Copyright 2002, IADC/SPE Dril ling Conference This paper was prepared for presentation at the IADC/SPE Drilling Conference held in Dallas, Texas, 26–28 February 2002 This paper was selected for presentation by an IADC/SPE Program Committee following review of information contained in an abstract submitted by the author(s). Contents of the paper, as presented, have not been reviewed by the International Association of Drilling Contractors or the Society of Petroleum Engineers and are subject to correction by the author(s). The material, as presented, does not necessarily reflect any position of the IADC orSPE, their officers, or members. Papers presented at the IADC/SPE meetings are subject to publication review by Editorial Committees of the IADC and SPE. Electronic reproduction, distribution, or storage of any part of this paper for commercial purposes without the written consent of the Society of Petroleum Engineers is prohibited. Permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. The abstract must contain conspicuous acknowledgment of where and by whom the paper was presented. Write Librarian, SPE, P.O. Box 833836, Richardson, TX 75083-3836, U.S.A., fax 01-972-952-9435. Abstract An extended-reach [ERD] well was planned and successfully drilled in Block 16/26 of the U.K. Central North Sea with water-based drilling fluid in an area where wells have historically been drilled with mineral oil-based and ester-based drilling fluids. With increasingly stringent environmental regulations, the current utilization of mineral oil-based fluids is dependent upon shipping all cuttings back to shore forprocessing and subsequent disposal, resulting in high supplemental costs. Additionally, potential adverse weatherconditions could temporarily preventing the transfer ofcuttings from the platform to a supply vessel, thereby curtailing the drilling operations and further increasing drilling costs. The operator realized that significant savings to the current overall well costs could be realized if a water-based drilling fluid system were successfully used to drill the large- diameter hole interval that produced the highest volumes of cuttings. Introduction The drilling program for the Britannia development well B-17 called for the intermediate hole interval to be drilled from the 20-in. casing shoe at ± 3,500 ft MD (± 3,400 ft TVD) to a TD of± 8,900 ft MD (± 7,600 ft TVD) with a final hole angle of63 degrees. Selection of the proper drilling fluid system has heretofore been predicated on the use of mineral oil-based and ester-based drilling fluids which provide efficient and cost- effective drilling through highly reactive shales. Usage ofmineral oil-based drilling fluids would require containment ofthe cuttings; however the containment facilities on this platform were considered inadequate for the large diameterhole size planned. The subject of this paper is to discuss the planning, preparation and drilling of the intermediate hole interval on Well B-17 with a water based drilling fluid. Several types ofwater-based systems have heretofore been used with little success. The need to develop a stable, shale-inhibiting water- based mud system was necessary since there would be a large quantity of cuttings generated in the large diameter interval. Due to the specific well plan, the success of achieving the objective would be dependent upon setting the 13 3/8-in. casing at the end of the build section. This would allow for the target productive zone to be drilled at the optimum angle ofattack as predicted by wellbore stability modeling. Well Design and Planning The well discussed in this paper was drilled as an extended- reach platform development well. The planned wellpath is found in Fig. 1. Wellbore stability issues were raised in both the interval containing the kick-off point and in the following interval that contained the tangent section. Information pertinent to both intervals is presented in this paper. Only in the large-diameter interval immediately under the 20-in casing were hole cleaning and hydraulics issues considered particularly demanding. Hence, the hydraulic issues raised in this paper are pertinent only to the large-diameter interval. In this interval, after kicking-off, the angle was planned to build quickly to 40° and held there until near the end of the interval, where hole deviation was planned to increase to 65°from vertical. The choice of a suitable water-based system must be based on the following criteria: • shale inhibition and analysis • mud weight optimization • hole cleaning efficiency IADC/SPE 74545 Successfully Replacing Oil-Based Drilling Fluids with Water-Based Drilling Fluids: Case Study Demonstrates Value of Extensive Planning and Execution in Extended-Reach Well R. Stawaisz and S. Taylor, Britannia Operating Limited, T. Hemphill, SPE, and U. Tare, SPE, Halliburton Energy Services, K. Morton, SPE, Chevron Petroleum Technology Company, and T. Valentine, Flowco Integrated Drilling & Environmental Services Co. Ltd.
