Masaferro Et Al 2003 TLE

5/28/2018 Masaferro Et Al 2003 TLE

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Conventional 2D and 3D seismic map-ping is not ideal for characterizing car-bonate reservoirs mainly because of thecomplexity and heterogeneity of car-

bonate systems. The unique depositionalsystems of carbonate environmentsmeans that a standard interpretationroutine is often inadequate and moresophisticated techniques are needed.

The purpose of this paper is todemonstrate an advanced methodthe application of visualization tech-niques to 3D seismic data of someselected carbonate reservoirs and toparticularly focus on certain techniquesthat successfully extracted seismicfacies and geometries characteristic ofcarbonate systems.

We approached the data analysis intwo ways. The first approach is toimprove the signal-to-noise ratio of theseismic data. This may be accomplished,for example, by applying noise reduc-tion techniques to improve the qualityof the seismic data or by making depo-sitional geometries explicit rather thanimplicit features. The second approachis to highlight specific geologic featuresthat have a three-dimensional extent,

and a geometry that may have little incommon with the orientation of the 3Dgrid of seismic data. For example, in anenvironment of hydrocarbon-bearingshoal complexes, there is an immediatefocus to the interpretation by initiallyisolating high-amplitude mounded-likestructures within the data. By combin-ing these approaches with well calibra-tion, it is possible to speed up theinterpretation (both in absolute and usertime), limit the potential model-bias ofan interpreter, and improve the qualityof the interpretation. The results showthat 3D visualization and processing dra-matically improved the quality of theseismic data which in turn generated anessential predictive tool for carbonatereservoir characterization.

Prograding shoal complex: KhuffFormation, Permian, Oman. The sed-iments of Khuff Formation in north-west Oman (Figure 1a) were depositedin a shallow, inner shelf restricted envi-ronment dominated by high-energyoolitic shoals and bars with protectedlagoons. Main depositional cycles show

the characteristics of trangressive-regressive carbonate-evaporite succes-sions, which consist of several stackedshallowing-upward cycles deposited

in subtidal, intertidal, and supratidalenvironments.

Structure-oriented filtering (SOF)was applied to the 3D seismic volume

18 THELEADINGEDGE JANUARY2003 JANUARY2003 THELEADINGEDGE

3D visualization of carbonate reservoirs

JOSELUISMASAFERRO, RUTHBOURNE, and JEAN-CLAUDEJAUFFRED, Shell International E&P B.V., Rijswijk, The Netherlands

INTERPRETERS CORNER

Coordinated by Rebecca Latimer

Figure 1. (a) Structure map of top reservoir interval. A, B, and C are the wells in this study.Color bar in two-way traveltime (TWT). (b) Seismic reflectivity cross-sections before and afterapplying structure-oriented filtering (SOF). Note improvement in resolution of reflection termi-nation and continuity within black square.

Figure 2. Image-filtered volume shows the interpreted seismic facies around K2 reservoir inter-val. Synthetic seismogram shows that the reflections were caused mainly by a change in poros-ity at the top and base of K2. Note change in polarity between the seismic cube and the seismicsection. See Figure 1 for location.

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to remove background noise and thusimprove definition and continuity ofreflections (Figure 1b). A series of seis-mic sections across the field shows howthe improved imaging depicts differentseismic geometries and facies thatchange laterally along the reservoirinterval (Figures 2-4). Khuff seismicfacies can be interpreted on the basisof external geometry, internal reflec-tion character, reflectivity, and lateralcontinuity. Interpreted seismic faciesinclude mounded continuous/discon-tinuous, progradational shingle, andprogradational sigmoid.

The mounded seismic facies is iden-tified by a series of reflections that out-lines a number of convex-upward ormound-shaped geometries. The extentof this facies is delineated by a promi-nent amplitude anomaly (Figure 3b).Within the mounded seismic facies,there is clear lateral change from inter-nally discontinuous to more continu-

ous seismic facies. The moundedcontinuous facies consists of moundstructures that show a series of low-angle dipping, internal reflections(Figures 2 and 4b). Occasionally, thecontinuous mounded facies varies lat-erally into more discontinuous to trans-parent reflections (Figure 4b).

