Improving the Working Environment and Drilling Economics Through Better Understanding of Oil-Based...

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Improving the Working Environmentand Drilling Economics Through

Better Understanding of Oil-Based DrillingFluid Chemistry

R.W. James, SPE, T. Schei, and P. Navestad, Phillips Petroleum Co. Norway, andT.A. Geddes, M.G. Nelson, SPE,

andD. Webster, Carless Refining and Marketing

SummaryThe relationships between oil-based drilling fluid composition andthe associated vapors have been quantified. The study documentsthe long- and short-term changes in base oil selection and fluidcompositions. The study is based on the generation and assess-ment of data collected from the vapor emissions of oil-based drill-ing fluids with varying compositions and at a range of tempera-tures.

The purpose of the study was to enable a better understandingof the potential working environment hazards when using mineraloil-based drilling fluids. One result of this understanding is thatnew rig construction designs and older rig upgrades can be per-formed more informatively. This will reduce the repetition of con-

tinual modification costs.

IntroductionControlling the amount of vapor in the workplace is important foroccupational health and safety reasons. It is commonly believedthat most vapors in the working areas come from the mineral baseoil of the drilling fluid. This is due to the base oil being the greatervolume of the drilling fluid, generally in excess of 50%. Studieshave shown this belief to be erroneous. The total hydrocarbonvapor from oil-based drilling fluids also includes vapor contribu-tions from drilling fluid additives and possibly from hydrocarbon-bearing formations which have been drilled with the fluid. Thismeans that when formulating a suitable drilling fluid it is impor-tant to minimize those components in the formulations that couldbe hazardous. Generally it is the lighter hydrocarbon componentsthat are most hazardous to personnel.

The traditional approach to minimizing the concentration oforganic vapor in the atmosphere has involved improving the char-acteristics of the base oils. However, field studies have shown thatreducing the vapor concentration in the headspace above the purebase oil, from 100 parts per million ppm to 10 ppm, for ex-ample, does not necessarily lead to the same percentage reductionof vapor in the work place atmosphere issued from the wholedrilling fluid see the Appendix.

The term headspace refers to the vapor phase associated withand in equilibrium with a respective substance or blend of sub-stances, liquid and/or solid.

A brief field history is given to support the reasons for thecontinued use of oil-based drilling fluids by the operator. In addi-

tion, the driving criteria for ongoing working environment studiesare discussed.

Phillips Petroleum Company Norway PPCoNhad used waterbased drilling fluids for drilling operations until the early 1990s.Drilling down to the chalk reservoir has been through tertiary clayformations primarily of the Miocene, Oligocene and Eocene ages.The clay formations have pore pressures of up to 1.68 specificgravity fluid weight equivalent. The clays are very reactive and

have a smectite bentonitic content of up to 35%. These character-istics provide very unstable drilling conditions in the presence ofaqueous drilling fluids. Subsidence of the depleted reservoir sec-tions, most notably in the Ekofisk field, has added to formationinstabilities especially when using water-based drilling fluids.

The drilling of wells with increasingly greater deviations andmore complex well paths necessitated the use of nonaqueous syn-thetic oil-based drilling fluids to stabilize the exposed formationsbeing drilled. Since 1990 there has been wider and more success-ful use of these fluids. However the Norwegian state pollutioncontrol authorities and the European pollution authorities were notentirely comfortable with the use and discharge of synthetic oil-based drilling fluids.

Consequently PPCoN moved towards an increased use of min-eral oil-based drilling fluids. This practice was coupled with thereinjection of cuttings and of contaminated oil-based drilling fluid.This form of drilling operation has eliminated any negative dis-turbance of the marine environment since there is a no dischargeto the sea.

PPCoN has also been challenged on two strategy fronts for itsintention of using mineral oil-based drilling fluids. These chal-lenges have been from the following.

The Norwegian Petroleum Directorate NPDregulatory con-trolling document, Quality assurance when documenting chemi-cal hazards to health and environment.

An item of concern resulting from an NPD audit of the 2/4Xplatform, a new platform purposefully designed in 1994 to useoil-based drilling fluids. The item reads, ... The NPD would like

to point out that choosing oil-based drilling fluids is controversial,from a working environment point of view, and would like toemphasize that the selection of equipment and ventilation systemsmust be thoroughly evaluated.

