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International Journal of Environmental Studies
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Heavy metals in drilling-waste leachates from East Java, Indonesia
Agoes Soegiantoa; Abdul Rohim Tualekab; Hamamic a Department of Biology, Faculty of Science and Technology, b Department of Occupational Health and Safety, Faculty of Public Health, c Department of Chemistry, Faculty of Science and Technology, Airlangga University, Surabaya 60115, Indonesia Online publication date: 25 August 2010
To cite this Article Soegianto, Agoes , Tualeka, Abdul Rohim and Hamami(2010) 'Heavy metals in drilling-waste leachates
from East Java, Indonesia', International Journal of Environmental Studies, 67: 4, 567 — 571 To link to this Article: DOI: 10.1080/00207233.2010.501624 URL: http://dx.doi.org/10.1080/00207233.2010.501624
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International Journal of Environmental Studies, Vol. 67, No. 4, August 2010, 567–571
Heavy metals in drilling-waste leachates from East Java, Indonesia AGOES SOEGIANTO*†, ABDUL ROHIM TUALEKA‡ AND HAMAMI§ †Department of Biology, Faculty of Science and Technology; ‡Department of Occupational Health and Safety, Faculty of Public Health; §Department of Chemistry, Faculty of Science and Technology, Airlangga University, Kampus C, Jl. Mulyorejo, Surabaya 60115, Indonesia Taylor and Francis 10.1080/00207233.2010.501624 GENV_A_501624.sgm
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(Received 14 June) International 0020-7233 Original 0Taylor 00
[email protected] AgoesSoegianto 2010 00000&Article Francis (print)/1029-0400 Journal of Environmental (online) Studies
This study examined the leaching toxicity characteristics of heavy metals in drilling-waste mud by the toxicity characteristic leaching procedure (TCLP). Ten heavy metal elements As, Ba, Cd, Cr, Cu, Pb, Se, Ag, Zn and Hg were investigated. Test drilling-waste mud samples were collected from eight active exploration wells. The TCLP results showed that the concentrations of the metals were below the Indonesian Regulatory Standards Nos. 18 and 85 (1999) regarding hazardous waste management. Barium was detected in all the leachates, and ranged from 0.40 to 6.59 mg/l. Mercury was below detectable levels at only two stations. Values of the other metals varied significantly from one station to another. Keywords: Drilling wastes; TCLP; Heavy metals; Exploration wells
1. Introduction The exploration of oil and gas reservoirs in Java has increased during the last 15 years. Many petroleum companies, both national and international (e.g. Premier Oil, Hess, PetroChina, Korean Development Company, Santos, Pertamina), have been authorised to drill in this region. The drilling mud used during the exploration process serves several important functions such as cooling and cleaning the bit, maintaining the pressure balance between the geological formation and the borehole, lubricating the bit, reducing friction in the borehole, sealing permeable formations, stabilising the borehole and carrying cuttings to the surface for disposal [1]. Two types of mud normally used in drilling operations are water-based mud (WBM) and oil-based mud (OBM). WBM is by far the most commonly used mud, both onshore and offshore. WBMs are widely used in shallow wells and often in shallower portions of deeper wells, but are not as effective in deeper wells. The use of WBMs generates 835 to 1550 tonnes of waste per well. Depending on the diameter and depth of the well, about 167 to 334 tonnes of that amount is drill cuttings [2]. WBMs use water as their base fluid and
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do not contain any oil. WBMs are economical, biodegradable and of low toxicity [2]. In many countries, WBMs and cuttings are both discharged on site. During the past 30 years, OBMs have been developed and refined to overcome the limitations of WBM usage. OBMs have been found to be the mud of choice for a range of special situations, including high temperatures, hydratable shales, high angle and extended-reach well and high density mud. Wells drilled with OBMs normally produce lower waste volumes than those drilled with WBMs because very little slumping or caving-in of the walls of the drill-hole occurs. The average volume of OBM waste is estimated at 239 to 954 tonnes per well [2]. The OBM base fluids are normally either diesel or mineral oil, even though many other types of low toxicity oils exist nowadays. Unlike WBMs, OBM waste cannot be simply discharged on site because it contains oil [3]. Because of deep wells, most drilling operations in Indonesia have to deal with high pressure and high temperature conditions. Some highly sensitive shale formations need to be drilled at intervals from 2286 to 3048 m. This condition requires high density oil-based mud of 57 to 64 mg/l [4]. Drilling-waste, especially used drilling mud and cuttings, may contain a complex array of hazardous substances that can threaten the environment and human health if not handled or disposed of properly. Such waste is, according to the Indonesian Government Regulations Nos. 18 and 85 (1999) regarding waste management, categorised as hazardous and might pollute domestic water sources. It was therefore necessary that tests be performed on the drill-waste to determine if the material contains toxic substances using the TCLP technique. This simulates the type of process a waste material in a landfill might be exposed to under natural conditions. To the best of our knowledge there are no previous data available regarding heavy metal leaching of drilling wastes from the petroleum exploration activities currently going on in the Java region. Previous reports were made only of the toxicity of drilling wastes and its effect on histological changes of the gills of tiger prawn post-larvae [5]. The object of this study was to examine the leaching toxicity characteristics of heavy metals in the drilling wastes in East Java, Indonesia, by the TCLP method.