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8/7/2019 Successfully Replacing Oil-Based Drilling Fluids With Water-Based Drilling Fluids Case
This paper was prepared for presentation at the IADC/SPE Drilling Conference held in Dallas,Texas, 26–28 February 2002
This paper was selected for presentation by an IADC/SPE Program Committee followingreview of information contained in an abstract submitted by the author(s). Contents of the
paper, as presented, have not been reviewed by the International Association of DrillingContractors or the Society of Petroleum Engineers and are subject to correction by theauthor(s). The material, as presented, does not necessarily reflect any position of the IADC or SPE, their officers, or members. Papers presented at the IADC/SPE meetings are subject topublication review by Editorial Committees of the IADC and SPE. Electronic reproduction,distribution, or storage of any part of this paper for commercial purposes without the writtenconsent of the Society of Petroleum Engineers is prohibited. Permission to reproduce in print isrestricted to an abstract of not more than 300 words; illustrations may not be copied. Theabstract must contain conspicuous acknowledgment of where and by whom the paper waspresented. Write Librarian, SPE, P.O. Box 833836, Richardson, TX 75083-3836, U.S.A., fax01-972-952-9435.
AbstractAn extended-reach [ERD] well was planned and successfully
drilled in Block 16/26 of the U.K. Central North Sea withwater-based drilling fluid in an area where wells have
historically been drilled with mineral oil-based and ester-based
drilling fluids. With increasingly stringent environmentalregulations, the current utilization of mineral oil-based fluids
is dependent upon shipping all cuttings back to shore for
processing and subsequent disposal, resulting in high
conditions could temporarily preventing the transfer of cuttings from the platform to a supply vessel, thereby
curtailing the drilling operations and further increasing drilling
costs. The operator realized that significant savings to the
current overall well costs could be realized if a water-baseddrilling fluid system were successfully used to drill the large-
diameter hole interval that produced the highest volumes
of cuttings.
IntroductionThe drilling program for the Britannia development well B-17called for the intermediate hole interval to be drilled from the
20-in. casing shoe at ± 3,500 ft MD (± 3,400 ft TVD) to a TD
of ± 8,900 ft MD (± 7,600 ft TVD) with a final hole angle of
63 degrees. Selection of the proper drilling fluid system hasheretofore been predicated on the use of mineral oil-based and
ester-based drilling fluids which provide efficient and cost-
effective drilling through highly reactive shales. Usage of
mineral oil-based drilling fluids would require containment o
the cuttings; however the containment facilities on this platform were considered inadequate for the large diamete
hole size planned.The subject of this paper is to discuss the planning
preparation and drilling of the intermediate hole interval onWell B-17 with a water based drilling fluid. Several types of
water-based systems have heretofore been used with little
success. The need to develop a stable, shale-inhibiting water-
based mud system was necessary since there would be a large
quantity of cuttings generated in the large diameter intervalDue to the specific well plan, the success of achieving the
objective would be dependent upon setting the 13 3/8-incasing at the end of the build section. This would allow for the
target productive zone to be drilled at the optimum angle o
attack as predicted by wellbore stability modeling.
Well Design and PlanningThe well discussed in this paper was drilled as an extended
reach platform development well. The planned wellpath is
found in Fig. 1. Wellbore stability issues were raised in boththe interval containing the kick-off point and in the following
interval that contained the tangent section. Information
pertinent to both intervals is presented in this paper. Only inthe large-diameter interval immediately under the 20-in casing
were hole cleaning and hydraulics issues considered
particularly demanding. Hence, the hydraulic issues raised inthis paper are pertinent only to the large-diameter interval. In
this interval, after kicking-off, the angle was planned to build
quickly to 40° and held there until near the end of the intervalwhere hole deviation was planned to increase to 65°
from vertical.
The choice of a suitable water-based system must be based
on the following criteria:
• shale inhibition and analysis
• mud weight optimization
• hole cleaning efficiency
IADC/SPE 74545
Successfully Replacing Oil-Based Drilling Fluids with Water-Based Drilling Fluids: CaseStudy Demonstrates Value of Extensive Planning and Execution inExtended-Reach WellR. Stawaisz and S. Taylor, Britannia Operating Limited, T. Hemphill, SPE, and U. Tare, SPE, Halliburton Energy ServicesK. Morton, SPE, Chevron Petroleum Technology Company, and T. Valentine, Flowco Integrated Drilling & EnvironmentalServices Co. Ltd.
