S P E 25058
`
`
`
`Society at Petroleum Engineers
`
`Practical Considerations of Horizontal Well Fracturing in the
`“Danish Chalk”
`
`K.A. Owens and M.J. Pitts, Maersk Oil 3t Gas A18. and H.J. Klampferer and
`SB. Krueger. Halliburton Services
`
`SPE Members
`
`Copyright 1992. Society of Petroleum Engineers Inc.
`
`This paper was prepared for presentation at the European Petroleum Conference held in Cannes. France. 16—13 November 1992.
`
`This paper was selected for presentation by an 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 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 Society of Petroleum Engineers. Its officers. or members. Papers presented at SPE meetings are subiect to publication review by Editorial Committees of the Society
`of Petroleum Engineers. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment
`of where and by whom the paper is presented. Write Librarian. SPE. P.O. Box 833836. Richardson. TX 75033-3335. U.S.A. Telex. 163245 SPEUT.
`
`ABSTRACI
`
`_
`_
`Placement of a propped hydrauhc fracture m a
`horizontal W911
`is dependent
`on several
`parameters. These parameters include toplcs
`such as IESEI‘VOII‘ condrtrons. dnllmg practlces.
`and completion techniques. This paper outlines
`some of the practical considerations that must be
`accounted for during the placement of proppant
`m a horizontal well- In describing, a Pmpped
`fracture treatment 011 an offshore horizontal well.
`the
`paper
`discusses
`treatment
`design
`considerations and verifies the operational and
`logistical improvements which can be made by
`utilizing a state-of-the—art stimulation vessel.
`
`INTRODUCTION
`
`_
`_
`_
`_
`Hydrauhc fracturing of honzontal wells IS often
`atirlic’iiiiil£1: ahformajrioil WT? coiwentioeal
`w s
`-
`IIlt EVEI'UCB C011 “10113 50 reun
`this . type 0f treatment. The Pan fidd in the
`Damsh sector of the North Sea 15 no exceptlon to
`this philosophy. The field. discovered in 1971. is
`produced from .the' Tertiary Pinia“ and
`Cretaceous Maastnchtlan chalks. typlfled by hlgh
`porosities (30%) and low permeabilities (1 md).
`Since the start of develoPment. all conventional
`deviated wells
`in this
`field were fracture
`
`stimulated to improve productivity. However.
`post
`stimulation production results were
`disappointing. A feasibility study performed on
`
`'
`'
`References and illustrations at end of paper.
`
`application of horizontal wells in the Dan field
`concluded
`that
`horizontal wells were
`economically
`attractive
`only
`by
`fracture
`stimulating multiple zones in the drainhole
`section and maintaining appropriate zonal
`iselation...” Therefore.
`in 1937 the operator
`commenced drilling of horizontal wells
`to
`increase the field's Production potential.
`
`The initial Dan horizontal wells were stimulated
`With flCid fracture treatments.
`the industry
`'
`'
`standard for a chalk reservoir. The placement of
`these treatments proved effective. however. the
`medium term production was limited due to the
`low formation integrity and consequent collapse
`of the induced fracture system. Propped fracture
`treatments replaced the acid treatments and the
`bonefits
`to productivity were quickly seen.
`However. the placement of proppant into some
`of the Dan horizontal wells became difficult. and
`in some cases impossible. The diffiaflties in
`placement are attributed to several
`factors.
`Principal among these is the direction of the
`horizonta1 wellbore relative to the preferred
`direction of the induced fracture.“ The situation
`is
`further
`complicated
`by
`the
`varying
`nonconformities
`that can exist at
`the near
`
`wellbore area. 5
`
`The theory and completion phflosophy utilized
`in performing multiple fracturing treatments in
`horizontal wells has been the topic of several
`revious
`e
`IS. 6'1"
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`esent
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`2
`
`PRACTICAL CONSIDERATIONS OF HORIZONTAL
`
`SPE 25058
`
`WELL FRACTURING IN THE DANISH CHALK
`
`some of the practical considerations necessary for
`placing prepped fractures in a horizontal well.
`This information is based on actual field data
`
`various
`during
`observations made
`and
`stimulation campaigns performed in the Dan
`field in which over 100 propped fracture
`treatments have been successfully placed from
`horizontal wells.
`
`PRETREATMENT PARAMETERS
`
`When performing propped fracture treatments in
`a horizontal well, knowledge of the far field—
`induced
`fracture direction is
`of
`extreme
`
`importance. The fracture direction in the Dan
`field was initially based on borehole breakout
`data and related back to stress orientation.