The hazards for personnel of uncontrolled exposure to the va-pors and mists from oil-based drilling fluids includes impacts onthe central nervous system such as dizziness, tiredness, headachesand nausea, and conditions such as pneumonia, bronchitis, bron-chial asthma and possibly cancer.1

The seriousness is emphasized knowing that some mineral baseoils can evaporate at a rate of 1 vol%/10 h at 70C.1 This tem-perature is not uncommon for a drilling fluid during drilling op-erations.

Headspace Measurement Observations From

Laboratory StudiesIn this section some of the possible sources of vapor emissionsfrom oil-based drilling fluids are described and alternative ways ofreducing them are discussed.

The concentration of vapor in the headspace of a diesel base oilis typically 100 ppm but may be as high as 1,000 ppm at 80C. Bycomparison the best of the more recent generation base oils withlow headspace characteristics have maximum headspace concen-trations of less than 30 ppm at 80C. It is also important to notethat the vapors given off by a diesel base oil, for example, containmore toxic compounds such as polycyclic aromatics than the morehighly refined base oils described herein.

The obvious way to obtain lower vapor concentration in theheadspace of a base oil is to use higher boiling components. How-

Copyright 2000 Society of Petroleum Engineers

This paper (SPE67835) was revised for publication from SPE 57551 first presented at the1999 SPE/IADC Middle East Drilling Conference held in Abu Dhabi, UAE, 8 10 November.Original manuscript received for review 22 February 2000. Revised manuscript received 27July 2000. Paper peer approved 14 August 2000.

254 SPE Drill. & Completion15 4, December 2000 1064-6671/2000/154/254/7/$5.00

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ever this results in two contrasting effects: the vapor pressuredecreases as the boiling point of the oil increases, and the viscos-ity increases as the boiling point increases.

For drilling and safety purposes the desired base oil shouldhave low viscosity, low vapor pressure and a high flashpoint. Thisis in addition to the requisite environmental properties. Meetingall these parameters simultaneously is not always possible. Acompromise must be reached in the form of a narrower boilingpoint range, resulting in lower base oil yields, higher byproductyields and as a consequence higher production costs for the re-finer.

Composition of Additives. An oil-based drilling fluid typicallyincludes

a base oil phase usually in excess of 50% by volume, a water phase containing salt and lime, an oil/water emulsifier liquid, a preferentially oil wetting agent liquid, possibly a liquid rheology modifier liquid, an organophillic clay viscosifier, and an inert additive, barite, for density control.

Drilling fluid additives are not an openly defined chemicalgroup. However the major additives in an oil-based drilling fluidsuch as emulsifiers, rheology builders and wetting agents can beviewed as active chemicals dissolved or dispersed in suitable sol-vents. Gas chromatographic analysis has revealed these additivesto be complex mixtures containing large proportions of highlyvolatile materials.

All the liquid additives studied have higher overall vapor pres-sures, and therefore headspaces, than the base oils studied. Thehigh vapor pressures may be attributed to either the additive sol-vents or to a chemical reaction/decomposition process involvingthe active parts of the additives.

Relative Headspace Values. The relative headspaces of the dif-ferent drilling fluid additives, including base oils, are significantand diverse. Study results indicate that the headspace for each ofthe liquid additives is generally at least an order of magnitudelarger than that of the base oils studied. A relationship is illus-trated where base oil A has been given the arbitrary value of 1Table 1.

Individual Drilling Fluid Additive Headspace and Reactions.

The total headspace of the individual drilling fluid additives isalso diverse Table 2. Total vaporization of small volumes, forexample, 1 L, of the samples at the higher temperature of 155Cis necessary to calculate an equivalent ppm/unit area for eachrespective sample.

The results from Table 2 indicate that various base oils exhibitmeasurable differences in total headspace; for example, base oil Bis typically twice that of base oil A. If improvements for occupa-tional health are to be addressed then the choice of base oil is oneof the many crucial factors which must be carefully considered.

The organophillic clays used in this study produced widely

varying headspace results and for clay A a significantly higherheadspace than the base oils. The emulsifier, wetting agent andliquid rheology modifier additives used produced higher head-spaces than either of the two base oils. Additionally, the wettingagent has a headspace approximately twice that of either of theother two additives. This may be due to a compound causing alarge spurious peak at approximately 12 to 16 minutes on thechromotogram. A similar peak was also seen in the analysis of thewhole drilling fluid system at the same retention time.

