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Proceedings of the 1st International Technology, Education and Environment Conference(c) African Society for Scientific Research (ASSR)

Co-Published By: Human Resource Management Academic Research Society 572

ASSESSMENT OF THE NATURALLY OCCURRING RADIOACTIVE MATERIAL(NORM) CONTENT OF HYDROCARBON EXPLORATION AND PRODUCTION

ACTIVITIES IN OGBA/EGBEMA/NDONI OIL/GAS FIELD, RIVERS STATE,NIGERIA.

AVWIRI, G. O1 and ONONUGBO C. P2

1Department of Physics,University of Port Harcourt,Rivers State,Nigeria2Department of Physics/Computer, Federal College of Education (Technical),Omoku, Rivers State, Nigeria

Email: [email protected]; [email protected]

AbstractThe concentration of the Naturally Occurring Radioactive material (Norm) of soil and sediment samples collected fromOgba/Egbema/Ndoni oil fields and their host communities was measured by determining the gross alpha and grossbeta activity concentration in twelve oil fields and their host communities. Determination of the gross alpha and grossbeta radioactivity of host community soil, field soil and field sediment samples were obtained by using gas flowproportional counter( EURISYS MEASURE-IN-20 low background multiple channel alpha/beta counter).Background measurement and plateau test was done to determine the background radioactivity and optimal operationalvoltage and frequencies. The gross alpha activity concentration in host community soil ranges from BDL to2590.0±34.0Bqkg-1 with a mean value of 289.16±7.0 Bqkg-1. While the gross beta activity concentration rangesfrom 1660.0± 27.0Bqkg-1 to 206,600.00±1906.0Bqkg-1 with a mean value of 22690.0±104.0Bqkg-1. In fieldsoil samples analyzed, the gross alpha activity concentration ranges from 17.0±1.0 Bqkg-1 to 1400.0±22.0Bqkg-1

with a mean value of 378.83±10.0Bqkg-1. The gross beta activity concentration in field soil samples ranges from3350.0±35.0Bqkg-1 to 110,090.0±1360.0Bqkg-1 with a mean value of 1782.0±267.0 Bqkg-1. Furthermore thegross alpha activity concentration in field sediment samples ranges from BDL to 620.0±15.0Bqkg-1 with a meanvalue of 203.66±6.0Bqkg-1 while the gross beta activity concentration ranges from 1070.0±79.0Bqkg-1 to22,590.0±459.0 Bqkg-1 with a mean activity value of 7485.92±165.0Bqkg-1. The mean alpha activityconcentration for the control soil sample was 22.78.0±1.02Bqkg-1 which is low compared with the observed alphaactivity values in community’s soil, field soil and field sediment samples respectively, while the mean gross beta activityconcentration was found to be 666.0±14.0 Bqkg-1 which is also lower than the observed beta activities on thesoil/sediment samples. The result indicates an elevation of Norm content due to hydrocarbon exploration andproduction in the area. This could be detrimental to health of individuals exposed to these radiations.

Keywords: Gross alpha, Gross beta, Norm, Natural radioactivity, Proportional counter, Sediment,Soil, Assessment.

Introduction

Naturally occurring radioactive materials (NORM) are found almost everywhere. NORM is inherentin many geologic materials and consequently encountered during geological related activities. NORMencountered in hydrocarbon exploration and production operations originate in subsurfaceformations that may contain radioactive materials such as Uranium and thorium and their daughterproducts, 226Ra and 228Ra. This can be brought to the surface in the surface in the produced waterin conjunction with oil and gas. In addition, radon gas a radium daughter, may be found in producednatural gas. In gas processing activities, NORM generally occurs as radon gas in the natural gasstream (Ajayi et al, 2009; Mokobia et al 2006).