`
`Additional data was gathered in the form of
`Anelastic Strain Recovery (ASR) measurements.
`Differential Strain Curve Analysis
`(DSCA),
`Acoustic Transmission, and an accidental well to
`well ljnkup via a fracture treatment performed
`from one of these wells.11 All of this data
`
`general North/ South fracture
`indicated a
`direction for the Dan field.
`
`The horizontal wells in the Dan field are drilled
`
`in a radial pattern from a centralized platform
`location. This pattern ensures optimum reservoir
`drainage but also results in wellbores that
`intersect the preferred fracture direction at any
`angle between 0 and 90 degrees. Figure 1 shows
`the relationship between some of
`the Dan
`horizontal well
`trajectories and the far field
`fracture
`direction. Horizontal wellbore
`
`trajectories which are not in alignment with the
`induced fracture direction can have difficulties in
`
`placing proppant during fracture stimulations
`due to near wellbore fracture width restrictions
`and tortuosity effects. 5
`
`induced fracture
`the
`Prior knowledge of
`direction in a field to be completed with
`propped fracture stimulated horizontal wells is
`of utmost importance. This information can be
`utilized together with the magnitude of the
`principal
`stresses
`to calculate the expected
`fracturing pressures for a horizontal wellbore
`with a particular trajectory angle relative to the
`induced fracture direction} Calculation of these
`
`fracturing pressures for wellbore trajectories
`
`416
`
`which are not in alignment with the far field
`fracture direction will ensure that the installed
`
`completion/productionequipment can withstand.
`the increased fracturing pressures associated
`with stimulating wellbores which have a large
`misalignment between the well trajectory and.
`fracture direction. Knowing the induced fracture
`direction will also allow for prestimulation
`contingencies to be in place should a misaligned
`horizontal wellbore not be able to accept a
`propped fracture treatment due to the inherent
`near wellbore width restrictions associated with
`
`this type of situation.
`
`A horizontal well
`
`that
`
`is
`
`to be fracture
`
`stimulated over multiple zones must be cased
`and cemented. The cementing of horizontal wells
`has been enhanced with inlproved technology to
`achieve bonding along the entire horizontal
`section. These improvements include formulation
`of zero frée water slurries, rotation and/or
`reciprocation
`of
`horizontal
`liners,
`high
`displacement rates, and the use of spacer trains
`formulated to maintain hydrostatic pressure
`while achieving the highest rate of turbulence
`and solids cleanout. Experience has shown that
`the cement job has to provide complete casing to
`formation bond and ensure zonal isolation.
`
`The wellbore area around the perforated interval
`that is to receive the fracture stimulation should
`
`have cement integrity and hydraulic seal that is
`of high quality. The formation area adjacent to
`the perforations will be subjected to increased
`stresses and damage during the perforating
`process. This phenomenon will necessitate a
`higher breakdown pressure to initiate the
`induced fracture from this area. If the cement in
`
`this vicinity is absent or of such poor quality that
`large channels are present. the fracturing fluid
`has
`the opportunity to travel along the
`casing/formation annulus and break down the
`formation in an area requiring lower pressure
`compared to the perforated interval. This has
`occurred in certain instances in the Dan field
`
`stimulation campaign and has led to premature
`screenouts. Figures 2 and 3 are examples of the
`effect
`that cement bond integrity has on
`proppant placement during fracture stimulations.
`These figures show the CET and stimulation
`treatment log over the corresponding area for
`
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`SPE 25053
`
`K.A. OWENS, MJ. PITTS, H.I. KLAMPFERER, S.B. KRUEGER
`
`3
`
`two different fracture stimulations in the same
`
`well. As can be seen from these figures, the
`perforated interval in the poor quality cement
`lbond area ultimately incurred a premature
`screenout and had high pumping pressures
`during the stimulation treatment. However, in
`the same horizontal wellbore where a treatment
`
`was performed in a perforated interval adjacent
`to good cement quality,
`the treatment was
`pumped as designed and at
`lower
`treating
`pressures. This type of experience has indicated
`that a cement bond log is necessary for a
`horizontal well stimulation candidate.
`If the
`
`cement log indicates that the wellbore area to be
`stimulated has poor cement quality, an alternate
`area where cement integrity is better should be
`picked.
