TEC 20 FPorturas Final

8/3/2019 TEC 20 FPorturas Final

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Categora: Marque con una X

Artculo Tcnico X Tesis Pregrado Tesis PosgradoDerechos de Autor 2011, ACIPET

Este artculo tcnico fue preparado para presentacin en el XIV Congreso Colombiano del Petrleo organizado por ACIPET en Bogot D.C. Colombia, 22 - 25 de Noviembre de 2011.

Este artculo fue seleccionado para presentacin por el comit tcnico de ACIPET, basado en informacin contenida en un resumen enviado por el autor(es).

SummaryThe near wellbore formation can be damaged by a variety of mechanisms. Based on field experience, an integrated approach isnecessary to identify the type of damage and to recommend a treatment for exploiting pre-existing completion hardware like screens,liners or Inflow Control Devices (ICD). A better understanding of the combined damage mechanisms occurring in both the matrixand the formation, combined with optimized fluid treatment design and its interaction via the existent completion, is expected to givean extended treatment lifetime and enhanced production.

This paper present how stimulation, well treatment and acidizing is better facilitated by Inflow Control Devices (ICDs) installedvery low permeability carbonates at the Bouri Field in Libya.

The performace of the ICDs for formation damage treatment and matrix stimulation is recommended to be sensitized in two modes:a) First in injection mode to assess fluid injectivity conformance, uniform distribution along the entire wellbore, fluid rates to

overcome pressure drop across nozzles and optimal volumes and time.

b) The second phase is to sense the same completion layout in production mode.Due to reservoir heterogeneities, it is unlikely that a conventional completion will treat, distribute treatment or stimulation fluidsuniformerly along the wellbore in the same way an ICD does. Furthermore, an ICD configuration has longevity that will allow chosenfluids, volume, placement method, repetitive or selective stimulations to a hardware ready to receive future emerging EOR technologytreatments for example nanomaterials, nanotubes or nano-microsensors, to maximize oil recovery.

IntroductionHorizontal well drilling traditionally helps to improve the oil recovery and avoid problems of premature gas and water breakthrough.In Bouri Field, offshore Libya, the main concern of the operator was to establish an advanced method of controlling gas and water encroachment in a fractured carbonate reservoir characterized by moderate to low permeability.This challenge and reservoir considerations required a new practical field implementation of the new ICD completion technologyaiming to improve the ultimate recovery of Bouri field by minimizing higher mobility fluid coning and balancing fluid influx toenhance the total well oil production in a double operation including a period of acidizing, stimulation and wellbore clean-up.Auxiliary completion elements for example swelling-packers were installed in tandem and were used to compartmentalize thehorizontal and build sections, to further enhance ICDs drawdown control and inimizing cross-flow issues in the carbonate reservoir.The completion required innovation and re-thinking of the traditional and established acid-wash treatment procedures, ultimatelyimproving the overall well clean-up. Integrated analysis methods using static wellbore hydraulic and dynamic simulators were

performed to generate flow profiles and calculate ICD pressure drop along the horizontal section. The models were updated usingresults from logging-while-drilling (LWD) and with real-time modifications to the initial design.To verify the inflow profile along the length of the ICD completion, two production logging (PLT) was conducted. The inflow profilescompared favorably with those predicted by the models and show that all ICD nozzles contribute to production.

ACIPET

ICDs in Injection and Production Modes for Formation Treatment, Stimulation andAcidizingFrancisco Porturas Luma Viloria-Gmez Mustafa Amari and Hosam Sharaf Schlumber er


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Bouri FieldThe Bouri Field is part of Block NC-41 and it is located N-NW of the Libyan capital city, Tripoli, about 120 kilometers off Mediterranean Sea coast (Figure 1).The field was discovered in 1970s, and has subsequently been developed with two platforms (DP3 and DP4) and 82 developmentwells. Since start-up, oil production has often been affected by high water cut (WCUT) and very high gas-oil-ratio (GOR) due to earlyconing and fingering phenomena via an extensive fracture network within the carbonate reservoir. These phenomena were notsignificantly reduced even after extended reach and horizontal well drilling which prompted the operator evaluated new technicalsolutions to address this problem.During end of 2009 two horizontal wells (here referred as Well 1 and Well 2), were drilled and completed with ICD technology to hasreduce the gas and or water coning and to evenly distributing reservoir inflow to limit the negative effects after occurrence of highmobile fluids breakthrough.

