納米材料如何應用于潤濕性變換.doc

原文；鏈接：JPT 2015年12月P74-75摘要：文章回顧了改變巖心潤濕性的幾類方法，概括性介紹了用于潤濕性改變納米材料的分類、作用方式、流體載體和存在的問題。A Study of Wettability-Alteration Methods With Nanomaterials Application納米材料如何應用于潤濕性變換The use of nanomaterials for alteration of wettability is a method that has grown in prominence after the development of techniques 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 in terms of efficiency on incremental oil recovery in waterflooding. 納米尺度的粒子合成技術在1980年代末發(fā)展后，使用納米材料改變潤濕性的方法也已取得突出進展。本文在介紹潤濕性改變的基本原理之后，討論納米材料是如何用于潤濕性改變的。眾多納米材料之中，納米二氧化硅和有機硅聚合物在幫助提高水驅采收率上有著更好的作用效果。Introduction介紹Wettability is the tendency of a fluid to spread over a specific surface and is relative to 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/oil/rock interactions in a reservoir. There are different types of rocks on the basis of these interactions and wettabilities: 潤濕性是一種流體相對于其他存在的流體系統(tǒng)分布在特定表面一個趨勢。可由液體的液滴與表面的接觸角作為定義。這是流體和巖石礦物之間的粘附力作用的結果。巖石的潤濕性范圍從強烈親水到強烈親油，并且是由于鹽水/石油/儲層巖石相互作用而成的。在這些交互作用和潤濕性基礎上，有多種不同類型的巖石。1. If no, or equal, tendency is shown from oil or brine to spread over the surface of the rock, the system is said to have neutral wettability or intermediate wettability. 1如果從石油或鹽水在巖石表面?zhèn)鞑ペ厔輿]有或者顯示相同的情況下，這個系統(tǒng)可稱為中等潤濕或中間潤濕性。2. Because different mineralogies coexist in an oil reservoir, different wettabilities are also expected. If this 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 behavior. This heterogeneous wettability behavior is known as fractional wettability. 2由于不同的礦物在同一油藏中共存，所以不同的潤濕性是也是如此。如果這種多樣化潤濕性在油藏中不可忽略，那么，在油藏的不同部位，可觀察到流體和巖石之間的不同的化學作用。因此，一些區(qū)域的儲層出現(xiàn)強親水特征，而其他區(qū)域則表現(xiàn)為強親油。這種非均勻潤濕行為稱為部分潤濕性。3. In some cases, the smaller pores are occupied by water and can be considered water-wet, 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在某些情況下，較小的孔隙被水填滿，可以被認為是親水的，而更大的毛孔被石油占據(jù)。這種類型的潤濕性分布稱為混合潤濕，一般這種類型的油藏殘余油飽和度較低，因為石油更容易從大孔隙中被驅出。 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. 固體/液體和液體/液體表面能量是由流體和巖石的化學成分決定的。換句話說，巖石礦物組成和流體的化學性質影響相對粘附張力，進而影響潤濕性。 The most common methods for wettability measurements, discussed in detail in the complete paper, include the following: 最常見的潤濕性測量方法在完整的論文里做了詳細討論，包括： 1. Amott wettability index 1。Amott潤濕指數(shù) 2. US Bureau of Mines （USBM） wettability index 2。美國礦山局（USBM）潤濕性指數(shù) 3. Combined Amott-USBM wettability test 3結合Amott-USBM潤濕性測試 4. Contact-angle methods 4接觸角法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 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. 因為任何潔凈的巖石都表現(xiàn)出親水行為，因為可以判斷所有油藏最初都是水濕的。水后來被運移進來的油所替代，有時會有一個從初始的水濕轉向相對親油的傾向。一些石油極性組分隨后起到表面活性劑的作用，穿透薄膜孔隙水然后強烈的吸附在巖石表面上。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. 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）. 基于礦物的組分構成，一些巖石有親水或親油性質。在親水介質中，水占據(jù)小孔隙并且覆蓋大孔隙的表面，而油則是在大孔隙中，并與上述水表面直接接觸。大孔隙中的水相對滲透率小，無論是在水驅之前（因為存在的油禁止水流動）還是水驅之后（因為殘余油飽和度阻礙水相對滲透率）。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 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 significant. 在一個親油系統(tǒng)中，液體的位置正好是相反的。當注水驅替時，水相對滲透率在較大的孔隙內增加，而且比在親水系統(tǒng)中更加阻礙石油的滲流速度。換句話說，與親水系統(tǒng)相比，親油系統(tǒng)不適合注水開發(fā)，因為大量石油將在水突破生產井后傾向于存留在親油系統(tǒng)內。