`
`to
`importance
`of
`area
`Another
`stimulation of horizontal wells is
`
`fracture
`formation
`
`pressure. This data is collected using a formation
`testing tool before running casing and provides
`valuable information that can be utilized in the
`
`design of fracture treatments to be performed in
`the particular horizontal well. Since the Dan field
`has
`been
`produced
`since
`1972
`through
`conventional wells and since .1987 through both
`conventional and horizontal wells,
`there are
`areas within the field that can have substantially
`different values of formation pressure. Figure 4
`shows an example of the differences in formation
`pressure which can occur along a horizontal
`section of a Dan field well. This information is
`very useful
`for
`fracture
`treatment design
`purposes
`since formation pressure (and its
`depletion from initial reservoir pressure) has a
`direct effect on fracture breakdown/propagation
`pressure,
`fracture fluid leakoff volume, and
`tortuosity effects when the horizontal wellbore
`and induced fracture are not in alignment. Prior
`knowledge of this information has increased the
`number of propped fracture treatments being
`placed according to design.
`
`DESIGN CONSIDERATIONS
`
`In preparing a propped fracture treatment design
`for
`a Dan
`field horizontal well,
`several
`conditions are reviewed. These parameters
`include mechanical and reservoir properties of
`the formation rock, fracture fluid characteristics.
`and proppant types.
`
`417
`
`One of the mechanical properties for the oil-
`bearing Maastrichtian chalk that has a significant
`impact on treatment design is modulus of
`elasticity. This formation has a very low Young's
`modulus of approximately 1 x 10‘ psi. This
`formation property allows for the creation of
`very wide (greater than 1 in.) induced fractures.
`The moderate porosity and low strength of this
`reservoir rock also creates a situation where
`
`formation creep can occur under drawdown
`conditions.” This chalk migration can cause
`premature production decline which eventually
`leads to the failure of conventional acid or
`
`propped fracturing treatments performed in this
`field. To reduce and/or defer the problem of
`chalk
`ingress
`into
`the
`induced
`fracture,
`stimulation treatments are designed to achieve a
`high proppant concentration (5 to 10 lb/ftz) in
`the fracture. This high proppant
`loading is
`possible due to the low modulus of
`the
`formation and the use of tip screenout designs.”
`
`relatively
`is
`formation
`The Maastrichtian
`homogeneous. Fracture diagnostic tests have
`shown a lack of stress contrasts in the reservoir
`
`layers which could act as fracture barriers in the
`reservoir layers. Therefore, all induced fractures
`made in this field are radial
`in nature. This
`
`information is important for determining the
`propped fracture sizes to be placed in the
`horizontal wells. The size of each stimulation
`
`treatment is determined by the radial distance to
`the oil/water contact and the gas /oil contact.
`Figure 5 shows an example cross section of a
`typical multiple fracture stimulated horizontal
`well in the Dan field containing varying fracture
`sues.
`
`Obviously, production optimization can be lost
`should a fracture treatment extend into the water
`
`or gas interval. Detailed fracture simulation. and
`real-time fracture diagnostics are performed to
`ensure that this risk is minimized. A state of the
`art simulation program is utilized for this task.”
`Post-stimulation production from these wells has
`confirmed that the tolerance between designed
`and actual fracture dimensions is close since
`
`excessive GOR development or high water
`production 'is not apparent for most situations.
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`4
`
`PRACTICAL CONSIDERATIONS OF HORIZONTAL
`
`SPE 25058
`
`WELL FRACTURING [N THE DANISH CHALK
`
`Fracturing fluids are also critical components in
`the design of fracturing treatments. At present,
`two different types of fracturing fluids are being
`used to stimulate the Maastrichtian chalk in the
`
`Dan field. One fluid system incorporates a
`titanate-based crosslinker and the other uses an
`antimony-based crossh'nker. Both of
`these
`systems utilize a hydroxypropylguar (HPG) base
`gel. Initial titanate treatments were performed
`with a 50 lb/Mgal HPG polymer loading. Iob
`experience has allowed this polymer loading to
`be reduced to a 40 lb/Mgal system without
`risking treatment placement. For the antimony-
`based fluids, a polymer loading of 50 1b/Mgal is
`still used. This is needed because this fluid
`
`system is being used at its upper temperature
`limitation. The antimony system is attempted to
`be used whenever possible due to the enhanced
`fracture conductivity (cleaner breaking fluid) that
`can be achieved with this fluid.
