Sand Control with Ceramic Screens inUnconsolidated Reservoirs demonstratedin the mature Gaiselberg OilfieldBy S. WILDHACK, S. MÜSSIG, F. STRAHAMMER, and M. LEITNER*

AbstractThe Oil Production in the operation CentreZIstersdorf of the Rohöl-Aufsuchungs AG(RAG) looks back to a long history and to agreat variety of different types of comple-tions. After the first oil bearing wellRAG-002 in 1937 the development of theRAG field started, followed by more explora-tions successes in the Gaiselberg oil field1938 onwards.Primarily the production comes from thesandstones reservoirs of the Sarmat, thedeeper horizons show usually a good com-paction paired with a reasonable permeabil-ity. The lower layers, however, are more andmore unconsolidated. For the prevention ofsand production and to protect the comple-tion equipment metal screens in combina-tion with gravel packs had been installed.Gravel Packs, however, generate an addi-tional pressure drop, which can lead in somecases to a production loss of up to 50% fromthe very beginning. In addition they areprone to abrasion and come with high com-pletion costs.With the completion of the new developedsand control screen based on ceramic mate-rials, the next step to sand control in uncon-solidated reservoir succeeded after the suc-cessful protection of well jewellery in wellsafter massive hydraulic frac operations [1,2, 3].In this article the construction, deploymentin the well Ga-016 below a sucker rod pumpas well as the analysis of the production per-formance is discussed. It will be demon-strated that with this application a funda-mental step in sand control in unconsoli-dated reservoirs has been achieved.

IntroductionExperience shows that erosion is a severeoperational issue in the oil and gas produc-tion of the exploration and production indus-try, and many operators suffer from sandproduction. Maersk Oil for example de-scribed erosion issues in the long horizontal

wells of their Valdemar field as well as intheir gas wells in the Tyra field. AtValdemar, proppant backflow during clean-up operations after massive frac treatmentshad to be faced as well as during bean-up. Inaddition to the resulting erosion of tubularsand sliding sleeves, the operator also facedeconomic losses during the long clean-upperiods at the end of the stimulation phase(rig standing idle during clean-up period),but also due the presence of sand in the facil-ities (filling-up separators) and flow restric-tions in pipelines. There is another eco-nomic incentive that is to phase out usingresin coated sand from the fracturingoperation due to its classification as a “red”chemical.In the Tyra field, the production of gas wellsturned unmanageable due to sand produc-tion and had to be shut in permanently so thatthe reserves had to be de-booked.In both cases, conventional sand controlmethods could not be applied due to the in-sufficient erosion resistance of the support-ing metal screens. Therefore, it was lookedinto alternative materials showing higherhardness and consequently better erosion re-sistance. With their unique properties ad-vanced ceramics were qualified, and a newsand screen design was developed whichoffers impressive advantages.In three wells of the Valdemar field, ceramicscreens were applied to protect the slidingsleeves while placing them opposite of theperforations, and a dedicated testing pro-gram including production logging and wellflow testing was performed in one of themwhich allowed evaluation of the performanceof the ceramic screened sleeves [1–3]

In all cases the ceramic sand screens per-formed according to expectations andshowed the high potential of the new sandcontrol technology.

Ceramic Sand Screen Design –General PrinciplesThe design of the ceramic sand screen con-sists of three construction elements: a stackof ceramic rings, two coupling elements anda fixing device to mount the assembly to atubular support.For the ceramic rings, sintered silicon car-bide (SSiC) was chosen as material. SSiCboasts a unique combination of properties,including excellent abrasion and corrosionresistance, low density, heat stability (up to1800 °C), high hardness and high stiffness.For more details see [1]. Table 1 comparesrelevant material data of silicon carbide, sili-con nitride, steel and hard metal.The SSiC ring geometry (ID, OD, and gapwidth/shape) can be freely chosen andadapted to nearly any prevailing wellboregeometry or well conditions. Preferably, therings are spherically dished on the bottomface of the rings providing keystone gapsthat are narrower on the outside surface ofthe ring. This design allows high laminarflow rates and prevents plugging of the gapby fines since any particle passing throughthe gap at the outer diameter will continue toflow through rather than lodging within thegap. The upper face of the rings shows anumber of equally spread bumps that areused to adjust the gap width of the ceramicstack. The gap width can be chosen accord-ing to the frac sand or any other grain size

