Risk assessment and remediation suggestion of impacted soil by produced water associated with oil production

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  • Risk assessment and remediation suggestion of impacted soilby produced water associated with oil production

    Hashim R. Abdol Hamid & Walid M. S. Kassim &Abdulah El Hishir & Salem A. S. El-Jawashi

    Received: 13 April 2007 /Accepted: 25 October 2007 /Published online: 20 December 2007# Springer Science + Business Media B.V. 2007

    Abstract Produced water is water trapped in under-ground formations that is brought to the surface alongwith oil or gas production. Oilfield impacted soil isthe most common environmental problem associatedwith oil production. The produced water associatedwith oil-production contaminates the soil and causesthe outright death of plants, and the subsequenterosion of topsoil. Also, impacted soil serves tocontaminate surface waters and shallow aquifers. Thispaper is intended to provide an approach for fullcharacterization of contaminated soil by producedwater, by means of analysis of both the producedwater and the impacted soil using several recommen-ded analytical techniques and then identify and assaythe main constituents that cause contamination of thesoil. Gialo-59 oilfield (29N, 21E), Libya, has beenchosen as the case study of this work. The field has along history of petroleum production since 1959,where about 300,000 bbl of produced water be

    discharged into open pit. Test samples of contaminat-ed soil were collected from one of the disposal pits.Samples of produced water were collected fromdifferent points throughout the oil production process,and the analyses were carried out at the labs of LibyanPetroleum Institute, Tripoli, Libya. The results arecompared with the local environmental limitingconstituents in order to prepare for a plan of soilremediation. The results showed that the mainconstituents (pollutants) that impact the soil are saltsand hydrocarbon compounds. Accordingly; an actionof soil remediation has been proposed to remove thesalts and degradation of hydrocarbons.

    Keywords Soil remediation . Produced water .

    Impacted soil

    Introduction

    Produced water is water trapped in undergroundformation that is brought to the surface along withoil or gas. It is by far the largest volume byproduct orwaste stream associated with oil and gas production.Management of produced water and its environmentaleffects, present challenges to the oil industry andenvironmental experts.

    Produced water can have different potentialimpacts on environment depending on where it isdischarged. For example, discharges to small streamsare likely to have a larger environmental impact than

    Environ Monit Assess (2008) 145:95102DOI 10.1007/s10661-007-0018-3

    H. R. Abdol HamidInternational Technological University,London, UK

    W. M. S. KassimAl Fateh University,Tripoli, Libya

    H. R. Abdol Hamid (*) :A. El Hishir :S. A. S. El-JawashiLibyan Petroleum Institute,Tripoli, Libyae-mail: hashimrahh@hotmail.com

  • discharges made to the open ocean by virtue of thedilution that takes place following discharges. Regu-latory agencies have recognized the potential impactthat produced water discharges can have on theenvironment and have prohibited discharges in mostonshore or near-shore locations.

    Produced water characteristics and physical prop-erties vary considerably depending on the geographiclocation of the field, the geological formation withwhich the produced water has been in contact forthousands of years and the type of hydrocarbonproduct being produced. Produced water propertiesand volume can even be varying throughout the lifetime of the reservoir.

    Many constituents found in produced water, whenpresent either individually or collectively in highconcentrations, can present a threat to aquatic life,soil, crops, and ecosystem.

    Oil and grease are the constituents of producedwater that receive the most attention in both onshoreand offshore operations, while salt content (expressedas salinity, conductivity, or total dissolved solids TDS-) is also a primary constituent of concern inonshore operations. In addition, produced water con-tains many organic and inorganic compounds that canlead to toxicity. Some of these are naturally occurringin the produced water while other are related tochemicals that have been added for well-controlpurposes. These vary greatly from location to locationand even over time in the same well (Veil et al. 2004).

    This paper is intended to provide an approach forfull characterization of contaminated soil by producedwater of Gialo-59 oilfield, where a bank of disposingpit has been chosen as a case study area, and analysisof both the produced water and the impacted soil

    samples have been carried out by mean of severalrecommended analysis and then identify and assay themain constituents that cause pollution of the soil.Then analyses results have been based to recommenda plan of soil remediation.

    Site visit and samples collection

    A bank of produced-water disposal pit has beenchosen as polluted land, (Figs. 1 and 2) which isperiodically covered by produced water and dried.The land was divided into 16 equal sampling units ofarea 16 m10 m each as shown in Fig. 3. Using ahand shovel, random duplicate soil samples werescooped out at depth of 20 cm within each unit. Atotal of 32 soil samples were collected from thepolluted land strip. One sample of uncontaminatedsoil was taken to be used as a reference. Ten samplesof produced water have been collected. S1S4 fromtwo separators (multi lines), S5S7 from settlingtanks, and S8S10 from pumping station were alsocollected as well.