`
`With experience and correct fracture simulation,
`fracture fluid volumes have been optimized to
`such an extent that the desired Tip Screenout
`style design is
`achieved in most of
`the
`treatments. Figure 6 is an example job treatment
`log indicating the pressure response seen from
`this type of treatment. A common design goal
`utilized in the Dan field stimulation campaign is
`to place 75% of the total proppant pumped in a
`treatment at concentrations above 10 lb/ gal.
`Maximum proppant concentrations are typically
`15 113/gal and in isolated cases, proppant
`concentrations exceeding 21 Ib/gal have been
`placed in the formation.
`
`Optimization of these treatments could not have
`been achieved without the use of bottomhole
`
`pressure (BHP) gauges. The data acquired from
`these gauges ensures that
`the best possible
`interpretation of a fracturing treatment can be
`performed. Since
`a
`typical Dan multiple
`stimulated horizontal well receives on average 7
`to 15 fracture treatments, BHP measurements
`from a stimulated zone are also utilized to
`
`Optimize the fracture treatment to be performed
`in an adjacent zone in the same well. The cost of
`using these. gauges is more than offset by the
`savings acquired (pad fluid reduction) by
`Optimizing
`sequential
`treatments
`in
`the
`horizontal section.
`
`The introduction of encapsulated type breakers
`into the fracture fluid system has also assisted in
`improving the net production response seen
`from the Dan field stimulated wells. The
`
`high
`loaded with
`are
`fluids
`fracturing
`concentrations (5 lb/MgaD of these breakers to
`ensure a controlled, and delayed, but complete
`break of the fracturing fluid. This is especially
`important in the area of gel filtercake buildup
`along the fracture face where a release of
`concentrated breaker can significantly improve
`the regained permeability of the fracture pack.
`
`the proppant material used in the
`Sand is
`fracturing treatments performed in the Dan field.
`The strength of this material is sufficient
`to
`withstand the closure stress of the Mass trichtian
`
`formation. The designed high proppant loading
`(5 to 10 lb/ftz) is used to combat creep, fines
`migration, and fracture fluid damage. All
`propped fracture treatments in Dan also receive
`a resin-coated sand (RC5) tail-in. This procedure
`is performed to prevent proppant
`flowback
`during production. This has proved successful
`compared to early treatments where no RC5 was
`used and sand production problems occurred.
`
`TREATMENT LOGISTICS AND PLACEMENT
`
`The propped fracturing treatments placed in the
`Dan field .are performed from a dedicated
`stimulation vessel. The volume of proppant and
`fracture fluids utilized in these treatments
`
`necessitates the use of this type of equipment. To
`perform stimulation treatments on a multiple
`zone horizontal well,
`it
`is essential
`to have
`equipment
`available
`that
`is designed for
`maximum versatility. A stimulation vessel fulfils
`this need.
`
`For example, the total volume of sand required
`for an individual Dan horizontal well may vary
`between
`2,000,000
`1b
`and
`12,000,000
`1b.
`Therefore, the vessel must have a large and
`flexible sand storage system. Typically, 2,000,000
`lb of sand is carried in one sailing and treatment
`size determines the reloading interval. The sand
`bins on the vessel have been designed such that
`different types and sizes of sand can be pumped
`at any time during the job should a change in
`treatment program become necessary.
`
`418
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`SPE 25053
`
`KA. OWENS. MJ. PI'ITS. HJ. KLAMPFERER, 3.3. KRUEGER
`
`5
`
`Sand capacity of the vessel is not the only area
`where the requirement of flexibility is needed.
`The vessel must have sufficient fluid capacity to
`provide
`up
`to
`1,000,000
`gallons
`of
`semicontinuous-mixed
`fluids
`of
`various
`
`properties to meet the expected needs. The fluids
`use a seawater base since carrying fresh water
`for mixing the fracture fluids would severely
`limit the vessels capability to carry the maximum
`amount of sand. A gel concentrate base fluid
`system is used to allow for instant job design
`modifications. These gel concentrates are blended
`at high pH to ensure long-term stability and
`when mixed at the correct ratio with seawater. a
`fast hydrating linear gel at the designed polymer
`loading is available for continuous pumping. The
`ability to continuously mix gelled fluid ensures
`that no gel has to be disposed of at the end of a
`treatment
`terminated earlier than designed.
`
`Another important factor in the performance of
`these treatments is the use of specially designed
`high-pressure treatment iron. Since a typical Dan
`horizontal well receives an average of 7 tolS
`treatments, a semipermanent surface frac line
`rigup has been adopted. This rigup utilizes two
`4-in. ID high-pressure lines initiating from the
`vessel-based
`high-pressure
`pumps
`and
`terminating at the frac header on the rig floor.
