The mud rotary drilling has been chosen as the consistent method in the
Southern ... rise and does not currently show any sign of impediment. • No
assessment ...
EFFECT OF MUD ROTARY DRILLING ON GROUNDWATER QUALITY AND THE ENVIRONMENTAL IMPACT ASSESSMENT OF ITS BY-PRODUCTS IN SOUTHERN NIGERIA
David O. Olukanni, (Ph.D) Nnamdi C. Ugwu, (B. Eng) Department of Civil Engineering Covenant University, P.M.B. 1023, Ota Ogun State, Nigeria.
E-mails:
[email protected] +234-8030726472
[email protected] +234-8039709912
INTRODUCTION • The way people go in search of water in most areas of the country for domestic purposes substantiate the fact that supply of improved water in both urban and rural areas is grossly inadequate. • Pressures on water resources are increasing as a result of human activity namely: i. ii. iii. iv. v.
Urbanization Population growth Increased living standards Growing competition for water and Pollution.
2
Problems responsible for this situation: •
Lack of priority given to the sector
•
Lack of financial resources
•
Lack of sustainability of water supply
•
Sanitation services
•
Poor hygiene behaviors
•
Inadequate sanitation
All these are evident in public places including hospitals, health centers and schools.
3
• As a measure to solving the imminent challenge in the daily shortage of water especially in most of our urban centers, attention has been shifted to open dug wells for groundwater resources. • Currently, the major source of potable water for communities, households and industries is the sinking and development of boreholes for harnessing ground water. • A borehole is a formation created in the ground by boring or drilling to access groundwater in underground aquifers. It can vary greatly in depth, 4 water volume and water quality.
• In their work Adekile and Olabode (UNICEF, 2009), stated that to meet the year 2015 MDGs and national goals it is estimated that 15,000 boreholes need to be drilled annually. • Oloyede in his paper “water is life” states that the government needs to sink 77,500 boreholes in Nigeria to meet domestic water demands (Oloyede, 2010). • This poses a challenge to all in the industry. The challenge is not just to contractors to meet demands and governments to supply funds but also to environmental monitors.
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• It is important that the activities of an industry this huge are not left unchecked and unregulated. A consistent failure to monitor the operators and their operations may in no time lead to a massive environmental disaster which will be expensive to remediate. • The disposal of drilling mud and cuttings has been observed to be of continuously growing concern especially to the researchers in the western world due to their numerous negative effects on the health, safety and environments (HSE) (Moseley,1983), Nigeria cannot be an exception in this regard. 6
Map of the world showing the location of Nigeria
7
Map of Nigeria
8
• Of the four major and current methods employed in drilling these boreholes, namely: i.
Auger drilling,
ii.
Percussion or hammer drilling,
iii. Mud rotary drilling and iv. Cable tool drilling, • The mud rotary drilling has been chosen as the consistent method in the Southern part of Nigeria because of its affordability and efficient operation. • It is not the only way to put a hole in the ground, but it is undoubtedly the most common, versatile and dependable method
9
Statement of Problem. • The development of these boreholes is continuously on the rise and does not currently show any sign of impediment. • No assessment has been undertaken to investigate the effects of mud rotary drilling process on groundwater quality and the environmental impact of its by-products. •
Borehole typically contains more minerals in solution than surface water and may require treatment to soften the water by removing minerals such as arsenic, iron and manganese.
•
Drilling fluid is the most abundant waste material produced after the completion of any drilling exercise
10
OBJECTIVES OF THE STUDY i.
To measure the concentration of the constituents of the byproducts of Mud Rotary Drilling.
ii. To find out if the drilling process has any effect on the ground water quality. .
11
DRILLING MUD Fluids injected into a well during its construction process. Its functions include: 1. Cleaning the cuttings from the face of the dill bit 2. Transporting the cuttings to the ground surface 3. Cooling the drill bit 4. Suspending the cuttings in the hole and dropping them in surface disposal areas
12
TYPES OF DRILLING MUDS •
Water Based Muds
•
Oil Based Muds
•
Synthetic Based Muds
13
Water Based Mud •
Water based Muds consist of water mixed with bentonite clay and barium sulphate (barite) to control mud density.
•
Other substances are added to gain the desired drilling properties. About 85% of all mud systems in the world today both in the oil and water well construction industry are water based (DTA, 2007).
14
Oil Based Mud • An oil-based fluid has oil as its continuous external phase and if water is present makes a dispersed or internal phase. • The solids in an oil-based fluid are oil-wet, all additives can be displaced in oil and the filtrate of the mud is oil but may contain 0-5% unintentional water. • Oil muds offer many advantages over water based muds. The high initial cost of the oil-based mud can be a factor in not selecting this type of mud system 15 (D.T.A., 2007).