8/7/2019 Successfully Replacing Oil-Based Drilling Fluids With Water-Based Drilling Fluids Case
2 R. STAWAISZ, S. TAYLOR, T. HEMPHILL, U. TARE, K. MORTON, AND T. VALENTINE IADC/SPE 74545
Once the suitable water-based drilling fluid system wasidentified, work began on optimizing its formulation for
this project.
Shale Inhibition and Analysis. Mineral oil-based drilling
fluids have always provided the most inhibitive drilling fluid
in this area where highly reactive shales are the rule. Thechallenge was to design a water-based drilling fluid system
having performance near that of the mineral oil-based drilling
fluids. An accurate understanding of the nature of shales that
will be encountered is critical to the success of designing a
high performance water-based mud system. It was determined
that a drilling window of no more than 10 days would beallotted to this interval because of the reactive nature of the
formations. Any time spent beyond this would probably result
in deterioration of the hole and resulting in a high risk of ultimately losing the hole.
The shales encountered in the Central Graben area of the
North Sea are some of the most chemically reactive found inany drilling area. These shales are found to contain high
percentages of smectite clays, which are prone to swelling anddispersion. These shales can readily disperse into the mud
system, which decreases control over the rheological
properties of the mud system. Shale analysis consisting of X-ray analysis, cation exchange capacity (CEC) and
exchangeable cations were conducted on cuttings from a
nearby well in the same block. The results are found in Table1. The shales contain a very high concentration of mixed layer
illite/smectite.
The DCM (Dielectric Constant Measurement) technique1
was also used to identify and quantify the risk associated withhydratable and reactive formations as encountered in the
Hordaland Group. A DCM analysis was performed on
(unwashed) cuttings from the 17.5-in hole interval of Well B-15 previously drilled with mineral oil-based drilling fluid. The
DCM provides a quantitative determination of rock properties by measuring the specific surface area per unit weight [m2/g],
thus representing the total hydratable surface area of a cuttings
sample. The DCM is dominated by the presence of smectiteand also strongly influenced by the presence of other
hydratable clays, the presence of which can be correlated with
specific surface areas as shown in the Table 2. The measuredDCM versus depth for this hole interval clearly indicates the
DCM increasing from 250 m2/g at the 20-in casing shoe to a
maximum of 580 m2/g at 7,500 ft TVD in the Alba and
Lothian formations as shown in Fig. 2. The DCM was used
during both the planning and drilling phases and proved to bean invaluable tool. The DCM showed where the most reactive
shales would be encountered and at what point changes in the
mud system should be made.
Mud Weight Optimization. Previous wells drilled from the
platform have had trajectories that built hole angles to 82
degrees in the deeper 12.25-in hole interval. The high angle of attack into a problematic shale at 12800-13000 ft TVD has
been a source of several hole instability occurrences. These
instabilities were mainly in the form of hole pack-offs andcollapse primarily due to weak rock strength and laminated
structure of the shale. As a consequence of the borehole
instability issues, a field-scale wellbore stability analysis wasconducted. The modeling used in the wellbore (in)stability
studies has been described previously2,3,4. The angle and
azimuth information at 13,000 ft TVD of two offset wells Aand B are shown on the minimum mud weight predictions
polar chart in Fig. 3. Table 3 contains the data used in the
analysis. Conclusions from the wellbore stability
study included:
• The higher hole angles in directions perpendicular to the
orientation of the maximum horizontal stress requiredhigher mud weights relative to wells drilled in the
directions of the maximum horizontal stress.
• The higher deviation angles required higher mud weights
that were thought to be destabilizing the problem shale on
a time-dependent basis. As a result, the higher densitiesserved to increase mud pressure penetration into the weak
shale laminations, thereby hastening wellbore
instability problems.
• The laminations in the shale limited the angle of attack
due to weak bedding plane-related rock strengthanisotropy. This meant that when the well trajectory was
parallel to the bedding planes more hole collaps
problems were observed as compared to when the wel
trajectory was perpendicular to the bedding planes, whererelatively fewer hole collapse problems were observed.