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0179-3187/12/II© 2012 URBAN-VERLAG Hamburg/Wien GmbH

* S. Wildhack, ESK Ceramics GmbH & Co. KG, Kemp-ten/Germany; S. Müssig, F. Strahammer, M. Leitner, Rohöl-aufsuchungs-AG (RAG), Vienna/Austria. Lecture, presen-ted at the DGMK/ÖGEW Spring Conference, April 19.–20.,2012, in Celle/Germany

Material Properties Stainless Hard Silicon SiliconSteel Metal Nitride Carbide

Knoop Hardness, HK 0.1 GPa <0.5 (Rc 30–40) 16 14.5 21–25

Compressive Strenght, MPa 2200 5000 >2500 2200–2500

Thermal Conductivity, W/(mK) 35–45 95 25–40 75–125

Density, g/m³ 7.8 14.9 3.2 3.1–3.2

Flexural Strenght (4 Point Bending), MPa N/A 1550 700–800 400–650

Young’s Modulus, GPa 200 520–620 310 410

Fracture Toughness Kic, MPa m0.5 N/A 10–20 6 4–6

Table 1 Comparison of typical material properties

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distribution resultingfrom sand production.Ideally, the ceramicrings are manufacturedwith three bumpsshaped as sphericalsegments ensuringonly point contacts be-tween the stackedrings. In combinationwith the sphericallydished ring shape, thisdesign is well suited toceramics, giving flexi-bility to the stack of ceramic rings andstability against torsion as well as flexure.The stack of ceramic rings is placed betweenthe upper and lower coupling elements andmounted on the tubular support (e. g. a slid-ing sleeve or a perforated base pipe). Clamp-ing features on both sides of the stack me-chanically constrain the ceramic rings. Theload is transferred to the stack of rings via anumber of spring elements and the couplingelements. The flexibility of the spring ele-ments enables the dissipation of any me-chanical stress that could be either imposedby torsion, bending, shock or temperatureinduced thermal stresses between metal andceramics. This type of clamping mechanismprevents any accidental damage of the basicsleeve and provides excellent damage-toler-ance to the ceramic assembly. In addition,the outer part of the assembly can be sur-rounded by a metallic shroud to protect theceramic screens from being damaged duringinstallation.The ceramic screen can be mounted on anytype of tube or tubular flow-through devicewith flexible lengths (Fig. 1).

Field Application at Rohöl-Aufsuchungs AG (RAG)Sand control has always been a major prob-lem in RAG’s oil production in Zistersdorf.The “Gaiselberg” and the “RAG” fieldswere discovered in 1937 about 50 km north-east of Vienna with an acreage of only 5 km².The production peaked in 1943 with320,000 t/a; the current production is~20,000 t/a from 30 production wells. Al-most 150 wells were drilled until 2011 intothe oil bearing reservoirs of the Badenien

and Samartien layers, the main boundary isthe so called “Steinberg Bruch”.More than 600 reservoir compartments andthe unconsolidated shallow reservoirs (aver-age depth about 900 m TVD), which are thegrowing part of the production in the devel-opment and capacity enhancement of thefields represent the biggest remaining po-tential of producible reserves. Almost 20producing wells are equipped with a sandscreen/gravel pack assembly.A great number of sand control methodshave been tested and applied over decades inthe fields of Zistersdorf and up to now thegravel pack was considered the best techni-cal and economical solution. It turned outduring planning of the gravel pack comple-tion that the distinction between vertical anddeviated production intervals is essential.For vertical wells the use of water-packs in-

cluding a pre-pack is recommended. To pre-vent the movement of pre-packed gravelpack with respect to the deviated well duringcompletion operation, no pre-pack shouldbe placed. The best solution for optimumgravel placement was the slurry pack.In the past, wire-wrapped sand screens madeof stainless steel were used with a gravelpack (usually mesh 20/40) in order to avoidany sand production. The system proved tobe reliable, but the performance of somegravel packs was crucial. In addition, somescreens collapsed due to the combination ofacid stimulations and/or erosion.The recently completed ceramic sand screendoes not require any gravel packing andshows a very low pressure loss during pro-duction, that results in reduced workovercosts and a higher gross production rate.

