Treatment of produced water from some wells in Mareb oil fields in Yemen

Abstract

Abstract

The aim of this study is to analyse and desalinize contaminated water produced from block 18 of Safer Company in Mareb- Yemen. To produce one barrel of crude oil, one barrel and half of water was obtained. This amount tended to increase with depletion of oil and gas, bearing in mind that the increase in water was an indication of depletion of oil. Hence the contaminated produced water needs to be treated with advance and cost effective technology. The waste-water produced in the Central Production Unit of Safer Company was estimated at 80,000 BPD. In this study the water-shut off technique was reviewed and guessed to be ineffective due the factor that the wells in these areas are deep with a high temperature that the viscosity of the shutting off materials would decline effectively. Therefore a novel technique was developed and investigated and found to be much effective and practical. This technique used adsorption of oil on a packed bed of bagasse. Bagasse was found to be a good adsorbent of emulsified oil at low pH (2.0). At conditions of ambient temperature, pH of 2.0, 0.70 m packed bed height and particle size of 1.5 mm, the percentage of oil adsorbed on bagasse was 98 %. The spent bagasse in addition to oil adsorbed could be used as a fuel with a calorific value of 38 kj/kg. The technique practiced in this work was first to settle the salt for 5 days and separate the salt crystals, then emulsifying the oil with a surface active agent. The mixture of brine water and oil was then eluted through a packed bed of bagasse of particle size of diameter 1.5 mm and 0.70 m height. The flow rate was adjusted so that the resident time was 320 minutes, this was the equilibrium time determined for adsorption. The eluted brine was almost oil-free with about 2 % traces of crude oil emulsion. The brine solution was then processed through single-stage Reverse Osmosis unit (RO) at pump pressure of 13 atmospheres. The unit was able to separate 98 % from the salt feed water at TDS level of 2500 to 3000 mg/L using pressure of 13.6 to 17 atmospheres and 24 L/m2.day. Today the state of the art technology uses thin film composite membranes in place of cellulose acetate and polyamide membranes. The composite membranes work over wide range of pH, at higher temperatures, and within broader chemical limits, enabling them to withstand more operational abuse and conditions more commonly found in most industrial applications. In general, the recovery efficiency of RO desalination plants increases with time as long as there is no fouling of the membrane