Radiological aspects of petroleum exploration and production in the sultanate of Oman

This thesis is a study of naturally occurring radioactive materials (NORM) activity concentration, gamma dose rate and radon (222Rn) exhalation from the waste streams of large-scale onshore petroleum operations. Types of activities covered included; sludge recovery from separation tanks, sludge farming, NORM storage, scaling in oil tubulars, scaling in gas production and sedimentation in produced water evaporation ponds. Field work was conducted in the arid desert terrain of an operational oil exploration and production region in the Sultanate of Oman. The main radionuclides found were 226Ra and 210Pb (238U - series), 228Ra and 228Th (232Th - series), and 227Ac (235U - series), along with 40K. All activity concentrations were higher than the ambient soil level and varied over several orders of magnitude. The range of gamma dose rates at a 1 m height above ground for the farm treated sludge had a range of 0.06 0.43 µSv h 1, and an average close to the ambient soil mean of 0.086 ± 0.014 µSv h 1, whereas the untreated sludge gamma dose rates had a range of 0.07 1.78 µSv h 1, and a mean of 0.456 ± 0.303 µSv h 1. The geometric mean of ambient soil 222Rn exhalation rate for area surrounding the sludge was mBq m 2 s 1. Radon exhalation rates reported in oil waste products were all higher than the ambient soil value and varied over three orders of magnitude. This study resulted in some unique findings including: (i) detection of radiotoxic 227Ac in the oil scales and sludge, (ii) need of a new empirical relation between petroleum sludge activity concentrations and gamma dose rates, and (iii) assessment of exhalation of 222Rn from oil sludge. Additionally the study investigated a method to determine oil scale and sludge age by the use of inherent behaviour of radionuclides as 228Ra:226Ra and 228Th:228Ra activity ratios.

Traffic and climate change impacts on water quality : measuring build-up and wash-off of heavy metals and petroleum hydrocarbons

Understanding the impacts of traffic and climate change on water quality helps decision makers to develop better policy and plans for dealing with unsustainable urban and transport development. This chapter presents detailed methodologies developed for sample collection and testing for heavy metals and total petroleum hydrocarbons, as part of a research study to investigate the impacts of climate change and changes to urban traffic characteristics on pollutant build-up and wash-off from urban road surfaces. Cadmium, chromium, nickel, copper, lead, iron, aluminium, manganese and zinc were the target heavy metals, and selected gasoline and diesel range organics were the target total petroleum hydrocarbons for this study. The study sites were selected to encompass the urban traffic characteristics of the Gold Coast region, Australia. An improved sample collection method referred to as ‘the wet and dry vacuum system’ for the pollutant build-up, and an effective wash-off plan to incorporate predicted changes to rainfall characteristics due to climate change, were implemented. The novel approach to sample collection for pollutant build-up helped to maintain the integrity of collection efficiency. The wash-off plan helped to incorporate the predicted impacts of climate change in the Gold Coast region. The robust experimental methods developed will help in field sample collection and chemical testing of different stormwater pollutants in build-up and wash-off.

The effect of high concentrations of calcium hydroxide in neutralised synthetic supernatant liquor : implications for alumina refinery residues

The presence of calcium hydroxide (Ca(OH)2) in Bayer residue slurry inhibits the effectiveness of the seawater neutralisation process to reduce the pH and aluminium concentration in the residue. An increase in the slurry pH (reversion), after seawater neutralisation, is caused by the dissolution of calcium hydroxide and hydrocalumite (solid components found in bauxite refinery residue). Reversion was not observed when the final solution pH was greater than 10.5, due to hydrocalumite being in a state of equilibrium at high pH. Hydrocalumite has been found to form during the neutralisation process when high concentrations of calcium hydroxide are present in the residue liquor. The dissolution of hydrocalumite releases hydroxyl (OH-) and aluminium ions back into solution after the seawater neutralisation (SWN) process, which causes pH and aluminium reversion to occur. This investigation looks at the effect of Ca(OH)2 and subsequently hydrocalumite on the pH and aluminium concentration in bauxite refinery residue liquors after the SWN process.

