Heat flow pattern,base of methane hydrates stability zones and BSRs in Shenhu Area,northern South China Sea

Using the collected 433 heat flow values, we estimated the bases of methane hydrate stability zone （BHSZ）, in northern South China Sea （NSCS）. Through comparing BHSZs with the depths of bottom simulating reflectors （BSRs）, in Shenhu Area （SA）, we found that there are big differences between them. In the north of SA, where the water depth is shallow, many slumps developed and the sedimentation rate is high, it appears great negative difference （as large as -192%）. However, to the southeast of SA, where the water depth is deeper, sedimentation rate is relatively low and uplift basement topography exists, it changes to positive difference （as large as ＋45%）. The differences change so great, which haven＇t been observed in other places of the world. After considering the errors from the process of heat flow measurement, the BSR depth, the relationship of thermal conductivity with the sediments depth, and the fluid flow activities, we conclude that the difference should be not caused by these errors. Such big disagreement may be due to the misunderstanding of BSR. The deviant ＂BSRs＂ could represent the paleo-BSRs or just gas-bearing sediment layers, such as unconformities or the specific strata where have different permeability, which are not hydraterelated BSRs.

Gas-hydrate formation,agglomeration and inhibition in oil-based drilling fluids for deep-water drilling

One of the main challenges in deep-water drilling is gas-hydrate plugs,which make the drilling unsafe.Some oil-based drilling fluids（OBDF） that would be used for deep-water drilling in the South China Sea were tested to investigate the characteristics of gas-hydrate formation,agglomeration and inhibition by an experimental system under the temperature of 4 ？C and pressure of 20 MPa,which would be similar to the case of 2000 m water depth.The results validate the hydrate shell formation model and show that the water cut can greatly influence hydrate formation and agglomeration behaviors in the OBDF.The oleophobic effect enhanced by hydrate shell formation which weakens or destroys the interfacial films effect and the hydrophilic effect are the dominant agglomeration mechanism of hydrate particles.The formation of gas hydrates in OBDF is easier and quicker than in water-based drilling fluids in deep-water conditions of low temperature and high pressure because the former is a W/O dispersive emulsion which means much more gas-water interfaces and nucleation sites than the later.Higher ethylene glycol concentrations can inhibit the formation of gas hydrates and to some extent also act as an anti-agglomerant to inhibit hydrates agglomeration in the OBDF.

Characterisation, Analysis and Design of Hydrated Cement Treated Crushed Rock Base as a Road Base Material in Western Australia

Hydrated Cement Treated Crushed Rock Base （HCTCRB） is widely used as a base course in Western Australian pavements. HCTCRB has been designed and used as a basis for empirical approaches and in empirical practices. These methods are not all-encompassing enough to adequately explain the behaviour of HCTCRB in the field. Recent developments in mechanistic approaches have proven more reliable in the design and analysis of pavement, making it possible to more effectively document the characteristics of HCTCRB. The aim of this study was to carry out laboratory testing to assess the mechanical characteristics of HCTCRB. Conventional triaxial tests and repeated load triaxial tests （RLT tests） were performed. Factors affecting the performance of HCTCRB, namely hydration periods and the amount of added water were also investigated. It was found that the shear strength parameters of HCTCRB were 177 kPa for cohesion （c） and 42~ for the internal friction angle （~）. The hydration period, and the water added in this investigation affected the performance of HCTCRB. However, the related trends associated with such factors could not be assessed. All HCTCRB samples showed stress-dependency behaviour. Based on the stress stages of this experiment, the resilient modulus values of HCTCRB ranged from 300 MPa to 1100 MPa. CIRCLY, a computer program based on the multi-layer elastic theory was used in the mechanistic approach to pavement design and analysis, to determine the performance of a typical pavement model using HCTCRB as a base course layer. The mechanistic pavement design parameters for HCTCRB as a base course material were then introduced. The analysis suggests that the suitable depth for HCTCRB as a base layer for WA roads is at least 185 mm for the design equivalent standard axle （ESA） of 10 million.

