STABILISATION/SOLIDI FICATION OF SYNTHETI C NORTH SEA DRILL CUTTINGS CONTA INING OIL AND CHLORI DE

1. Page 0
STABILISATION/SOLIDIFICATION OF SYNTHETIC NORTH SEA
DRILL CUTTINGS CONTAINING OIL AND CHLORIDE
Marwa S. Al-Ansary (1)
and Abir Al-Tabbaa (1)
(1) Engineering Department, Cambridge University, United Kingdom
Abstract ID Number: a220
Author contacts
Authors E-Mail Fax Postal address
Marwa S. Al-
Ansary
msma3@cam.ac.uk +441223339713
Engineering
Department,
Cambridge University,
Trumpington St.,
Cambridge CB2 1PZ,
United Kingdom
Abir Al-Tabbaa aa22@eng.cam.ac.uk +441223339713
Engineering
Department,
Cambridge University,
Trumpington St.,
Cambridge CB2 1PZ,
United Kingdom
Contact person for the paper: Marwa S. Al-Ansary
Presenter of the paper during the Conference: Marwa S. Al-Ansary
11
Total number of pages of the paper (this one excluded): 10

2. Page 1
STABILISATION/SOLIDIFICATION OF SYNTHETIC NORTH SEA
DRILL CUTTINGS CONTAINING OIL AND CHLORIDE
M.S. Al-Ansary (1) and A. Al-Tabbaa (1)
(1) Engineering Department, Cambridge University, United Kingdom
Abstract
On the UK Continental Shelf, up to 80,000 tonnes wet weight of oily drill cuttings are
produced annually. These are heterogeneous wastes generated from the petroleum drilling
industry, composed of significant percentages of hydrocarbons, heavy metals and chlorides.
Since 1992, the discharge of drill cuttings containing more than 1% oil-on-cuttings has been
prohibited. Moreover, the extensive increase in tipping fees, imposed by the Landfill Tax in
October 1996, has hindered the landfilling of drill cutting as a viable option. Therefore, drill
cuttings are a big problem for which the petroleum industry is keen to find solutions. This
paper examines the use of stabilisation/solidification (S/S) as a technique to treat North Sea
drill cuttings either as a pre-treatment prior to landfilling or for potential re-uses in
construction products. Given the known difficulties with stabilising/solidifying oils and
chlorides, this paper uses synthetic typical North Sea drill cutting mixes which contain typical
average concentrations of hydrocarbons (4.2% w/w) and chloride (2.03% w/w) only to
compare the ability of the different binder systems to treat them. A number of conventional
S/S binders, namely Portland cement, hydrated lime, pulverised fuel ash and blastfurance
slag, as well as novel binders, namely MgO cements, zeolites, silica fume, cement kiln dust,
and compost were used. The water to dry binder ratio used was 0.4:1 and the dry binder
content by weight was up to 30%. A set of physical tests (unconfined compressive strength),
chemical tests (NRA leachability) and micro-structural examinations (using SEM) were
conducted on the different mixes. The paper presents the behaviour of the various drill
cuttings and binder mixes and compares their relative performance.
Key words: stabilisation/solidification, drill cuttings, petroleum industry, North Sea,
industrial by-products, wastes.
1. INTRODUCTION
Drill cuttings are one of the inevitable wastes generated from the drilling process of oil
exploration activities. Drill cuttings are heterogeneous wastes that are composed of significant
percentages of hydrocarbons, water, heavy metals and water-soluble salts such as chlorides
and sulphates. The cuttings are produced when the drilling activity commences with
continuously pumping down a fluid known as ‘drilling mud’ into the drill pipe. Not only does
the drilling mud provide the necessary lubrication and hydrostatic head that prevents the
collapse of the pipe walls, but it also transports the rock debris (i.e. drill cuttings) to the
surface, as shown in Figure 1(a). On return to the drilling facility, the mixture of cuttings and
mud are processed in a circulation system in order to clean the cuttings and recover as much
of the mud as possible [1]. The recycled drilling mud is reused again in the drilling, while the
drill cuttings are either discharged at the seabed (before 1992) or disposed of in landfill.