With the exception of organophilic clay A, all drilling fluidadditive headspace reduced with time when aged in an open bea-ker with heating and stirring. The wetting agent peak at 12 to 16minutes was present but diminished initially at a greater rate thanthe overall headspace values.

Laboratory prepared drilling fluids made using organophilic

clay A exhibited an initial decrease in headspace followed by anincrease at approximately 20 hours tailing off at 24 hours Fig. 1.This cyclic effect was analogous to that of the spurious peak seenat 12 to 16 minutes in the organophilic clay A fluids.

Both laboratory prepared drilling fluids with organophilic clayB showed an overall decrease in headspace over the 24-hour pe-riod. This decrease is analogous to the expected decrease in head-space which was observed with the base oils only.

The 12 to 16 minute peak was also observed in the organo-philic clay B drilling fluids at T0, the time at which these fluidsproduced the highest headspace concentration. Organophilic clayA drilling fluids had greater headspace concentrations than theorganophilic clay B throughout the aging experiment Fig. 2.

TABLE 1 RELATIVE HEADSPACES OF MUD COMPONENTS

ComponentRelative Headspace

at 35CRelative Headspace

at 50CRelative Headspace

at 80C

Base oil A 1.0 1.0 1.0

Base oil B 2.0 2.5 2.0

Emulsifier 17.8 16.7 8.6

Rheology modifier 23.7 23.0 10.7

Wetting agent 37.7 32.4 11.8

Organophilic clay A 0.18 0.05

Organophilic clay B 0.05 0.04

TABLE 2 INDIVIDUAL MUD COMPONENT ANALYSIS*

Temperature Base Oil A Base Oil BClay

AClay

B EmulsifierRheologyModifier

WettingAgent

Density 0.828 0.816 0.980 0.908 0.900

Total vaporization 155C 39.4 38.9 46.7 43.2 42.9

35C 0.1 0.3 7.8 0.3 4.3 5.5 12.2

50C 0.3 0.9 9.7 12.9 25.2

80C 2.8 6.2 49.0 5.3 45.2 54.2 83.2

120C 27.6 48.7

*Total headspace values of individual mud components given as ppm.

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This was indicative of the presence of the 12 to 16 minute peak.Generally, the headspaces of base oil A drilling fluids were lowerthan those of base oil B.

Analysis of Hot Rolled Laboratory Drilling Fluids. The follow-ing observations were made from the analysis of the hot rolledlaboratory produced fluids:

in all instances, the headspace increased with hot rolling; base oil A/organophilic clay B drilling fluid consistently had a

lower headspace than the other drilling fluids; a very prominent peak occurred at retention times of approxi-

mately 12 to 16 minutes in all laboratory produced mud systemsboth before and after hot rolling;

in base oil A drilling fluids, light hydrocarbon componentswere produced to a greater extent with organophilic clay B thanwith organophilic clay A.

The results are summarized in Table 3.

Field Drilling Fluids. Representative field drilling fluid sampleswere collected and forwarded for testing in the laboratory. Eachfield drilling fluid sample was analyzed at 35, 50, and 80C. Allthe chromatograms exhibited excessive light hydrocarbon sub-stances which were not seen in any of the individual additives, orin any of the laboratory prepared drilling fluids.

The field samples produced higher total headspace than any ofthe laboratory produced drilling fluid samples. This could be at-tributed to miscellaneous additives which had not been providedfor inclusion in the laboratory prepared samples or, alternatively,to drilled formation cuttings contamination and/or interference.Although precise replication of field drilling fluid headspace wasnot possible in the laboratory, results have shown that the labora-tory samples are useful predictive tools for field drilling fluidheadspace quantitation.

Further Investigative WorkThe appearance of the spurious peak at 12 to 16 minutes in the

laboratory prepared samples was a concern. Various investiga-

tions were performed to determine the provenance of the spuriouspeak registered on some of the chromatograms at retention timesof between 12 and 16 minutes.

The Catalytic Effect of Organophilic Clays. Six different com-binations of clay, brine and base oil A were refluxed at 80C and

regularly sampled over a 10-day period. Aliquots of the appropri-ate samples were analyzed by total vaporization using an HS40XLautosampler to emulate liquid injection by gas chromatography.

