Sea Water Injection System

Sea body of water Injection SystemIn order to improve the anele recovery in an oil do chief(prenominal) the pellet of sea water is used to increase the pressure internal the reservoir and enhance the oil production. The graph presumption in radiation pattern 1 is a typical seawater pellet trunk, before the guesswork address, water must have a treatment to decrease the erosion pass judgment caused by seawater in yell lines, surface and downhole injection equipments. The treatment is based in a mechanistic de-aeration process and chemic chatterer injection to decrease the concentration of oxygen in seawater. escort 1. Seawater Injection SystemIn a normal feat of the seawater injection organization the conditions of the process are 150,000 set per day, pipe diameter of 8 inches at 25 C, however in term of corroding parameters the data is provided in table 1, this table shows that the mechanical deaeration process tighten up the most quantity of atomic number 8 con centration in seawater. submit 1. Concentration of Oxygen in normal exertionConcentration of O2 in different UnitsPPBmg/lmole/m3Feed Seawater7,00070.22After mechanical de-aeration process speed of light0.10.003After pack rat superman100.010.0003With the data provided, the corrosion yard in normal cognitive process condition is 0.0454mm/ course (the calculation step by step including unit of measurement conversion are shown in the appendix) hence the corrosion evaluate is far-off little(prenominal) than the company acceptable value which is 0.1 mm/year, and it means that the formation is working properly.It has been found that the mechanical de-aeration equipment requires repair, and it impart be out of operation for surrounded by one and three months.Water carcass Injection without a mechanical de-aeration processCalculating the lay out flow come out minginess with the pursual equationConcentration of Oxygen however with the sum of Scavenger dosing = 6.910 ppm K is the mass transfer coefficient and it calculations and unit conversions are shown in the appendix.Calculating the eating away considerpresumptuous the of import component of the pipe Iron indeed n= 2M= 55.84 g/molDensity 7.87 g/cm3 nowadays we weed discriminate the corrosion localise of each episode and determine the implications of operating the system without the mechanical de-aeration.Hence the corrosion calculate will increase 502 cadences without the mechanical de-aeration. Based on this resolving power it is obvious that the most important process for oxygen removal is the mechanical deareation.The company request the assessment in a technically and economically establish of suasion three operational solutions during the repair of the mechanical de-aeration equipment.For the given acceptable corrosion browse less than 0.1 mm/year, a corrosion vagabond value of 0.09 mm/year was used to calculate the implications of the contingent solutions.a. Decreasing the Flow RateAssuming an acceptable corrosion Rate of 0.09 mm/year,From the equation above we seat reach the Current densityWith current density we hatful reach mass transfer coefficient kat once we shadower reach the new Sh numberWith Sh number we can hold up Re numberThis value of Reynolds number means that we are in the transition regime between laminar endure and exuberant play.Now we can reach the flow rateFrom the technical hitch of view and based on the concepts of blands mechanics, decreasing the flow volume to 260 barrels per day will generate a laminar flow (Re less than 3000) on the pipe, in other words it means that the velocity will not be in the required optimum range of 1.5 m/s to 2.5 m/s, according to Streeter. Doing the calculations the velocity will reach a very slow value of 0.014 m/s in the pipe, which is by far lower than the minimum value of 1 m/s. thusly technically, the reduction of flow rate to reach an acceptable corrosion rate is not a affirmable so lution.In addition, this kind of diminution of the flow rate (577 propagation lower than the original) would have impacts on the oil well. Specifically, it would not be able to maintain the pressure at the desired level and therefore would have a big impact on oil production leading to money loss.b. Increasing the amount of scavengerAssuming an acceptable corrosion Rate of 0.09 mm/yearFrom the equation beneath we can reach the concentration of Oxygen that we aim to contain in the water in order to have an acceptable corrosion rateUsing Sodium sulfate as scavenger the following chemical reply will proceedHence form the stoichiometry of the reaction the relation between the compounds will be 2 moles of Scavenger and 1 mole of Oxygen. consequently the amount of scavenger Sodium sulfate carryed is = In an injection flow rate of 150,000 bbl/dayBased on scavengers calculations we need to provide the system with a high amount of scavenger to reduce the oxygen concentration that giv es an acceptable corrosion rate, it is up to 1.3 ton per day, it is near 80 times to a greater extent than amount of scavenger used in normal operation, which is about 17 kg per day.On the economically point of view, if the scavenger will substitute mechanical de-aeration for a month, the need of scavenger will be approximately 40 ton per month. By apply the commercial price of scavenger 0.64 USD/kg (https//www.icis.com), it will represent just about 832 USD/day and scaling it to a month it will cost most 24,960 USD/month.c. wearing InhibitorCorrosion inhibitor