The shingled prograding facies isidentified by a series of shingled, high-amplitude clinoforms (Figures 3a and4a). In map view, this facies is delin-eated by elongated amplitude anom-alies showing the 3D architecture ofthe clinoforms. Toward the north, thegeometry changes from shingled tolow-angle sigmoid facies (Figures 2 and5). The orientation of the clinoformsindicates a general direction of progra-dation to the west from the interior ofthe seismic mound complex.

The 3D seismic imaging of thereservoir enabled construction of a cal-ibrated depositional model. The resul-tant reservoir model contains both thestratal patterns and geometries fromseismic-to-core calibration and prop-erty distribution from core and logdata. This integrated model explained

the superior production of well A(drilled through the mounded shoalcomplex) compared with surroundingwells.

Middle Miocene isolated build-up,Luconia Province, Malaysia. A seriesof seismic sections through build-upshow different depositional geometriesand seismic facies that characterize fivereservoir zones (Figures 6 and 7). Theseismic facies can be determined on the

basis of internal reflection character,lateral continuity, and three-dimen-

0000 T HELEADINGEDGE JANUARY2003 JANUARY2003 THELEADINGEDGE

Figure 3. Image-filtered volumes showing interpreted seismic facies. (a) Top view of the seismiccube shows the 3D extent and overlap of prograding units. Note change in polarity between theseismic cube and the seismic section. See Figure 1 for location. (b) Image-filtered volume shows theinterpreted mounded seismic facies. Top view of seismic cube shows amplitude anomaly (blackcircular line) that delineates extent of the mounded facies. Note change in polarity between theseismic cube and the seismic section. See Figure 1 for location.

Figure 4. Flattened seismic sections. (a) Same seismic line as in Figure 3a showing main directionof progradation to the west. Some shingled units seem to prograde slightly to the east. (b) Cross-section to the south of line in Figure 2 showing variability of prograding geometries from sigmoidsin the north to shingled to the south. Note also incipient prograding reflections that were not probably resolved with seismic resolution. See Figure 1 for location.

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sional geometry. Seismic facies were

then calibrated using logs and part ofone cored well.The internal architecture of the

build-up was previously interpreted,based on porosity contrast, to consistof five reservoir zones. Reservoir zones1 and 2 exhibit a pronounced asym-metry in terms of seismic geometries(Figure 7). Zone 1, toward the west/southwest end of the platform, is char-acterized by high-amplitude, stacked-reef/mounded seismic facies (Figures8 and 9). The remainder (approximatelytwo-thirds) of the platform consists of

parallel, onlapping seismic reflections.

Zone 2 shows N/NE-prograding seis-mic facies, which changes to more con-tinuous to transparent reflections(Figure 7). Seismic facies in zones 3 and5 consist of high-amplitude, more orless continuous, flat-lying reflections(Figure 7). The intermediate reflection(marker reflection in Figure 6) is con-tinuous throughout the area and wasused to flatten the seismic sections.Seismic facies in zone 4 is characterized

by shingled seismic geometries in thesouthern part of the build-up changingto more continuous, high-amplitude

reflections toward the north. Zone 5shows more continuous reflectionssometimes interrupted by localizedmounded facies (Figure 7b).

Seismic images of the seismicreef/back-reef facies were extractedusing gate-amplitude extractions, flat-tened semblance volumes and body-checking (Figures 8-10). Root meansquare (rms) amplitude extraction usingan amplitude window of 30 ms wasapplied to extract the reef/moundedseismic facies in zone 1 (Figure 8). Therms amplitude is calculated within adefined window (Figure 8b). Because ofthe extra reflections in the reef seismicfacies, a constant amplitude window (30ms) was run through the entire seismicvolume to give higher output amplitudevalues (red and green in Figure 8). Theresult is an amplitude map that showsa narrow distribution of higher ampli-tudes that correspond to the reef seismicfacies confined to the W/SW part of the

build-up. The back-reef/lagoonal seis-mic facies is also captured by the ampli-tude extraction as an amplitude anomalyadjacent to the reef seismic facies (Figure8).

