of CO2 sequestration are presented,including CO2 phase behavior,CO2-water-rock interaction,and CO2 trapping mechanisms. Then storage capacity and CO2 injectivity are discussed as the main determinants of the storage potential of saline aquifers. Next,a site section process is addressed considering b...     

Research on a novel composite gel system for CO<Subscript>2</Subscript> breakthrough

A composite gel was prepared for plugging CO2 channeling, which is a serious problem for enhanced oil recovery with CO2. A composite gel which is one of the materials for successful control of CO2 channeling during CO2 injection process was studied in this paper. SEM and nano particle size analysis were used to describe this material’s microstructure. Its effect on CO2 channeling control was evaluated with core flow experiments. Both the rheological test and core plugging experiments indicated that both acr...     

Sensitivity analysis of CO<Subscript>2</Subscript> sequestration in saline aquifers

Carbon capture and storage (CCS) technology has been considered as an important method for reducing greenhouse gas emissions and for mitigating global climate change. Three primary options are being considered for large-scale storage of CO₂ in subsurface formations: oil and gas reservoirs, deep saline aquifers, and coal beds. There are very many large saline aquifers around the world, which could make a big contribution to mitigating global warming. However, we have much less understanding of saline aquifers than oil and gas reservoirs. Several mechanisms are involved in the storage of CO₂ in deep saline aquifers, but the ultimate goal of injection of CO₂ into the aquifers containing salt water is to dissolve the CO₂ in the water. So it is important to study the solubility trapping and sensitivity factors of CO₂ in saline aquifers. This paper presents results of modeling CO₂ storage in a saline aquifer using the commercial reservoir simulator ECLIPSE. The objective of this study was to better understand the CO₂/brine phase behavior (PVT properties) and quantitatively estimate the most important CO₂ storage mechanism in brine-solubility trapping. This would provide a tool by performing theoretical and numerical studies that help to understand the feasibility of CO₂ geological storage. A 3-dimensional, 2-phase (water/gas) conceptional reservoir model used finite, homogenous and isothermal formations into which CO₂ is injected at a constant rate. The effects of main parameters were studied, including the vertical to horizontal permeability ratio k _v/k _h, salinity, and residual phase saturations. The results show that the vertical to horizontal permeability ratio has a significant effect on CO₂ storage. Moreover, more CO₂ dissolves in the brine at lower k _v/k _h values.     

Precise model for estimating CO<Subscript>2</Subscript>—oil minimum miscibility pressure

The CO₂—oil minimum miscibility pressure (MMP) is an important parameter for screening and selecting reservoirs for CO₂ injection projects. For the highest recovery, a candidate reservoir must be capable of withstanding an average reservoir pressure greater than the CO₂—oil MMP. Knowledge of the CO₂—oil MMP is also important when selecting a model to predict or simulate reservoir performance as a result of CO₂ injection. This paper, presents a new alternating conditional expectation “ACE”-based model for estimating CO₂—oil MMP. The ACE algorithm estimates the optimal transformation that maximizes the correlation between the transformed dependent variable “CO₂—oil MMP” and the sum of the transformed independent variables that represent reservoir temperature and different components of oil composition. Predicted values of the CO₂—oil MMP from the developed ACE-based model were compared with the experimental and calculated values from the most common correlations reported in the literature for CO₂—oil MMP prediction. The results showed that the ACE-based model is superior to other commonly used correlations. Regarding other correlations, the ACE-based model yielded the highest correlation coefficient (0.9878), the lowest average relative error (0.7428%), and the lowest standard deviation of error (1.2265). The text was submitted by the author in English.     