3. Page 2
Figure 1(b) shows a sample of North Sea drill cutting that is dark in colour with a pungent
odour.
Figure 1: (a) Offshore Drilling Activity Generating Drill Cuttings,
(b) raw drill cuttings and (c) treated drill cuttings by thermal desorption
Drilling mud is a dense, sophisticated and extremely expensive material composed of
many chemical compounds. Depending on the type of the base fluid, there are three kinds of
drilling mud: water-based mud (WBM), oil-based mud (OBM) and synthetic-based mud
(SBM) as in Table 1 which presents their relative merits. The typical composition of the
drilling mud is reported in Table 2 [2].
Table 1: Comparison between the merits of drilling mud/fluid systems
Criteria Water-based
mud (WBM)
Oil-based
mud (OBM)
Synthetic-based
mud (SBM)
Least Cost 1 2 3
Environmental Friendly 2 3 1
Technicality 2 3 1
Safety 2 3 1
Base Material Water Diesel Oleaginous (oil-like)
Table 2: Typical drilling mud composition [2]
Compound WBM (%w/w) OBM/SBM (%w/w)
Barite 57.6 69.5
Base oil 25.8
Bentonite 4.1 0.3
Calcium chloride 2.0
Caustic soda 1.2
Emulsifiers 1.8
Oil wetting agent 0.1
Polyanionic cellulose (PAC) 1.2
Salt 33.0
Soda Ash 1.0
Starch 1.2
Xanthan 0.5
Other 0.2 0.5
Drill Mud Circulation System
Recycled Mud
Drill Cuttings
+ Mud
Drill Cuttings
contaminated with
oil and chemicals
(b)(a)
(c)

4. Page 3
Factors affecting the choice of the correct drilling mud include: formation lithology and
pressure, well design, strength and temperature, logistics and rig type, and environmental and
health considerations [1]. The main drilling mud in the North Sea platforms is either water-
based or synthetic-based system, while oil-based mud has been banned since 1984 because of
its hazardous diesel content. The physical characteristics and the chemical composition of the
drill cuttings vary significantly according to the type of drilling mud used, local geology, oil
well location, oil operator and drilling techniques, recovery technique, exposure/disposal
scenarios of the cuttings, weathering and bacterial conditions.
2. LEGISLATIONS AND LAWS
Significant negative ecological impacts have been experienced adjacent to many oil and
gas platforms in the North Sea when the cuttings are discharged to the seabed [2] and [3].
This is reflected in the recent stringent environmental regulations issued under European
legislation, particularly the UK legislation controlling the discharge of the drill cuttings from
the North Sea platforms. One of the main areas of legislature governing the discharge of drill
cuttings in the North Sea is the Oslo and Paris Commission (OSPARCOM) Decisions 92/2
and 2000/3, which prohibits any discharge at sea for oil-based mud (OBM) cuttings
containing more than 1% oil-on-cuttings by weight. In compliance with OSPARCOM, the
UK has ceased any discharge of mineral oil contaminated cuttings into the sea since January
1997. It is predicted that more rigorous forthcoming legislation will be imposed on the
discharge of both water-based mud (WBM) and synthetic based mud (SBM) cuttings [4].
Moreover, the UK Department of Trade and Industry (DTI) had reached an agreement with
the UK operators to have Zero discharge of cuttings by the end of year 2000 [5].
From April 2004, drill cuttings will no longer be classified as ‘special waste’ in the UK,
but will fall within the EU Directive’s definition of ‘hazardous waste’ [6]. Therefore, if the
cuttings are to be disposed of to landfill, the cuttings will be charged at the standard rate for
active wastes under the UK landfill tax (which now stands at £14/tonne). On the other hand,
from July 2004 there will be no permitted hazardous waste landfills in Scotland [6]. Similarly,
in England and Wales the number of hazardous landfill will be reduced. Therefore, the tipping
fees will increase markedly over the next 3 years as the availability of landfills is reduced and
hazardous landfills become rare in the UK. Consequently, the UK petroleum industry is
currently facing a pressing need to manage the quantity and composition of drill cuttings.