Reservoir challengesBouri Field main challenges are sudden breakthrough of gas and/or water ocurring during production life, reducing the overall welland reservoir recovery efficiency.Bouri is a carbonate reservoir of low-to-fair horizontal permeability, and of good vertical connectivity. Reservoir faults are non-sealing, and fracture effects are more pronounced closer to the faults. Micro-fraturing is also present in the upper-most layers, thusadding more complexity to the existing gas-coning problem. The field is still producing under primary recovery mechanism, is above

bubble-point, and is supported by strong bottom and edge aquifer presence.With good matrix permeability, the development production strategy has been to drill wells in trajectories that avoid intersection of known fractures and faults, while placing new wells away as far as possible from the gas and water contacts.The main challenge in Bouri Field, besides the heel-to-toe effects, was the presence of a large gas cap overlying the oil column

expected to have an important impact on production performance with time. This scenario was simulated by maximizing the gasfraction in different segments of the horizontal section, assuming initial reservoir conditions elsewhere.

Nozzle based ICD principlesThe pressure drop through a nozzle based ICD is a result of the static energy in the fluid being converted into kinetic energy andabsorbed in the fluid downstream of the nozzle as described by the Bernoulli equation. Nozzle based ICDs are independent of fluidviscosity, and have been successfully installed in a large number of wells worldwide.

The nozzle pressure drop is described by:

Where:

P N = pressure across ICD nozzles, Cu = units conversion constant, = density of fluid, v = velocity, Cv = dimensionless flowcoefficient of the nozzle, q = flow rate and A = total cross section area of the nozzles.

The constant Cv is determined by nozzle geometry and flow, and has a typical value between 1.0 and 1.5 (dimensionless).

At the reservoir sand-face or carbonate-face, the Darcy law:

Where: P F = pressure across the formation, = density of fluid, v = velocity, q = flow rate, A = total cross section area of the nozzles,

k = permeability, = viscosity.

ICD Function and OperationReservoir fluid enters the screen and flows between the screen jacket and base pipe into the housing and through the ceramic nozzlesWhen fluid enters the nozzles, the potential energy is transformed into kinetic energy, which is absorbed in the main flow through the

base pipe, thus resulting in a pressure drop between the annulus and the tubing. Figure 3 shows the ICD hardware available both for production (Figure 3a), injection (Figure 3b) and its interaction with the reservoir (Figure 3c).Different nozzle sizes are available for eaxaple with 1.6 mm, 2.5 mm and 4 mm, making it possible to design the ICD completion tothe required well geometry and flow rates and available pressure drawdown. This is what essentially allows fine-tuning of thesystem, where the nozzle size and number can be tailored to balance the well influx profile and eliminate the heel-to-toe drawdown

Aq

vCv

vCu P N == ,

2 2

2

F F P Lk

v Aq

k L

P =

=


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FRANCISCO PORTURAS, LUMAY VILORIA-GOMEZ, MUSTAFA AMARI and HOSAM SHARAF ACIPET

effects in long horizontal wells. The ICD nozzle setting can be preset, or alternatively may be performed on-site making the systemvery flexible to calibration with real-time operational data.

The wire wrapped screen part of the ICD system is for optimizing particle size distribution in case of bridging material and need for sand control or solid particle retention (non-consolidated formations), or in the case of consolidated formations its main function isonly to allow flow from the reservoir into the production string.