Comparison and application of different empirical correlations for estimating the hydrate safety margin of oil-based drilling fluids containing ethylene glycol

As the oil and gas industries continue to increase their activity in deep water, gas hydrate hazards will become more serious and challenging, both at present and in the future. Accurate predictions of the hydrate-free zone and the suitable addition of salts and/or alcohols in preparing drilling fluids are particularly important both in preventing hydrate problems and decreasing the cost of drilling operations. In this paper, we compared several empirical correlations commonly used to estimate the hydrate inhibition effect of aqueous organic and electrolyte solutions using experiments with ethylene glycol （EG） as a hydrate inhibitor. The results show that the Najibi et al. correlation （for single and mixed thermodynamic inhibitors） and the Ostergaard et al. empirical correlation （for single thermodynamic inhibitors） are suitable for estimating the hydrate safety margin of oil-based drilling fluids （OBDFs） in the presence of thermodynamic hydrate inhibitors. According to the two correlations, the OBDF, composed of 1.6 L vaporizing oil, 2% emulsifying agent, 1% organobentonite, 0.5% SP-1, 1% LP-1, 10% water and 40% EG, can be safely used at a water depth of up to 1900 m. However, for more accurate predictions for drilling fluids, the effects of the solid phase, especially bentonite, on hydrate inhibition need to be considered and included in the application of these two empirical correlations.

Progress of Gas Hydrate Studies in China

A brief overview is given on the gas hydrate-related research activities carried out by Chinese researchers in the past 15 years. The content involves: (1) Historical review. Introducing the gas hydrate research history in China; (2) Gas hydrate research groups in China. There are nearly 20 groups engaged in gas hydrate research now; (3) Present studies. Including fundamental studies, status of the exploration of natural gas hydrate resources in the South China Sea region, and development of hydrate-based new techniques; (4) Future development.

Effect of distortion degree on the hydration of red mud base cementitious material

The interaction of Si anions with Al sites during the hydration process was observed by NMR, IR and SEM to understand the reaction mechanism of the hydrates formation mixed with oil shale calcined at different temperatures. As the reaction progressed, the coordination of Al （Ⅳ, Ⅴ, and Ⅵ） changed almost completely to Ⅳ, when mixed with oil shale calcined at 700 ℃. However, when mixed with oil shale calcined at 400 ℃, some 6-coordination of Al still remained in the hydrates. Under the function of alkaline solutions, which were produced with the hydration of clinker, a certain amount of Si and Al atoms dissolved or hydrolyzed from aluminosilicate, formed geomonomers in solutions, and then polycondensed to form networks.

Hydration Process of Cement-Based Materials by AC Impedance Method

AC impedance is a new method to study the changes of pore structure and the hydration degree during the hydration and hardening process of cement paste by the change of the electrochemical parameters. Employing AC impedance method, we studied the hydration and hardening process of cement paste with fly ash and slag, and analyzed the influence of different hydration age, water-binder ratio and mineral admixture on the impedance parameters. Moreover, we compared the results with those by the conventional porosity testing method and X-ray diffraction method. The results showed that AC impedance could be taken as a new technology in cement and concrete research.

Comparative Molecular Mechanics and Quantum Mechanics Study of Monohydration of Nucleic Acid Bases