The mixtures prepared were flask 1: organophilic clay B, brine,base oil A, flask 2: organophilic clay B, base oil A, flask 3: brine,base oil A, flask 4: organophilic clay A, brine, base oil A, flask 5:organophilic clay A, base oil A, and flask 6: base oil A.

Within each reflux system, the total headspace remained unaf-fected with time, but the proportion of lighter shorter retentiontimehydrocarbon components increased.

The presence of brine with organophilic clay B and base oil Aproduced a greater proportion of light material 5 to 60 minutesretention time than the organophilic clay B/base oil A samplealone.

The organophilic clay A/brine/base oil A sample followed a

similar trend to the previous observation but to a lesser extent.Within the brine/base oil A sample, without clay present, there

was a pronounced appearance of low boiling material between166 and 238 hours. This material is the same as that seen whenclay is present.

Total Vaporization of Laboratory Drilling Fluids WithoutBarite.The total vaporization experiments of laboratory drillingfluids without barite being present were carried out as part of thequantitation work to convert the headspace area count into ppmvapor in the headspace. Barite had already been determined asinert and was therefore inconsequential to any results. The spuri-ous peak at 12 to 16 minutes was not present in any of the fluidtotal vaporization experiments performed at 155C, whether limewas present or not. It only occurred at lower temperatures of 80,

50, and 35C and under normal headspace conditions. Therefore,

Fig. 1 Headspace of mud samples aged in a beaker at 80C.

Fig. 2 Headspace of base oil samples aged in a beaker at 80C.

TABLE 3 ANALYSIS OF HOT ROLLED MUDS*

Base Oil A/Organophilic

Clay B

Base Oil A/Organophilic

Clay A

Base Oil B/Organophilic

Clay B

Base Oil B/Organophilic

Clay A

Before hot rolling 21.6 27.8 35.9 39.7

After hot rolling 25.9 29.2 37.6 45.4

*Headspace of hot rolled fluids given as ppm.

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the presence of this peak could not be attributed to a pH depen-dent reaction, but may have been due to some kind of equilibriumreaction in which the material was continually decomposed andreformed. This cyclic phenomenon was further demonstrated byaging of the fluids in open beakers.

Drilling Fluids Prepared Without Major Additives. The spuri-ous peak at 12 to 16 minutes was not observed in any of thelaboratory drilling fluids prepared without emulsifier, wettingagent, or viscosifying additives. This suggests that these additivesare required for generation of the spurious peak.

Gas ChromatographyMass Spectrometry. Samples of drillingfluids and the wetting agent were heated to 80C in closed vials.Using a syringe the vapor was sampled and injected through aflow splitter into the gas chromatograph/mass spectrometer GC/MS for analysis.

The following molecules were identified in the wetting agent:ethanalmolecular weight, 44, propanone58, butan-1-ol mostabundant, 74, butan-2-ol trace, 74, propane, butane, pentane,heptane, decane, undecane, dodecane, and tridecane.

In base oil A/organophilic clay B mud the following moleculeswere identified: ethanal 44, propanone 58, butan-1-ol mostabundant, 74, and butan-2-ol trace, 74.

The headspace of n-butanol was determined and the retentiontime of the major peak14 minutesconfirmed some of the aboveobservations and test results.

Oil Drilling Fluids Mist and Vapor Exposures in theFieldGeneral. Human exposure to oil mist and vapors while drillingwells with oil-based drilling fluids on a drilling rig or platform arefrom the following:

the drill floorskin shale shakers, desanders, desilters, and centrifuges: inhalation

of mist and vapors, and skin exposure when under maintenance drilling fluid tanks: inhalation of mist and vapors, and skin

when taking fluid samples or cleaning flowlines transferring the fluids: inhalation of mist and va-

pors, inhalation of formation gas from the wellbore repairing of associated equipment unitsskin

fluid manual mixing: inhalation of mist, dust from the addi-tives, and skin exposure.