The findings of the wellbore (in)stability study supportedchanging the well trajectory design for the B-17 well so tha
the problem shale encountered in the 12.25-inch hole interva
would be drilled at lower angle to help reduce instability
problems. This change in the well design required a shallowerdepth for the kick-off point and the build-and-hold section inthe previous large-diameter interval.
Hole Stability Modeling for the Large-Diameter Interval
After the initial data gathering exercise, a borehole stability
analysis was performed for the large-diameter interval. Table
4 includes the modeling input parameters used. A mud weightschedule with an initial mud weight of 11.5 lbm/gal and a fina
mud weight of 12.5 lbm/gal was developed as a result of
wellbore stability studies and offset data. The predicted mud
weights were based upon the anticipated hole angle with
depth. The minimum mud weights necessary to initiate hole
collapse and breakdown are depicted graphically in Fig. 4. Forany increases in mud weight above the 12.5 lbm/gal level, care
must be taken to avoid differential sticking across any
permeable zones encountered while drilling the section.
Hole Cleaning Efficiency Modeling. Once the mud weights
required to maintain a stable borehole were identified, the prewell planning study then focused on hole cleaning in the large
diameter interval below the 20-in casing. The hole cleaning
calculation methodology used in this paper was developed
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SUCCESSFULLY REPLACING OIL-BASED DRILLING FLUIDS WITH WATER-BASED DRILLNG FLUIDS:IADC/SPE 74545 CASE STUDY DEMONSTRATES VALUE OF EXTENSIVE PLANNING AND EXECUTION IN EXTENDED-REACH WELL 3
from earlier steady-state hole cleaning modeling work 5.6. Key
parameters involved in hole cleaning modeling include:
• Mud density
• Fluid rheological parameters
• Cuttings size and shape
• Pump rate• Hole geometry
• Drill pipe eccentricity
• Hole angle
Since publication of the earlier papers, two more major
factors were integrated into the calculations. These factors,
described by others 7,8 include:
• Drill pipe rotation
• Rate of penetration
To quickly summarize the model’s numerical methods, the
following important items are calculated:
• The fluid rheological parameters are calculated using the
Herschel-Bulkley rheological model. The numerical
model and its parameters have been
described previously9.
• With estimated values for drill pipe eccentricity, the point
velocities in all sections of the annulus are calculatedusing numerical techniques.
• Particle settling velocities for both static and dynamic
cases are calculated using the methodology proposed
earlier by Chien 10.
• A fine-mesh grid scheme valid for eccentric wellbores isused to model the annulus cleaning efficiency.
• The volume of cuttings removed by drill pipe rotation for the input drilling conditions is approximated and adjusted
for ROP.
• Dimensionless cuttings bed height predictions are
calculated as fractions of the annular diameter projectedto be covered by a permeable cuttings bed. This
prediction corresponds to the case where flow rate and
drill pipe rotation ceases and all cuttings settle on the low
side of the hole.
• With the effect of drilled cuttings taken into account, the
calculated pressure drops and circulating annular muddensities for each section of a wellbore are integrated
together to arrive at a final annular mud weight and ECD.
Hole Cleaning Simulations. Once the proper mud weight wasdetermined for use in drilling the large-diameter interval
below the 20-in casing shoe, hole cleaning and hydraulic
simulations were initiated. The goal of the extensive pre-wellsimulation process was to determine the ranges of various
drilling fluid and operational parameters that would provide
good hole cleaning while drilling with WBM and keep ECD
below the fracture gradient at the 20-in casing shoe.
Many variables were investigated in the pre-well planning
process, which included:
• hole diameter: 17.5-in and 16-in
• drill pipe size: 5.5-in and 6.625-in
• hole deviation: 40° and 65°
• average cuttings diameter: 0.25-in to 0.75-in• drill pipe rotation speed: 50 – 110 rev/min
• drilling fluid rheological properties
A water-based drilling fluid having the rheologica
properties and density given in Table 2 [Fluid 1] served as the
principal test case for hydraulic simulations. As this fluid was
a WBM subjected only to moderate temperature and pressureconditions downhole, surface fluid density and rheologica
properties were not adjusted for downhole condition
However simulations were later run to help determine the
effect of increasing the WBM rheological properties onhole cleaning.