Study of Separation Behavior of Activated and Non-Activated MOF-5 as Filler on MOF-based Mixed-Matrix Membranes in H<Subscript>2</Subscript>/CO<Subscript>2</Subscript> Separation

In this study, cubic and tetragonal structures of MOF-5 (C-MOF-5 and T-MOF-5) were successfully synthesized, characterized and incorporated into cellulose acetate (CA) polymer matrix in the range of 6, 9 and 12 wt % to fabricate mixed matrix membranes (MMMs). The effects of smaller pore size of T-MOF-5 and more ZnO molecules in T-MOF-5, on the H₂ and CO₂ permeation properties of C-MOF-5/CA and T-MOF-5/CA MMMs were investigated. The all novel MMMs were prepared using the solution casting method and characterized by FTIR, TGA and SEM. SEM images as well as results of FTIR and TGA analyses confirmed good adhesion between both MOF-5s and CA matrix. Addition of both C-MOF-5 and T-MOF-5 into the CA improved the gas transport properties of the CA, especially in H2 separation. The H₂/CO₂ selectivity continued the increasing trend at 9 wt % and did not significantly reduce even at 12 wt % due to good adhesion between both MOF-5s and CA. The highest H₂/CO₂ selectivity was obtained at 12 and 9 wt % loading of C-MOF-5 and T-MOF-5, respectively. By changing the filler from C-MOF-5 to T-MOF-5, the increasing and reducing of adsorption site of H₂ and CO₂ (respectively), and also reducing in pore size, caused the appearance of H₂ permeability to not change much but the CO2 permeability to reduce. Accordingly, the H₂/CO₂ selectivity in all T-MOF-5/CA MMMs is higher than that in all C-MOF-5/CA MMMs. According to obtained results, the activated MOFs (i.e., C-MOF-5 in this study) are not always the best choices for separation process.     

二氧化碳驱封窜技术降本节能研究

前期用于治理大庆油田CO_2驱试验区气窜问题的泡沫封窜技术由于成本过高,未能进行大规模推广应用。科研人员通过优选泡沫剂与稳泡用的弱凝胶,形成了低成本的凝胶泡沫,通过实验对优选出的泡沫剂及弱凝胶的耐酸性、耐温性的评价,最终确定了凝胶泡沫配方。该体系基液黏度8~12 m Pa·s;成胶时间3~7 d可控;发泡体积550 m L;泡沫半衰期60 d以上。在提高体系性能的基础上,成功地将泡沫体系的单方液成本降低了60%,并实现了单井节约用水1000 m~3;单井节约用电50400 k Wh;单井节约CO_2 1000 L。     

Mono- and Bimetallic Mo(W)S<Subscript>2</Subscript>/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> and Mo(W)S<Subscript>2</Subscript>/SBA-15 Hydrotreating Catalysts Based on SiMo<Subscript>12</Subscript> and SiW<Subscript>12</Subscript> Heteropoly Acids

Mono- and bimetallic Mo(W)S₂ catalysts supported on γ-Al₂O₃ and SBA-15 have been prepared using the Keggin heteropoly acids (HPAs) H₄SiMo₁₂O₄₀ and H₄SiW₁₂O₄₀. The catalyst samples have been analyzed by temperature-programmed reduction with hydrogen, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. Catalytic properties have been examined in the joint hydrotreating of dibenzothiophene and naphthalene on a flow-through unit. It has been shown that the use of mesoporous silica SBA-15 as a support can reduce the average length of Mo(W)S₂ particles from 4.9 to 3.7 nm and increase the average number of layers and the particle size of the active phase, changes that lead to an increase in catalytic activity by a factor of ~3 relative to the alumina-supported counterparts. The use of a mixture of SiMo₁₂HPA and SiW₁₂HPA for preparing MoW catalysts leads to a significant enhancement of catalytic activity, which is apparently due to the formation of mixed active sites.     

