Evaluation of formation damages during filter cake deposition and removal process:The effect of primary damage on secondary damage

The properties of oil and gas formation could be significantly damaged during drilling and completion operations as a result of mud invasion,fluid incompatibility and interaction with rock minerals.This paper presents a systematic method for evaluating formation damage during filter cake deposition(primary damage)and removal process(secondary damage).The role of primary damage in the evolution of secondary damage was also investigated.The interaction of the filter cake solvent(chelating agent solution)with the rock samples was implemented through core flooding experiment.Nuclear Magnetic Resonance(NMR)was used to evaluate the properties of the rock sample,pre and post filter cake deposition and removal processes.The results show that secondary damaged is a strong function of the location and the intensity of the primary damage.The rock type and its pore structure also play important roles in both primary and secondary damage.The extent of secondary damage depends on the amount of barium sulphate deposited during primary damage.The chelating agent used to dissolve the barites in sandstones,deposited the barite in the small pores while it enlarges the bigger pores.In contrast,the chelating agent in the carbonate samples had multiple barite deposition points.

Physical properties and filter cake structure of fine clean coal from flotation

In order to improve the dewatering rate and the effect of fine clean coal(FCC), the advanced method offine coal( 0.5 mm) dewatering and the correlated basic theory were investigated in this study. It was found that the dewatering by sleeve type press filter was an efficient way of FCC dewatering. On the other hand, the results also proved that particle size distribution, volatile matter, ash content, pore size distribution and specific surface area of coal particles of FCC samples, as well as viscosity and density of FCC slurry, were important parameters in determining the process of efficient dewatering. Especially, wet mass to dry mass, specific resistance of average mass, compressibility factor and microstructure of filter cake explained the reasons and mechanisms of fine clean coal efficient dewatering.

The Influence of Surface Energy on the Washing Quality of Filter Cakes

The washing of filter cakes, especially the displacement washing, represents an important aspect in science researches and industrial applications. A lot of ongoing researches are focussed on impurities, which are dissolved in the mother liquid (e.g. sodium chloride) and washed out with the identical pure liquid without impurities. The project flushing focuses on systems with two chemically different liquids. The main aim is to exchange an organic solvent by water. This article focuses on the adsorption effects during a washing process with solid systems of different wetting behaviours.

DEM-CFD study of the filter cake formation process due to non-spherical particles

The formation of a filter cake during the filtration of a suspension with non-spherical particles is studied using a multi-sphere model in a simulation that couples the discrete element method with computational fluid dynamics.The implementation of the coupling with a drag model that considers orientation,sphericity,and the presence of surrounding particles for non-spherical particles is tested for single particles and suspensions by comparing the terminal velocities with empirical results.Phenomena predicted in the simulations,such as the presence or absence of initial oscillations and changes in the orientation of a particle,are consistent with experimental observations reported in the literature.The variation in the void fraction of a filter cake with respect to the particle sphericity is obtained and compared with experimental trends reported in the literature.Furthermore,complex interdependencies of the particle sphericity,void fraction,and pressure drop of a filter cake for a wide range of fluid conditions are investigated.

Effects of slurry viscosity and particle additive size on filter cake formation in highly permeable sand

Filter cake is critical to maintaining the stability of the excavation face of an underwater shield tunnel in a high-permeability stratum.In a high-permeability formation,generating an effective filter cake on the excavation face is difficult with a pure bentonite slurry,which penetrates the ground and may not achieve the required suspension pressure.Determining how to efficiently and quickly form a thin and low-permeability filter cake on the tunnel working face has become a key engineering problem in the construction of slurry shield tunnels in high-permeability strata.In this study,the relationship between slurry viscosity and the slurry pressure gradient of pure bentonite was established by performing slurry permeability experiments.The influence of slurry viscosity on the formation of the filter cake in a high-permeability formation was studied under different pressure gradients.In addition,the effect of additive particle size on the slurry filter cake formation was analyzed by introducing additives with different particle sizes to pure bentonite slurries with different viscosities.The test results indicate that(1)for the pure bentonite slurry,the critical initial pressure gradient can be used as a rough indicator of the formation of the filter cake,and the relationship between the critical maximum pore diameter and the average pore diameter of the for-mation can be compared to establish and analyze the formation law of the slurry filter cake;(2)adding particles to the slurry can enhance the effect of the pure bentonite slurry;and(3)adding coarse-grained materials can effectively improve the film-forming effect.The slurry is more compact when the particle size is close to the average pore size of the formation.