Exposure by inhalation can be quantified more explicitly. Anadult, when resting, requires and breathes approximately 5 L ofair/min. This may increase to 20 L/min under duress when, forexample, performing heavy maintenance work.1

Health, environment, and safety information about all thechemicals and additives used offshore must be available on loca-tion in Norway. This information will be in a Material Safety DataSheetMSDS. The MSDS contains information of recommendedsafety protective equipment and clothing to be used, and recom-mended handling procedures are stated. Proprietary informationregarding the chemical components of an additive is not alwaysavailable to the worker handling the additive. However informa-tion systems are required which allow the drilling operator the

necessary safety controls for additive and product handling. Theinformation advises when breathing masks are to be used, whenprotective clothing and rubber gloves are required, etc.

The Norwegian regulations require that workers at any locationmust be able to operate comfortably and safely. A shale shakeroperator is not allowed to perform his or her tasks for long periodswearing full breathing apparatus with air bottles in lieu of accept-able area ventilation. Should air quality conditions be inferior,ventilation systems must be installed or improved to meet re-quired standards. But again, air ventilation systems must considernoise levels and must remain within limits.

The regulatory air quality administrative norm, or thresholdlimit, for oil mist on the Norwegian Continental Shelf is 1 mg/m3

of air for an 8-hour work shift, or at the established 0,60 mg/m3

for a standard 12-hour offshore work shift. The administrativenorm for oil vapor is 50 mg/m3 for an 8-hour exposure period, orat the established 30 mg/m3 for a 12-hour shift.

The Drilling Platform.Field sampling for this paper was per-formed on the PPCoN Ekofisk 2/4X platform. The 2/4X drillingplatform was planned and constructed through the mid-1990s.The drilling rig area was intentionally designed for the use ofoil-based drilling fluids. However the first well drilled of the 50well slots available was a dedicated reinjection well for formationcuttings and oil-based fluids associated with those cuttings. Thereinjection well was drilled with an alpha olefin-based synthetic-based fluid and the cuttings with associated drilling fluid were

discharged into the sea.The drilling fluid areas of the platform rig were carefully con-structed to ensure that safety, general working environment con-ditions, and ergonomics would not be compromised.

All fluid flowlines were covered, although not necessarilysealed. Hatches and openings in the fluid flowlines, such as wherethe flowline enters the shale shaker trough, were allowed. Theshale shaker trough was not completely closed so as to allow thetrough to be manually cleared of cuttings when necessary. Thethree shale shakers were completely enclosed by ventilation cano-pies that covered all sides. The cuttings ditch was also covered.All cuttings were transported from this ditch in an enclosed con-veyor to the cuttings slurrification unit for pulverizing and prepa-ration for reinjection.

The drilling fluid mixing tanks and storage tanks were alsocompletely enclosed with the exception of fluid sampling ports.The flowline ditch distributing the drilling fluid to respective tankshad an opening for fluid sampling purposes.

Temperature differentials of the drilling fluid and the atmo-spheric temperature can be 70C. Therefore vaporization and con-densation of the fluid are stimulated, thereby increasing the op-portunity of exposure.

The mixing of all fluid additives is performed mechanically.That is, powdered and liquid additives are dosed from enclosedpurpose-built bulk containers. The exception here is for specialtyadditives such as lost circulation materials which are used lessfrequently and are considered hazard free.

Field Mist and Vapor Sampling. Sampling for levels of oil mistand vapor were performed on the Ekofisk 2/4X drilling rig on 3and 4 December 1997. Sampling was performed the drilling

through a 12 14-in. section the higher pressured reactive clay for-mations. Sampling at this time was intentional since the fluid tem-peratures were at the maximum expected temperature of 70C.This provided worst case mist and vapor results.

The base oil used in the drilling fluid was one of only threeavailable at the time that could meet the PPCoN technical speci-fications. The specifications are as followsdensity at 15C, minimum 0.8 g/cm3;viscosity at 40C, maximum 3.5 cStokes;initial boiling point, C, minimum 260C;final boiling point, C, maximum 295C;flashpoint, C, minimum 115C;pourpoint, C, minimum 18C;aromatic content, %vol, maximum 0.5%vol.

