The Study Of The Technology On Decalcification And Descaling For High Salt Oilfield Sewage

The produced sewage of Binnan Oil Production Plant of Shengli Oil Field is mainly acidic and highly salty.Influenced by the complexity of produced sewage and its treatment process,scaling occurs to varying degrees from the treatment process of the sewage treatment station,the water transmission pipe network to the bottom of the well,which hinders the normal production of the oilfield and reduces the crude oil recovery to a certain extent.Therefore,it is urgent to address the problem of easy scaling of produced wastewater in the oilfield.This paper explores the methods and processes for efficiently and economically capturing and removing scaling ions from oilfield produced wastewater at Binnan Oil Production Plant.The paper pioneered the use of a circulating fluidized bed to add adsorbent settling agents to the reaction bed layer.By utilizing the high-speed fluidization of the fluidized bed to the slow settling of the settling section,the precipitation and precipitation of scaling ions are accelerated,achieving the goal of efficiently and economically capturing and removing scaling ions.The paper mainly conducts experimental research from the following aspects.Firstly,the decalcification performance of three precipitants was investigated,and it was determined that using HCO₃^-carried in oilfield sewage and adding proper amount of sodium hydroxide could remove calcium ions more economically and efficiently.Through condition optimization experiments,it was found that the suitable conditions for adding alkali for decalcification of wastewater from Binyi Oilfield are:adding 0.60 g/L alkali,and the Ca²⁺concentration of the decalcified water sample can be reduced from 697.39mg/L to 111.82mg/L,with a decalcification rate of 83.97%;The suitable conditions for adding alkali for decalcification of wastewater from Bin’er Oilfield are:adding 0.40 g/L alkali and 0 70 g/L,with 0.05t/quarter of modified activated carbon added,the Ca²⁺concentration of the water sample after decalcification can be reduced from 1086.17mg/L to 216.43mg/L,and the decalcification rate can reach 80.07%.Secondly,through the experimental investigation of different adsorbents,the results show that the activated carbon modified by Potassium permanganate sulfuric acid has significant adsorption sedimentation and decalcification performance,and its decalcification rate is increased by 69.74%compared with that without adsorbents.The modified activated carbon was characterized by BET and FT-IR,and the results showed that the micropores of the modified activated carbon decreased and the pore size slightly increased.The infrared spectrum of the modified activated carbon showed more hydroxyl and carboxyl groups generated;According to the Boehm titration method,the surface hydroxyl group of modified activated carbon increased from0.4295mmol/g before modification to 0.9862mmol/g,while the carboxyl group increased from 1.3486mmol/g before modification to2.5705mmol/g.Thirdly,a fluidized bed experimental setup was used,using modified activated carbon as an adsorbent and settling agent.The effects of the amount of alkali solution and adsorbent and settling agent on the removal of scaling ions from wastewater samples from Bin’er Oilfield were investigated,and the appropriate amount of modified activated carbon was found to be 1.00g/L;The concentration of Ca²⁺in the water sample after decalcification can be reduced from 1086.17mg/L to 144.46mg/L,with a decalcification rate of 86.70%,which is 20.14%higher than the66.56%decalcification rate without adsorbent.Fourthly,based on the ion composition of the wastewater from Bin-1and Bin-2 oilfields and the ion composition of the water samples after decalcification treatment,the scaling trend of the treated water samples was calculated and predicted according to the SY/T 0600-2016 standard.The suitable treatment conditions for Bin-1 oilfield wastewater were obtained:room temperature,air stripping space velocity of 7.5h^-1,blowing for 30 minutes,Na OH addition of 0.60g/L,and the cost of treating water was about 1.46 yuan/m3（pharmaceutical cost）;The suitable treatment conditions for wastewater from Bin’er Oilfield include room temperature,air stripping space velocity of 7.5h^-1,stripping time of40min,NaOH addition rate of 0.40g/L,Na₂CO₃addition rate of 0.7g/L,and modified activated carbon addition rate of 0.05t/quarter.The cost of water treatment is approximately 1.50yuan/m3（pharmaceutical cost）.The concentration of Ca²⁺in the water sample after decalcification can be reduced from 1086.17mg/L to 144.46mg/L,with a decalcification rate of86.70%,which is 20.14%higher than the 66.56%decalcification rate without adsorbent.Fifthly,according to the SY/T 5273-2014 standard,the average corrosion rate and scaling rate of Binyi decalcification treatment water were measured by the static hanging method to be 0.1585（mm/a）and0.2254（g/cm²·a）,respectively.Compared with the original wastewater,the average corrosion rate of Binyi decalcification treatment water decreased by 50.14%and 42.04%,respectively.The average corrosion rate and scaling rate of the water treated by Bin Er decalcification are0.0619（mm/a）and 0.1396（g/cm²·a）,respectively.The average corrosion rate has decreased by 83.99%compared to its original wastewater,and the scaling rate has decreased by 70.72%,meeting the requirements for oilfield reinjection water.