Simulation of an ICD prior, during and after field completionOperator ICD goals were: a) reduce, minimize, delay early gas brekthrough, including stabilising or reducing WCUT and, b) facilitateand enhance performance of acidizing and stimulation fluids, including an efficient wellbore clean-up.Therfore, prior to ICD instalation, a series of sensitivity are evaluated to address constraints, minimize risk and to plan for a timelyinstallation. This first step benefits of nodal simulation, the output being a base case and definition of a completion layout, number of nozzles and sizing for each ICD segment, as well as the minimum number and location of ICD completion segments or compartmentsor zonal isolation.In the case of Bouri wells, both open-hole and ICD completion system alternatives were tested and comparing various sensitivityscenarios. Figure 2 shows a composite display of the ICD sensing in production mode, where the results show in one page the mainfactors per segment, for example PI, cummulative flow, flux, and pressure responses.This allow to evaluate the influence of permeability contrasts and fractures early in the well planning process. Later, the base case will

be subject to a re-visit and integration of real-time data. Now the base case is updated, refined and ready for field installation.Preliminary design was done on the basis of a permeability profile extracted from a-priori reservoir model knowledge.The final completion design was built using real-time logs (LWD data) as input, which provided petrophysical properties from theactual well trajectory. There is uncertainity when extracting permeability from logs; therefore it is important to run sensitivities onhorizontal and vertical permeability even if a field function is available. The saturation profile was also obtained from LWD data.Real time logs were continuosly evaluated while the well was being drilled and were used to calibrate the ICD model prior to the finalcompletion installation. Mud losses were closely monitored to further locate the presence of fractures or high-permeability thief zones.The final ICD configuration was obtained after running numerous sensitivity scenario models, evaluating different nozzle sizes, anddifferent number of nozzles and packers to be placed along the horizontal section to segment the well accordingly.ICD simulation responses was done both in injection and in production modes.In production mode , the results showed potential in decreasing total well GOR upon gas-breakthrough, thus achieving the firstreservoir recovery challenge.In injection mode , the simulation results showed injection conformance of acidizing and stimulation fluids, thus achieving the secondoperational goal.Finally the ICD nozzle configuration was adjusted at the wellsite before installation. The horizontal section of Well 1 was subdividedinto 7 compartments from heel to toe and included 13 ICD joints and 7 swell-packers. Figure 4 shows the completion layout and theresulting wellbore compartmentalization over the permeability profile.After ICD installation, two baseline PLT logs were acquired for Well 1 and Wee 2 (Figure 5), to verify and evaluate the inflow profilealong the ICD completion. The PLT log showed an inflow profile in-line with prediction, with small discrepancies attributed to designrates vs. PLT choke setting.The comparison results show very close agreement between the simulated and observed PLT results (Figure 6b).

ICD material technology and swellable packersBouri Field is producing with a high content of H 2S and CO 2, needing Nickel alloy metallurgy to overcome the severity of theenvironmental reservoir conditions. All equipment parts, including base pipe, ICD housing and wirewrap section, housing, was builtin Inconel 825 or 28Cr-32Ni materials including inserts for all of the ceramic nozzles used.Swell packers were tested to the same oil-based mud (OBM) used by the operator and has been tested in the laboratory to 30% HClconcentrations without showing defects or problems. This were installed in a tandem of four packers over a length of 4 meters to

ensure efficient compartmentalization for the acidizing and stimulation and further well production.

Operationa challenges Running the ICD system in a 6 open-hole section presented a unique challenge. The aim during drilling was to make the hole lesstortuous, minimizing the wellbore dogleg severity to accept the 4 1/2 liner assembly.The maximum OD of the tools was 5.832 (ICD housing), a very tight fit for completion deployment. Therefore oil swellable packershave had to be modified and engineered to a lower OD to ease running in hole.Roller reamers were utilized before running casing, proving to be very useful in smoothing the borehole before the stiff assembly of liner was run through the buildup section.


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The liner was run with a 2 7/8 inner wash string to enable circulation. Bottom-up circulation to condition the oil-based mud (OBM)was performed until clean returns and gauged hole was achieved. Finaly the string deployment went very smooth and the onlychallenge was to plug the shoe to pump the well-stimulation treatment via the ICD nozzles. Several options were discussed includinginflatable packer and a ball seat system, which was was ultimately chosen to plug the shoe.