`The high-pressure connection between the
`stimulation vessel and the rig is made with high-
`pressure hoses. This system. which has a larger
`ID than traditional frac iron, reduces the velocity
`through each line and the corresponding
`erosional damage. It also eliminates the need for
`a third frac line to be employed. which is the
`case when traditional frac iron is used at the
`
`typical Dan frac rates of 40 to 50 bbl/min. A
`combination of rigid, 4-in.
`frac iron and high-
`pressure hoses is used in the rigup on the
`drilling
`rig. The
`frac
`iron
`uses Clamp
`connections, with most of the joints being 30 ft
`long, thus drastically reducing the number of
`connections and potential leak areas. Two 4-in.
`high-pressure hoses connect the frac header to
`the rigid iron located at the bottom of the v-
`door. Utilizing these hoses has eliminated the
`need for implementing a large number of swivel
`unions. as are typically employed in traditional
`frac rigups. This semipermanent system, with its
`larger ID, superior clamp Connection compared
`to the traditional hammer connection, and
`
`419
`
`overall reduction in the number of connections
`
`has reduced the time lost during pressure testing
`by 80%. Figure 7 gives a schematic of this rigup.
`
`the
`To perform these fracturing treatments,
`stimulation vessel must have pump capacity in
`excess of 10,000 hydraulic horse power. Most of
`the treatments performed to date in the Dan field
`have been with long-stroking, high—pres sure
`pumps called intensifiers. This name reflects the
`hydraulic intensification process by which these
`pumps derive their power. These pumps have
`demonstrated
`extremely
`high
`reliability.
`Experience has shown that this system maintains
`high operational duration with an extremely low
`incidence of mechanical problems. These pumps
`have proven their capability to pump fluids at
`high pump rates
`and extreme pmppant
`concentrations for long periods of time without
`failure.
`
`All fracturing fluid additives are blended to the
`designed specifications
`through the use of
`metering systems. These metering systems
`ensure precise measurement of all additives. and
`reduce waste. The metering systems are linked to
`a computerized data base which provides
`updated volume/additive usage information to
`maintain stringent quality control.
`
`The data acquisition system plays an important
`role in the placement of a fracturing treatment.
`A multi-tasking computer is used to record data,
`perform real-time data analysis, provide job
`plots, and run design program. All recorded
`parameters are displayed in the fracturing
`control center located aboard the stimulation
`
`include wellhead
`vessel. These parameters
`treating pressure, slurry injection rate. slurry
`density, proppant
`concentration.
`calculated
`BHTP, stage and cumulative fluid volumes, as
`well as fracturing fluid pmperties at various
`stages of the mixing process. The data recorded
`is only of importance when it is displayed in
`such a format that it can be used efficiently by
`the personnel performing the treatment. The
`relevant data needs
`to be displayed both
`digitally and graphically in a simple format. such
`that the stimulation engineer can be provided
`with
`updated
`information
`to maintain
`continuous control of the fracturing treatment.
`The
`computerized
`data
`acquisition/design
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`6
`
`PRACTICAL CONSIDERATIONS OF HORIZONTAL
`
`SPE 25053
`
`WELL FRACTURING IN THE DANISH CHALK
`
`system should also provide sufficient flexibility
`such that design changes made during a
`treatment can be incorporated and displayed
`instantly. Figure
`3
`provides
`an
`example
`treatment job plot containing many of the
`relevant parameters measured and utilized
`during a typical Dan field fracture treatment.
`
`Quality control of the fracturing fluids is another
`area of importance for maintaining design and
`placement control of a fracturing treatment.
`Pretreatment fluid system checks of additive,
`breaker, and crosslinker concentration as well as
`fluid viscosity are verified. During the treatment,
`fracture fluid quality control is also maintained
`since this parameter is critical to ensure designed
`placement of the stimulation treatment. Fluid
`samples are taken during each job stage and
`checked for correct gel loading (viscosity), pH
`level, hydration time, and crosslink time. All
`samples are retained and placed in a water bath
`set at reservoir temperature (165“ F) to ensure
`that these fluids will break within the designed
`time period. These quality procedures ensure
`complete control over the designed fluid system.
`Experienced fluid engineers coordinate measured
`fluid data
`to the
`fluid blending/ systems
`personnel as well as to the stimulation engineer
`on a continuous basis. Any desired change in
`fluid properties can be performed within a short
`period of time.