Coherence or semblance was alsocalculated from the reflectivity data andthen flattened to the continuous reflec-tion interpreted as a flooding surface(Figure 9). A time slice through a flat-tened semblance volume shows a better-defined, linear seismic reef trend withhigh output values; lower semblancevalues represent the onlapping reflec-tions of the back-reef seismic facies morerandomly distributed. The lowest sem-

blance values (white in Figure 9) indicategreater similarities between traces thatcorrespond to the more continuous seis-mic facies in the off-reef, lagoonal setting.Bodychecking was applied to the reflec-tivity volume to extract the high-ampli-tude seismic bodies of the seismicreef/back reef facies, by defining themaximum amplitude range of con-nected voxels for this particular seismicfacies (Figure 10). The result is a 3D dis-tribution of detected bodies that showsthe seismic reef tract and onlapping

back-reef facies.

Upper Cretaceous ramp-type carbon-ate reservoir, Natih E Formation,Oman. SOF was applied to the origi-nal 3D seismic data for the study fieldto (Figures 11-12):

reduce/suppress noise, improvinglateral reflection continuity and seis-mic facies especially at the crest top(main reservoir area),

improve reflection termination andgeometries to better define reservoir


Figure 5. Flattened seismic section and time slice of line in Figure 2 showing map extent of progra-dational sigmoids versus mounded seismic facies. Time slice was taken at the reservoir level indi-cated by the yellow line (108 ms flattened two-way traveltime).

Figure 6. (a) Top reservoir 3D graphs showing distinctive characteristic relief of the LuconianMiddle Miocene build-up. (b) Seismic section across the two wells with superimposed gamma raylogs. Black arrows are interpreted downlap reflections. (c) Gamma ray, density, and synthetic seis-mogram showing the five reservoir zones.

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architecture, improve the definition of the top

Natih E horizon by smoothing outprevious noisy horizon interpreta-tion,

produce attribute volumes such assemblance (Figure 13a), filtered sem-

blance and combine dip and azimuth(Figure 13b) to constrain struc-tural/stratigraphic interpretation.

The original 3D data were used asa reference to compare and constrainthe image-processed seismic. Threemain seismic facies were recognized

based on reflection geometry, reflec-tion continuity, and seismic reflectivity:

1) Prograding facies are restricted tothe northern part of the field (Figure 11)and consist of low-angle dipping, high-amplitude reflections. The high ampli-tude character of the sigmoids isinterrupted locally by dimming ampli-tudes caused by the overlap between

the termination of one sigmoid and thebeginning of the next one. Time slicesthrough the flattened reflectivity vol-ume show remarkably well the sig-moid overlapping and thus theeast-west trend of the prograding units(Figure 14a). The calculated combineddip and azimuth volume (flattened onNatih E horizon) also shows the trendof progradation (Figure 13b).

2) Continuous/semicontinuous faciesform the majority of seismic faciesobserved within the Natih E interval(Figure 11b). It is characterized by high-amplitude, parallel to subparallel seis-mic reflections. Occasionally, reflectioncontinuity is disrupted, either by faultsor by remnant seismic noise

3) The chaotic-to-transparent facies isrepresented by discontinuous reflec-tions with low-to-moderate reflectivity.This facies is associated with internalfaulting and/or nonorganized noiseand occurs at the southern crestal partof the field (Figure 11b). Possible gas-escape effects also obscure reflectiondefinition in the crestal part of the field.The areal distribution of this facies isshown clearly in the flattened reflec-

tivity volume at different levels withinthe reservoir (Figure 11).Analysis of seismic facies and

geometries provided an initial frame-work to constrain the lateral strati-graphic correlation based on core andlog data. Permeable units within aggra-dational geometries in the crestal area(interpreted as ramp-crest shoal com-plex) seem to continue into the waterleg (Figure 11b). This interpretationevolved into a subsurface model sce-nario that could explain the provenanceof high water cuts observed in the field.