Treatment, stimulation and acidizing fluidsAfter completion of a new well, its productivity depends on reservoir quality as well as the drilling and completion practices used.In Bouri Field, the impact of operational practices on well production is mainly due to damage induced by the drilling mud to the near wellbore region which can significantly restrict flow performance to a point where large acid treatments are a necessary pre-requisite for the wells to start producing from this carbonate reservoir.The near-wellbore damage is interpreted as filter-cake build-up against the carbonate face, necessary to avoid losses of the drillingfluids to the formation during drilling.The main challenge for horizontal wells even completed with cemented liner and perforation is proper filter-cake removal procedureto enhance the well cleanup and final productivity.A common practice for well clean-up after running the ICD completion is to bullhead through the inner string (run to the bottom of thecompletion) and sting-in the lower pack-off to allow the treatment to go the annulus side. This way both the ICD completion and theformation carbonate-face will be swept from any debris and filter-cake dissolved, with any residue transported to the surface beforesetting the upper packer. This methodology presents major well control concern in Bouri, since the well might go on total losses if thefilter-cake is removed prior the installation of final completion hence the filter-cake removal treatment should be performed onlyafter running the final completion.

Based on the above considerations, a new mud cake clean-up treatment design was performed in the following steps:

1. Treatment Fluids Selection:In order to select the fluids for best good dissolution and dispersion of potential damage in the formation, filter-cake was first made inthe laboratory from a sample of the drilling mud. Figure 7 shows a picture of the filter-cake made in the local lab .The created mud-cake has shown very good dispersion on the solution of the mud base-fluid with 10% multi-function surfactant(F105) and 0.3% of surfactant (F103) under downhole temperature. Dispersed mud-cake was filtrated thought a 270 mesh screen toensure clean-up fluids could be flowed back through a 250 mesh screen of ICD system during main treatment. In addition, 15% HCLMud Clean-up Solution was recommended for tubular pickling and wettability change.

2. Fluids Placement:The first challenge of conveying treatment fluids along the horizontal section is to avoid plugging ICDs with any solid debris that may

be lying inside the liner since fluids that will be squeezed will not be passing through any screen. The second challenge is toeffectively cover the whole horizontal open-hole section interval with treatment fluid without the use of chemical diversion

techniques.Considering the above requirements, the following operational measures were selected:a. Plug-off the completion bottom pack-off assembly to ensure that all treating fluids are squeezed though the ICDs, using the

advantage of fluid diversion behavior of installed completion for the horizontal open-hole section.

b. Circulate the well underbalanced with diesel and viscous fluids to lift-out any debris present in the completion that might plug theICD nozzles during subsequent injection / stimulation with the use of Coiled Tubing cleanout technology for fill clean-outoptimization.

c. Perform tubing clean-up via Coiled Tubing to remove any metal content (Figure 7c) present in the tubulars which might createsecondary precipitation when fluids are being pumped. This operation is to also clean-out any excess thread-dope / grease usedduring completion that could otherwise damage the formation if it got entrained in the treating fluid.

d. Spot the designed mud clean-up fluids using the Coiled Tubing along the horizontal section and apply a surface pressure in order to squeeze the fluids to the formation.

e. Perform 15% HCl squeeze to clean the near well bore carbonate-face by spotting the fluids using the Coiled Tubing, using thedual injection technique in order to achieve sufficient injection rate allowing diversion of the treatment along all ICDs.

3. Well Clean-up:The Coiled Tubing N 2 lifting was selected as the best option for creating enough drawdown against the formation to enhance theclean-up and allow the well to flow-back quickly.


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Results and further work:

The first two ICD well completions in Bouri field, offshore Libya, show good results for both well stimulation, acidizing and

production confirmed by two baseline PLT production logs. ICD installations are expected to provide better performance than conventional completions by balancing fluid influx, pressure drawdown and delaying the potential early gas breakthrough. The ICDs also facilitated a uniform acidizing andstimulation fluid distribution along the entire wellbore.

Nodal analysis steady-state hydraulic modeling aided in early ICD feasibility and base case simulation of scenarios,stablishing the final ICD design which allowed for an efficient and timely field operation.

Dynamic simulations are necessary to evaluate ICD system performance with time. ICD removable housing options were used in both wells and real-time data facilitated on-site nozzle size refinement using

fully adjustable ICD equipment. Correct application of new technology, team work and planning, has been applied in Bouri Field, Libya, to minimize gas

production, lift more dry oil and achieve more efficient reservoir drainage. ICD equipment is a proven technology that will be further evaluated for its overall benefits in Bouri field, Libya, and

potential application in future wells to be drilled.