Ethylene oligomerization in the presence of ZrO(OCOR)<Subscript>2</Subscript>-Al(C<Subscript>2</Subscript>H<Subscript>5</Subscript>)<Subscript>2</Subscript>Cl-Modifier catalytic system

The kinetics of ethylene oligomerization and molecular-mass distribution of resulted oligomers on ZrO(OCOR)₂-Al(C₂H₅)₂Cl and ZrO(OCOR)₂-Al(C₂H₅)₂Cl-modifier catalyst systems, where the modifier was CCl₄, vinyl acetate, or zinc stearate, were studied depending on the modifier: ZrO(OCOR)₂ and Al(C₂H₅)₂Cl: ZrO(OCOR)₂ molar ratios, ethylene pressure, temperature, and modifier nature.     

低渗透油藏CO2驱封窜用CO2/N2响应性纳米分散体系的研制

针对低渗透油藏CO2驱波及效率低和气窜的问题,合成一种CO2/N2响应性纳米SiO2来控制气窜指进,增加CO2驱的波及范围;利用红外光谱、热重分析等方法对合成的CO2/N2响应性纳米SiO2进行表征研究,在分散条件下对其进行粒径分析、响应性、吸附量、分散稳定性等系统研究,并采用岩心流动装置对CO2/N2响应性纳米SiO...     

Study of a mass transfer-reaction model for SO<Subscript>2</Subscript> absorption process using LAS/H<Subscript>2</Subscript>SO<Subscript>4</Subscript> solution

A regenerative absorption process for removal of SO_x from FCC off-gas using LAS/H₂SO₄ solution as absorbant was studied and pilot-plant experiments were carried out. A mass transferreaction model for the SO₂ absorption process was established based on pilot-plant experiments, and the concentration distribution of components in the liquid film, and the partial pressure and mass transfer rate of SO₂ along the height of the absorption tower, was calculated from this model. The numerical simulation results were compared with the experimental results and proved that the model can be used for describing the SO₂ absorption process.     

Selective dimerization of styrene to 1,3-diphenylbutene-1 in the presence of [(acac)Pd(PAr<Subscript>3</Subscript>)<Subscript>2</Subscript>]BF<Subscript>4</Subscript>/BF<Subscript>3</Subscript>OEt<Subscript>2</Subscript> catalytic systems

Selective dimerization of styrene to 1,3-diphenylbutene-1 in the presence of [(acac)Pd(PAr₃)₂]BF₄ + BF₃OEt₂ catalytic systems, where R = C₆H₅, o-CH₃C₆H₄, p-CH₃C₆H₄, or o-CH₃OC₆H₄, has been studied. Under the optimal conditions (B/Pd = 8, T = 75°C, R = C₆H₅), the conversion of styrene to the products exceeds the conversion for the known analogs and reaches 1.5 tons of styrene/g-atom of palladium with amounts of dimers and trimers of 91 and 9%, respectively. The dimers consist of up to 100% 1,3-diphenylbutene-1 with a trans/cis isomer ratio of 95/5.     

CO2驱凝胶封窜体系研究进展

由于油气间黏度差异大和油藏的非均质性,在CO2驱油过程会发生气窜从而降低CO2的波及效率。凝胶体系是CO2驱油过程中的有效封窜剂,在中外都有着广泛的应用。介绍了延缓交联聚丙烯酰胺凝胶、预交联凝胶颗粒、两级封窜凝胶体系、泡沫凝胶这4种凝胶体系的封窜机理以及研究进展。延缓交联丙烯酰胺凝胶流动性强,价格低廉,但是成胶强度、成胶时间不可控并且不耐酸性腐蚀。预交联凝胶颗粒成胶时间、成胶强度可控且耐高温耐高矿化度,但是粒度较大,无法进入渗透率较低的地层。两级封窜凝胶体系结合了刚性凝胶与小分子的优势,能够同时封堵不同尺寸的裂缝,但是对于超过特定尺寸的裂缝,封堵效果将会下降。泡沫凝胶对地层伤害小,但是不耐高温。目前,用于CO2驱气窜的凝胶体系存在着不耐酸性腐蚀的问题,如何使长期处于CO2酸性环境下的凝胶体系保持稳定是未来的研究方向。     