Fig. 1 Ceramic screen mounted on 3.5″ sliding sleeve, a) during assembly and b) prototype covered by protective shroud

Fig. 3 Ceramic screen assembly: three screen modules (each 5 ft long) with interconnectors, bull nose, centralizers and cross over

Fig. 2 Seismic section of the Gaiselberg and RAG fields

The Ceramic Screen for GA-016For longer ceramic sand screens, a modularsetup is preferred where metal intersectionsalign the individual ceramic screen section.This set-up was chosen for the screen used inGaiselberg GA-016. The existing comple-tion, in which the filter had to be introduced,allowed a maximum screen OD of 2.2″. Thescreen was designed accordingly, with a maxOD of 2.12″. In order to cover the perfora-tion zone (stretching over 3 m), three screenmodules (each with 5 ft length) were inter-connected with metal joints which are pro-

tected by a poly-meric tube. The slotwidth of the ceramicring stack with 200µm was adapted tothe particle size dis-

tribution of the formation sand of the zone inproduction. The stack was mounted on aslotted liner with an ID of 0.95″. On the tip, astainless steel bull nose was attached. Toconnect the screen with the tubing, a 1.9″non-upset crossover was chosen. In the up-per and lower sections centralizers wereused to enable an easier deployment and acorrect setting of the screen in the perfora-tion zone. In Figure 3, the assembled screenis shown in the workshop.The sand screen has been installed in De-cember 2011 after the reservoir has been

perforated in the Sarmatian 13 formationwhich is known to consist of unconsolidatedsand. In Figure 4 the completion of the wellis shown.The well was completed with a conventionalworkover rig operational in the Zistersdorfproduction department. Some pictures of thecompletion of the well show the simplicityof the workover and the key features of thesand screen.On Dec. 15, 2011 the well was set on produc-tion with a rate of some 50 m³/d, fluid leveland the percentage of fines in the productionstream were monitored regularly. Withintwo weeks the percentage of fines droppedto zero, which allowed the rate to be in-creased to 90 m³/d. This was reflected in-stantaneously in a drop of the fluid level. Therate increase did not lead to any new produc-

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Fig. 4 Completion drawing of GA-016

Fig. 5 Unpacking the sand screen

Fig. 6 Before deployment, left the bull nose with centralizer Fig. 7 a) Top of sand screen with centralizer, b) Packer

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tion of fines. After six weeks of constant,fines-free flow there was evidence that a sec-ondary gravel pack was formed outside thescreen.In order to investigate the performance ofthe well in more detail a MURAG 20 system(Fully Automated Fluid Level MeasurementTool) was installed on Feb. 9, 2012. A dedi-cated test programme was designed to testthe full functionality of the sand screen. In afirst step the production rate was decreasedto 60 m³/d. An immediate reaction of thefluid level was monitored. After a couple ofdays the production rate was increased againto 90 m³/d and as expected an immediate re-action of the fluid level together with a shortpeak of fines was observed, the level stabi-lised after a short period of time. The finalproof of stable borehole conditions wasachieved when the well was completely shutin for two days, again an immediate increaseof the fluid level was observed, whichshowed that the slots of the screen were free,and even more after re-starting the produc-tion about 1% fines were produced for half aday and disappeared. Production rate andfluid level are stable since then. Unfortu-nately the chosen reservoir for this test pro-duces with a water cut of 99%, so that theeconomical success is only marginal. Agraphical overview of the productionperformance is given in Figure 8On the side line a comparison was made be-tween Sonolog and MURAG fluid level de-tection, the measured values are alwayscomparable as expected. The Sonolog, how-ever, measures only in tubing length steps(some 10m), whereas the Murag system de-livers values between the couplings. Theevaluation of the production performance ofwell GA 16 shows the successful applicationof an innovative sand control concept, whichhas the potential of replacing costly anddifficult gravel pack operations.