`
`fracturing
`A typical Dan horizontal well
`treatment is initiated by performing an injectivity
`test with base linear gel. This test confirms the
`capacity of the formation to accept stimulation
`fluids at fracturing rates. It also gives a measure
`of pressure response due to near—wellbore
`tortuosity caused by misalignment between the
`horizontal wellbore and the far field fracture
`
`inadequate cement bond
`direction and/ or
`integrity. Following
`the
`injection
`test,
`a
`diagnostic test is performed with crosslinked
`fluid
`to
`confirm that
`critical
`fracturing
`parameters
`such as
`leakoff are within the
`sensitivity
`limits utilized
`in
`the
`fracture
`treatment design. Finally, the main treatment is
`initiated and implemented. Upon completion of
`the treatment, the zone is isolated and these
`procedures are repeated in the subsequent zones
`within the horizontal. wellbore. Compliance to
`
`the above-described procedures has resulted in
`over 100 propped fracture treatments being
`successfully placed from horizontal wells in the
`Dan field.
`
`CONCLUSIONS
`
`1 .
`
`Knowledge of reservoir properties such
`as fracture direction, formation pressure,
`and principal
`stress magnitudes
`is
`necessary
`for
`design
`of
`installed
`completion/production equipment that
`can withstand the increased fracturing
`pressure associated with stimulating
`wellbores which
`have
`a
`large
`misalignment between the well trajectory
`and fracture direction.
`
`2.
`
`a
`for
`are necessary
`logs
`Cement
`horizontal well stimulation candidate to
`
`ensure that
`
`the wellbore area in the
`
`vicinity of the interval to be perforated
`has cement
`integrity and a hydraulic
`seal that is of high quality. Utilization of
`this
`information has
`increased the
`
`number of propped fracture treatments
`being placed according to design in the
`Dan field.
`
`are
`
`treatments
`
`fracture
`Propped
`designed for high proppant loading and
`pumped
`utilizing
`a
`tip screenout
`technique to combat the effects of chalk
`migration. This design philosophy has
`increased the medium term productivity
`from the Dan field.
`
`Detailed design simulation and fracture
`diagnostics are necessary to maintain
`stringent
`control
`over
`fracture
`dimensions. Production results have
`
`validated the accuracy of the Dan field
`designed fracture treatments.
`
`BHP measurement gauges are utilized
`on
`every
`fracturing
`treatment
`to
`maintain
`detafled
`post-stimulation
`diagnostic evaluation and ensure for
`Optimization of subsequent zones to be
`stimulated in the horizontal wellbore.
`
`3.
`
`4..
`
`5.
`
`420
`
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`SPE 25053
`
`K.A. OWENS. MJ. PI'ITS. HJ. KLAMPFERER, 5.3.. KRUEGER
`
`7
`
`6.
`
`Cormct selection of fracturing fluids and
`proppant are critical design criteria for
`achieving maximum productivity and
`minimizing stimulation cost.
`
`3.
`
`Darngaard. A... Bangert, D.S.. Murray.
`DJ. Rubbo, RP. and Stout. G.W.: "A
`Unique Method for Perforatin3. Fracturing.
`and Completing Horizontal Wells," Paper
`SPE 19282, 1989.
`
`A resin-coated sand tail—in is performed
`on every Dan propped stimulation
`treatment to prevent proppant flowback
`during production. This procedure has
`proved to be very successful.
`
`A customized "semipermanent" frac iron
`rigup is utilized for the placement of
`multiple fracture treatments in a Dan
`horizontal well. This system has proven
`superior due to time savings during
`rigup and reduced leak correction at
`connections as compared to traditional
`hammer union. smaller ID type frac iron.
`
`Treatment logistics and placement have
`been
`improved
`on these
`complex
`propped hydraulic fracturing treatments
`performed
`in
`the Dan
`field
`by
`maintaining stringent quality control and
`detailed data measurement. acquisition.
`and display. This
`is only possible
`through the use of a state-of—the— art
`stimulation vessel.
`
`ACKNOWLEDGEMENTS
`
`The authors wish to thank the management of
`Maersk Olie 03 Gas AS. Texaco Denmark Inc .,
`Shell Olie 0g Gasudvinding Danmark BV
`(Holland),
`and Halliburton
`Services
`for
`permission to publish this work.
`
`REFERENCES
`
`1.
`
`Andersen. SA... Hansen. SA.
`and
`Fjeldgaard. K: "Horizontal Drilling and
`Completion, Denmark, " Paper SPE 18349,
`1988.