Figure 7. Prograding reef system initiated as smaller build-ups that then coalesced through time

filling in the space available to form a larger platform. (a) Flattened seismic section showing characteristic seismic facies and lateral heterogeneity within the five reservoir zones. (b) Seismic sectionshowing seismic reef facies and prograding foresets within reservoir zone 5.

Figure 8. (a) Gate amplitude map showing map distribution of the interpreted seismic reef facies.Red/green = high amplitudes and blue/light blue = low amplitude. (b) Flattened seismic sectionshowing the reef/back reef seismic facies. Amplitude gate of 30 ms indicated with red arrows.

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Malampaya Field, Philippines.Texture mapping was applied to a seg-mented seismic volume defined by thetwo horizons corresponding to the topand base of the reservoir in MalampayaField. Two distinctive interpreted seis-mic facies were identified and then run

as training sets through the seismic vol-ume (Figure 15a). The first training setrepresents the seismic character simi-lar to the western part of the build-up(chaotic, steeply dipping discontinu-ous reflections). The second representsseismic facies from the interior of the


Figure 9. Flattened volume semblance showing high semblance values (dark blue) that correspond

to the reef seismic facies. Intermediate semblance values represent the less linear back-reef deposits.Low semblance values indicate flat-lying reflections interpreted as lagoonal seismic facies. Redarrows indicate interpreted paleo-wind directions for the Middle Miocene.

Figure 10. (a) Example of bodychecking defined for amplitude range of 0-60. The result shows theextracted bodies contained within that range. (b) Bodychecking on reflectivity volume using cali-brated amplitude ranges to extract reef/back-reef seismic bodies. Red, blue, and pink extracted bodiesshow the linear space distribution of the seismic reef tract. Green and orange extracted bodies repre-sent the seismic back-reef deposits.

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build-up (high-amplitude, continuouflat-lying reflections). Several attributerelated to amplitude, continuity ansimilarity between traces, and dip anazimuth were calculated to extracthese seismic facies. The results arshown in Figure 15a, which represenslices through the calculated texturvolume. Blue represents the calculatetexture for the marginal reef-relateseismic facies and light green the morinternal seismic lagoonal facies. Thtwo seismic textures were exported tthe static reservoir simulator and useto constrain different model scenario

Bodychecking was carried out othe porosity volume generated fromthe acoustic impedance data within threservoir unit. The objective was to analyze the porosity distribution aninvestigate sizeable porosity bodiethat could be used to constrain threservoir modeling. Bodychecking waapplied over a wide range of poros

ity thresholds, and porosity bodiewith 2% threshold were extractedFigure 15b shows the connected bodies displayed in the same volume witdifferent colors, making it possible tanalyze the distribution of the connected porosities and the relationshi

between porosity ranges. The porositdistribution shows more seismicderived porosities in the northern paof the Malampaya build-up than in thsouth.

Conclusions. Combining 3D seismvisualization techniques with core anlog calibration provided a robusmethodology for interpretation of ca

bonate reservoirs. Case studies in thpaper demonstrate the use of the diferent image processing techniques thighlight key seismic geometries anfacies for various types of carbonat


Figure 11. (a) Isochore map of the Natih E interval and seismic facies map. (b) Interpreted seismicsection across the field. OWC = oil water contact.

Figure 12. Seismic reflectivity cross-section before and after applying structure-oriented filtering.Yellow arrows indicate significant improvement in continuity and definition at reflection termina-tions. Truncation and progradation geometries are now more obvious in the filtered volume. Reddots are artifacts from image filtering.

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systems. These studies showed thataccurate seismic imaging of the reser-voir architecture becomes an impor-tant predictive tool for reservoircharacterization because it helped to

build a 3D geologic framework withinwhich depositional facies can be dis-tributed in time and space. Calculationof volume-based attributes producednew volumes of data that helpedextract the 3D geometries within thereservoir.