Image Analysis on Detachment Process of Dust Cake on Ceramic Candle Filter

Based on the analysis of high-speed video images, the detachment behavior of dust cake from the ceramic candle filter surface during pulse cleaning process is investigated. The influences of the dust cake loading,the reservoir pressure, and the filtration velocity on the cleaning effectiveness are analyzed. Experimental results show that there exists an optimum dust cake thickness for pulse-cleaning process. For thin dust cake, the patchy cleaning exists and the cleaning efficiency is low; if the dust cake is too thick, the pressure drop across the dust cake becomes higher and a higher reservoir pressure may be needed. At the same time there also exists an optimum reservoir pressure for a given filtration condition.

基于混凝预处理的超滤净水工艺研究进展

膜污染是超滤工艺大规模运用的主要限制性因素,介绍超滤膜净水工艺膜污染的原理及其污染物。详述基于混凝预处理的三种超滤膜工艺:传统超滤工艺、短流程超滤工艺、一体式絮体-超滤工艺。以短流程超滤工艺为重点,阐述近年来以混凝预处理工艺来缓解超滤净水工艺膜污染的研究成果。总结了滤饼层结构对膜污染的影响,以及混凝预处理缓解超滤膜污染的作用原理,为膜法水处理工艺技术工程应用提供参考。

压滤过程中煤泥滤饼结构演化规律及组合药剂优化机理

煤泥滤饼结构对脱水效果有重要影响,采用自制加压脱水装置及CT扫描等方法研究了压滤脱水过程中滤饼结构特性及其演化规律。将压滤过程修正为4个阶段,其中滤饼脱水阶段主要脱去滤饼内部水分,此阶段滤饼孔隙结构越发达则压滤脱水效果越好;滤饼压缩阶段主要对滤饼进行最后压缩,此阶段滤饼可压缩性越高,滤饼最终的孔隙率和含水量就越低。并采用聚合硫酸铁(PFS)和α-半水石膏(α-HH)对煤泥进行助滤实验。从煤泥颗粒絮团结构、滤饼物相组成、滤饼三维结构等多方面分析了助滤机理。结果表明:PFS和α-HH联合使用显著提升了煤泥的过滤效果,通过中心组合设计(CCD),确定了2者最佳药剂量为1711.44 g/t和48.33 mg/g。在最佳条件下,滤饼含水量降低至16.97%,过滤速度提高至145.89 mL/(s·m^(2))。α-HH的加入使滤液Zeta电位的绝对值降低到1.45 mV,从而降低了煤泥颗粒之间的静电排斥力,增强了PFS的絮凝效果,使絮状物的弦长增加到71~171μm。同时在PFS体系中,α-HH的水化反应被加速,形成大量二水石膏晶体,在煤泥絮体中形成交织的骨架,发挥了骨架构建体的作用,使煤泥压滤脱水指数(I_(CD))提升至176.30,增强了滤饼强度,使压滤过程中煤泥滤饼孔隙率从12.14%提高到14.39%,提高了煤泥滤饼的孔隙配位数及连通性从而提高了过滤效果。

复合药剂强化浮选精煤加压脱水效果研究

为了降低浮选精煤滤饼水分、加快成饼速度,选择分子量为700万的非离子型聚丙烯酰胺(PAM)和非离子型表面活性剂(L-64),采用分别添加和混合添加等加药方式,在实验室加压过滤系统进行了脱水试验。通过接触角测量、红外光谱测试、滤液表面张力测量和絮团形态观测的方式研究复合加药强化脱水的机理。结果表明:PAM能加快脱水速度但降水效果一般,L-64能明显降低精煤水分但过滤速度一般;复合添加药剂能有效减少成饼时间和降低滤饼水分,相同药剂添加量的情况下,先加PAM后加L-64更有利于降低滤饼水分,先加L-64后加PAM更有利于减少成饼时间。提出了基于滤饼水分和成饼速度的双目标脱水效率强化水平评价模型,给出了复合药剂的最佳用量。复合加药能提高煤表面的疏水性,降低滤液表面张力,并且形成疏松透气性良好的絮团结构,有利于煤颗粒间毛细水的脱除,具有降低滤饼水分、提高过滤速度的双重功效。