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During exploration and extraction processes, various operational practices contribute to or induceNORM occurrence, namely remote sensing methods of mapping and explosives associated withseismic exploration, drilling equipment and activities and down –the –hole geophysical loggingmethods. In some instances, radioactive marker bullets are employed as an aid in relative depthdeterminations. The gamma ray log is used to locate the bullets after casing has been set. Radioactivetracers are also used in evaluating the effective of well cementing and under ground water and crudeoil flow direction for the purpose of correlation (Ajayi et al ,2009). In some cases, various amountsof radioisotopes are injected with the secondary recovery flooding fluids to facilitate flow.

In Nigeria and other countries, many studies have been carried out on the radioactivity matrices (Tchokossa, 2006, Ajayi et al,2009, Diad et al, 2008, Al-Masri and Suman2003; Isinkaye andShitta,2010 and Fatima et al,2008). It has been noted that radiation is part of the natural environmentand it is estimated that approximately 80% of all human exposure comes from naturally occurringradioactive materials. Hydrocarbon exploration and production activities have the potential toincrease the risk of radiation exposure to the environment and humans by concentrating thequantities of naturally occurring radiation beyond normal background levels (AJayi et al ,2009).

EPA(2005) on environments, health and safety online stated that the more radiation dose a personreceives, the greater the chance of developing cancer, leukemia, eye cataracts, Erithemia,hematological depression and incidence of chromosome aberrations. This may not appear until manyyears after the radiation dose is received (typically, 10-40 years). Ogba/Egbema/Ndoni localgovernment area oil fields produce about 80% of the total crude oil and gas supply in the NigerDelta region of Rivers state. Yet none of the research works done so far has addressed the NORMcontent of the hydrocarbon exploration and production activities and its radiological impact on theworkers and the general public. This study therefore, seeks to assess the Norm content ofhydrocarbon exploration and production activities and to estimate the radiological health implicationto the general public and oil/gas workers.

Material and MethodsThe Study Area

The study area lies with latitude 513¹N and 522¹N and longitude 633¹E and 642¹ north west ofthe Niger Delta region of Nigeria(UNDP,2006). It is one of the onshore oil producing area of

Rivers state. The area which is one of the highest oil and gas production onshore of Niger Delta hasover 900 oil wells with over thirteen active oil fields and playing a host to three multinationalcompanies (Abali,2009). The area is criss-cross with network of pipelines carrying either oil or gas tothe flow stations from the different oil wells (UNDP, 2006).Oil activities started in Onelga in 1964 and production started in 1966 and ever since been in acontinuous operation with increase in the number of drilled oil wells. Gas flaring and oil spillage dueto rupture of pipe leakage has been the major environmental pollutant in the area.

Onelga has a topography of flat plains netted in a web of rivers –the Niger, Sombreiro(Nkissa),Orashi and their tributaries as well as dotted creeks. The tertiary lithostratigraphic sequence of theNiger Delta consists in an ascending order of the Akata, Agbada and Benin formations respectively.With the Benin formation making up an overall clastic sequence of about 9000-12,000m thickdeposits (Ajayi et al,2009). The paralytic Agbada formation is a sequence of alternating sandstoneand shales. Major hydrocarbon accumulations are found in the intervals between the Eocene and the


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Pliocene. The lowest unit the Akata formation is a uniform marine shale int that may contain lensesof abnormally over pressured siltstones or fine grained sandstones. Oil and gas occurrence in theNiger delta are concentrated mainly in the sand stoneformation(Ajayi et al,2009).

Sample Collection and PreparationThirty six soil/sediment samples were collected form the twelve active oil fields and their hostcommunity using the stratified random sampling metfollowed as reported earlier (Ozlem, Hasan and Mahm 2009). Figure 1 is the map of the study areaindicating the sampling points.

Figure 1: A sketch of the Ogba industrial Areas showing sampling areas.

