Influence of Drilling Fluid on oil Recovery in Homogenous Reservoirs - Essay Example

? Influence of Drilling Fluid on oil Recovery in Homogenous Reservoirs Mining industries around the globe are under constant scrutiny as far as the treatment of contaminated water is concerned. There is mounting pressure for mining industries to adopt effective and advanced methods that are environmentally sustainable. Water management has often been the most challenging, as well as long term environmental liability. Needless to say, as significant as 70 percent produce of mines in the world, produce water contaminated by metals, which come from acid mines drainage and process streams (Srivastava & Majunder, 2008). The waste water, such as that containing metal and sulphate contaminates, are accompanied by far reaching environmental consequences. Moreover, the costs associated with managing these consequences are significant. This paper gives an overview of water contamination in the mining industries, followed by an exploration of the common methods under development and operation. Considering that current water treatment techniques have varied limitations, this paper proposes a way forward for mining industries to avoid water contamination. There are various elements within the earth crust, which include hydrogen, carbon, nitrogen, sodium, magnesium, phosphorous, sulphur, chlorine, potassium and calcium. These constitute 99 percent of the earth living matter. On the other hand, there are fourteen essential elements. These include boron, fluorine, silicon, manganese, iron, cobalt, and copper, among others. Metals such as Mercury, lead, cadmium, arsenic, chromium, copper manganese and zinc are not essential, and their interaction with the aquatic environment is hazardous. On the other hand, heavy metals are a class of metallic elements that contain relatively high densities whose low concentrations are highly toxic. The atomic metals have atomic weight that range from 63.5 to 2006. Heavy metals can are additionally classified as toxic metals, precious metals and radio-nuclide. Radionuclides include uranium and thorium. Precious metals include silver and gold, among others (Srivastava & Majunder, 2008). Acid solutions result from the interaction of the ground or of surface water with the acidic materials, such as pyrites that are found in rocks at the mines, piles of earthen refuse and auger holes. The iron sulphide mineral pyrites are usually found near subsurface coal seams, together with compounds containing aluminium and manganese, among other metals. In the presence of oxygen, rainwater or ground waters contact sulphur to form sulphuric acid. Acid concentration in the acid mine drainage can reach as significant levels such as ten thousand times the neutral water. Evidently, this presents a powerful leaching agent with the potential of dissolving significant amounts of metal substances, as well as additional leaching substances that are common at most mine sites. Rock layers and earth above the coalmines contain traces of metals such as iron, aluminium and manganese, but can also contain other heavy metals such as lead and cadmium (Han & Chan, 2006). These metals dissolve in the acid mine drainage and are washed into water sources through run off. Eventually, such metal concentrations harm aquatic organisms such as fish. For instance, dissolved iron precipitates can kill aquatic organisms that serve as food for fishes. Iron precipitate can result in fish gill clogging. Additionally, iron precipitation in the drainage channels alter aquatic food chains; thereby adversely affecting fish populations. Treatment of waste water The concern for environmental scientists has been to establish possible ways of regulating hazardous metal concentrations and mitigate associated environmental concerns. Methods in the treatment of the acid mine drainage can be broadly categorized into two; active treatment and passive treatment methods. Active techniques entail mechanical addition of the alkaline solutions with the aim of raising PH concentrations besides precipitating metals. Passive treatment techniques entail natural chemical and biological reactions that take place in the micro-biological controlled chemical reactors. These processes take place without mechanically powered assistance. The undesirable consequences of heavy metals and cyanide pollution can be mitigated by treating water before discharging. Basing on their toxicity and regulatory demands, it is imperative for mining firms to remove metal contaminants from water before releasing them into environments. So far, the available treatment techniques are as follows. Heavy metal removal and recovery The Physicochemical heavy metal removal techniques The current common, conventional method of separating heavy metal anions from waste waters entail coagulation-flocculation, chemical precipitation, filtration, flotation, reverse osmosis, evaporation recovery, electrostatics, electrochemical processes and ion exchange. According to Han, Chan, 2006), it is possible to apply hybrid processes of electro coagulation and membrane filtration to separate heavy metals form water. Despite the fact that their treatment method can be applied in the waste water treatment, Precipitation is the most common method of the mentioned methods since it is also the most economical. However, the technique entails the production of the significant amounts of sludge that requires