Offshore Testing, Methods, and Results. Sampling for oil mistand vapor concentrations was performed using National Institutefor Occupational Safety and Health NIOSH method No. 5026and the American Society for Testing and Materials ASTMmethod. These test procedures are explained briefly. A dosimeteractuated by a pump is used to draw air through collection filters tomeasure oil mist concentrations. A 37 mm filter house with adouble glass fiber filter, Gelman type A/F, was used which wasconnected to a jumbo charcoal tube SKC type lot No. 226 be-hind the filter holder. Oil vapor drawn onto the active charcoal inthe jumbo charcoal tube was absorbed to enable quantitative mea-surements to be made. To achieve controlled air flow across thefilter, a portable battery air pump with an adjustable air flow typeSKC 224-PCEX was used. The calibrator type was Gilabrator

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from Gilan Instrument Corporation. A bubble generator cali-brates the air flow, controlled to 1.5 Lmin. Pre- and post-calibration tests were performed for each pump used.

In the shale shaker room, the testing apparatus was located atthe bottom end of each of the three shakers 1,2, and3nearthe nonsealing door covers Table 4. The door covers close offan opening which is needed in the shaker ventilation canopies toallow shaker screen replacements to be made. Changing of shakerscreens is a manual function. One testing unit was located on eachof the two persons 4 and 5 attending to the area. One unitwas located on the wall 6 directly across a walkway in front ofthe shakers, and one unit was located outside the shaker room ona walkway 7. Results are provided for both oil mist and vaporconcentrations from these areas.

Two of the units 1 and 2 located on the shale shakersindicate oil mist concentrations greater than 500% of the thresholdallowance. This was later determined to be the result of an oil-based drilling fluid splash from changing a shaker screen, collect-ing a drilling fluid sample, or washing the screens with a highpressure spray gun. It reiterates the care that must be taken whenperforming these studies and the need to use experienced testingpersonnel for correct interpretation of the results. The unit locatedon third shaker3, however, still indicated that the threshold limithad been maginally exceeded. Vapor exposures at these locationswere also excessive.

Air sampling units were also used to measure the mist and

vapor concentrations in the drilling fluid tank area Table 5. Twounits 8 and 9 were attached to two persons working in thearea, and one unit10was stationed above the active fluid tanks.All units registered very low levels of mist and vapors in com-parison to the threshold levels allowed.

Further air sampling units 11, 12, and 13 were used inthe cuttings slurrification unitTable 6. The function of the slur-rification unit is to receive oil fluid coated cuttings after they havebeen processed on the shakers, blend them with sea water, andmechanically pulverize them into a pumpable slurry or fluid. Theslurry is then transferred to an injection pump and pumped into aselected formation zone in the dedicated reinjection well. The oilfluid coated cuttings are blended into a resultant slurry which hasapproximately 15% solids, 10% oil from the drilling fluid, and75% sea water. All units registered very low levels of mist and

vapor in comparison to the threshold levels allowed.

All air sampling tests were performed in the presence of anoil-based drilling fluid which contained a base oil which was incompliance with the previously mentioned technical specifica-tions.

Laboratory Analysis Methods and Results.The oil in theTenax tubes and glass fiber filters from the respective testing ap-paratus units was extracted with freon and analyzed by Fouriertransform infrared FTIR spectrometry to determine the concen-tration of oil mist and vapor. The samples were analyzed against acalibration curve established using the base oil as a control. Theoil mist and vapor readings were then quantified for the n-alkanevalues from nC-12 to nC-32.

The results of the samples taken from the two persons Table 4,sampler positions 4and 5in the shale shaker room are speci-fied below. The results have indicated that the exposure ofn-alkane saturated hydrocarbons in the oil mist was greatest in thenC-15 to n C-17, and n C-21 to n C-27 ranges. The vapor n-alkaneconcentrations were greatest in the n C-13 to nC-16 and n C-19 tonC-27 ranges.

Information regarding the concentrations of shorter n-alkanevalues was not available for inclusion in this paper.

Controlling Related Economics

Personnel safety is ranked without doubt the foremost criterion bywhich to address and adhere to for drilling operations. By cor-rectly understanding oil-based drilling fluids chemistries an opera-tor can control associated operational costs more effectively.

Controlling Initial Drilling Fluid Formulations. The laboratorystudies have shown that improved physical and chemical under-standing must be gained for any proposed base oil. Also, thechemistry of the additives must be known and early laboratoryblending studies are needed to determine possible negative syner-gistic effects. By controlling the types of additives used and byoptimizing their synergistic effects, the opportunity for a saferworking environment is established.