For each of the twelve oil fields and their host communities, one (1) sample of community’s soiland field soil was collected each and one (1) sample of field sediment was collected from the oilfields making a total of thirty-six soil/sediment samples. Also thrfrom non oil bearing community as control samples. About 2kg of soil and sediment samples werecollected and put in vacuum black plastic bags directly after collection to prevent them fromatmospheric humidity and once arrivesediments were removed from the bags to dry in the air at room temperature for several days. Then

both soil and sediment samples were dried in an oven at 80

The samples were sieved through a stainless steel sieve (75Each pellet were transferred into a 2in diameter stainless steel planchette in the detector and werecounted for gross alpha and beta radioactivity using theProcedure (ISO 9696 and ISO 9697) for the measurement of gross alpha and beta activity soil. Thebackground measurements, sample efficiency and the plateau test were carried out using standardmethods (ASTM, 1995).

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Pliocene. The lowest unit the Akata formation is a uniform marine shale int that may contain lensesof abnormally over pressured siltstones or fine grained sandstones. Oil and gas occurrence in theNiger delta are concentrated mainly in the sand stones reservoir at various levels of the Agbada

Sample Collection and PreparationThirty six soil/sediment samples were collected form the twelve active oil fields and their hostcommunity using the stratified random sampling method and sample preparation proceduresfollowed as reported earlier (Ozlem, Hasan and Mahm 2009). Figure 1 is the map of the study area

Figure 1: A sketch of the Ogba industrial Areas showing sampling areas.

the twelve oil fields and their host communities, one (1) sample of community’s soiland field soil was collected each and one (1) sample of field sediment was collected from the oil

six soil/sediment samples. Also three soil samples were collectedfrom non oil bearing community as control samples. About 2kg of soil and sediment samples werecollected and put in vacuum black plastic bags directly after collection to prevent them fromatmospheric humidity and once arrived in the Energy Research center laboratory, Zaria, thesediments were removed from the bags to dry in the air at room temperature for several days. Then

both soil and sediment samples were dried in an oven at 80C for 12 hours and grinded with mortar.

samples were sieved through a stainless steel sieve (75m) and reduced to powder for pelleting.Each pellet were transferred into a 2in diameter stainless steel planchette in the detector and werecounted for gross alpha and beta radioactivity using the International Standards OrganizationProcedure (ISO 9696 and ISO 9697) for the measurement of gross alpha and beta activity soil. Thebackground measurements, sample efficiency and the plateau test were carried out using standard

The Counting Equipment

574

Pliocene. The lowest unit the Akata formation is a uniform marine shale int that may contain lensesof abnormally over pressured siltstones or fine grained sandstones. Oil and gas occurrence in the

s reservoir at various levels of the Agbada

Thirty six soil/sediment samples were collected form the twelve active oil fields and their hosthod and sample preparation procedures

followed as reported earlier (Ozlem, Hasan and Mahm 2009). Figure 1 is the map of the study area

the twelve oil fields and their host communities, one (1) sample of community’s soiland field soil was collected each and one (1) sample of field sediment was collected from the oil

ee soil samples were collectedfrom non oil bearing community as control samples. About 2kg of soil and sediment samples werecollected and put in vacuum black plastic bags directly after collection to prevent them from

d in the Energy Research center laboratory, Zaria, thesediments were removed from the bags to dry in the air at room temperature for several days. Then

C for 12 hours and grinded with mortar.

m) and reduced to powder for pelleting.Each pellet were transferred into a 2in diameter stainless steel planchette in the detector and were

International Standards OrganizationProcedure (ISO 9696 and ISO 9697) for the measurement of gross alpha and beta activity soil. Thebackground measurements, sample efficiency and the plateau test were carried out using standard



The counting equipment used for the gross alpha and gross beta counting is the gas filledproportional counter with 450mgkm3 thick window of diameter 0.06m. It is a EURISYSMEASURE IN 20 low background multiple (eight) channels alpha and beta counter. The countingsystem incorporates interference from high energy cosmic radiation into the measuring environment(ISO, 1997; Onoja 2004). The counting gas is an argon-methane mixture in the ratio of 90% to 10%.The instrument was calibrated following the ISO calibration standard procedure (ISO , 1997).

