纳米材料如何应用于润湿性变换

1、原文；链接：JPT 2015年12月P74-75摘要：文章回顾了改变岩心润湿性的几类方法，概括性介绍了用于润湿性改变纳米材料的分类、作用方式、流体载体和存在的问题。A Study of Wettability-Alteration Methods With Nanomaterials Application纳米材料如何应用于润湿性变换The use of nanomaterials for alteration of wettability is a method that has grown in prominence after the development of techniques

2、for synthesizing nanosized particles in the late 1980s. In this paper, after a review of the fundamentals of wettability alteration, a discussion of nanomaterials used for wettability alteration is provided. Among these nanomaterials, nanoparticles of silica and polysilicone indicate better results

3、in terms of efficiency on incremental oil recovery in waterflooding. 纳米尺度的粒子合成技术在1980年代末发展后，使用纳米材料改变润湿性的方法也已取得突出进展。本文在介绍润湿性改变的基本原理之后，讨论纳米材料是如何用于润湿性改变的。众多纳米材料之中，纳米二氧化硅和有机硅聚合物在帮助提高水驱采收率上有着更好的作用效果。Introduction介绍Wettability is the tendency of a fluid to spread over a specific surface and is relative to

4、other existent fluids in that system and is defined by the contact angle of a droplet of the fluid and the surface. It is a result of adhesion forces between the fluid and the minerals of the rock. The wettability of a rock ranges from strongly water-wet to strongly oil-wet and is a result of brine/

5、oil/rock interactions in a reservoir. There are different types of rocks on the basis of these interactions and wettabilities: 润湿性是一种流体相对于其他存在的流体系统分布在特定表面一个趋势。可由液体的液滴与表面的接触角作为定义。这是流体和岩石矿物之间的粘附力作用的结果。岩石的润湿性范围从强烈亲水到强烈亲油，并且是由于盐水/石油/储层岩石相互作用而成的。在这些交互作用和润湿性基础上，有多种不同类型的岩石。1. If no, or equal, tendency is s

6、hown from oil or brine to spread over the surface of the rock, the system is said to have neutral wettability or intermediate wettability. 1如果从石油或盐水在岩石表面传播趋势没有或者显示相同的情况下，这个系统可称为中等润湿或中间润湿性。2. Because different mineralogies coexist in an oil reservoir, different wettabilities are also expected. If thi

7、s variety in the reservoir is not negligible, then, in different parts of the reservoir, different chemical interactions between fluids and rocks are observed and, consequently, some areas of the reservoir indicate strongly water-wet behavior whereas some other areas indicate strongly oil-wet behavi

8、or. This heterogeneous wettability behavior is known as fractional wettability. 2由于不同的矿物在同一油藏中共存，所以不同的润湿性是也是如此。如果这种多样化润湿性在油藏中不可忽略，那么，在油藏的不同部位，可观察到流体和岩石之间的不同的化学作用。因此，一些区域的储层出现强亲水特征，而其他区域则表现为强亲油。这种非均匀润湿行为称为部分润湿性。3. In some cases, the smaller pores are occupied by water and can be considered water-wet,

9、 while larger pores are captured by oil. This type of wettability distribution is known as mixed wettability, in which the residual oil saturation is low because the oil is displaced more easily from larger pores. 3在某些情况下，较小的孔隙被水填满，可以被认为是亲水的，而更大的毛孔被石油占据。这种类型的润湿性分布称为混合润湿，一般这种类型的油藏残余油饱和度较低，因为石油更容易从大孔隙

10、中被驱出。 The solid/fluid and fluid/fluid surface energies are governed by the chemical compositions of the fluid and rock. In other words, the mineralogy of a rock and chemical properties of the fluid influence the relative adhesive tensions and, consequently, wettability. 固体/液体和液体/液体表面能量是由流体和岩石的化学成分决定

11、的。换句话说，岩石矿物组成和流体的化学性质影响相对粘附张力，进而影响润湿性。 The most common methods for wettability measurements, discussed in detail in the complete paper, include the following: 最常见的润湿性测量方法在完整的论文里做了详细讨论，包括： 1. Amott wettability index 1。Amott润湿指数 2. US Bureau of Mines （USBM） wettability index 2。美国矿山局（USBM）润湿性指数 3. Comb

12、ined Amott-USBM wettability test 3结合Amott-USBM润湿性测试 4. Contact-angle methods 4接触角法Because any clean rock exhibits water-wetting behavior, it is believed that all petroleum reservoirs were initially water-wet. This water was later displaced by oil because of migration, and sometimes there is a shift

13、to relatively oil-wet compared with the initial wetting tendency. Some polar components of oil then act as surfactants and penetrate through the thin film of water on the pore surfaces and adsorb strongly on the rock. 因为任何洁净的岩石都表现出亲水行为，因为可以判断所有油藏最初都是水湿的。水后来被运移进来的油所替代，有时会有一个从初始的水湿转向相对亲油的倾向。一些石油极性组分随后