Hole angle. Two hole angles were used in the simulations
40° for the upper part and 65° for a short section near the
bottom of the 16-in interval.
Hole and drill pipe sizes. All hole cleaning modeling was
done using two hole ID and two drill pipe OD sizes. The
operator had a two-fold purpose here:
1. They wanted to see how much worse cleaning would be
with a 17.5-in bit compared to cleaning with a 16-in bit.
2. With each hole diameter, the operator wanted to compare predicted cleaning with 5.5-in drill pipe compared with
that using 6.625-in drill pipe.
In Fig. 5, cleaning simulation results are shown for the 2
hole-size / drill pipe combinations at 40° and 65° from
vertical. These 2 simulations represent the best and wors
cases. The results at 40° show that good cleaning was to be
expected for 0.25-in diameter cuttings at the pump rates usedin the simulations. As expected, cleaning efficiencies
improved with increasing pump rate and smaller hydraulic
diameter. In the simulations at 65°, HCE predictions were
lower than those at 40°. Moreover, the spread between thesimulation results widened significantly.
Average particle diameter . The effect of particle diameter on
hole cleaning was also investigated. Particle size can
significantly affect particle slip velocity under staticconditions, and the effect is even greater under dynamic
conditions. In the simulations performed here, a range of
particle sizes from 0.25-in to 0.75-in average diameter wasimulated for the two deviation angles.
Fig. 6 shows the simulation results for the 2 hydraulic
diameter cases at 40° and 65° from vertical. In thesesimulations, pump output was held at 1000 gpm with 80
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SUCCESSFULLY REPLACING OIL-BASED DRILLING FLUIDS WITH WATER-BASED DRILLNG FLUIDS:IADC/SPE 74545 CASE STUDY DEMONSTRATES VALUE OF EXTENSIVE PLANNING AND EXECUTION IN EXTENDED-REACH WELL 5
Based on the review of various drilling fluid candidates, it
was determined that a KCl/Polymer system was the bestchoice. The other water-based mud systems considered were:
These other systems had limitations that disqualified themfor further consideration. The silicate mud system had been
used by another operator on a nearby well in a similar interval
and had numerous problems with this system and ultimately
displaced to a mineral oil-based mud. Calcium chloride mudshave been used in the Gulf of Mexico but not in the North Sea
and problems controlling the fluid loss and rheological
properties have been reported. A KOH/Lime system had
previously been used on a nearby well with less than desired
results. Sodium chloride based systems have been used in the
North Sea with mixed results. Because of the high swellingcontent of the shales present, the NaCl-based system was not
predicted to be very successful in application here.
Drilling Fluid Formulation. The formulation for the whole mud dilution volume wasdivided into two sections based on the DCM results. This
volume was built by blending premix, brine and drillwater
with the required products in order to achieve the desired
formulation. Prior to use, all dilution volume was weighted
with barite to within ±0.3 lbm/gal of the active mud weight.
The most important aspect regarding the use of water-based
muds is the judicious use of whole mud dilution. Additionally,active mud volume should be dumped as required to maintain
continuous and adequate whole mud dilution. The plan was to
minimize the requirement for adding products directly to theactive system. As depicted by the DCM, the mud system
would be formulated initially with a KCl concentration of 30-
50 lbm/bbl [8.6–14.3 wt%] KCl. A fully soluble glycol was
also programmed at a concentration of 3-4% by volume. This
system was planned to drill down to top of the Alba formation
[± 6500 ft TVD]. The formulation for this section is found in
Table 5. At this depth, there was a substantial increase in theDCM surface area indicating a more chemically reactive
formation would be encountered to the total depth of the
interval. The mud system was then modified to increase KClconcentration to 50-60 lbm/bbl [14.3-17.2 wt%], maintain the
same glycol concentration as before, and begin additions of ashale-stabilizing surfactant. The formulation for the interval
below the Alba formation is also found in Table 5.The proprietary shale-stabilizing surfactant has been used
with good results by the operator on Gulf of Mexico wells.
The shales in this section are very reactive and it was
concluded that the mud system should be formulated with allrequired additives that would provide the most inhibition that
could be attained in the water-based mud system. It was
emphasized that the shale-stabilizing additives should be
added to and maintained in the active mud system prior todrilling the reactive intervals.