Stability of hydrotalcites formed from Bayer refinery environmental control processes

Bauxite refinery residues (red mud) are derived from the Bayer process by the digestion of crushed bauxite in concentrated sodium hydroxide at elevated temperatures and pressures. This slurry residue, if untreated, is unsuitable for discharge directly into the environment and is usually stored in tailing dams. The liquid portion has the potential for discharge, but requires pre-treatment before this can occur. The seawater neutralisation treatment facilitates a significant reduction in pH and dissolved metal concentrations, through the precipitation of hydrotalcite-like compounds and some other Mg, Ca, and Al hydroxide and carbonate minerals. The hydrotalcite-like compounds, precipitated during seawater neutralisation, also remove a range of transition metals, oxy-anions and other anionic species through a combination of intercalation and adsorption reactions: smaller anions are intercalated into the hydrotalcite matrix, while larger molecules are adsorbed on the particle surfaces. A phenomenon known as ‘reversion’ can occur if the seawater neutralisation process is not properly controlled. Reversion causes an increase in the pH and dissolved impurity levels of the neutralised effluent, rendering it unsuitable for discharge. It is believed that slow dissolution of components of the red mud residue and compounds formed during the neutralisation process are responsible for reversion. This investigation looked at characterising natural hydrotalcite (Mg6Al2(OH)16(CO3)∙4H2O) and ‘Bayer’ hydrotalcite (synthesised using the seawater neutralisation process) using a variety of techniques including X-ray diffraction, infrared and Raman spectroscopy, and thermogravimetric analysis. This investigation showed that Bayer hydrotalcite is comprised of a mixture of 3:1 and 4:1 hydrotalcite structures and exhibited similar chemical characteristic to the 4:1 synthetic hydrotalcite. Hydrotalcite formed from the seawater neutralisation of Bauxite refinery residues has been found not to cause reversion. Other components in red mud were investigated to determine the cause of reversion and this investigation found three components that contributed to reversion: 1) tricalcium aluminate, 2) hydrocalumite and 3) calcium hydroxide. Increasing the amount of magnesium in the neutralisation process has been found to be successful in reducing reversion.

Traffic and climate change impacts on water quality : measuring build-up and wash-off of heavy metals and petroleum hydrocarbons

Understanding the impacts of traffic and climate change on water quality helps decision makers to develop better policy and plans for dealing with unsustainable urban and transport development. This chapter presents detailed methodologies developed for sample collection and testing for heavy metals and total petroleum hydrocarbons, as part of a research study to investigate the impacts of climate change and changes to urban traffic characteristics on pollutant build-up and wash-off from urban road surfaces. Cadmium, chromium, nickel, copper, lead, iron, aluminium, manganese and zinc were the target heavy metals, and selected gasoline and diesel range organics were the target total petroleum hydrocarbons for this study. The study sites were selected to encompass the urban traffic characteristics of the Gold Coast region, Australia. An improved sample collection method referred to as ‘the wet and dry vacuum system’ for the pollutant build-up, and an effective wash-off plan to incorporate predicted changes to rainfall characteristics due to climate change, were implemented. The novel approach to sample collection for pollutant build-up helped to maintain the integrity of collection efficiency. The wash-off plan helped to incorporate the predicted impacts of climate change in the Gold Coast region. The robust experimental methods developed will help in field sample collection and chemical testing of different stormwater pollutants in build-up and wash-off.