DNA is the most important biological molecule and its hydration contributes essentially to the structure and functions of the double helix. We analyze the monohydration of the individual bases of nucleic acids and their methyl derivatives using methods of Molecular Mechanics (MM) with the Poltev-Malenkov (PM), AMBER and OPLS force fields, as well as ab initio Quantum Mechanics (QM) calculations at MP2/6-31G(d,p) level of theory. A comparison is made between the calculated interaction energies and the experimental enthalpies of microhydration of bases, obtained from mass spectrometry at low temperatures. Each local water-base interaction energy minimum obtained with MM corresponds to the minimum obtained with QM. General qualitative agreement was observed in the geometrical characteristics of the local minima obtained via the two groups of methods. MM minima correspond to slightly more coplanar structures than those obtained via QM methods, and the absolute MM energy values overestimate corresponding values obtained with QM. For Adenine and Thymine the QM local minima energy values are closer to those obtained by the PM potential (average of 0.72 kcal/mol) than by the AMBER force field (1.86 kcal/mol). The differences in energy between MM and QM results are more pronounced for Guanine and Cytosine, especially for minima with the water molecule forming H-bonds with two proton-acceptor centers of the base. Such minima are the deepest ones obtained via MM methods while QM calculations result in the global minima corresponding to water molecule H-bonded to one acceptor and one donor site of the base. Calculations for trimethylated bases with a water molecule corroborate the MM results. The energy profiles were obtained with some degrees of freedom of the water molecule being frozen. This data will contribute to the improvement of the molecular mechanics force fields.

基于油基钻屑制备压裂支撑剂的室内研究

针对热解析后脱油钻屑处理难和处理方式单一的问题,开展了将油基钻屑残渣制备成免烧压裂支撑剂的研究,研究了钻屑与水泥比、CMC添加量、石膏添加量和养护天数共4个因素对免烧压裂支撑剂性能影响。结果表明,在原料配比较优的情况下,制备工艺为钻屑水泥比0.67(质量比),石膏添加量为6%(质量分数),CMC添加量为4%(质量分数),养护时间28 d。该条件下制得的压裂支撑剂颗粒体积密度为1.47 g/cm^(3),视密度为2.52 g/cm^(3),35 MPa下颗粒破碎率为1.57%。经扫描电子显微镜与X射线衍射仪分析发现,此时压裂支撑剂内部结构致密,孔隙封闭,水化产物CaO·SiO_(2)·nH_(2)O凝胶和钙长石类物质有利于提高压裂支撑剂的综合物理性能。为脱油钻屑残渣利用提供新的方向。

气体水合物合成研究进展

水合物法捕集与封存CO_(2)气体可服务于大规模减排的技术需求,加速“碳中和”目标的实现,对应对气候变化具有重要意义。从气体水合物的基本性质、生成机理及模型,多孔介质中水合物合成,水合物合成的分子动力学模拟等方面,综述了前人针对水合物合成领域的研究现状,提出了气体水合物合成过程中存在的科学问题,并对气体水合物的发展及煤系地层CO_(2)水合物的封存方向进行了评价。研究认为,CO_(2)气体的溶解度是限制准确计算多孔介质中水合物储气量的关键因素;气体水合物的局部结构化(成核)机制复杂,仍需深入研究;高纬度及永久冻土区煤系地层可作为水合物法封存CO_(2)气体的地下空间。

井研地区筇竹寺组页岩储层水平井钻井井壁稳定性评价

川西南井研区块筇竹寺组页岩气具有良好的开发前景,但由于对其岩矿组分、力学性质、水化特征等认识程度较低,钻井井壁稳定性认识不清,导致出现掉块、阻卡等复杂情况。为了充分认识该区寒武系筇竹寺组地层的井壁稳定性,明确粉砂质页岩水化作用及其对坍塌压力的影响规律,在岩石力学实验的基础上,研究不同钻井液浸泡时间对岩石力学参数的影响规律,建立考虑水化作用的井壁稳定性预测模型,分析不同井斜方位下坍塌压力的差异。研究结果表明:筇竹寺组伊蒙混层含量高,具有一定膨胀性,水化作用后导致岩石强度降低,对井壁稳定性有较大影响;不同钻井液体系对井壁稳定性的影响有差异,总体上油基钻井液更有利于井壁稳定;考虑了水化作用的井壁稳定预测模型更加符合实际,以此为依据,通过优化钻井液设计可以有效降低井壁失稳风险,提高钻井时效。