Synthetic Based Mud • Synthetic-based fluid is a mud where the base fluid is a synthetic oil. This is most often used on offshore rigs because it has the properties of an oil-based mud. • Synthetic-based fluids are free of inherent contaminants, unlike conventional oil-based drilling fluids. As a result, they are more benign environmentally, as demonstrated by aquatic toxicity testing. 16
ENVIRONMENTAL IMPACT OF WBM •
WBMs deposited on seabed sediments may smother benthic animals and, if in the form of fine particles suspended in the water, can interfere with respiration in small marine animals and fish.
•
Like other muds, they commonly contain additives that can be extremely toxic, even in low concentrations (Patin, 1998).
•
In soils with high seepage and high water table, WBM may affect ground and surface water. They may also alter the soils pH value and have effects on the plant life. 17
EFFECT OF DRILLING FLUIDS ON GROUNDWATER
The United States Environmental Protection Agency states that mud rotary drilling process has the ability to pollute existing underground aquifers if the drilling fluid contains harmful additives (EPA, 1986). These injections of drilling fluids to the surrounding soil have the ability over time in extended drilling to seep deeper horizontally into the aquifer.
18
Mud Pit (seepage may occur at this point)
Mud Mix Ratio
Carboxymethylcellulose (CMC) Polyanionic cellulose (PAC) Source: Onyia(2011)
19
DISPOSAL METHODS IN NIGERIA i. ii. iii. iv.
On site burial Pumping into flowing water bodies Pumping into vegetation Pit abandonment
20
Mud spilled into Vegetation in Bayelsa
Mud Spilled into vegetation in Rivers
SITE VISIT
The first five sites were visited in the course of this study and we were able to obtained samples from the last 2 sites:
1.
Oraeri community in Anambra State
2.
Yenegoa in Bayelsa State
3.
Ohaji Egbema in Imo State
4.
Ndoni LGA, Rivers State
5.
Forcados Island Delta State.
6.
Abalemabie community, Bonny, Rivers State
7.
Ekpoma in Edo State
21
SITE VISIT
Sampling in one of the sites visited
22
Unlined Pit
Lined Pit
23
Elevated Pit
Mud Tank
SAMPLE ANALYSIS
The samples for Oraeri and Yenegoa were tested at the Laboratory of Transocean Nig Ltd, Nigeria.
The Samples for Ndoni, Forcados and Ohaji were tested in Hamilton Technology laboratory.
The Water sample analysis were done by the Niger Delta Basin Development Authority. 24
RESULTS Comparative values of all sites visited in mg/l
Parameters
Oraeri Yenegoa Ohaji
Ndoni Forcados
1
pH value
8.2
8.1
8.2
8.0
8.0
2
Manganese
224
211
123.8
114
314
3
Copper
92
76
73
96
96
4
Lead
16
19
36
15.3
25.3
5
Nickel
70
49
36
49
62.1
6
Zinc
45
65
4.0
65
79.51
7
Chromium
320
320
423
373.2
371.03
8
Arsenic
2
2
2.7
3
3.2
9
Mercury
Trace
Trace
2.93
1.8
1.8
10
Iron Content
14
39.6
122.8
45
229.3
25
Graphical representation of the sites investigated showing concentration of heavy metals 450
Concentrations (mg/l)
400
Manganese
350
Copper
300
Lead Nickel
250
Zinc
200
Chromium
150
Arsenic
100
Mercury
50
Iron Content
0
Oraeri
Yenegoa
ohaji
ndoni
Forcados
26
Elevated pit mixture in process
Mud tank mixture in process
27
Interpretation of Experimental Results pH value:
The pH value/rating of the entire drilling fluid waste collected from all sites fell within the 8.0 – 8.5 range. This shows that drilling fluids released to the environment are alkaline in nature. The pH values (8.0 – 8.5) are not considered harmful to the environment.
28
Chromium
Heavy metals are dangerous because they tend to bioaccummulate.
The range of chromium in the waste fluid ranged from 320mg/l to 423 mg/l with an average value of 371.03mg/l.
Chromium is an element which attaches itself to bentonite when it is mined in its raw state.
A very small amount of the chromium in soil, however, will dissolve in water and can move deeper in the soil to underground water.
Long-term exposure can cause kidney and liver damage,29 and damage too circulatory and nerve tissue.