additional treatment. Ion exchange and reverse osmosis effective reduce heavy metal ion concentration in waste waters, but their applications are limited and subject to various advantages such as high operational and material costs, to add to limited ph ranges for the ion exchange resins Reverse osmosis Reverse osmosis has the capacity to remove both inorganic and organic compounds. Its removal mechanisms are aided by its high rejection rates. Additionally, removal osmosis can withstand high temperatures. The inherent shortcomings are that the process requires high pressure, a phenomenon associated with high energy consumption. Additionally, the high pressures make the system susceptible to fouling of membranes. Electro dialysis Electro dialysis process can be used to remove heavy metals from waste water. It is effective and suitable for metal concentration less than 20 milligrams per litre. However, the end results are accompanied by the formation of the metal hydroxides. Moreover, the process entails high energy cost, to add to the fact that these methods can not be applied for metal concentrations beyond 1000 milligrams per litre. Ultra filtration Ultra filtration process can be applied for the removal of metal compounds with relatively high molecular weights. The technique requites relatively small spaces. However, it is associated with high operation costs; it is prone to membrane fouling and involves sludge generation that requires disposal. Ion exchange Ion exchange technique can be applied in the removal of dissolved compounds. The process is advantageous because it does not entail generation of sludge; hence, it time consuming. However, not all ion exchange resins techniques are effective for metal removal. Additionally, they are accompanied by high capital costs. Chemical precipitation Precipitation can be applied in the removal of heavy and divalent metals. It is advantageous since it is simple and requires relatively low capital costs. However, the process entails sludge generation; hence, high operation costs that follow sludge disposal. Coagulation-flocculation Coagulation-flocculation can be utilized in the removal of heavy and suspended solids. This process takes the short time for settling out suspended solids; hence, improved sludge production. Since sludge generation, it is subject to relatively high operation costs associated with the disposal of sludge. Dissolved air flotation Dissolved air flotation can be applied in the removal of metals and suspended solids. It is a relatively cheap process with short hydraulic retention times. However, it requires subsequent treatments so as to improve efficiency of heavy metal removal. Nano-filtration can be applied in the removal of metal sulphate salts. The method is effective for the removal of water hardness associated with magnesium (ii) and calcium (ii) ions. The technique processes are effective even when under as low pressures as 7 bar but is associated with high capital, as well as operational costs. Electrochemical precipitation Electrochemical precipitation technique is suitable for the removal of heavy metals. This technique is not affected by acidic and basic conditions. Additional, the method is applicable for the treatment for high concentrations such as 2000 milligrams per litre but requires high capital investment to add to high operational costs. Membrane electrolysis Membrane electrolysis technique can be applied in the removal of metal impurities. This technique can effectively treat waste water with metal concentrations as low as 10 milligrams per litre. On the other hand, it can effectively treat concentrations as high as 2000 milligrams per litre. However, the technique is disadvantageous because it is associated with high energy consumption. Even so, mine waste treatment technologies can be classified into two; waste containment and prevention technologies and waste treatment technologies. The following methods are currently applicable whereas some are under development. Heavy metal Sorption and Bio sorption techniques The quest for new technologies pertaining to the elimination of toxic chemicals from water has shifted concentration to the bio sorption, processes based on the binding capacities of metal on various biological materials. Bio sorption techniques demonstrate a particularly high potential of replacing the conventional technologies of heavy metal removal from waste waters. This is reflected in its cost effectiveness, availability of bio sorbent biomass, as well as efficiency. Bio sorption is the process of removal of metals, metalloid species, particulates and compounds from solution by use of biological materials. Currently, natural and industrial wastes are attracting attention as cheap sorption materials. Sorption processes facilitated by Microorganisms Micro organisms applied in these processes include prokaryotes and eukaryotes. Like all organic cells, microbial cells absorb metal ions. However the capacities of sorption among these cells are highly varied and depend upon the nature of non-microbial biomass and non-microbial biomass, as well as microbial organisms (Han & Chan, 2006). There are two distinguishable processes; bioaccumulation and bio-absorption. In the events of bioaccumulation, metals are accumulated within the cells wherein the transportation of metals across cell membranes has to be metabolically active. On the other hand, bio sorption entails binding of the metal organic