Neutralization of acid sulfate solutions using bauxite refinery residues and its derivatives

This investigation has shown that by transforming free caustic in red mud (RM) to Bayer hydrotalcite (during the seawater neutralization (SWN) process) enables a more controlled release mechanism for the neutralization of acid sulfate soils. The formation of hydrotalcite has been confirmed by X-ray diffraction (XRD) and differential thermalgravimetric analysis (DTG), while the dissolution of hydrotalcite and sodalite has been observed through XRD, DTG, pH plots, and ICP-OES. Coupling of all techniques enabled three neutralization mechanisms to be determined: (1) free alkali, (2) hydrotalcite dissolution, and (3) sodalite dissolution. The mechanisms are determined on the basis of ICP-OES and kinetic information. When the mass of RM or SWN-RM is greater than 0.08 g/50 mL, the pH of solution increases to a suitable value for plant life with aluminum leaching kept at a minimum. To obtain a neutralization pH greater than 6 in 10 min, the following ratio of bauxite residue (g) in 50 mL with a known iron sulfate (Fe2(SO4)3) concentration can be determined as follows: 0.04 g:50 mL:0.1 g/L of Fe2(SO4)3.

Shahejie−Shahejie/Guantao/Wumishan and Carboniferous/Permian Coal−Paleozoic Total Petroleum Systems in the Bohaiwan Basin, China (based on geologic studies for the 2000 World Energy Assessment Project of the U.S. Geological Survey)

This report discusses the geologic framework and petroleum geology used to assess undiscovered petroleum resources in the Bohaiwan basin province for the 2000 World Energy Assessment Project of the U.S. Geological Survey. The Bohaiwan basin in northeastern China is the largest petroleum-producing region in China. Two total petroleum systems have been identified in the basin. The first, the Shahejie–Shahejie/Guantao/Wumishan Total Petroleum System, involves oil and gas generated from mature pods of lacustrine source rock that are associated with six major rift-controlled subbasins. Two assessment units are defined in this total petroleum system: (1) a Tertiary lacustrine assessment unit consisting of sandstone reservoirs interbedded with lacustrine shale source rocks, and (2) a pre-Tertiary buried hills assessment unit consisting of carbonate reservoirs that are overlain unconformably by Tertiary lacustrine shale source rocks. The second total petroleum system identified in the Bohaiwan basin is the Carboniferous/Permian Coal–Paleozoic Total Petroleum System, a hypothetical total petroleum system involving natural gas generated from multiple pods of thermally mature coal beds. Low-permeability Permian sandstones and possibly Carboniferous coal beds are the reservoir rocks. Most of the natural gas is inferred to be trapped in continuous accumulations near the center of the subbasins. This total petroleum system is largely unexplored and has good potential for undiscovered gas accumulations. One assessment unit, coal-sourced gas, is defined in this total petroleum system.

Adsorption of reactive dye on seawater-neutralised bauxite refinery residue

This investigation has demonstrated the need for thermal treatment of seawater neutralised red mud (SWRM) in order to obtain reasonable adsorption of Reactive Blue dye 19 (RB 19). Thermal treatment results in a greater surface area, which results in an increased adsorption capacity due to more available adsorption sites. Adsorption of RB 19 has been found to be best achieved in acidic conditions using SWNRM400 (heated to 400 �C) with an adsorption capacity of 416.7 mg/g compared to 250.0 mg/g for untreated SWNRM. Kinetic studies indicate a pseudosecond-order reaction mechanism is responsible for the adsorption of RB 19 using SWNRM, which indicates adsorption occurs by electrostatic interactions.

Preventing industrial scale using bauxite refinery residues

An Australian green power (AGP) company produces energy from burning biomass from the sugar industry and recycled wood waste, however alkali in biomass is released into a recirculating stream that forms a scale as it becomes more concentrated. This investigation has shown that the addition of Bayer liquor (alumina waste residue) successfully removes scale-forming species from the recirculating stream and thus has the potential to reduce the rate of scaling. Characterisation of the scale and Bayer precipitates has been performed using X-ray diffraction (XRD), infrared spectroscopy (IR) and inductively coupled plasma optical emission spectroscopy (ICP-OES).