Arsenic (As)
The permissible limit of arsenic in agricultural soils is 7.5mg/l. A conservative risk analysis shows that Arsenic Concentration in soil can reach 15mg/l without hazard to exposed organisms (Dukha & Miller, 1999). The arsenic levels in the drilling fluid ranged from 2mg/l to 3.2mg/l. This result shows that the soil at the end of the drilling will still be safe for both plant and organisms in the area. Exposure to inorganic arsenic can cause various health effects, such as irritation of the stomach and intestines, decreased production of red and white blood cells, skin changes, lung irritation and many other diseases.
30
Lead (Pb)
High levels of exposure to lead may result in toxic biochemical effects in humans which in turn cause problems in the synthesis of haemoglobin, effects on the kidneys, gastrointestinal tract, joints and reproductive system The United States Environmental protection Agency’s standard for lead in bare soil in recreational and work areas is 150 mg/l by weight and 450 mg/l for non-useable land areas. The lead content in the waste drilling fluids showed an average lead content of 16mg/l with a maximum value of 36mg/l at the Ohaji These levels of lead recorded pose no serious threat to the 31 soil and vegetation around the site.
Mercury (Hg)
The mercury content in the drilling fluid from the sites investigated ranged from trace quantities to a maximum of 2.93mg/l. Suggested permissible levels of mercury in soil were found to be 2.27mg/l and 6.5 mg/l of soil depending on soil conditions (Wang et al., 1982). Inorganic mercury poisoning is associated with tremors, gingivitis and/or minor psychological changes, together with spontaneous abortion and congenital malformation. Also causes damage to the brain and the central nervous system, while foetal and postnatal exposure have given 32 rise to abortion, congenital malformation and development changes in young children.
Nickel (Ni)
The Nickel content in the drilling fluid is within the range of 36 – 70 mg/l. The average nickel content at the surface levels of various soils is from 1.5-20 mg/L, lower concentrations occur on light sandy soil and are on average 5.6mg/l or greater occur in clay soils (Barałkiewicz 1999). High Nickel content soils easily pollute shallow ground water sources and has adverse effect on plant life (Lenntech, 2009). Small amounts of Nickel are needed by the human body to produce red blood cells, however, in excessive amounts, can become mildly toxic. long-term exposure can cause decreased body weight, heart and liver damage, and skin irritation.
33
Copper (Cu)
The analysis on the waste drill fluid showed the concentrations of copper in the waste drill fluid which ranged from 76mg/l - 96mg/l The European Commission has set its permissible soil copper content as to fit within the range of 20-43 mg/l of soil (Nauman and Khalid 2010). These copper values exceed permissible amounts in soils, plants around the site may absorb the copper and when consumed may cause irritation to the digestive system. High doses can cause anemia, liver and kidney damage, and stomach and intestinal irritation. 34
Manganese (Mn)
The concentration of the manganese content in the waste fluid ranged from 114mg/l – 314mg/l The total amount of manganese in soils is typically around 0.25%, and is normally measured at 6g/l. It can be as high as 13% in some volcanic soils. (Incitec, 2003). Manganese effects occur mainly in the respiratory tract and in the brains. Symptoms of manganese poisoning are hallucinations, forgetfulness and nerve damage. Manganese can also cause Parkinson, lung embolism and bronchitis. 35
Iron (Fe)
The readings of the iron content in the waste drilling fluid ranged from 14mg/l to 229.3mg/l The iron content of the fluid varied sharply in several sites. The high iron content in some wells can be said to be due to the iron content in the surrounding soils around the aquifer. Special attention should be given to plants, air and water in these areas. 36
GROUNDWATER CONDITIONS The
results show very little and negligible contamination from the heavy metals present in the drilling fluid.
Manganese
presence in the drill fluid approached 314mg/l but was found to be near negligible in the water sample.
Chromium
presence in the drill fluid approached 423mg/l but was found to be near negligible in the water samples.
Iron
content in the water from some wells was however found to be higher than WHO levels in some wells but was also far below the quantities found in the waste drilling fluid.