matter, a process that does not require energy. For the micro organism’s case, metals are usual fixed to functional groups that lie outside of the cell walls and include carboxyl, amine and hydroxyl groups. Mechanisms that contribute bio sorption include ion exchange, adsorption, electrostatic interaction and precipitation. Non viable microbial biomass show high affinities for metal ions compared to viable cells, and this is attributable to the absence of competing protons that could be produced during metabolic reactions. Besides sorption by the cell wall, metals can also get attached to organic substances or extracellular polymeric compounds, as well as compounds produced by metabolically-active organisms. Sorption processes using non living biomass Most current studies pertaining to sorption have inclined on microbial systems such as those consisting of micro algae, bacteria, and fungi (Sengil & Ozacar, 2004). Even so, all organic substances exhibit high affinity for metal species. The process of bio-sorption using non living biomass is fast and entails solid phase, which consists of bio-sorbent or sorbent materials; and liquid phase, which contains solvents materials such as water. Considering that there is the high affinity for sorbent material for the sorbate species, the sorbate is attracted to the sorbent and bound through various mechanisms. The degrees of sorbent affinities sorbate species is a determinant for the distribution between the liquid and solid phases (Sengil & Ozacar, 2004). Sorption by Natural and Inorganic Sorbents Both locally-available natural material and industrial products that are can be utilized as low cost adsorbents. Natural materials such as clay and zeolite have been widely applied in the treatment of waste water following their high capacity of metal binding. According to Han & Chan, 2006), zeolite treated with sodium chloride has improved removal capacity for metal ions such as chromium compared to zeolite alone. This points out that the chromium adsorption capabilities are dependent on the extent of chemical treatment of the sorbents. It has also been established that metal removal processes by zeolite involved complex processes such as adsorption and ion exchange. On the other hand, clay is also perceived as a mineral with a high capacity of ion exchange. There are three types of clay that can be applied in the sorption processes. These are bentonite, kaolinite and montmorillonite. Montmorillonite has the highest ion exchange capacity compared to other clay types (Wilhelm, Mack, Dunkan & Burgese, 2009). Alkalinity producing systems (APS) APS utilize the combination of the anaerobic compost wetland and anoxic limestone drain. This technique entails pond water with a depth of 3 to 6 feet that overlie an 18 inch organic material layer, which is usually the compost with 18 to 24 inches. Acid water is added over the materials resulting to the creation of head by the column of water, which then forces the through organic materials. In this process, ferric ions are precipitated and oxygen is consumed following the decomposition of organic matter. Alkalinity could be increased by the reduction processes of the sulphates and iron. The resultant acid water, which mainly contains ferric ions and dissolved oxygen having filtered through the organic substrates, is directed into the limestone layer that lies under the organic matter. Waste water prevention and containment technologies Dewatering Dewatering technique entails removal of principal reactants contained in pyrite oxidation, a process that theoretically stops the production of acid mine drainage. It is expectable that no contamination occurs when there is no water to move the reaction products from the pyrite surfaces. Despite the fact that the processes of complete removal of water is natural impossible, reduction in the amount of water interacting with the pyritic materials can significantly mitigate the effect of acid mine drain on water bodies. The removal of water to limit contact with pyritic material could entail pumping. Otherwise, the process could also entail quick drainage of water from the pyritic materials to avert reactions that result into formation of acids. High wall drains, French drains, chimney drains and bottom drains are some of the reliable methods that can be effective; applied in the in the moving water from refuse, fills and spoils (Gonzalez, Araujo, Pelizaro, Lemos & Souza , 2008). Re-vegetation Establishment of vegetation is a pivotal process in the reclamation of acid land mines. This process is effective in checking on soil erosion and encourages mine soil re-development. However, the effectiveness of the re-vegetation process may be subject to selection and placement of mine soils suitable for the post mining vegetation, as well as selecting vegetation varieties that are suitable for the mine soils and subsequent land activities. Plastic lining and soil cover techniques This technique entails the creation of covers consisting man made or natural material that that facilitate the diversion or retardation of oxygen and water into areas containing acidic rocks. Plastic liners are seldom used since covering large waste volumes proves relatively expensive; hence, are only effective in the coverage of small areas of acidic material. Surface and Well diversions These techniques are highly recommended for mining operations in areas consisting rocks with high acidic concentrations. These