Ensuring Ventilation Systems Are Effective. The older drilling

modules in the greater Ekofisk area have been upgraded to ensure

TABLE 4 OIL MIST AND VAPOR RESULTS FROM THE SHAKER ROOM

Shale Shaker RoomOil Mist Result

(mg/m3)TLV*

(mg/m3)Oil Vapor(mg/m3)

TLV*(mg/m3)

Shaker 1 (stationary) (1) 5.52 0.60 63.3 30



Person 1 (P) (4) 0.40 0.60 35.0 30

Person 2 (P) (5) 0.06 0.60 3.2 30

Stationary wall (S) (6) 0.17 0.60 5.9 30

Walkway west (S) (7) 0.03 0.60 3.5 30

*TLVThreshold level value for a 12-hour period.

TABLE 5 OIL MIST AND VAPOR RESULTS FROM THE DRILLING FLUID TANK AREAS

Drilling Fluid Tank AreasOil Mist Result

(mg/m3)TLV*


TLV*(mg/m3)

Mud pit (person) (8) 0.04 0.60 1.4 30

Mud pit (person) (9) 0.05 0.60 1.0 30

Mud pit (stationary) (10) 0.05 0.60 1.0 30


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acceptable working environmental conditions are maintained. Up-grading the ventilation facilities of the shaker rooms and fluidstorage tank rooms has been challenging and costly. This is due tothe structural changes necessary in the confining shaker rooms forinstalling adequate ventilation systems. In conjunction with theinstallations, wind and sheltering walls have needed restructuringto enable controlled air flows which allow a ventilation system tofunction correctly. Simultaneously, drilling fluid and atmospherictemperature differentials increased as improved drilling technolo-gies enabled higher drilling penetration rates, hence higher fluidtemperatures. This only aggrevated the ability to correctly vent theareas in question. The greater temperature differentials gave riseto greater condensation and vapor quantities. The upgrade of onesuch shaker room alone cost U.S. $385,000.

Similarly, a recent shaker room upgrade on a mobile rig built inthe 1990s for drilling with oil-based drilling fluids cost U.S.$575,000. This upgrade was necessary to ensure that personnelcan function in an acceptable working environment in an ergo-nomically acceptable manner.

The studies discussed in this paper have indicated that ventila-tion systems and working areas must be constructed adequately nomatter what base oil and fluid systems are used. However thestudies have also indicated that fluid-related rooms with inferiorventilation systems can be very expensive to correct at a laterdate. For this, the selection of less hazardous oil-based drillingfluids remains an advantage.

The Benefits of Offshore Monitoring. Irrespective of the ad-equacies of ventilation systems in the drilling fluid areas of adrilling rig, benefits can be gained from oil mist and vapor moni-toring Table 3. This is so because there are areas that requirepersonnel attendance for maintenance purposes. For example, en-closed drilling fluid circulating, processing, and storage tank areasmust be entered for inspection or cleaning purposes. Shakerscreens need to be replaced when broken therefore the ventilationcanopy on the respective shaker needs to be opened and manuallyentered. Drilled cuttings may need to be cleared manually from ashale shaker trough.

A careful systematic mist and vapor monitoring program willhelp identify the less safe working areas of a drilling rig or, con-versely, identify when the condition of an area is less acceptableduring particular types of operations. Gathering this informationof oil mist and vapor levels from different areas will correctlyindicate whether an area needs modification.

Recommendations

This investigation has identified a number of alternative ap-proaches that could be taken to improve conditions. They are thefollowing.

Using base oils rather than the more volatile solvents presentlyemployed as diluents for the active ingredients in the additivescould eliminate the effects of additive solvents on the headspace.Further experimental work will be required to determine the ef-fectiveness of this approach.

Identifying the causes for the catalytic effect of clays may de-termine whether certain clays and amine salt treatments in manu-facturing processes have a greater catalytic effect on headspacevalues.

Extended investigation into component aging should be re-peated over a longer time period 96 hours with sampling atshorter intervals in order to establish the cycle and origin of the 12to 16 minute spurious peak.

To obtain more information about the production of the 12 to16 minute spurious peak, the three additives rheology modifier,wetting agent, and emulsifiershould be aged over 96 hours but indifferent combinations to assess any interactions among them.

ConclusionsA number of conclusions can be established from the informationpresented.