Results and Discussions

The two acceptable gross alpha and beta radioactivity counting modes (alpha only and beta (+)mode) only whose respective voltages are 1650 and 1700V were employed to count the preparedsoil/sediment. The results of the gross alpha and beta activity in host community soil, field soil andfield sediment are presented in table 1 below.

Table 1: Gross Alpha and Beta Activity Concentration for the Different Soil and SedimentSamples in the Fields.

S/N

SAMPLED OILFIELD

SOIL/SEDIMENT SAMPLE ACTIVITY (βqkg-1)Host Comm. Soil Sample Field Soil Sample Field Sediment Sampleα-activity β– activity α-activity β– activity α-activity β– activity

1 Ebocha 2590.0±34.0 206,600.0±1906.0

170.0±18.0 3350.0±35 47.0±1.0 6040.0±121

2 Mgbede 47.0±1.0 9460.0±135 75.0±2.0 4250.0±70 14.0±6.0 1500.0±111.0

3 Obiafu BDL 2490.0±32 120.0±3.0 18250.0±182.0

380.0±11.0

22520.0±450.0

4 Obrikom 93.0±2.0 6850.0±107.0

220.0±4.0 15220.0±257.0

BDL 1070.0±79.0

5 Ebegoro 35.0±13.0 1320.0±24.0 160.0±3.0 14780.0±167.0

440.0±2.0 3770.0±100.0

6 Omoku 69.0±2.0 10260.0±146

300.0±3.0 12030.0±105.0

250.0±3.0 7450.0±91.0

7 Erema 170.0±8.0 1660.0±27.0 1230.0±23.0

3970.0±36.0

220.0±4.0 34250.0±269.0

8 Idu-Ogba 140.0±3.0 13040.0±132.0

17.0±1.0 5200.0±146.0

620.0±15.0

2430.0±24.0

9 Obagi 46.0±2.0 5240±100.0 580.0±16.0 3220.0±27.0

35.0±1.0 2440.0±67.0

10 Ogbogene 100.0±10.0 1760.0±32.0 74.0±2.0 9820.0±170.0

90.0±21.0 4240.0±120.0

11 Odugiri 60.0±7.0 4370.0±29.0 200.0±3.0 13660.0±119.0

58.0±2.0 3040.0±100.0

12 AgweWest

120.0±2.0 9230.0±85.0 1400.0±22.0

110090.0±1360.0

290.0±3.0 10810.0±122.0

AVERAGE 289.16±7.0 22690.0±104.0

378.83±10.0

17820.0±267.0

203.66±6.0

7485.92±165.0

Table 2: Alpha and Beta Activity Concentration in control Samples



S/N SAMPLE TYPE α- ACTIVITY(βqkg-1)

β – ACTIVITY (βqkg-

1)SAMPLEEFF %

1 Soil 33.0±1.0 1660.0±14.0 90.522 Soil 20.10±0.42 98.0±2.34 80.213 Soil 15.24±0.12 240.0±10.1 100

Average 22.78±1.02 666.0±11.20

Table 1 shows the gross alpha and beta activity concentration in host community soil, field soil andfield sediment samples. From table 1, the gross alpha activity concentration in host community soilranges from BDL to 2590.0±34.0Bqkg-1 with a mean value of 289.16±7.0 Bqkg-1. While the grossbeta activity concentration ranges from 1660.0± 27.0Bqkg-1 to 206,600.00±1906.0Bqkg-1 with a meanvalue of 22690.0±104.0Bqkg-1. In field soil samples analyzed, the gross alpha activity concentrationranges from 17.0±1.0 Bqkg-1 to 1400.0±22.0Bqkg-1 with a mean value of 378.83±10.0Bqkg-1. Thegross beta activity concentration in field soil samples ranges from 3350.0±35.0Bqkg-1 to110,090.0±1360.0Bqkg-1 with a mean value of 1782.0±267.0 Bqkg-1. Furthermore the gross alphaactivity concentration in field sediment samples ranges from BDL to 620.0±15.0Bqkg-1 with a meanvalue of 203.66±6.0Bqkg-1 while the gross beta activity concentration ranges from 1070.0±79.0Bqkg-