14、起到表面活性剂的作用，穿透薄膜孔隙水然后强烈的吸附在岩石表面上。On the basis of the component minerals, some rocks have water-wetting or oilwetting natures. In a water-wet medium, water captures the small pores and also coats the surface of the larger pores while oil filaments are in the larger pores on the mentioned water surface

15、. The water relative permeability in larger pores is small both before coreflooding （because presence of oil prohibits water mobility） and after coreflooding （because the residual oil saturation impedes water relative permeability）. 基于矿物的组分构成，一些岩石有亲水或亲油性质。在亲水介质中，水占据小孔隙并且覆盖大孔隙的表面，而油则是在大孔隙中，并与上述水表面直接接

16、触。大孔隙中的水相对渗透率小，无论是在水驱之前（因为存在的油禁止水流动）还是水驱之后（因为残余油饱和度阻碍水相对渗透率）。In an oil-wet system, the positions of the fluids are reversed, and during waterflooding, the water relative permeability in larger pores increases and impedes the oil movement faster than in a water-wet system. In other words, an oil-wet

17、system is not a good candidate for waterflooding compared with a water-wet system because more oil would reside in an oil-wet system after water breakthrough. In some cases in which the oil-/water-viscosity ratios are high, breakthrough happens very early and the residual oil saturation becomes sign

18、ificant. 在一个亲油系统中，液体的位置正好是相反的。当注水驱替时，水相对渗透率在较大的孔隙内增加，而且比在亲水系统中更加阻碍石油的渗流速度。换句话说，与亲水系统相比，亲油系统不适合注水开发，因为大量石油将在水突破生产井后倾向于存留在亲油系统内。此时如果油水粘度比又很高，将造成明显的水线突破过早、残余油饱和度过高的问题。Wettability-Alteration Methods 润湿变换方法Several methods are used to alter wettability. Most of these methods cannot be used in large scale

19、because of their expense and are only used to treat small cores for experiments that require cores of different wettabilities. These wettability-alteration methods include the following. 多种方法可用于改变润湿性。这些方法大多数由于成本过高不能大规模使用，只能用于实验室岩心实验，得到不同润湿性的小块岩心。这些润湿变换方法包括以下几种。Treatment With Organosilanes. Organo-si

20、lanes are widely used as wettability-altering agents in different industries. In other fields, they are used as hydrophobic agents, which can be interpreted as oil-wetting agents in the petroleum industry. 有机硅烷处理法。有机硅烷在不同行业被广泛用作润湿改变的试剂。在其他领域，他们是作为疏水性试剂，在石油工业可以被解释为油润湿剂。Treatment With Naphthenic Acids

21、. 环烷酸处理法。Naphthenic acids are long chains of heavy organic compounds; the label refers to all the carboxylic acids seen in crude oil. They are viscous and insoluble in water but completely soluble in organic solvents and oil. Because of their toxicity, environmental hazards, and high viscosity, they

22、 can be used only in laboratory scales to alter wettability. In general, naphthenic acids make a carbonate core more oil-wet because of the reaction of the naphthenic acid and calcium carbonates. However, silica cores show the opposite behavior. 环烷酸是带有大量有机化合物的长链，是指所有的在原油标签羧酸，粘滞且完全不溶于水，但溶于有机溶剂和石油。因为他

23、们有毒性、危害环境且粘度高，只可以用在实验室尺度改变润湿性。在一般情况下，环烷酸能和钙碳酸盐发生反应使碳酸盐岩更亲油，但在硅质砂岩中则产生相反的变化。Treatment With Asphaltenes. Asphaltenes are heavy componenets of crude oil that are considered polar. As mentioned previously， all rocks are considered to be initially water-wet， although during oil migration some of them tur

24、ned partially oil-wet. Presence of asphaltenes in crude oil is one of the reasons for this wettability alteration. Asphaltenes rupture the thin film of water and are ad-sorped to the rock surface in large pores， which can cause the larger pores to exhibit oil-wetting behavior. 沥青质处理法。沥青质是原油中的重质组分，被认

25、为是极性物质。如前文所提到的，所有的岩石被认为最初是亲水的，然而在油运移期间其中一些部分变为亲油。原油中沥青质的存在便是润湿性改变的原因之一。沥青质破坏的薄膜水并吸附在大孔隙的岩石表面，可导致大孔隙亲油。Thermal Methods. During the oil migration that turned water-wet rocks to partially oil-wet rocks， when a critical capillary pressure was reached， the heavy oil components penetrated through the thic

26、k water films on the pore surfaces and， by deposition on the surface， made the surface oil-wet. This process can be reversed by heating in silicate rocks. Heating causes the deposited （adsorbed） active agents to be desorbed， leaving a water-wet surface again. Most of the naturally fractured reservoi