3. TREATMENT METHODS AND CURRENT PRACTICE
The petroleum industry’s current practice is to treat the cuttings before any re-use or
disposal option in order to remove oil from the cuttings and to reduce the leachability of other
contaminants. However, the presence of high percentages of contaminants is the main
hindrance to the reuse option. Current treatment methods include bioremediation in-situ,
bioreactors, land farming, re-injection, respreading, thermal desorption, mechanical
separation, distillation, stabilisation and combustion. Figure 1(c) shows a sample of drill
cuttings treated by thermal desorption. Suggested applications for the treated drill cuttings [5]
include their reuse in: (a) concrete products such as concrete/cement, aggregate, blocks and
bricks, (b) coastal defence, (c) land reclamation, (d) roads and cycle paths, (e) pipe beddings,
(f) landfill cell construction, (g) landscaping applications such as noise abatement mounds, fill
material, top soil admix and embankments in a brackish environment, and (h) as a fuel.
4. STABILISATION/SOLIDIFICATION (S/S) TREATMENT
Solidification is defined as a process converting waste into a durable, dense and monolithic
entity with structural integrity that is more compatible for storage, landfill, or reuse [7].

5. Page 4
Stabilization is a chemical process used to minimise the hazardous potential and leachability
of waste by converting the contaminants into a form, which is less soluble, mobile, or toxic
[7]. S/S has many advantages since it requires minimal energy input and results in minimal
emissions to air [5]. However previous work has faced some limitations and disadvantages in
terms of utilising this technique to treat drill cuttings [4] and [5]. The problems mainly
resulted from the interference of high concentrations of organic compounds, chlorides and
bentonite with the hardening and the curing processes of cement. Furthermore, the presence
of high percentages of chloride prohibited the use of drill cuttings in reinforced concrete
applications.
Very little work has been published in the UK and elsewhere describing the use of S/S in
the treatment of drill cuttings and most has been related to subsequent landfilling rather than
reuse [8]. One UK source reported that S/S with cement or pulverised fuel ash (PFA) is a
viable solution [4] and concluded that the disadvantage of this option is the high embodied
energy from cement, transportation of the additives and increased bulk material for disposal.
There are few works that have been published describing the use of S/S technique in order to
treat drill cuttings for further use. A source in Turkey used kalonite, gypsum, bentonite,
clinker, lime and fly ash to stabilise drill cuttings prior to landfilling and for use in road
construction applications [9]. A source in Algeria recommended the stabilisation of drill
cuttings with the addition of 70% of a hydraulic binder for subsequent use as a sub-base
material in road construction [10].
5. NORTH SEA CASE STUDY
Between 1986 and 1995, 313 wells (on average) were drilled in the North Sea each year. It
is estimated that about 1,000 tonnes of cuttings will be generated from each well if drilling
continues at this rate. Therefore, over 300,000 tonnes of drill cuttings may be produced
annually [5]. However, the UK Continental Shelf (UKCS) is currently estimated to produce
between 50,000 to 80,000 tonnes wet weight of oily drill cuttings annually [4]. On the other
hand, the old drill cuttings piles located at the North Sea bed are approximately equal to 1.3
million cubic meters, which has been built up on the North Sea bed in different locations [3].