compound will reduce the corrosion rate by preventing both anodic and cathodic reactions. Anodic inhibitor will be adsorbed onto coat surface to form protective film and prevent metal dissolution while cathodic inhibitor will minimize O2 reduction reaction by forming non-conducting film on metal surface. And in technical term it could be the solution of the problem. However, from the calculations, we know that corrosi on rate without the mechanical deareation is 22.5 mm/year and the aim is to decrease the corrosion rate infra 0.1 mm/year. Based on the corrosion inhibitor risk category that is proposed by Hedges (2000), if the evaluate uninhibited corrosion rate is graeter than 6 mm/year inhibition is unlikely to provide integrity for the full field life. thence corrosion control of the system could not be efficient with a however corrosion inhibitor because of the high requirement of availability.Based on the results of the three possible options, on the economically point of view decreasing the injection flow rate will impact in the production of oil, and decreasing the main product (oil) of the industry it will have terrible effects in the oil company. Therefore in the corrosion engineering point of view the most accurately solution is to increase the amount of scavenger (Na2SO3) in order to reach a corrosion rate of 6 mm/year and then with the addition of corrosion inhibitors the corrosion rate can be reduce to an acceptable value of less than 0.1 mm/year.The social disease of O2 scavenger has to be interrupted for 8 hours per week for the injection of the biocide. During this time if there was not the corrosion inhibitor, the Corrosion rate would be 22.5 mm/yr. but if the Corrosion inhibitor inhibition rate is 98.5% (as from 6mm/yr to 0.09mm/yr), the corrosion rate would beTherefore the Corrosion rate would be The Corrosion rate is slightly above the required norm (0.002 mm/yr), but in the worst case scenario, 3 months with no deaerator, due to the fact the Corrosion rate with the mechanical deaerator is 0.0454 mm/yr which is 0.0546 mm/year less than the required standard. So, in a year perspective the slightly more amount of Corrosion will be not significant and the system will work properly.Also, the amount of Na2SO3 needed to reach a CR of 6 mm/year is 905 Kg/day and it will cost around 580 USD/day.Finally, in order to choose the ideal corrosion inhibitor resea rch lab tests must be performed in the same seawater that will be used. In situ tests would help to assure the quality of the results.Streeter, Victor L. Handbook of fluid mechanics. McGraw-Hill, ed 1 (1961).Hedges, B. (2000) The Corrosion Inhibitor Availability Model, NACE International, Paper 00034.Water system Injection with a mechanical de-aeration process and Oxygen scavenger additionConsidering the water system injection above and the following data we can reach a corrosion rate value in the following steps.Data providedPipe Diameter = 8 inch, therefore the Area A = 50.26 in2 = 0.032429 m2Volume Flow Rate = 150000 bbl/dInitial Oxygen Concentration = 7 ppmConcentration of Oxygen After Mechanical De-aeretion = 100 ppbConcentration of Oxygen After Scavenger dosing = 10 ppbKinematic Viscosity 1.05 X 10-6 m2/sSchmidt number = 505Calculation of Re numberCalculation of Sh snatchIn turbulent Flow calculation of Diffusion coefficientFrom Sh number we can reach the mass transfer c oefficient kNow calculating the constrain current density with the following equationConcentration of Oxygen after(prenominal) mechanical de-aeration and Scavenger dosing = 0.01 ppmCalculating the Corrosion RateAssuming the main component of the pipe Iron thereforen= 2MFe 55.84 g/mol 7.87 g/cm3For 8 hours per week, the O2 scavenger dosing is interrupted for biocide to be injected. So, there is an Availability of = The Corrosion rate at a concentration of 0.1ppm of O2 isWater system Injection without a mechanical de-aeration processCalculating the limit current density with the following equationConcentration of Oxygen only with the addition of Scavenger dosing = 6.910 ppmCalculating the Corrosion RateAssuming the main component of the pipe Iron therefore n= 2M= 55.84 g/molDensity 7.87 g/cm3Now we can compare the corrosion rate of each case and determine the implications of operating the system without the mechanical de-aeration.Hence the corrosion rate will increase 502 times w ithout the mechanical de-aeration.Evaluation of the following operational solutionsDecrease the flow rate of waterAssuming an acceptable corrosion Rate of 0.09 mm/yearFrom the equation above we can reach the Current densityWith current density we can reach mass transfer coefficient kNow we can reach the new Sh numberWith Sh number we can obtain Re numberThis value of Reynolds number means that we are in the transition regime between laminar flow and turbulent flow.Now we can reach the flow rateIncreasing the amount of scavengerAssuming an acceptable corrosion Rate of 0.09 mm/yearFrom the equation above we can reach the Current densityFrom the equation below we can reach the concentration of Oxygen that we need to contain in the water in order to have an acceptable corrosion rateUsing Sodium sulfate as scavenger the following reaction will proceedHence form the stoichiometry of the reaction the relation between the compounds will be 2 moles of Scavenger and 1 mole of Oxygen.Therefore the amount of scavenger Sodium sulfate needed isHence we need In an injection flow rate of 150000 barrels per day