27、rs show oil-wetting behavior， and， therefore， waterflooding would not be successful in these systems. Water will imbibe into the cores but will only pass through the fractures and result in very low recoveries. However， by heating the reservoir by hot water or steam injection， the system could exhib

28、it more-water-wetting behavior and higher recoveries may result. The water front locates the wetting transition. 加热法。原油在运移期间，亲水岩石只是部分变为亲油岩石，当储层达到临界毛细管压力时，原油重质组分可透过孔隙表面上的厚水膜，沉积在岩石表面，使表面亲油。这个过程可以通过加热硅酸盐岩逆转。加热可使沉积（吸附）物质解吸，留下亲水表面。大多数的天然裂缝性储层表现为油湿，因此在这种储层中注水是不会有效的。水只会通过裂缝然后被岩石基质吸收，导致采收率非常低。然而，通过注入热水或蒸汽，储

29、层系统可能会变为水湿，采收率提高。注水前缘位于润湿过渡带。Surfactants. Surfactants are the only materials also used on a large scale to alter the wettability and improve the recovery. By use of these surfactants and caustics， the interfacial tension is reduced and more oil is produced; however， because of adsorption of these su

30、rfactants and the precipitation caused by the presence of divalent cations in the brine， only 5% incremental oil is produced. Because of the high residual oil saturation， an oil-wet reservoir is typically not a good candidate for waterflooding; however， by use of surfactants， the interfacial tension

31、 can be reduced or the wettability can be shifted toward a more-water-wetting system， which improves the recovery factor. 表面活性剂法。表面活性剂是唯一的同样可用于大规模改变润湿性提高采收率的材料。通过使用这些表面活性剂和腐蚀剂，界面张力降低，更多的石油产出。然而，由于这些表面活性剂的吸附消耗、与盐水中二价阳离子相互作用沉淀，导致只能提高5%的石油产出。因为残余油饱和度高，在一个亲油油藏注水效果通常很差。然而，通过表面活性剂的使用，可以减少界面张力或造成润湿性反转，提高采收

32、率。Wettability Alteration With Nanomaterials 纳米材料改变润湿性Use of nanomaterials is a recent， and in many cases highly effective， method of wettability alteration. Because the sizes of particles are reduced， their effectiveness is greatly increased. However， this precision in wettability alteration causes

33、the method to become more expensive and less feasible. 使用纳米材料是近期的改变润湿性的方法，在很多情况下作用效果显著。因为粒子的尺寸降低，它们的有效性大大提高。遗憾的是，这种精密的改变润湿性的方法更加昂贵和不实用。In most cases， the wettability of a core has to be modified to reach a preferable oil recovery; however， in some rare cases （mostly experimental）， a surface with a s

34、pecific wettability is needed and therefore the fabrication of surfaces with a specific wettability is required. Adjusting the wettability of a surface by nanostructures while it is being fabricated can be achieved by electrochemical methods， plasma etching， or electrospraying. 在大多数情况下，改变岩石的润湿性是为了得到

35、更好的原油采收率，然而，在少数情况下（主要是实验），达到某种特定的表面润湿性十分必要，因此特定的润湿性表面的制造也是必要的。纳米结构调整表面的润湿性可以通过电化学方法，等离子体蚀刻或电子喷雾来实现。Nanopolysilicone （NPS） is a nanoparticle used to alter the wettability in cores. NPSs are classified into three groups: lyophobic and hydrophilic polysilicone （LHP）， neutrally wetting polysilicone （NWP

36、）， and hydrophobic lipophilic polysilicone （HLP）. Nanopolysilicone（NPS）是一种用于改变岩心的润湿性室的纳米颗粒。NPS分为三种：疏水性和亲水性有机硅聚合物（LHP）、中等润湿性有机硅聚合物（NWP）和疏水亲脂性有机硅聚合物（HLP）。By adsorption of LHP on the pore surface， the oil-wetting system would be altered to water-wet， which would increase the relative permeability of oi

37、l and decrease the oil relative permeability. This situation is favorable in a waterflooding process. NWP adsorption reduces the surface tension and increases the oil relative permeability generally， which is also favorable. However， adsorption of HLP is not favorable because it makes the pore surfa

38、ce oil-wet， which would increase the residual oil saturation in a flooding process. HLPs are transferred by diffusion and convection， and， in the case of accumulation， they would cause pore blockage and reduction in porosity and absolute permeability. LHP在孔隙表面吸附，亲油系统将被改为亲水，这将增加油的相对渗透率，降低水相对渗透率。这种情况利于水驱过程。NWP吸附降低了表面张力，一般来说增加油相对渗透率，也是有利的。然而， HLP的吸附是不利的，因为它使孔隙表面亲油，这将增加水驱过程中残余油饱和度。HLP以扩散和对流方式运移，随着时间积累，会造成孔隙堵塞，降低孔隙度、绝对渗透率。HLP makes a system more oil-wet， and， in contrast， LHP makes a system more water-wet. By adding LHP to a water-wet system， the media become extremely water-wet， which would hin