1 to 22,590.0±459.0 Bqkg-1 with a mean activity value of 7485.92±165.0Bqkg-1.

Table 2 show the gross alpha and gross beta activity of the control samples. The mean alpha activityconcentration for the control soil sample was 22.78.0±1.02Bqkg-1 which is low compared with theobserved alpha activity values in community’s soil, field soil and field sediment samples respectively,while the mean gross beta activity concentration was found to be 666.0±14.0 Bqkg-1 which is alsolower than the observed beta activities on the soil samples. Comparison of the results of mean grossalpha and beta activity in the host community soil, filed soil and field sediment samples with thegross alpha and beta activity of the control samples has shown that the gross alpha and beta activityof the control samples were far less than the gross alpha and beta activity of the soil/sedimentsamples. This is an indication that the NORM content of the oil fields sampled and their hostcommunities has been elevated due to hydrocarbon exploration and production activities in the area.Figure 2 is a graphical comparison of the gross alpha activity of the soil/sediment samples with thegross alpha activity of the control soil samples. While figure 3 is a comparison of gross beta activityof the soil/sediment samples with the gross beta activity of the control samples. Gross alpha andbeta activity graphs exceeded that of the control in both figure 2 and 3.



Fig.2: comparison of gross alpha activity concentration in soil samples with the standard UNSCEARstandard for soil.

Fig 3: Comparison of gross Beta activity concentration in soil/sediment samples with gross betaactivity of the control soil sample.

0

500

1000

1500

2000

2500

3000

EBO MGB OBI OBR EBE OMO ERE IDU OBA OGB ODU AGW

Field Code

Gro

ss

Alp

ha

Ac

tiv

ity

(Bq

/kg

)

Host Comm.Soil

Field Soil

Field Sed.

STANDARD

0.00

25,000.00

50,000.00

75,000.00

100,000.00

125,000.00

150,000.00

175,000.00

200,000.00

225,000.00

EBO MGB OBI OBR EBE OMO ERE IDU OBA OGB ODU AGW

Field Code

Gro

ss

Be

taA

cti

vit

y(B

q/k

g)

Host Comm.Soil

Field Soil

Field Sed.

CSS



Figure 4: contour map of gross alpha activity in soil/sediment samples

Fig 5 : contour map of gross beta activity concentration in Bqkg-1 of soil/sediment samples.

Figure 4 and 5 show the iso-gross alpha and beta maps (contour radiological maps) expressed inBqkg-1, dry weight. The data show that the gross alpha and beta activity concentration of

soil/sediment sample are not uniformly distributed. Areas bounded by latitude 522¹-523¹ and

longitude 638¹- 640¹ has an elevated gross alpha activity concentration while areas bounded by

latitude 522¹- 526¹ and longitude 638¹- 640¹ has an elevated beta activity concentration. Otherareas have varying low values of alpha activity concentration and relatively high beta activityconcentration. This non-linear distribution of alpha activity and beta activity in the oil fields sampledcould be an indication that the cause of an elevated NORM in the oil fields is not strictly from thegeological constituents, thus the enhancement of the NORM content of this environment which leadto enhancement of gross alpha and gross beta activity may have been due to modification and



degradation due to industrial activities in the area. The obtained results showed that the gross alphaand gross beta radioactivity concentrations in soil and sediment samples were found to be relativelyhigher than observed results in the works(Ozlem et al,2009;Ajayi et al,2009,Yuanxun et al,2003;Stephen,2004). This can be explained by the oil and gas exploration and production activities in thearea which discharges their waste into cellar pits or ponds and sometimes into the water bodies andwaste dumps. As a result of these activities, NORM content of the area is enhanced.