Small amounts of the major additives appear to increase theoverall headspace of a drilling fluid by a disproportionate amount.

Some organophilic claysclay A in this studyexhibit a markedeffect on the vapor concentration in the headspace of a drillingfluid system. This effect may be attributed to the clay itself, somekind of catalytic effect, or to a reaction with one or more of themajor additives.

Because the liquid additives such as the emulsifier and wettingagent have an incommensurate effect on drilling fluid headspaces,using an alternative carrier fluid for these additives could improvethe situation.

The contribution of drilling fluids to the hydrocarbon vapors inthe workplace may be assessed by calculations before a fluid sys-tem is used in the field.

Ventilation systems in working areas must be constructed ef-fectively no matter what base oil and fluid systems are used.

Monitoring of oil mist and vapor will correctly indicate theneed to improve conditions in that area.

AcknowledgmentsThe authors acknowledge permission to publish this paper fromPhillips Petroleum Company Norway and the Co-Venturers, in-cluding Fina Exploration Norway S.C.A., Norsk Agip A/S., ElfPetroleum Norge A.S., Norsk Hydro Produksjon A.S., TOTALNorge A.S., Den Norsk Stats Oljeselskap A.S., and Saga Petro-leum A.S.

References1. Aschehoug, S.H. and Zachariassen, G.H.: Oil-Based Drilling Fluids

and the Working Environment, MS thesis 1996.

Appendix 1Definition of Headspace Analysis. Headspace analysis involves

sampling the vapor phase that is in equilibrium with a liquid in asealed vial and injecting this vapor onto a gas chromatographiccolumn for quantitative analysis.

Instrument Conditions.Headspace sampler: Perkin Elmer HS40XL

Inject time 0.2

Sample shaker On

Needle temperature 160C

Transfer temperature 170C

GC cycle time 140 minutes

Thermostat time 20 minutes

Pressurization time 3 minutes

TABLE 6 OIL MIST AND VAPOR RESULTS FROM THE SLURRIFICATION UNIT

Slurrification UnitOil Mist Result

(mg/m3)TLV*


TLV*(mg/m3)

Slurry unit (stationary) (11) 0.01 0.60 8.6 30

Slurry unit (person) (12) 0.11 0.60 6.1 30

Slurry unit (stationary) (13) 0.90 0.60 4.0 30


James et al.



7/7

Withdrawal time 0

Vial venting On

Carrier gas 15 psi

GC Conditions

Carrier gas Helium, 10 psi

Column CP SIL SCB50 m0.53 in-ner diameter

Totakl split vent 15 mL/min1

Septum purge 5 mL/min1

Air 40 psi

Hydrogen 15 psi

GC temperature program

35C for 10 minutes

Ramp 5C minutes1 to 60C

Ramp 2C minutes1 to 235C

Hold at 235C for 20 minutes

Injector temperature: 175C

Detector temperature: 295C

SI Metric Conversion Factors

ft 3.280 8.33 E01 m

psi 6.894 757 E00 kPa

SPEDC

Reagan W. James is a senior drilling engineer with Phillips Pe-troleum Co. Norway (PPCoN) involved with the use of fluids fordrilling operations, permanent well plugging, and abandon-ment operations. e-mail: [email protected]. Trond M.Schei is a senior industrial hygienist for PPCoN. He was coordi-nating medic for offshore platforms. Schei completed nursingeducation at Sanitestsforeningens Skole. Pal Navestad is cur-rently an information technology (IT) system specialist with PP-CoN. Before joining PPCoNs IT group, he worked as an indus-trial hygienist. Navestad holds a candidate of scientificinorganic chemistry degree from Chemistry U. of Oslo. Tho-mas A. Geddes is Research and Development Manager atCarless Refining and Marketing, responsible for all laboratory

activities. He holds an Honors degree in chemistry from Edin-burgh U. Guy Nelson is a senior chemist at Carless Refiningand Marketing, responsible for development work relating todrilling fluid base oils, printing ink distillates, process oils andfeedstocks. He holds a Special Honors degree in chemistryfrom U. of Sheffield. Debbie Webster is a senior research anddevelopment chemist for performance fluids at Carless Refin-ing and Marketing. Her experience includes the fine chemicaland pharmaceutical industries. She is a graduate of Open U.

260 James et al.


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