5.1 Physical and chemical characteristics of the drill cuttings in the North Sea
Different studies have been carried out to understand the physical characteristics and
chemical composition of the drill cuttings in the North Sea, which vary significantly from one
oil well to another. The studies were mainly carried out by two organisations RF- Rogaland
Research (Norway) and UKOOA (the United Kingdom Offshore Operators Association), in
addition to other commercial and academic endeavours. The data gathered were from the
following oil wells: Alwyn, Beatrice, Beryl B, Case N4, Clyde, Cod, Fulmar A, Heather A,
NW Hutton, Nelson, Niniam, Oseberg B, Oseberg C and Ekofisk [1-5 and 11-13]. Due to the
heterogeneous nature of the composition of drill cuttings, many contamination scenarios can
be considered. However, most of the data on the drilling mud and cuttings were highly
classified and confidential. In this research, the experimental methodology is based on
processing the available published data from the literature and personal communications. This
provided the range of values, shown in Table 3, from which the statistical average
composition of the North Sea drill cuttings was calculated and used. The main contaminants
were found to be hydrocarbons, chlorides, barium (from barium sulphate (barite) which is a
weighing agent in the drilling mud and is the main cause of the high pH of the cuttings), zinc,
chromium, lead and iron. The case considered here is of hydrocarbon and chloride
contamination only.

6. Page 5
Figure 2: Synthetic
drill cuttings
Table 3: Range of properties of the North Sea drill cuttings
Property Value Property Value
Particle size 4 µm – 20mm Liquid Limit 33 – 70%
Gravel 1 – 7% Plastic Limit 16 – 35%
Sand 8 – 33% Plasticity Index 14 – 32%
Silt 37 – 62% Density 1.3 – 2.7g/cm3
Clay 16 – 25% Shear Strength 1.2 – 40kN/m2
Water content 14 – 35% PH 8 – 10.1
Hydrocarbons Up to 22.4% Chloride Up to 3.5%
5.2 Experimental methodology
The full experimental programme considered a number of contaminant scenarios, which
include a combination of average and maximum concentration and different contaminant
combinations. In this paper however the special case of contamination of hydrocarbons and
sodium chloride alone is being considered. This is because conventional binders have been
shown to be generally ineffective in the S/S of these two contaminants. Hence the paper
discusses the results of the North Sea case study representing the averages of organic
compounds (4.20% w/w) and chlorides (2.03% w/w i.e. 3.32% NaCl) only.
5.2.1 Drill cutting mixes
Since the soil strata and contaminant levels vary significantly from one location to another
in the North Sea, it was important to use synthetic drill cuttings. A number of trial soil mixes
were produced and tested in order to ensure behaviour similar to the real drill cuttings. The
hydrocarbon contaminants were modelled using paraffin oil and the chloride using sodium
chloride. The properties of the selected mixed are shown in Table 4. It was noticed that the
addition of paraffin oil and sodium chloride did not significantly affect the Atterberg limits.
Sodium hydroxide was added to the soil mix in order to provide an alkaline medium of the
cuttings.
Table 4: The synthetic drill cuttings and their properties
5.2.2 Binder system
Ten different binders were utilised to treat the soil mixes as summarised in Table 5 and
described below. Apart from the PC only binder, all the other binders contained 50% PC
except MgO-cement 1 which contained only 2% PC. The water to dry binder ratio used was
0.4:1. The two groups of binders that were used were as follows:
(a) Conventional binders:
- Portland Cement (PC)
- Hydrated lime
- Pulverised fly ash (PFA) or Fly Ash (Class F), a stable, fine powder, which is a by-product
from the combustion of pulverised coal in coal-fired power stations
- Blastfurnace slag (BFS), which is a by-product, produced from the iron manufacturing
process by chemical reduction in a blast furnace
Soil composition Value Property Value
Sand content 10% Water content 27%