The gross alpha radioactivity concentration in soil samples is defined as the total radioactivity of allalpha emitters which in this case is mainly due to uranium and radium and thorium isotopes(Osmond and Ivanovich,1992). The values of gross alpha radioactivity originating from these alpha-emitters in soil samples depend on the geological characteristic of the area, content of mineralcomponent and the type of activities in the area. Alpha emitters mixed to ground water by filteringfrom soil have contributed to the increased concentrations of gross alpha in well water samples. Thegross beta radioactivity in soil is due to the natural long-lived isotopes 40K, 210Pb and 228Ra (Cothernet al, 1986). Others are artificial isotopes, such as 90Sr and 137Cs. However, the gross beta activity insoil samples in the studied area could be affected by hydrocarbon exploration and productionactivities that discharge effluent in cellar pits, water bodies, around the plant and the surroundingenvironment. Precipitation and flooding erode radionuclide on surface soils.

ConclusionThe main target of this work was to assess the naturally occurring radioactive material (Norm)content of a hydrocarbon exploration and production of Ogba/Egbema/Ndoni fields bydetermining gross alpha and beta radioactivity concentrations. In the host community soil, field soiland field sediment samples, the concentration of the gross alpha and beta were higher than that ofthe control samples from a non- oil bearing community. Natural radioactivity is directly related to thekind of geological layers and of their physico-chemical conditions. But the contour maps in figure 4and 5 shows a non-linearity of the distribution of these radionuclide indicating that the cause ofNorm elevation which lead to enhanced gross alpha and beta radioactivity might not be fromgeological constituent of the area but due to industrial activity in the area. The overall result shows agross radiological pollution of the area which could be detrimental to the health of the oil workersand the general public as continuous exposure can lead to build up of radionuclide in the body whichcould lead to cancer and other related sicknesses. Therefore we recommend further studies onradiological burden of the water resources of the area and ascertain safety measure to limit exposureto these ionizing radiations.

References

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Al-masri and Siman (2003). NORM waste management in the oil and gas industry: the SyrianExperience. Journal of Radioanalytical and Nuclear chemistry. 256 (1):159-162.

ASTM,(1995). Standard Test Method for alpha particle radioactivity of water. ASTMD1943-90.

ASTM,(1995). Standard Test Method for beta particle radioactivity of water. ASTMD1890-90.



Diab,H.M,Nouh,s.a.,Hamdy,A.,&El-fiti,S.A.(2008). Evaluation of Natural radioactivity in aCultivated area around a fertilizer factory. Journal of Nuclear and Radiation physics.3 (1)53-62.

Fatima et al,(2008). Measurement of Natural Radioactivity and Dose rate gamma radiation of theSoil of Southern Punjab, Pakistan. Radiation Protection Dosimetry.128 (2):206-212.

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International Standard Organization (1997). ISO 9696. Water Quality: Measurement of GrossAlpha activity in non-saline water.

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Onoja R.A.(2004). Survey of gross alpha and beta radioactivity in well water from Zaria area.Radiation Biophysics. Ahmadu Bello University, Zaria. Unpli. M.Sc thesis.

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Stephen, G.M.(2004). Background radioactivity in sediments near Los Alamos, New Mexico.Science of the Total Environment, 328:143-159.

Tchokossa, P. (2006). Radiological study of oil and gas producing areas in Delta state, Nigeria.Unpbl. Ph.D thesis , Obafemi Awolowo University, Nigeria.

Yuanxun et al,(2003).PIXE and radioactivity measurements for elemental determination in riverWater and sediment samples. Journal of Radioanalytical and nuclear chemistry, 258: 415-419.

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