Conclusion and Way ForwardThe new development of an advanced sandcontrol device based on ceramic materialwas successfully deployed as full functionalsand screen in well GA-016. The screendemonstrated excellent performance interms of production stability at expectedlevel and the amount of fines produced dur-ing bean-up operations. It could be shown,that the borehole situation around the screenis stable despite the unconsolidated reser-voir. No clogging and no erosion occurred asexpected. The installation proved to be sim-ple and cost-efficient. With the deploymentof the ceramic sand screen in GA-016 a sig-nificant improvement in production perfor-mance and longevity of productionequipment has been achieved.Four candidate wells producing from uncon-solidated reservoirs have been identifiedthat are completed with gravel packs withsub-optimal production performance. Aftercompletion of this investigation two of the

four candidate wells will be completed withceramic sand screens, so that a direct com-parison with gravel packed wells is possible.At the time of writing this article, it was de-cided to pull the screen in the GA-016 wellas the investigated zone in this well showedan uneconomically high watercut and re-usethe screen in another well.

Literature[1] S. Müssig, S. Wagner, A. Kayser, S. Wildhack:

The development of ceramic screens to preventsand influx and erosion in stimulated productionwells. Oil Gas European Magazine 36, 3/2010, p.126 ff.

[2] H.-H. Kogsboll, S. Wagner: Ceramic screenscontrol proppant flowback in fracture-stimulatedoff shore wells. World Oil, 3/2011, p. 43 ff.

[3] S. Müssig, P. E. Henriksen, S. Wildhack, C.Lesniak: Ceramic Screens, an innovative mile-stone in Sand Control. SPE 146721, Proc. ATCEDenver 2011.

Stefanie Wildhack holds anMSc in Material Science of theBergakademie Freiberg, Ger-many and a PhD in MaterialScience of the Technical Uni-versity Stuttgart, Germany. Be-tween 2003 and 2006 she wascoordinating interdisciplinary

industry projects at the Steinbeis Transfer CentreTechnical Ceramics in Stuttgart Germany. In 2006,she joined ESK Ceramics GmbH & Co. KG, Kempten,Germany where she was working in Research and De-velopment as well as Project Management with focuson silicon carbide and nitride materials. Since 2009she is concentrating on projects in Oil & Gas andheaded the development of the PetroCeram® SandScreens.

Siegfried Müssig holds a Di-ploma and a PhD in Physicsand Physical Chemistry of theTechnical University of Karls-ruhe, Germany. Between 1982and 2002 he held a number oftechnical and management po-sitions at BEB Erdöl and Erdgas

GmbH. In 2002 he joined Shell Exploration and Pro-duction B.V., where he worked between 2002 and

2005 as Smart Field Regional Coordinator for theMiddle East and Africa operating from The Hague fol-lowed by a position as UGS Development Manager atRohöl-Aufsuchungs AG (RAG) in Vienna, Austria be-tween 2005 and 2008 and a position as Manager WellTechnology for Maersk Oil, Copenhagen, Denmarkbetween 2008 and 2011. In 2011 he returned to RAGand is working as Technology and Quality Manager.

Franz Strahammer joined Roh-öl-Aufsuchungs AG (RAG) in1983 where he was working astrainee at one of the drilling andworkover rigs in Upper Austria.After the completion of the ed-ucation as foreman for engi-neering and production engi-

neering he was responsible for Maintenance andWorkovers in the Zistersdorf Oil Field, Lower Austriafollowed by a two year education Production Technol-ogy at the Bohrmeisterschule in Celle, Germany.Since 1995 he is leading RAG’s production operationat the Zistersdorf oil district.

Manfred Leitner holds an MScin Petroleum Engineering ofthe Mining University Leobenand the Colorado School ofMines in Golden, CO. Between2001 and 2006 he worked as aReservoir Engineer withExxonMobil Production Com-

pany in Germany and Norway. Between 2006 and2009 he was employed as a Reservoir Engineer andTeam Leader for Gas Reservoir Engineering forRohöl-Aufsuchungs AG (RAG) in Vienna, Austria.From 2010 until 2012 he was Head of the Oil Produc-tion Area Zistersdorf in Lower Austria. Since 2012 heis working as a Reservoir Manager for RAG E&P Na-tional in Vienna, Austria.

Fig. 8 Production Performance GA-016