电晕驻极滤袋对荷电微细颗粒物捕集效率

本文利用单针-板电极负直流高压电晕放电装置对针刺毡滤袋进行电晕驻极处理,设计搭建了由线-板式预荷电器和驻极滤袋集尘装置组成的复合电/袋过滤实验平台,系统的研究了电晕驻极滤袋对未荷电、单极荷正电、单极荷负电以及双极荷电的0.3~10μm微细颗粒物捕集效率,对比了不同风速条件下驻极滤袋对不同荷电类型微细颗粒物捕集效率的稳定性.实验结果表明:相比于原始滤料捕集未荷电颗粒物,库仑作用的引入使得驻极滤料捕集荷电颗粒物具有更高的效率,尤其是对于粒径0.3μm颗粒物提升效果最为明显,荷正电、荷负电和双极荷电使其捕集效率从79.9%分别提升到99.9%、99.3%和98.6%;基于库仑力的静电捕集效率还能够补偿由于风速增大而造成的机械捕集效率降低幅度,对于粒径0.3μm颗粒物,荷正电、荷负电和双极荷电使其捕集效率差值从9.4%分别降低到0.06%、0.2%和5.2%.更具体地说,即库仑引力作用强于库仑斥力作用,且两者均优于异相荷电凝并作用.此外,利用扫描电镜技术分析了不同荷电类型颗粒物在驻极滤袋表面沉积的微观形貌结构,提出了相应的尘饼生长理想化模型用于进一步解释以上实验结果.该研究结果可为进一步发展静电-机械双效捕集脱除微细颗粒物提供参考.

陕西榆林废弃钻井液固液分离技术研究

采用稀硫酸作为破胶剂,通过室内抽滤实验对各种常用絮凝剂进行了优选,优化了废弃钻井液固液分离配方,即采用酸化破胶后加入3.09 g/L硫酸铝和3.09 g/L硫酸铁,能够将废弃钻井液进行脱稳分离。经陕西榆林现场应用表明,废弃钻井液应用此技术脱稳后,一次压滤成功,滤饼中平均含水量为31.79%。与前期固液分离效果相比,滤饼平均含水量降低了17.90%,废弃钻井液处理成本降低了10.21%。

带气吹卸除装置的搅拌罐式过滤机残余滤饼去除率的试验研究

针对搅拌罐式过滤机卸料后存在残余滤饼的问题,设计了一套带气吹卸除装置并进行试验,研究了不同喷嘴类型、喷嘴吹扫角度、喷嘴距离滤饼表面高度对残余滤饼去除率的影响。结果表明:在喷嘴类型选用槽缝式吹气喷嘴、喷嘴吹扫角度45°、喷嘴距离滤饼表面高度选择100 mm、气源压力0.3 MPa、吹扫时间15 min的条件下,残余滤饼去除率最高,该结果可为该装置的工业化应用提供参考。

一种扰动滤层的过滤装置研究

常规的固液两相过滤装置,由于滤渣在滤网上不断沉积,使用一段时间就会形成滤饼,一旦滤饼形成以后,过滤阻力会越来越大,需及时从过滤介质上清除滤饼,清除滤饼会造成过滤过程中断,配套设备复杂,操作麻烦等问题。本文针对常规过滤装置的存在的问题,提出一种滤层扰动过滤的思路,通入的两相流直接冲击滤饼层,过滤过程在滤饼层受到扰动的情况下持续进行,滤饼层的紧实度将小于通常过滤过程形成的滤饼层,从而提高了过滤效率和过滤的质量;同时在过滤器侧面增加滤网,可使滤清液能够在底部流通不畅的情况下通过侧面排出,延长过滤网清理、更换的时间,提高过滤效率。