Cycloaddition of cage and polycyclic diazo compounds to C<Subscript>60</Subscript> fullerene catalyzed by Pd(acac)<Subscript>2</Subscript>-2PPh<Subscript>3</Subscript>-4Et<Subscript>3</Subscript>Al

Spirohomofullerenes were synthesized by cycloaddition of cage and polycyclic diazoalkanes generated in situ by oxidation of hydrazones of camphor, 2-adamantanone, and cholestane-3-one to C₆₀ fullerene in the presence of the Pd(acac)₂-2PPh₃-4Et₃Al three-component catalyst. It was found that the spiro-homofullerenes obtained from hydrazones of 2-adamantanone and cholestane-3-one and C₆₀ fullerene do not undergo thermal isomerization to the corresponding spiro-methanofullerenes.     

Kinetics of cyclohexene hydrocarbalkoxylation with cyclohexanol catalyzed by the Pd(PPh<Subscript>3</Subscript>)<Subscript>2</Subscript>Cl<Subscript>2</Subscript>-PPh<Subscript>3</Subscript>-<Emphasis Type="Italic">p</Emphasis>-toluenesulfonic acid system

The reaction kinetics of cyclohexene hydrocarbalkoxylation with cyclohexanol catalyzed by the Pd(PPh₃)₂Cl₂-PPh₃-p-toluenesulfonic acid system was studied over the temperature range 363–393 K. The reaction rate was found to be a nonlinear function of the Pd(PPh₃)₂Cl₂ concentration or a nonmonotonic function of the PPh₃ and cyclohexanol concentrations or p _CO. The experimental data were interpreted in terms of a mechanism that involves ion pairs containing alkyl and acyl palladium complexes of the cationic type as intermediates. Based on the quasi-steady-state approximation, a rate equation was obtained to adequately describe the experimental data. The rate equation parameters were estimated using the least squares technique. The apparent activation energies of these parameters were determined. The heats of formation of Pd(PPh₃)₂(C₆H₁₁OH)₂, Pd(PPh₃)₂(CO)₂, and Pd(PPh₃)₄ complexes from Pd(PPh₃)₂(C₆H₅CH₃)₂ were estimated. A symbatic change in these values with the donor-acceptor properties of ligands was demonstrated.     

Kinetic aspects of the effect of the palladium phosphine complex Pd(PPh<Subscript>3</Subscript>)<Subscript>2</Subscript>Cl<Subscript>2</Subscript> and free triphenylphosphine on hydrocarbomethoxylation of cyclohexene

The influence of temperature on the dependence of the cyclohexene hydrocarbomethoxylation reaction catalyzed by the Pd(PPh₃)₂Cl₂-PPh₃-p-toluenesulfonic acid system upon the Pd(PPh₃)₂Cl₂ and PPh₃ concentrations has been studied. The data have been interpreted in terms of the mechanism that involves as intermediates ion pairs containing cationic hydride, alkyl, and acyl palladium complexes. Using the quasi-equilibrium concentration approximation, a rate equation has been derived to adequately describe the experimental data. The parameters of the rate equation were estimated by the least-square technique. The apparent activation energies of these parameters have been determined, and the ratio between the enthalpies of the formation of inactive [Pd(PPh₃)₄] and \(H\mathop {Sol}\limits^ \oplus [Pd(PPh_3 )_2 (Cl)(Sol)]^ - \) complexes from [Pd(PPh₃)₂(Sol)]₂ has been evaluated on their basis.     

Exhaustive schemes for refining C<Subscript>3</Subscript>-C<Subscript>4</Subscript> hydrocarbon fractions

Exhaustive schemes for efficient refining of the C₃-C₄ hydrocarbon fraction using zeolite type Y catalysts to obtain a high-octane additive are proposed. Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 5, pp. 6–7, September–October, 2008.