37
Drilling Operation in Progress
Groundwater from the borehole
38
Water quality characteristics of selected boreholes S/N
Parameter
Unit of
Ajowa Arogbo Obinehin Araromi Abetobo Igbogurin Jiringho
W.H.O
Measurement Guideline 1
Colour
Pt. Co. Unit
15
2
Odour
Subjective
Unobjectionable
3
Taste
Subjective
Unobjectionable
4
Conductivity
uS/cm
5
Nitrate
(Ondo) (Ondo) (Ondo)
(Ondo)
(Ondo)
(Ondo)
(Ondo)
1
20
20
10
1
5
10
-
46.9
41.8
48.9
56
58.9
97
120.24
mg/l
45
-
-
-
-
-
0
.042
(NO3) 6
Nitrite (NO2)
mg/l
3.0
.013
-
-
-
-
0
0
7
Iron
mg/l
0.3
.14
1.88
.06
.07
.26
4
2.71
8
Copper
mg/l
2.0
.15
.53
.4
.22
.09
-
.21
9
pH
6.5 – 8.5
6.8
6.78
6.38
6.54
5.64
6.0
7.96
10 Turbidity
FAU
5
.05
5.0
10
1.0
.1
.22
1.0
11 Chlorine
mg/l
0.3 (after
-
-
-
-
-
0
-
0
-
-
--
-
-
.03
-
-
-
-
-
30mins)
residuals 12 Chromium
mg/l
0.05
13 Arsenic
mg/l
0.01
14 Fluoride
mg/l
1.5
.22
0
-
-
.02
-
39 .63
15 Chloride
mg/l
250
.0
16
64
110
900
5.5
112.0
S/N Parameter
Unit of
W.H.O
Ajowa arogbo obinehin araromi Abetobo Igbogurin Jiringho
Measurement Guideline 16
Total
mg/l
30.0
mg/l
26.8
20
40
160
230
29
200
11.44
16.28
8.8
37.8
31.24
67.2
9.6
69.12
58.52
10
19.2
.078 0
.9
Alkalinity 17
Carbon Dioxide
18
Sulphate
mg/l
250
19
Phenol
mg/l
1.5
.018
.084
.084
20
Manganese
mg/l
0.5
1.1
.21
.9
21
Total Hardness
mg/l
400
42.6
22
6
90
56
27
66
22
Calcium
mg/l
20
18
6
72
44
18
50
mg/l
22.6
4.0
0
18
12
9
16
mg/l
32.0
43
115
11
10
23.3
180.6
20.8
58.2
8.6
60
69
92.8
Hardness 23
Magnesium Hardness
24
Total
11
Suspended Solids 25
Total Dissolved
mg/l
1000
Solids 26
Acidity
mg/l
2.0
4.0
6.0
6.0
43
4046
27
Salinity
PPT
.1
.1
.15
.17
16
2
28
Total Coliform
11
0
0
28
6
MPN/100ml
0
32
Comparison of ground water quality to drilling fluid effluent concentration in mg/l Ground Water Quality S/N
Parameter
Unit
Ikorigho Adelesema
Igbokoda Average drill
Ajowa Araromi
Abetobo
Jiringho
(Ondo)
(Ondo)
(Ondo)
(Ondo)
(Ondo)
(Ondo)
(Ondo)
waste values
1.53
90.14
1
Iron
mg/l
0.14
0.07
0.26
2.71
0.3
3.56
2
Copper
mg/l
0.15
0.22
0.09
0.21
0
0.14
3
pH
6.8
6.54
5.64
7.96
7.4
7.11
5.33
8.1
4
Chromium
mg/l
0
--
-
.03
-
-
-
371.03
5
Arsenic
mg/l
-
-
-
-
-
2.58
6
Manganese
mg/l
0.9
-
0.6
0.062
197.36
0.9
96
41
CONCLUSION Nickel
and Copper were found to be in excess above permissible limits to be deposited in soils
Groundwater
impurities were far below the effluents concentrations from the drilling fluids. Nickel and copper concentration in the ground water were extremely negligible
Mud
Rotary Drilling can be described as a relatively safe process for harnessing groundwater 42
RECOMMENDATION
Contractors should carry out regular tests on their drill fluids when working in environmentally sensitive areas “Site cleanup and restoration” clauses should be added and insisted on by clients when preparing and signing contracts. Further research should be carried out on this topic. The test should show a comparison between the initial concentrations of the heavy metals of the drilling fluid and the final concentration. This will 43 enable the effect of the soil formation on the fluid quality to be monitored properly.
Secondary mud pits should be constructed alongside the functional mud pit(s). The secondary pit will have to be lined with cement or properly laid block work to prevent seepage into the soil. This secondary mud pit will be used as a reservoir for spent drill fluid during the process. The drilling fluid will be allowed to evaporate. The sludge left at the end of the drilling process will then be covered with the excavated material on site and permanently buried.
44
Acknowledgement Transocean Nig Ltd Hamilton Technology laboratory Niger Delta Basin Development Authority Nnamdi Ugwu Civil Engineering Department, Covenant University Surfactant Associates SURBEC ENVIRONMENTAL Pro Cleanse WATER FILTRATION MCAFEE &TAFT JOHNSTON & ASSOCIATES Mr. Steve Vance Mr. Bruce A. Stower BENHAM Water Technologies for Emerging Regions WaTER.ou.edu. University of Oklahoma
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