LogisticsPit volume requirements were reviewed prior to drilling this
section to ensure that there would be sufficient volumeavailable to mix and store the required mud and to carry ou
the necessary dilution of the premix with drillwater. A total of
3250 bbl available volume was identified.A total volume of 2800 bbls of concentrated KCl brine (70
lbm/bbl) was prepared and shipped to the rig. The
concentrated brine would be cut back as required with
drillwater. Drillwater is preferable to seawater, since the latterwill require pre-treatment to remove divalent ions before
blending with premix. If drillwater stocks were depleted, i
was planned to use pre-treated seawater to blend withthe premix.
A minimum of 3000 bbl of KCl polymer premix was
predicted to be required for this interval; 2000 bbl of which
could be shipped to the rig before the beginning of the sectionwith a second batch of premix being shipped out at a laterdate, when required. Due to logistical and surface pit
constraints it was not considered possible to offload all the
KCl polymer premix prior to displacing the well to KC polymer water based mud. All premixes were to be agitated on
a regular basis to ensure homogeneity of the batches.
Drilling Parameters and Guidelines
• It was determined that the rate of penetration would be
limited in order that an annular cuttings load of 4% byvolume would not be exceeded. This essentially limited
the ROP to a maximum of 150 ft/hr at the minimum
circulating rate of 1000 gpm.• In the event of mud pump failure, it was decided tha
drilling would be suspended if the circulating rate fel
below 1000 US gal/min and only be continued when 1000
US gal/min could be re-established.
• Frequent wiper trips were considered to be essential inorder to determine the hole condition.
• The level of overpull required for tripping out of the hole
is one of the most accurate indicator on the rig with whichto determine the degree of hole cleaning efficiency
Torque and drag levels were to be monitored while
drilling the large-diameter interval.
• It was decided that the hole would be circulated clean
based on visual confirmation at the shakers prior to wipertrips and no arbitrary time limits on the time taken for the
shakers to clean up were set.
• Adequate and constant rotation of the drillstring wasconsidered to be critical with respect to hole cleaning
particularly in the tangent section. Therefore, in order to
optimize hole cleaning the drillstring would be constantly
rotated at a minimum of 120 rev/min with the only
exception being sliding during the two build sections.
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SUCCESSFULLY REPLACING OIL-BASED DRILLING FLUIDS WITH WATER-BASED DRILLNG FLUIDS:IADC/SPE 74545 CASE STUDY DEMONSTRATES VALUE OF EXTENSIVE PLANNING AND EXECUTION IN EXTENDED-REACH WELL 7
volume at TD. The glycol concentration was determined by
use of a hand held refractometer that proved to be easy to use,accurate and reliable.
An initial 4 lbm/bbl treatment of the proprietary shale
stabilizing surfactant was the principal exception to direct product addition to the active mud system. The treatment was
added while drilling prior to entering the Alba formation.There was a noticeable improvement in the cuttings integrity
and also cuttings travel on the screens after the initial
treatment. It was decided to maintain a product concentration
of ± 4 lbm/bbl thereafter. Moreover, there was no increase in
the rheological properties with additional of the material, afeature that is desirable for a shale inhibition agent. It is
somewhat difficult to quantify the value of the shale-
stabilizing surfactant as this is the only use to date in theregion and offset comparative data is not available. However,
the proprietary surfactant is considered an essential component
for any similar intervals drilled with KCl polymer water-based
fluids in the future.
Actual Equivalent Circulating Densities. Pressure-while-
drilling tools were used while drilling the well to monitor
downhole circulating pressures. Fig. 10 shows an example
section from the PWD log as measured on well B-17. In thissegment from the 16-in interval, the ECD is measured to be
about 0.1 lbm/gal higher than the static mud density. Three
points near the end of the large diameter interval were selectedfor study of circulating ECD. For each of the selected points,
rotary drilling operations were in progress [e.g., no sliding]
and all necessary data including BHA configuration were
available. Actual PWD results were compared with resultsusing the same hydraulic / hole cleaning model used in the
pre-well planning. Key drilling parameters used in the
comparison are found in Table 3.The results show very good agreement between the model
predictions and actual field data. Average errors in ECD
predictions were:
• Average error 0.073 lbm/gal eq
• Average % error 0.60 %
Fig. 11 shows the measured and predicted ECD and actual
mud weights for the three cases. As noted earlier, pre-well
predictions of ECD under simulated drilling conditions rangedfrom 12.35-12.45 lbm/gal eq. Some differences in ECD values
between the predictions and the actual are expected since
various drilling parameters [e.g., ROP, drill pipe rpm, fluidrheology, etc.] used while drilling were different from those
used in the simulations. The results show that predictionsmade in the pre-well planning process can closely
approximate field results when similar operating parameters
are used. With enhanced advances in hydraulic modeling,these predictions are now better than “ballpark” estimates.