Silt (rock flour) content 50% pH 9
Clay 1 (Polywhite kaolin E-grade) 20% Plastic Limit 24.6%
Clay 2 (calcium bentonite) 20% Liquid Limit 50.6%
Paraffin oil of dry soil 4.2% Sodium Chloride 3.32%

7. Page 6
(b) Novel binders:
- MgO-cement, which is a mixture of PC, PFA and reactive magnesia and is argued to be a
more sustainable type of cement than PC [14]. The magnesia in the MgO-cement hydrates
to give brucite and carbonates to give magnesite and hydromagnesite
- Zeolites (Clinoptilolite), which is an aluminosilicate mineral that has a rigid, 3-D crystalline
structure. The zeolite framework is similar to a honeycomb consisting of interconnected
tunnels and cavities allowing the free movement of water in and out of the structure while
the framework remains rigid
- Cement kiln dust (CKD), which is a by-product from the manufacturing of PC
- Compost (Coir), which is peat free compost produced from the coir element of coconut
husks
- Silica fume/microsilica, which is a by-product from electric arc furnaces that are used in the
manufacture of ferrosilicon or silicon metal
Table 5: Summary of the binder systems used
5.2.3 Sample preparation and testing
The solid constituents of the drill cuttings were first mixed together with the water, to
which the sodium chloride and sodium hydroxide were added; and the paraffin oil was then
added. The wet binder was then prepared and added to the drill cuttings. The dry binder
content by weight was 10%, 20% and 30%. After thorough mixing, the drill cuttings and
binder mixes were placed into cylindrical moulds (50mmx100mm) and left to cure for 28
days at a temperature of 21 ± 2°C and a relative humidity of 93% ± 3%. It was observed that
due to the relatively high oil content, pockets of oil formed which appeared as voids within
the outer surface of the samples and thus some oil leaked out of the samples on demoulding.
Up to three samples from each mix were tested for their unconfined compressive strength
(UCS), leachability and leachate pH and microstructure using SEM.
5.3 Experimental results and discussion
A set of physical and chemical tests together with microstructural examinations was
conducted on the different mixes. These are presented in separate sections below.
5.3.1 Unconfined compressive strength (UCS)
A summary of the UCS at 28 days is presented in Figure 3. The different mixes were
presented in the order of their relative strength at 30% dry binder content. The UCS results
reveal that the PC, BFS-PC and microsilica-PC produced the highest UCS although not in the
same order as the dry binder content changed. On the other hand, the compost-PC and MgO-
cement 1 mixes yielded the lowest strength at all binder contents. For all the mixes the UCS
Binder system Dry binder
composition
Ratio by weight of
dry binder
Water: dry
binder
1 PC PC 1 0.4 : 1
2 MgO-cement 1 PFA : MgO : PC 90 : 8 : 2 0.4 : 1
3 MgO-cement 2 PFA : MgO : PC 4 : 1: 5 0.4 : 1
4 Zeolite (Clinoptilolite) Zeolite : PC 1 : 1 0.4 : 1
5 Microsilica Microsilica : PC 1 : 1 0.4 : 1
6 Compost (Coir) Compost : PC 1 : 1 0.4 : 1
7 Hydrated Lime Lime : PC 1 : 1 0.4 : 1
8 Blast Furnace slag BFS : PC 1 : 1 0.4 : 1
9 Pulverised Fly Ash PFA : PC 1 : 1 0.4 : 1
10 Cement Kiln Dust CKD : PC 1 : 1 0.4 : 1

8. Page 7
increased as the dry binder content increased. For the 10% dry binder addition, the UCS
ranged between 92kN/m2
and 1,584kN/m2
, for the 20% between 133kN/m2
and 3,543kN/m2
and for 30% binder addition between 183kN/m2
and 4,708kN/m2
.
Figure 3: UCS at 28 days of all binders
Depending on the management scenario of the treated material, different minimum values
of UCS apply. For burial purposes the UCS value can be as low as 140kN/m2
[15], for the
production of blocks and bricks and for load bearing concrete materials the values would be
much higher at 3MN/m2
and 7MN/m2
respectively [8]. Lower UCS value could find
applications in areas where low-grade materials are acceptable or simply to be used as
improved ground. Given the very wide range of UCS values above, all the mixes, based on
their UCS values, are likely to find suitable applications.