大宗煤基固废膏体充填材料少水化配比优化研究

为解决西部采煤区固废多、处理难的问题,以宁东矿区的脱硫石膏、粉煤灰、水泥为主要原料,对原料的微观形态及少水配比的煤基固废膏体充填材料的成分进行分析,以初期流动性、脱模后7 d和28 d的抗压强度为指标进行充填材料配比优化。设计了3因素3水平17组配比方案,建立响应面回归模型,分析单因素及多因素交互作用对少水充填材料强度和流动性的影响。研究结果表明,粉煤灰与水泥质量比是影响少水充填材料强度的重要因素,料浆质量分数是影响少水充填材料流动性的重要因素。少水配比的煤基固废膏体充填材料的最优配合比:脱硫石膏质量分数53%,粉煤灰与水泥质量比2∶1,料浆质量分数74%。波速与强度的响应关系表明,可以利用充填体的波速来预测其强度。

多源煤基固废胶结充填体力学及变形破坏特征试验研究

【目的】为研究多源煤基固废胶结充填体的力学特性及变形破坏规律,选择5种典型煤基固废,开展了煤基固废胶结充填体(Coal-Based Solid Waste Cemented Backfill,CBSWCB)的单轴压缩、声发射响应及微观结构测试试验。【方法】分析了CBSWCB单轴抗压强度的影响因素和交互作用,建立了基于交互作用的抗压强度影响因素四维空间可视化模型,结合CBSWCB的声发射及微观结构特征,阐明了单轴压缩条件下的力学演化特征及宏观变形破坏规律,从微观角度进一步论证了CBSWCB承载过程中水化反应机理及宏细观联系。【结果和结论】试验结果表明:(1)单轴抗压强度的主要影响因素是质量分数,而炉底渣掺量的影响程度最小。(2)单轴压缩下CBSWCB的宏观变形破坏由塑性、弱劈裂破坏逐渐向脆性、剪切破坏转化。(3) CBSWCB试件声发射参数演化可以分为上升期、平静期、活跃期、稳定期,声发射累计振铃计数曲线呈现明显的“阶梯状”增长,累计振铃计数在上升期和平稳期内缓慢增加,在活跃期急剧增加,在稳定期逐渐趋于平缓。(4)水泥掺量偏低以及多源煤基固废充填材料属性差异导致水化反应程度有限,水化产物数量较少是CBSWCB单轴抗压强度普遍偏低的主要原因。研究结果可为多源煤基固废用于充填开采提供一定参考依据。

石墨电极棉线基微流体肼燃料电池

为找到性价比高且安全环保的供电设备,搭建以水合肼为燃料、石墨为电极以及棉线为流道材料的无催化剂微流体燃料电池(MFC),并进行性能测试。石墨管阳极、石墨棒阴极组合的MFC电化学性能最佳,电池于燃料浓度为0.075 mol/L、NaOH浓度为1.0 mol/L及电极距离为4 mm时,具有11.10μW/cm^(2)的最大功率密度和121.45μA/cm^(2)的电流密度。搭建的MFC具有材料简单、成本低且组装方便等特点,无需外部泵维持共层流,作为便携式设备具备集成化和小型化的潜力。

基于响应面法的地热钻采碳纳米管复合水泥基材料的研究

针对现有导热固井水泥存在的性能不足问题,本文研制了一种新型地热钻采碳纳米管复合水泥基材料(CNTs-CC)。首先,选用石墨、氮化硅作为主要导热填料,硅微粉作为热稳定材料,碳纳米管作为协同增强填料,初步研制出纳米复合水泥材料基础液;其次,基于响应曲面法Box-Behnken试验设计,开展17组配比优化试验,构建了以2 d抗压强度和导热系数为响应指标的二次多项式预测模型,结合方差分析和响应曲面考察了各因素对响应指标的影响,并得到胶凝材料最优配比;最后,对复合水泥基材料的工程性能进行评估,并结合XRD与SEM研究了材料的水化机理。结果表明:复合水泥基材料的导热性能与抗压强度受多因素交互作用影响,其中早强剂与减水剂交互影响显著;CNTs-CC水泥石28 d抗压强度达8.15 MPa,导热系数为2.236 W/(m·K);导热填料不参与水化过程,碳纳米管粉可发挥“填充”及“桥连”效应,外加剂调控水化进程。