Drilling AccomplishmentsThere were several accomplishments during this first attempto drill the chemically reactive interval with a water based
mud system. The accomplishments were as follows:
• Two build sections - one at 40° and the other at 63° were
drilled successfully and there were no reportedsliding problems.
• There was minimal overpull on trips which was attributed
to good hole cleaning in the highly deviated interval.
• The 13 3/8-in casing was successfully run with minima
problems to the programmed depth.
• No wiper trip was required prior to running the 1
3/8-in casing.
• No down time related to mud related incidents and th
interval was drilled within the prescribed time frame.
• Hole conditions and cuttings integrity were excellen
throughout the interval.
• There was no downtime related to dilution volume
handling on the rig.
ConclusionsKey conclusions that come from this study include:
• The DCM was considered as a valuable tool for
distinguishing the reactive shale intervals and used to
dictate what mud treatments were required.
• The hole cleaning and hydraulic model used in this study
proved to be quite useful in the pre-well planning processas well as in the post-well analysis.
• A WBM having a rheological profile similar to that of
Fluid 1 was recommended. Use of high viscosity fluids
similar to Fluid 2 should be avoided in the highangle sections.
• The particle diameter of drilled cuttings was demonstrated
to be an important factor for hole cleaning efficiency in
the large diameter interval. Less aggressive PDC bits with
reduced cutter diameters were recommended and used sosmaller cuttings would be cut and cleaned more
efficiently from the wellbore.
• A maximum ECD of 12.35-12.45 lbm/gal was predicted
while drilling with a 12 lbm/gal with Fluid 1 in the
simulated operating ranges. Moreover, the ECD measurednear the bottom of the 16-in interval agreed quite closely
with those generated in the pre-well planning.
•
Extensive wellbore stability and hydraulic modeling inthe pre-well planning can greatly increase likelihood of
success in non-routine drilling situations.
AcknowledgementsThe authors wish to thank Britannia Operating Ltd., ChevronTexaco Petroleum Technology Company and Halliburton
Energy Services Inc., for permission to publish and presen
this paper.
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Rev/min – revolutions per minute [rpm]TD – Total Depth
TVD – Total Vertical Depth
WBM – Water-Based Drilling Fluid
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A New, Rapid Method To Characterize Shale at the Wellsite,"SPE 23887, 1992 IADC/SPE Conference, February 18-21, 1992,
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the mechanics and chemistry of drilling fluid/shale interaction”, paper IADC/SPE 25728, presented at the IADC/SPE DrillingConference, Amsterdam, 23-25 February 1993.
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Conference, Houston 3-4 April 1996.4. Tare, U.A., Mody, F.K.: "Novel Approach to Borehole Stability
Modeling for ERD and Deepwater Drilling”, SPE 52188, 1999
SPE Mid-Continent Operations Symposium, Oklahoma City,OK, USA, 28-31 March, 1999.5. Kenny, P., Sunde, E., and Hemphill, T.,: "Hole Cleaning
Modeling: What’s ‘n’ Got To Do With It?" SPE Paper No.35099, presented at the 1996 IADC/SPE Drilling Conference,
New Orleans, Louisiana, March 12-15.6. Hemphill, T. and Pogue, T., “Field Applications of ERD Hole
7. Sanchez, A., Azar, J., Bassal, A., and Martins, A., “Effect of Drillpipe Rotation on Hole Cleaning During Directional-WellDrilling”, SPE Drilling & Completion (June 1999), 14
No. 2, 101.8. Isambourg, P., Bertin, D., and Brangetto, M., “Field Hydraulic
Tests Improve HPHT Drilling Safety and Performance”, SPE
Drilling & Completion (December 1999), 14 No. 4, 219.9. Hemphill, T., Pilehvari, A., and Campos, W., “Yield Power Law
Model More Accurately Predicts Mud Rheology”, Oil & GasJournal (August 23, 1993), 45-50.