5.3.2 Leachability
The NRA leaching test [16] is the UK-approved leaching test in which 100g of the mix,
after reducing it particle size to less than 5mm, are mixed with 1 litre of an extraction fluid
and agitated for 24 hours. The extraction fluid used was de-ionised water, which was
carbonated down to a pH of 5.6. The leachates of 28-day mix samples were analysed for
chloride using ion chromatography (IC) and the results are summarised in Figure 4.
The original chloride content in drill cuttings of 2.03% is equivalent to 20,300mg/kg. This
means that the maximum leached chloride concentrations in the leachate test in the worst-case
scenario for 10%, 20% and 30% dry binder mixes would be 17,800, 15,850 and 14,290mg/kg,
respectively. The results in Figure 4 show that for the 10% dry binder mixes the chloride
content in the leachates ranged between 10,670 and 16,640mg/kg, for the 20% binder mixes
between 12,020 and 14,680mg/kg whilst for the 30% binder mixes between 9,970 and
13,910mg/kg. Figure 4 shows that in most cases the leached concentration decreased as the
dry binder content increased with the zeolite-PC mix being the main exception to this rule.
The 30% dry binder mixes generally performed the best with PC, PFA-PC, Lime-PC and
MgO-cement 2 mixes giving the best results. Concentrations were typically reduced by up to
31% of the original concentrations in the drill cuttings. The UK landfill acceptance criteria
limit values for chloride concentrations in compliance leaching tests are 800mg/kg,
15,000mg/kg and 25,000mg/kg for inert waste, stable non–reactive hazardous waste and
hazardous waste respectively [17]. This shows that all binder mix concentrations exceeded the
PC
BFS-PC
Microsilica-PC
Zeolite-PC
CKD-PC
PFA-PC
MgO-Cement2
Lime-PC
Compost-PC
MgO-Cement1
30%
20%
10%
0
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
UCS(kN/m2)

9. Page 8
limit value for inert waste but the 20% and 30% binder mixes are all below that for the non-
reactive hazardous waste. These results show that the drill cuttings have at least been reduced
from a hazardous to a non-reactive hazardous waste.
Figure 4: Chloride leachability from all the mixes at 28 days
The oil leaching was measured by the Partition-Gravimetric method, which is a crude
method, used in order to compare the relative ability of the different binder mixes to reduce
the paraffin oil concentration. In this test dissolved or emulsified oil is extracted from water
by intimate contact with an extracting solvent, in this case toluene. Figure 5 shows the
leachate concentrations of the paraffin oil, which indicate that microsilica-PC, MgO-cement 2
and MgO-cement 1 are the best mixes for all the dry binder contents. In addition, the PC,
compost-PC and BFS-PC mixes performed very well for the 20% and 30% dry binder mixes.
It is worth noting that the compost-PC 30% dry binder mix absorbed most of the oil.
Figure 5: Leachability of the paraffin oil from all the mixes at 28 days
The original paraffin oil content in drill cuttings of 4.20% is equivalent to 40,200mg/kg.
This means that the maximum leached paraffin oil concentrations in the leachate test in the
worst-case scenario for 10%, 20% and 30% dry binder mixes would be 35,260, 31,400 and
28,300mg/kg respectively. The results in Figure 5 show that for the 10% dry binder mixes the
oil content in the leachates ranged between 28,600 – 21,400mg/kg, for the 20% binder mixes
between 2,000 – 27,800mg/kg whilst for the 30% binder mixes between 606 – 16,770mg/kg.