三乙醇胺对水泥-石灰石粉胶凝材料体系水化特性的影响研究

为了研究三乙醇胺对水泥-石灰石粉胶凝材料体系水化特性的影响,采用了等温量热、X射线衍射、热重等测试方法探究了三乙醇胺作用下胶凝材料体系的水化进程和水化产物的演化;并采用相边界成核与生长模型探究了三乙醇胺作用下胶凝材料体系的水化动力学过程。结果表明:三乙醇胺能够加速水泥-石灰石粉胶凝材料体系的水化,增加水化产物的生成,从而增加了其水化程度;另外,三乙醇胺能够增加水化产物早期的成核与生长速率,减小水化产物早期的相边界成核与生长面积。

聚合物及小分子类页岩抑制剂研究进展

本文概述了聚合物及小分子类页岩抑制剂研究进展,特别关注国内外近年的相关研究成果。文章系统介绍了用于表征黏土水化膨胀和评价抑制剂性能的实验方法。此外,文章分类讨论了无机盐类、聚醚胺类、天然改性材料和聚合物类抑制剂的特点,展望了水基钻井液中页岩抑制剂的应用方向和主要发展趋势。

DES+CTAB复配驱油剂体系提高低渗致密砂岩油藏采收率机理

针对低渗致密油藏注水困难、采收率低等问题,利用尿素基深共晶溶剂(DES)与十六烷基三甲基溴化铵(CTAB)复配的驱油剂体系,对驱油剂在低渗致密油藏中的降压增注和提高采收率机理进行了研究。研究结果表明:①驱油剂体系可以将油水界面张力降低至10^(-3)mN/m以下,大大提高了洗油效率;②驱油剂体系可有效抑制黏土矿物水化,避免了低渗致密砂岩中黏土矿物水化膨胀带来的流体敏感性损害;③驱油剂体系可对砂岩表面进行界面修饰,驱油剂溶液浸泡后样品的油相接触角由25.8°增加至61.4°,亲水性增强,亲油性减弱,有助于吸附在岩石孔隙壁面的油膜脱落;④超前注入驱油剂的注入压力降低率平均为79.64%,采收率平均为50.96%,远大于常规水驱(一次注水→注驱油剂驱→二次注水)的采收率。

水泥基材料无机纳米改性的研究进展

高性能水泥基复合材料的研究受到了广泛关注,纳米材料在促进水泥水化、提升水泥微观结构的致密性以及改善水泥基材料的力学性能和耐久性方面表现出色,赋予水泥基材料多样功能性的同时,减少水泥的添加量。从材料的机理层面出发,将不同维度的无机纳米材料对水泥基材料的水化、微观结构、力学性能以及耐久性等方面的影响进行了系统梳理,并展望了未来无机纳米材料改性水泥基材料的研究方向。

水化温升抑制剂对钙类膨胀剂变温膨胀效能的影响

研究了水化温升抑制剂TR01B对掺钙类膨胀剂砂浆性能的影响。结果表明:TR01B主要影响砂浆的早期抗压强度,对凝结时间也有一定的影响,但对后期抗压强度的影响较小;掺TR01B可以降低水泥早期水化放热速率峰值、温度峰值及放热量;TR01B能够调控钙类膨胀剂的膨胀效能,延缓了水泥早期水化产物的生成,同时不影响水泥后期的水化程度。