2. Materials and methods 2.1. Sampling sites and sample collection This study tested drilling wastes (mixtures of used drilling mud and cuttings) from eight exploration wells namely, UPN, UPW, UPS, UPA, KMK, MYB, MYS and BJS (figure 1). The waste samples tested were collected from active field systems of two petroleum company drilling sites. The samples were stored in uncontaminated polyethene containers, maintained at 0–4°C and immediately transported to the laboratory for analysis. Figure 1.
Location of petroleum exploration wells (★).
2.2. TCLP test Heavy metals leached from the drilling wastes were assessed using TCLP as described by the United States Environmental Protection Agency [6]. The samples were crushed to particle sizes less than 9.5 mm in diameter. The crushed sample was extracted with acetic acid (pH 2.88), 20 times the weight of the sample. The extraction vessel was kept agitated in an endover-end manner at 30 rpm for 18 h. The leachates were passed through a 0.45 µm membrane filter to remove suspended solids. Analysis for the metals As, Ba, Cd, Cr, Cu, Pb, Se, Ag and Zn in the leachates was carried out using an atomic absorption spectrophotometer (Varian
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Heavy metals in drilling-waste leachates from East Java, Indonesia
Figure 1.
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Location of petroleum exploration wells (★).
Spectra AA 220 FS). Mercury concentrations were measured using vapour generation accessories connected to the atomic absorption spectrophotometer. Each leachate was analysed in duplicate and the average values taken. Heavy metal concentrations were quoted in mg/l.
3. Results and discussion Table 1 shows the heavy metal concentrations in the drilling-waste leachates. Barium was detected in all the samples, and ranged from 0.40 to 6.59 mg/l. The concentration of barium at all stations was relatively higher than that of other metals. Similar results have been reported by other researchers [7–9]. They attributed the elevated barium levels to the barite (BaSO4) usually added to the drilling mud to increase its density. Mercury was below detectable levels at only two stations. Selenium was in undetectable levels at all the stations, whereas the other metals As, Cd, Cr, Cu, Pb, Ag and Zn in the leachates exhibited a high variation among all the exploration wells. The values of these metals varied significantly from one station to another. Neff [10] compared the ranges of concentrations of metals found in drilling fluids and marine sediments and found that drilling fluids had concentrations of barium and chromium that fell outside the observed range naturally occurring in marine sediments. Candler et al. [11] investigated potential sources of heavy metals in drilling-waste discharges and noted that most of the cadmium and mercury in such discharges accumulated in sediments near the discharge site. Cuttings from drilled formations apparently contribute a significant percentage of heavy metals found in drilling-wastes. Salomons and Forstner [12] reported that there was a correlation between mercury and barium concentrations in sediments near drilling-
5.0 100.0 1.0 5.0 10.0 5.0 0.2 1.0 5.0 50.0
Maximum limita
0.001 0.10 0.005 0.05 0.03 0.01 0.001 0.007 0.03 0.008
Detection limit
Indonesian Regulation Standard Nos. 18 and 85 (1999).
a
Arsenic Barium Cadmium Chromium Copper Lead Mercury Selenium Silver Zinc
Heavy metal 0.017±0.002 6.59±0.19