The UK landfill acceptance criteria limit value for mineral oil (C10-C40) content in the waste is
500mg/kg for inert waste landfill [17]. In the absence of corresponding limit values for
compliance leaching tests, those for total organic carbon of 500, 800 and 1000mg/kg for inert,
stable non-reactive hazardous and hazardous waste are quoted here. This shows that all the
8500
9500
10500
11500
12500
13500
14500
15500
16500
17500
0 1 2 3 4 5 6 7 8 9 10
ChlorideLeachateConc.mg/kg
10%
20%
30%
PC
PFA-PC
CKD-PC
Compost-PC
Lime-PC
Zeolite-PC
BFS-PC
MgO-cement1
MgO-cement2
Microsilica-PC
100
1000
10000
100000
0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 9.5 10 10.5
ParaffinOilLeachateConc.
mg/kg
10% 20% 30%
PC
PFA-PC
CKD-PC
Compost-PC
Lime-PC
Zeolite-PC
BFS-PC
MgO-cement1
Microsilica-PC
MgO-cement2

10. Page 9
concentrations apart from one are above the leachate limit for hazardous waste. The leachate
concentration for the 30% compost-PC mix of 606mg/kg, means that this mix would be
classed as a stable non-reactive hazardous waste. These results indicate that a high binder
content would be required to reduce the oil concentrations to acceptable levels.
The NRA leachate pH is usually used as an indicator of how the heavy metals will behave.
However, as there is no heavy metals included in this case study, the leachate pH was
measured to provide the range of pH achieved for when heavy metals are included. The
leachate pH values shown in Table 6 show a range between 10.32 and 12.67, with most over
11. For stabilised/solidified materials a pH of between 7 and 11 is usually recommended.
Hence the pH values are at the upper end of this range and might require reduction by for
example reducing the percentage of cement in the binder.
Table 6: Average NRA leachate pH at 28 days
5.3.3 Scanning electron microscopy (SEM)
Figure 6 shows typical SEM micrographs of all the mixes at 28 days. Those results have
not yet been studied in detail but differences between some of the mixes are clear. What is
also clear is the absence of ettringite and the abundance of gel-like hydration products typical
of calcium silicate hydrate (CSH). The mixes are now being additionally tested using Energy
Dispersive X-ray Analysis (EDX) to identify the various elemental compositions to help
identify specific compounds present.
Figure 6: SEM micrographs of all the 30% dry binder mixes at 28 days
6. CONCLUSIONS
Drill cuttings are highly variable materials depending on the type of drilling mud, oil well
location and soil strata, oil operator and drilling techniques, recovery technique,
exposure/disposal scenarios of the cuttings and weathering and bacterial conditions leading to
difficulty in testing real or typical materials. The results of this work show that the UCS of the
Binder system pH for
10%
pH for
20%
pH for
30%
Binder system pH for
10%
pH for
20%
pH for
30%
PC 12.11 12.45 12.42 Lime-PC 12.52 12.61 12.67
BFS-PC 11.90 12.14 12.28 Compost-PC 11.93 12.19 12.39
Microsilica-PC 10.32 10.53 10.58 PFA-PC 11.82 12.15 12.25
Zeolite-PC 11.83 12.03 11.97 MgO-cement 1 10.34 10.84 10.98
CKD-PC 11.87 12.40 12.52 MgO-cement 2 11.79 12.18 12.32
PC CKD-PC BFS-PC
Compost-PC Lime-PC MgO-cement 1
Microsilica-PC
PFA-PC
Zeolite -PC
MgO-cement 2

11. Page 10
drill cuttings-binder mixes at 28 days ranged between 92kN/m2
and 4,708kN/m2
depending
on the binder used. This is a very wide range of UCS values and covers a wide range of
feasible applications. The NRA leachate concentrations of chloride ranged between
9,970mg/kg and 16,640mg/kg. This shows that some of the binders have reduced the chloride
content in the drill cuttings sufficiently for them to be classified as non-reactive hazardous
waste instead of hazardous waste. The oil leaching concentrations ranged between 600mg/kg
and 27,800mg/kg and generally decreased as the dry binder content increased. The leachate
pH values were between 10.32 and 12.67. The SEM micrographs indicated the absence of
ettringite and the abundance of gel-like hydration products typical of CSH.
ACKNOWLEDGEMENT
The authors are grateful to Cambridge Overseas Trust, Overseas Research Student Awards
Scheme and BP Egypt for their provision of financial support to the first author.
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