techniques have the capacity to control water direction and volume; hence, avert the impact of acid mine drainage on receiving water bodies. Surface diversion entails the construction of drainage ditches that to drain of water quickly from the mines before infiltrating into the underlying acidic rocks. This diversion process is effectively achieved through creation of new channels to covey water across disturbed areas or creation of ditches on the uphill sides of the surface mines. These processes may be combined with lime loading technique that entails diversion of water into the alkaline material receptacles. These can then pick up alkalinity before being allowed to flow into spoils or underground mine fills. The effectiveness of these methods depends upon periodic replenishment of limestone (Han, Zhao, Xu & Li, 2009). Underground Mine fills and injection As a result of the passages in underground mines and geological land mines, mine waters are often acidic. The processes of fully filling mines or creating barriers to cut of interconnectivity in the mines could significantly improve water quality and reduce metal concentrations in the waters. The effectiveness of this process depends on the availability and cost of materials needed to fill the land mines. In particular, waste products such as fly ashes and steel slugs are highly applicable in such situations. Underground Mine Sealing Mine sealing can considerably reduce the acid mine pollution, especially those associated with abandoned underground mines. The main factors affecting the design, selection and construction of the mine seals is subject to hydraulic pressure that the seals have to be subjected once the sealing processes have been completed. There are two types of mine seals, the dry mine seal and the wet mine seal. Dry mine seals are walls at the entrances of mines which limit water from draining into the entrance. Wet seals are walls across mine entrances that restricts air and allows water to flow through the seal. The main target of this technique is to limit air or water access into the mines; hence, restrict the production of the acid mine drainage (Deventer, Feng,& Aldrich, 2005). Lime treatment For quite some time, mining operations have often based on lime technique to reduce the amount of metal concentration in the mine waste waters. However, the main shortcoming of this treatment technology is that the treated water does not meet the required standards. In this regard, these methods have additionally required the application of secondary treatment techniques, which are not only relatively expensive, but also complex to deploy. Another weakness of lime treatment technique is that it simply changes the metal contaminants from one form to another, that is, from forms of water to sludge. Considering that sludge contains heavy metals, it requires storage and monitoring, processes that take a long period; hence, creating long-term environmental challenge. Considering the setbacks and costs associated with the lime treatment technique, environmentally responsible mining companies are grappling to develop and adopt the most effective, affordable and yet the most sustainable approach of finding a solution to the dilemma (Han &Chan, 2006). The recent innovations have prompted most mining industries to come up with industry-specific treatment technologies, which allow operations to remove contaminants and produce quality water that meet the set standards, as well enables them capitalize waste water streams as revenue-generating commodities. These sustainable approaches to water treatment have been gaining momentum around the world, especially in the sites of Jiangxi Company limited, China’s largest copper producing company (Gadd, 2009) References Chan, C. &Wang, J. (2009). Biosorbents for Heavy Metals Removal and their Future. Biotechonolgy 27 (23):195-226 Deventer, J. & Feng, D. & Aldrich, C. (2005). Removal of Pollutants from Acid Mine Waste water Using Metallurgical By-product Slugs. September purify Technology 40 (1): 49-62 Gadd,M. (2009). Biosorption: Critical review of Scientific Rationale, Environmental Importance for Pollution Treatment. Biotechnol 84(3): 13-29 Gonzalez, H., Araujo, L, Pelizaro, B. Lemos, G., & Souza G. (2008). Coconut Coir as a Biosorbent for Chromium from Laboratory Waste Water. Hazard Mater 59:252-253 Han, R, Zhao, X. Xu, Y & Li, Y. (2009). Characterization and Propertiesof Iron Oxide Coated with Adsrbent for Removal of Coppe in Fixed Bed Solutions. Chem Eng, 149:123-131. Han, J. & Chan, C. (2006).Bio sorption of heavy Metals by Microalgae Isolate. Colloid Interface science 35: 3025-3030. Jennings, R., Neuman D. & Blicker, P. (2008). Acid Mine Drainage and Effects on Fish Health and ecology.Bozeman, MT: Group Publication. Kaur, M., Gaurg, K. & Sud, D. (2007). Removal of Hexavalent Chromium from solution by Agricultural Waste Biomass. Hazard Master 140 (3):64-68 Mohammed, D., Smith, F., Mohammed,J, & Pitmann, C. (2007). Copper Adsorbition from Solution by Herbeceous Peat. Colloidal Interface Science 269: 303-309. Sengil, A. & Ozacar, M. (2004). Biosorption ofd Copper ions from solution by Mimmos Tanina gel, Hazard Mater 157:277-285 Srivastava, N. & Majunder, C. (2008). Novel Biofiltration Methods for the Treatment of Heavy Metals from Industrial Water. Hazard Master. 51(8):1-8 Wilhelm, B., Mack, C., Dunkan ,R. & Burgese, E. (2009). Biosorption of Precious Metals. Biotechnology 25: 264-279 Read More