SUCCESSFULLY REPLACING OIL-BASED DRILLING FLUIDS WITH WATER-BASED DRILLNG FLUIDS:IADC/SPE 74545 CASE STUDY DEMONSTRATES VALUE OF EXTENSIVE PLANNING AND EXECUTION IN EXTENDED-REACH WELL 9
Table 1-Mineralogy and CEC Analysis by Depth From Offset Well
% of Total Sample Mixed Mixed Layer % of clay fraction Mixed Total CEC Exchangeable Cations
Depth Chlor Illite Layer Illite Smec Kaol Chlor Illite Layer Illite Smec Total Na K Ca Mg
SUCCESSFULLY REPLACING OIL-BASED DRILLING FLUIDS WITH WATER-BASED DRILLNG FLUIDS:IADC/SPE 74545 CASE STUDY DEMONSTRATES VALUE OF EXTENSIVE PLANNING AND EXECUTION IN EXTENDED-REACH WELL 11
Table 6-Drilling Fluid Properties During Drilling Operations, 16-in Interval
SUCCESSFULLY REPLACING OIL-BASED DRILLING FLUIDS WITH WATER-BASED DRILLNG FLUIDS:IADC/SPE 74545 CASE STUDY DEMONSTRATES VALUE OF EXTENSIVE PLANNING AND EXECUTION IN EXTENDED-REACH WELL 13
Fig. 3−Minimum mud weight predictions as a function of hole angle and azimuth for the 12-1/4-inch interval.
Fig. 4−Mud weight predictions and actual mud weights used in drilling as a function of hole angle for the 16-in interval.
Well A
Field Mud Wt = 11.4 ppg
No Significant Instabilities Observed.
10.35 10.82 11.3 11.78 12.25 12.73 13.2 13.68 ppg
Polar Chart for Predicted Mud Weight to Prevent Shear Failure (Collapse)Modeling TVD = 13000 ft, 6%Horizontal Stress Anisotropy, Poro-elastic Analysis
Note: Significant Instability Problems
are predicted at these hole anglesand azimuths.
N-S
Well B
Field Mud Wt = 11.4 ppg
Some Instabilities Observed.
Tight hole and Pack-offs.SCALE
8
10
12
14
16
18
0 10 20 30 40 50 60 70 80 90
Hole Angle [degrees]
M u d W e i g h t [ l b m / g a l ]
Pred. Min. MW Pred. Max. MW Actual MW
8/7/2019 Successfully Replacing Oil-Based Drilling Fluids With Water-Based Drilling Fluids Case
SUCCESSFULLY REPLACING OIL-BASED DRILLING FLUIDS WITH WATER-BASED DRILLNG FLUIDS:IADC/SPE 74545 CASE STUDY DEMONSTRATES VALUE OF EXTENSIVE PLANNING AND EXECUTION IN EXTENDED-REACH WELL 15
Fig. 7−Hole Cleaning Efficiency predictions by pump rate for two fluid rheological profiles.
Fig. 8−Predicted ECD at TD by pump rate and ROP level, 16-in interval, 0.25-in cuttings.
Fig. 9−Predicted ECD at 1000 US gpm by ROP level, 16-in interval, 0.25-in cuttings.
11.8
12
12.2
12.4
12.6
40 50 60 70 80 90 100 110
Rate of Penetration [ft/hr]
E C
D [ l b m / g a l e q ]
16 /
6.625-inSurf
MW
ECD-0ROP
0
20
40
60
80
100
800 1000 1200
Pump Output [gpm]
H C E
%
Mud 1
Mud 1 - under DP Mud 2
Mud 2 - under DP
11.8
12
12.2
12.4
12.6
700 900 1100 1300
Pump Output [gpm]
E C D [ l b m / g a l e q ]
Surf MW
No ROP
50 ft/hr
75 ft/hr
100 ft/hr
8/7/2019 Successfully Replacing Oil-Based Drilling Fluids With Water-Based Drilling Fluids Case