    Experimental analysis

    Many parameters have been determined for both soiland produced water samples in order to characterizethe polluted site and to develop guidelines for soilrestoration and remediation (Abdul Hamid 2004).

    Fig. 1 Produced water disposal pit at Gialo-59 oilfield, Libya

    Fig. 2 Delineated land at the bank of the produced-waterdisposal pit, Gialo-59 oilfield, Libya

    96 Environ Monit Assess (2008) 145:95102

  • 1. Soil samples tests: soil samples were air dried andpassed through a 10-mesh sieve. pH and electricalconductivity (EC) were determined in 1:1 soil:water extraction by ION450 Ion Analyser, thenanions and cations, were determined as theASTM procedures D3561-96, D511-93 (Re ap-proved 1998), and D4327-97. Sodium adsorptionratio (SAR) was calculated. Total PetroleumHydrocarbon (TPH) was determined by CVHmodel Infracal TOG/TPH Analyzer according toEPA-Approval protocol (413.2 and 418.1/600/4-79-020).

    2. Produced Water samples tests: direct pH and ECwere determined as well as cations & anions.TPH was determined by an EPA-Approval proto-col (413.2 and 418.1/600/4-79-020).

    Results and discussion

    Figure 4 shows pH values for soil, which are rangedfrom 6.73 and 7.52. The normal pH range for soil is69. Therefore it could be considered that pH of soilare within the normal rang (Deuel and Holliday 1997).Figure 5 shows EC values for soil are varied between18,590 and 189,922 mhos/cm where the normalEC for soil should be less than 4,000 mhos/cm, andthat is indicates to exist of high concentration of saltsin the soil. Accordingly the anions and cations resultswere very high as it showed in Tables 1 and 2. Wherethe Anions vary between; (chloride: 5,786 and76,510 ppm), (Sulphate: 767 and 2,178 ppm), (Bicar-bonate: 41 and 61 ppm) and cations vary between(Sodium: 3,350 and 45,500 ppm), (Potassium: 110 and

    6.750

    6.800

    6.850

    6.900

    6.950

    7.000

    7.050

    7.100

    7.150

    7.200

    7.250

    7.300

    7.350

    7.400

    7.450

    B A

    Fig. 4 pH Values for con-taminated soil, Gialo59 oil-field, Libya

    Fig. 3 Schematic showingpit delineated by unit, siteswithin units and replicatecore locations

    Environ Monit Assess (2008) 145:95102 97

  • 680 ppm), (Calcium: 720 and 3,000 ppm), Magne-sium: 126 and 1,118 ppm). While for reference soilsample the Anions are (chloride: 272 ppm), (Sulphate:421 ppm), (Bicarbonate: 43 ppm) and Cations are(Sodium: 265 ppm), (Potassium: 35 ppm), (Calcium:60 ppm), Magnesium: 24 ppm) which are consideredlow and within the normal limits.

    SAR values for the soil were calculated accordingto the following equation (SAR Na

    .pCa 2

    Mg 2), (Deuel and Holliday 1997), as it shown inTable 3, where vary between 21.42 and 137.86, whichis considered high in comparing with normal value(equal or less than 12), where for reference sample is5.17, which is accepted.

    Figure 6 shows total petroleum hydrocarbon (TPH)for soil samples, where vary between 164 and24,000 ppm, and that is indicates impaction of soilby discharged hydrocarbon associated produced water.

    The determined pH for produced water is shown inFig. 7, with a range between 6.41 and 7.16, which isclose to accepted criteria. Where E.C. values ofproduced water are varying between 20,773 and61,087 mhos/cm, which is refer to high concentra-tion of ionic constituents (salinity) in produced water,(Fig. 8). Therefore the obtained results of anions andcations were high, as shown in Table 4. The anionsvary between (chloride: 6,235 and 27,529 ppm),(Sulphate: 1,276 and 1,864 ppm), (Bicarbonate: 220and 1,537 ppm) and the cations vary between(Sodium: 5,050 and 15,000 ppm), (Potassium: 150and 370 ppm), (Calcium: 60 and 1,840 ppm),(Magnesium: 85 and 807 ppm).

    Figure 9 depicts the total petroleum hydrocarbon inproduced water with a range between 2 and 354 ppm.The variation in TPH values of produced water is dueto the difference in oil/water ratio through thedifferent location of sampling points throughout theprocess till the disposal pit.

    Impact and remediation action

    The impaction can be summarized as follows:

    1. The soil is badly infected by brain water over longterm of disposing; so that high concentration ofanions and cations