`
`Andersen, SA... Conlin. JM., Fjeldgaard,
`K.
`and' Hansen.
`S.A.:
`"Exploiting
`Reservoirs with Horizontal Wells: The
`Maersk Experience, " Oilfield Review (July
`1990).
`
`10.
`
`11.
`
`12.
`
`421
`
`and
`SA...
`ILA... Andersen.
`Owens,
`Economides, M.].: "Fracturing Pressures
`for Horizontal Wells. " Paper SPE 24822.
`1992.
`
`Wellers, L., de Pater, C]... Owens, RA...
`and Kogsboll. H.H.:
`"Geometry
`of
`Hydraulic
`Fractures
`Induced
`from
`Horizontal Wellbores. " Paper SPE 25049.
`1992.
`
`].—C. and
`I.D., Roegiers,
`McLennan,
`Economides. M.].: "Extended Reach and
`Horizontal Wells. " Reservoir Stimulation
`(second edition). MJ. Economides and
`KC. Nolte
`(eds)
`Prentice Hall,
`Englewood Cliffs 1989.
`
`Behrmann. LA. and Elbe]. ].L.: (1992),
`"Efiect
`of Perforations
`on
`Fracture
`Initiation. " JPT, pp. 608-615.
`
`Veeken. C.A.M., Davies, DE... and
`
`"Limited Communication
`].V.:
`Walters,
`Between Hydraulic Fracture and (Deviated)
`Wellbore. " Paper SPE 18982, 1989.
`
`El Rabaa. W... (1989): ”Experimental Study
`of Hydraulic Fracture Geometry Initiated
`from Horizontal Wells. " SPE 19720.
`
`Yew. CH... and Schmidt, LH. (1989): "On
`Fracture Design of Dem'ated Wells." SPE
`19722.
`
`Van der Hook, P.I., Bussink, PG]... and
`Van Munster. ].G.: "Koninklijke/Shell
`Exploratie en Produktie Laboratorium.
`Confidential Project Paper.
`
`P... and Hijdendaal, H.G.:
`de Bree,
`Koninklijke/ Shell Exploratie
`en
`Produktie Laboratorium. Confidential
`
`Project Paper .
`
`7 of 12
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`

`PRACTICAL CONSIDERATIONS OF HORIZONTAL
`
`SPE 25053
`
`WELL FRACTURING IN THE DANISH CHALK
`
`13.
`
`'14..
`
`Smith, M.B., Miller, W.I<., and Haga, 1.:
`"Tip Screen Out Fracturing: A Technique
`for Soft, Unstable Formations, "
`SPEPE
`(May 1987), 95-103.
`
`Cleary, M.P., Wright, CA, and Wright,
`T.B.: " Experimental and Modeling Evidence
`for major Changes in Hydraulic Fracturing
`Design and Field Procedures," Paper SPE
`21494, 1991 ..
`
`Fracture direction N5W
`
`MFA-15
`
`
`
`Fig. 1—Well trajectory/fracture deviation angles
`in the Dan field.
`
`422
`
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`

`1-1I-3l 1'
`
`
`
`I ”-1-.'
`
`.1.1....I—-I'll_I
`
`'II__""
`
`—II'IIl-—I-—
`
` I
`
`I—---
`-Ill-III..._l
`
`mull
`
`= — E
`
`E
`
`I:
`
`
`
`
`CEMENT BOND LOG
`
`DD-
`
`1111: Pressure PSI
`
`Bth Pressure PSI
`
`Slurry Density SGU
`Slurry Rate RPM
`
`21H}
`
`lflflfl
`
`12mm
`
`8317
`
`Izmiii
`
`12mm
`
`flflfl
`
`T291}
`
`4300
`
`241]}
`
`140:}
`
`fie:
`
`IF
`
`WWII?
`
`Il—_-1IIIII 'IIIIIl-IIIIIl- —I_
`
`CEMENT BOND LO
`
`Di:-
`
`Thin Pressure {PSI}
`Elh Pressure (PS!)
`
`Us}
`
`Slurry Densin [SGU
`Slurry Rate (RPM)
`
`
`31m
`54m
`
`'fimeWinules)
`
`1::
`
`I 31!]
`
`143.0
`
`Ti Winn ies)
`
`Fig. 2—Send-prepped treatment perfermed en zene with peer cement quality.
`
`Fig. 3—Send-prepped treatment perienned en zone with geed eement quality.