钱塘江粉土对泥浆和泥膜渗透特性影响

杭州未来规划33条过江通道,多数采用泥水盾构技术,因为泥浆会在开挖面形成阻止地下水的泥膜。在实际工程中,钱塘江粉土会混入泥浆导致泥浆和泥膜的特性发生变化,可能导致工程事故的发生,针对这一现象,系统探讨钱塘江粉土对泥浆性能和泥膜渗透特性的影响,通过滤失试验分析比较16种不同压力下的泥浆试样,获得了泥膜的孔隙比-渗透系数-压力的相互关系参数,并计算了不同压力下不同泥浆形成的泥膜渗透系数。加入钱塘江粉土后,含有PAA-Na(1200)的泥浆粘度增大最明显,增大了1.79倍;而含有CPAM的泥浆所生成的泥膜平均渗透系数增大172倍,含有APAM的泥浆渗透系数缩小为原来1/20。钱塘江粉土的加入可能导致同样压力变化下渗透系数变化更小,为预防相关工程问题提供科学依据与解决方案。

A Study on Enhancement of Filtration Process with Filter Aids Diatomaceous Earth and Wood Pulp Cellulose

在这份报纸，为困难的固体 / 液体的材料提高过滤被过滤的研究，例如高度粘滞，高度象材料一样的 compactible 或胶化，被介绍。过滤器帮助硅藻的土和木浆纤维素被用来由在一个生物健康产品的过滤改进过滤器蛋糕结构和性质提高过滤并且一高度粘滞化学纤维聚合物融化产品。固体 / 液体的系统的性质，在不同流动的过滤评价，特定的蛋糕抵抗，蛋糕湿，过滤率，过滤为过滤器帮助选择和评估的混浊，和操作优化被调查。结果成功地被用于工业过程，并且能为类似的过滤应用程序被用作引用。

Theoretical Study and Analysis on Properties of Filter Aids

Pressure filtration and filter aids should be adopted in filtration of high-viscosity molten chemical fiber containing foreign materials and gel particles. Theoretical analysis and argumentations on manners of assisted filtration and specific requirements of filter aids are performed. Measurement and comparison on properties of several filter aids are also carried out, conclusions and suggestions are put forward.

柴油机DPF孔道内积碳层的运动及分布特性

为研究积碳层对柴油机颗粒捕集器(DPF)堵塞失效的影响,采用连续流体介质与固体颗粒层离散元耦合的方法,结合DPF可视化试验加以验证,研究DPF孔道内不同形状、尺寸和厚度的积碳层运动以及分布.结果表明:积碳层表面积越大,发生拥塞的位置越靠近孔道后段;圆形轮廓的积碳层易于相互堆叠,三角形轮廓的积碳层拥塞段会集中于孔道中段,正方形轮廓的积碳层拥塞段的结构较为稳定.积碳层长度与DPF进口孔径比例为0.5时,拥塞段的密度与长度会明显增加,但是拥塞段的稳定性会降低.随着积碳层厚度增加,拥塞段的位置会靠近孔道前段.

重晶石螯合解堵剂作用机理及其评价方法研究

以重晶石加重剂为主要成分的钻井液滤饼形成的重晶石堵塞是造成油气储层伤害、影响油气产量的主要因素之一。常规的酸化解堵措施难以溶解重晶石堵塞物,而研制高性价比的非酸螯合解堵剂并制定科学的解堵施工工艺是解决重晶石堵塞的有效工程手段。氨基多羧酸螯合剂通过与重晶石表面的钡离子形成强螯合物,促进重晶石的快速溶解,有助于解除重晶石滤饼堵塞。文章归纳了常见的氨基多羧酸螯合剂的结构特征,从螯合解堵机理角度认为DTPA对重晶石堵塞的油气井解堵效果最佳;同时分析了常用的螯合解堵剂评价方法的优缺点,建立了一套准确、简单、快捷的重晶石螯合解堵剂性能的评价方法。相比于其他评价方法,高温动态溶解率评价方法具有实验耗时短、对实验器材要求低、实验结果直观等优点,推荐使用高温动态溶解率评价方法去评价螯合解堵剂的性能。