此時如果油水粘度比又很高，將造成明顯的水線突破過早、殘余油飽和度過高的問題。Wettability-Alteration Methods 潤濕變換方法Several methods are used to alter wettability. Most of these methods cannot be used in large scale 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. 多種方法可用于改變潤濕性。這些方法大多數(shù)由于成本過高不能大規(guī)模使用，只能用于實驗室?guī)r心實驗，得到不同潤濕性的小塊巖心。這些潤濕變換方法包括以下幾種。Treatment With Organosilanes. Organo-silanes 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. 有機硅烷處理法。有機硅烷在不同行業(yè)被廣泛用作潤濕改變的試劑。在其他領域，他們是作為疏水性試劑，在石油工業(yè)可以被解釋為油潤濕劑。Treatment With Naphthenic Acids. 環(huán)烷酸處理法。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 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. 環(huán)烷酸是帶有大量有機化合物的長鏈，是指所有的在原油標簽羧酸，粘滯且完全不溶于水，但溶于有機溶劑和石油。因為他們有毒性、危害環(huán)境且粘度高，只可以用在實驗室尺度改變潤濕性。在一般情況下，環(huán)烷酸能和鈣碳酸鹽發(fā)生反應使碳酸鹽巖更親油，但在硅質砂巖中則產生相反的變化。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 turned 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. 瀝青質處理法。瀝青質是原油中的重質組分，被認為是極性物質。如前文所提到的，所有的巖石被認為最初是親水的，然而在油運移期間其中一些部分變?yōu)橛H油。原油中瀝青質的存在便是潤濕性改變的原因之一。瀝青質破壞的薄膜水并吸附在大孔隙的巖石表面，可導致大孔隙親油。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 thick 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 reservoirs 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 exhibit more-water-wetting behavior and higher recoveries may result. The water front locates the wetting transition. 加熱法。原油在運移期間，親水巖石只是部分變?yōu)橛H油巖石，當儲層達到臨界毛細管壓力時，原油重質組分可透過孔隙表面上的厚水膜，沉積在巖石表面，使表面親油。這個過程可以通過加熱硅酸鹽巖逆轉。加熱可使沉積（吸附）物質解吸，留下親水表面。大多數(shù)的天然裂縫性儲層表現(xiàn)為油濕，因此在這種儲層中注水是不會有效的。水只會通過裂縫然后被巖石基質吸收，導致采收率非常低。然而，通過注入熱水或蒸汽，儲層系統(tǒng)可能會變?yōu)樗疂?，采收率提高。注水前緣位于潤濕過渡帶。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 surfactants 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 can be reduced or the wettability can be shifted toward a more-water-wetting system， which improves the recovery factor. 表面活性劑法。表面活性劑是唯一的同樣可用于大規(guī)模改變潤濕性提高采收率的材料。通過使用這些表面活性劑和腐蝕劑，界面張力降低，更多的石油產出。然而，由于這些表面活性劑的吸附消耗、與鹽水中二價陽離子相互作用沉淀，導致只能提高5%的石油產出。因為殘余油飽和度高，在一個親油油藏注水效果通常很差。然而，通過表面活性劑的使用，可以減少界面張力或造成潤濕性反轉，提高采收率。Wettability Alteration With Nanomaterials 納米材料改變潤濕性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 the method to become more expensive and less feasible. 使用納米材料是近期的改變潤濕性的方法，在很多情況下作用效果顯著。因為粒子的尺寸降低，它們的有效性大大提高。遺憾的是，這種精密的改變潤濕性的方法更加昂貴和不實用。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 specific 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. 在大多數(shù)情況下，改變巖石的潤濕性是為了得到更好的原油采收率，然而，在少數(shù)情況下（主要是實驗），達到某種特定的表面潤濕性十分必要，因此特定的潤濕性表面的制造也是必要的。納米結構調整表面的潤濕性可以通過電化學方法，等離子體蝕刻或電子噴霧來實現(xiàn)。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）， and hydrophobic lipophilic polysilicone （HLP）. Nanopolysilicone（NPS）是一種用于改變巖心的潤濕性室的納米顆粒。NPS分為三種：疏水性和親水性有機硅聚合物（LHP）、中等潤濕性有機硅聚合物（NWP）和疏水親脂性有機硅聚合物（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 oil 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 surface 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，親油系統(tǒng)將被改為親水，這將增加油的相對滲透率，降低水相對滲透率。這種情況利于水驅過程。NWP吸附降低了表面張力，一般來說增加油相對滲透率，也是有利的。然而， HLP的吸附是不利的，因為它使孔隙表面親油，這將增加水驅過程中殘余油飽和度。HLP以擴散和對流方式運移，隨著時間積累，會造成孔隙堵塞，降低孔隙度、絕對滲透率。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