`
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`

`SPE 25058
`
`.
`
`00- Prop Cone. lbigal
`—H—Tubing press. (psi)
`
`*-*-Slurry rate (born)
`
`3400
`
`JEBIHJ
`
`.3200
`
`.31EHJ
`
`.SIJEHD
`
`E 2000
`E 2500
`E
`a 2200
`
`E
`E 2000
`$250”
`E
`'1 23““
`2200
`
`[I 2400
`
`20
`2000
`
`000
`
`15““
`1250
`
`#31?
`
`2000
`
`2250
`
`2500
`
`2250
`
`4500
`4250
`4000
`5250
`5500
`5250
`5000
`HORIZONTAL DISTANCE FROM PLATFORM (ft)
`
`4250
`
`5000
`
`5250
`
`5500
`
`5250
`
`Fig. d—Formallan pressure 00. lataral extanalon of 0 Dan horizontal.
`
`MFA-17
`
`E
`053°” WELL PATH
`0
`3’
`l—
`062m
`E
`0.
`”J 6600
`a
`
`5°00
`
`5300 a
`“3
`g
`1.
`'—
`--""=r=r__v_-!!.Y=r=2;v.= 520° .0.
`5916.30_________
`_ "WWW____
`E
`0
`6600 EI
`
`he
`._ _
`ull-.23.—w‘“ —
`~—
`_
`' -‘V_
`
`a—..
`
`30°“
`700°
`HORIZONTAL DISTANCE FROM PLATFROM (FT)
`
`900°
`
`1
`
`100 O
`
`-
`
`‘
`
`0.0
`
`.
`
`.
`'
`-
`=
`.I
`
`0'6“
`
`r'fi'fi’
`09"
`
`.
`
`64.0
`
`1800
`
`I
`l
`.
`i
`00011"
`00.0
`
`
`
`Sand slurry
`on formation
`/
`,ff'"
`“M -. a“...
`
`.
`
`{HEN/f
`
`0"...
`g'
`' ME
`|
`1
`.
`
`“-4
`._._-
`
`- __--__.....
`04.0
`
`400
`
`_
`80
`
`-
`
`-
`
`.-._.._
`.
`._.
`_
`.
`192.0
`128.0
`' Time (Minutes)
`
`_.__-_._ _-
`250.0
`
`-
`320.0
`
`'07:
`E
`
`E '
`
`23
`
`{.0
`
`0'}
`a:
`
`i—
`0:
`E
`I
`E
`0
`:5
`m
`
`50.00
`
`mi;
`
`
`
`l
`0000
`I
`I
`._
`iI
`40.00
`: 30'0
`(it
`7200
`i. 50 0
`”WWW/J“
`l
`E 30.00
`i
`-
`E- 5400 W |
`.
`0)
`"Pmuh'fi
`I
`i
`0' 20.00
`in-.. .- +----- .......+ _.....
`i 40—0
`0: 3000
`-
`‘
`.mfi‘flvfiflw
`|
`0 J
`l 20 0
`10.00
`|=
`i
`'i
`i
`l.
`i
`is
`i”
`. __h_—..___—.—+HH—.——.—.*r. '4“ 1
`
`
`
`120.0
`192.0
`256.0
`320.0
`Time (Minutes)
`
`ZONE:
`
`PROPPANT TOTAL (LBS) STIMULATION DESIGN: RADIUS (FT)
`
`HQ— fi'TIP screen-001000001002.
`
`1
`2
`3
`4
`5
`0
`7
`3
`9
`
`500.000
`750.000
`750.000
`1.000.000
`1.000.000
`1.000.000
`1.000.000
`2.100.000
`500.000
`
`125
`150
`150
`1?5
`175
`175
`175
`200
`125
`
`Fig. -5'—'Crnaa section of a Dan atimulated horlzantal wall.
`
`10 of 12
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`

`

`4” HP FLEX HOSE
`50 FEET
`
`4" IRON
`
`931?
`
`4" HP FLEX HOSE
`50 FEET
`
`4" VALVE
`
` 4H
`
`SPE 25053
`
`_-—m
`
`4" HP FLEX HOSE
`50 FEET
`
`4” SWIVELS
`
`FLAPPER CHECKS
`
`
`
`
`
`UVERBUARD
`LINE
`
`”
`
`l
`
`_
`VALVE
`
`"
`
`2
`
`1502 TEES
`
`“————“——_—
`
`Fig. 7—FI'HCIUI'B treatment line schematic.
`
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`