In the Permian Khuff example,reservoir image-filtering considerablyimproved reflection termination andsubsequent delineation of the topo-graphically distinct shoal grainstonecomplex from the prograding units.Integration of seismic geometries andfacies with core and log data provideda reliable geologic and static model thatcould explain well performance.

In the Middle Miocene Luconianisolated build-up, a combination of vol-

ume semblance, gate-amplitude extrac-tions, and bodychecking techniquesallowed identification of depositionalgeometries within the five reservoirzones. Extracted geometries showedthe 3D spatial distribution of the seis-mic facies through time. Transgressiveportions of the cycles are expressed asflat-lying, high-amplitude reflections.Highstand conditions provided moreaccommodation space in whichaggrading reef/back-reef and pro-grading seismic facies developed.Recognition of seismic facies hetero-geneities had implications on the final

building of the static model in terms oflateral correlation of stratigraphic units

between the wells and on the 3D dis-tribution of petrophysical properties.

Application of SOF dramaticallyimproved definition and continuity ofreflections in Natih E reservoir. Timeslices through flattened, image-filteredreflectivity, semblance, and combinedvolume dip and azimuth helped delin-eate the reservoir zone. Integration ofseismic interpretation calibrated withthe cored well, logs, and outcropanalogs produced a static reservoir

model that could explain high watercuts in the field. Texture and body-checking were successfully applied tothe Malampaya seismic data set toquickly identify and classify seismicfacies and to extract the seismicallydetected good porous zones within thereservoir. The results showed the vol-ume distribution of seismic facies andporosity zones, which were used asinput to target potential good wells andas a reference to constrain reservoirquality distribution.


Figure 13. (a) Semblance volume calculated from the original reflectivity data and from the imagefiltered data. Red square indicates approximate location of the field. (b) Combined dip and azimuthtime slices applied to flattened reflectivity data showing orientation of prograding geometries. At 0time no preferred orientation is observed. Orientation of clinoforms is obvious at 16 ms below the

flattened reference horizon.

Figure 14. (a) Time slices through flattened, filtered reflectivity volume. Time slices at 16 and 20ms below the flattened reference horizon (top Natih E) show amplitude dimming caused by theoverlapping between termination of one clinoform and beginning of the next (red arrows). (b)Flattened seismic section showing low-angle progradation. Flatten horizon = top Natih E. Red dotsare artifacts from image filtering process.

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Suggested reading. The coherencecube by Bahorich and Farmer (TLE,1995). Integrated 3D reservoir model-ing based on 3D seismic: The TertiaryMalampaya and Camago build-ups, off-shore Palawan, Philippines by Grotschand Mercadier (AAPG Bulletin, 1999).Fast structural interpretation with struc-ture-oriented filtering by Hcker andFehmers (TLE, 2002). TLE

Acknowledgments: This paper is a modified ver-sion of a more extended paper which will be pub-lished in an upcoming AAPG special volume.The authors thank Shell InternationalExploration and Production B.V. for permissionto publish this paper. Petronas, Sarawak ShellBerhad, Shell Philippines, and PetroleumDevelopment Oman are gratefully acknowledged

for giving permission to publish the data in thepaper. We acknowledge the contribution of theSeismic Volume Interpretation Team (VOICE)and the Carbonate Development Team withinShell Technology Applications and Research(SEPTAR). Our paper has benefited fromnumerous discussions with Gregor Eberli,Updesh Singh, Volker Vahrenkamp, and TaurySmith.

Corresponding author: [email protected]


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Figure 15. (a) Texture classification applied to prestack depth-migrated(PSDM) data. The texture analysis was based on second moment, semblance,and co-occurency. Green = continuous, high-amplitude reflections corre-sponding to the intra-buildup, lagoonal seismic facies. Blue = chaotic, steeplydipping, discontinuous, marginal seismic facies. (b) Bodychecking results forcalculated porosity from acoustic impedance data. Cross-section and timeslices show porosity distribution.

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Masaferro Et Al 2003 TLE