Acknowledgements

We want to acknowledge our colleagues at ENI E&P and Mellitah Oil & Gas for valuable discussions and input during this work andSchlumberger Team for cooperation and service during the planning and execution phase.

References1. Davila, E. et al.: First Applications of Inflow Control Devices (ICD) in Open Hole Horizontal Wells in Block 15, Ecuador, SPE123008,

LACPEC, Cartagena, Colombia, 31 May-3 June 2009.2. Gudmundseth, M. et al.: Successful installation of Straddle With Inflow Control Device To Restrict Gas Influx, A Case History From The

Heidrun Field, SPE 121534, EUROPEC/EAGE Annual Conference and Exhibition held in Barcelona, Spain, 1417 June 2010 .3. Amari, M. et al.: Practical Consideration on Operations and Production Management through the deployment of Inflow Control Devices

for Horizontal Wells, Bouri Field, Libya, IPTC-14126, Petroleum Technology Conference held in Bangkok, Thailand, 1517 November 2011.

Figures


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Figure 1 Bouri Field location, Mediterranean Sea.


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Figure 2 . Example of an integrated approach to establish the initial base case in ICD production mode , even before drilling the well and should be ready prior to theICD completion. a) oil flux acummulated for each defined compartment, b) rock properties and its response given as flux from the reservoir into the well and c)


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Figure 3 ICD hardware integrated with sand control, a) for producer wells and b) for injector wells and c) ICD components and basic diagramme of interaction between reservoir and wellbore (open anulus case of consolidated reservoirs, sandstones and carbonates).

Figure 4 Completion lay-out of Well 2, showing ICD sections, segments length and location of swell packers for zonal isolation and further compartmentalization for acidizing and stimulation (facilitated by the ICDs and to be performed any time).

a) PLT profile of Well 1, showing fluid profile and ICD section contribution and entry points


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b) PLT profile acquired at Well 2, showing fluids profile and ICD section contribution and entry points

Figure 5 PLT logs acquired after the ICD installation, showing fluid profile and ICD section contribution and entry points for a) Well 1 and b) Well2. Both wells differ in well trajectory and challenges, for example gas is higher in Well 1 than Well 2. Well 2 logging did not reach TD, and it is contributing about 4.4% from the 2deepeste ICDs. ICDs after acidizing and well stimulation show oil contribution along the entire wellbore and efficient gas mitigation. PLT logs show that all ICDsections and nozzles are contributing to production and acted efficiently to acidizing and stimulation (the ICD architecture is ready for timely stimulation operations or future EOR-ERA enhancement solutions, when required).

a) Cummulative gas production from toe-to-heel b) PLT and simulation results

Figure 6 Results comparison of the ICD completion and after stimulation and acidizing . a) Cumulative gas production (from toe-to-heel) show theICD completion benefits, where open-hole case has an early gas breakthrough at the heel of the well, while the ICDs are minimizing the gas coning,

b) Comparison between the simulation results and PLT log measurements along the well completion length. ICDs performed, only minor discrepancies between the PLT log and the simulations.

Aq

vC v

vC u P N == ,

2 2

2

4.4% of total production iscoming from the 2deepest ICDs


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a) Filter cake made in the local lab b) Dispersed filter cake in Mud Clean OB fluid

c) Sample of completion debris that wascollected during the well clean-out

d) Mud Cake solution screening

Figure 7. Treatment fluid selection, a few steps. a) dispersed mud-cake was filtrated through a 270 mesh screen, b) dispersed filter cake in MudClean OB fluid c) Perform tubing clean-up via Coiled Tubing to remove any metal content, d) To ensure clean-up fluids could be flowed back through a 250 mesh screen of ICD system during main treatment. In addition, 15% HCL Mud Clean-up Solution was recommended for tubular

pickling and wettability change. Fluid selection for reservoir completion or any acidizing or stimulation solution is of paramount importance for well performance.

270 Mesh screen

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TEC 20 FPorturas Final