CHAPTER 5 SEISMIC RESERVOIR CHARACTERIZATION.

Transcription

1 CHAPTER 5 ISMIC RERVOIR CHARACTERIZATION.

2 ISMIC RERVOIR CHARACTERIZATION Centrl Scotin Slope Study CANADA June 2016 Ojectives: Chrcterize the snd distriution, using the Mrthon nd Verits 3D post-stck seismic volumes, in order to guide the lithofcies distriution for GDE mpping. Workflow nd methodology: The coustic inversion of the two seismic cues hs een performed using InterWell softwre to generte denoised synthetic seismic with enhnced frequency ndwidth. The different steps of the inversion re the following: Well-to-seismic clirtion of the 5 wells ville in the 3D: Annpolis-G-24, Blvenie-B-79, Cheucto-K-94, Crimson-F-81 nd Glenelg-J-48; A priori model uilding using the key interpreted horizons to define the structurl grid; Acoustic inversion. From well dt, coustic impednce does not llow cler discrimintion of snds from shles nd other lithologies (Figure 2). Moreover, the snd eds re quite thin nd potentilly too thin for seismic resolution (pproximtely 25m). Therefore, lithologies cnnot e directly predicted from the coustic impednce volume resulting from inversion. It ws then decided to perform seismic fcies nlysis on the H, L nd M snd interpreted horizons, using oth supervised nd non-supervised K-mens clssifiction, in order to chrcterize the lterl vritions of these snd intervls. The principle of seismic fcies nlysis is to nlyze the chrcter of the seismic trces or the reflectivity trce t the reservoir level nd relte its vritions to the geologicl properties of the reservoir: The non-supervised pproch consists in seismic trce clssifiction, here with the k-mens technique, without giving ny geologicl priori informtion from the wells. It gives neutrl, ojective view of the seismic dt set; With the supervised pproch, priori geologicl informtion is introduced vi the selection of typicl wells, grouped in n clsses. Ech clss is linked to prticulr chrcteristics of the wells, for exmple the porosity rnge, to define n clsses. Trining trces re extrcted in the vicinity of the typicl wells, within the thickness under investigtion, nd re used to uild discriminnt function in order to otin n clsses seismic fcies mps. Severl seismic ttriutes (RMS, Similrity) hve lso een clculted on the 2 seismic volumes t different levels (seed, K94, K101, K130) in order to highlight potentil res of interest nd to identify the lterl vritions. The mps resulting from the seismic reservoir chrcteriztion were then used s guide for GDE mps construction. 2 Figure 1: Loction mp of the Verits nd Mrthon 3D cues with the ville wells. The two cues overlp in the region of Annpolis-G-24 nd Crimson-F-81 wells. The Blvenie-B-79, Cheucto-K-90 nd Glenelg-J-48 wells re locted within the Verits survey only. Figure 2: () RHOB, DT, PHIE, AI nd fcies logs t the Annpolis-G-24 well. Snds do not hve cler coustic impednce signture llowing them to e differentited from other lithologies. () AI vs PHIE cross-plot t the 5 wells ville in the 3D, elow K101. Snds cnnot e discriminted using coustic impednce only. Ojectives nd methodology PL. 5.1

3 ISMIC RERVOIR CHARACTERIZATION Centrl Scotin Slope Study CANADA June 2016 Mrthon coustic inversion: The well-to-seismic clirtion results on the Mrthon seismic cue re stisfctory (Figure 3) The estimted phse rottion (0 ) nd the finl results re coherent with those of the previous seismic interprettion; The Mrthon inversion gives stisfctory results, with good ttenution of rndom noise, s illustrted y the noise mps (Figure 4); Acoustic impednces resulting from inversion re likely to e impcted y the uril trend; to remove this trend seismic chrcteriztion (Seismic Fcies Anlysis nd ttriute computtion) hs een performed on the seismic reflectivity resulting from inversion m Figure 3: Good well-to-seismic clirtion results t the Annpolis-G-24 nd Crimson-F-81 wells on the Mrthon seismic. Notice the strong ttenution of seismic mplitudes elow K94. Figure 4: Noise mps clculted on Mrthon (200ms elow top T50) efore () nd fter () inversion. The correltion vlues re higher fter inversion: the inversion hs ttenuted rndom noise. PL. 5.2 Mrthon coustic inversion

4 ISMIC RERVOIR CHARACTERIZATION Centrl Scotin Slope Study CANADA June 2016 Verits coustic inversion: The well-to-seismic clirtion results on the Verits seismic cue re stisfctory (Figure 5); An AGC (Amplitude Gin Control) hs een pplied to the Verits cue during seismic processing (Figure 6). Becuse of this process, seismic mplitudes re not preserved. Acoustic inversion is strongly impcted y this mplitude homogeniztion nd inversion results re therefore not relile; The Verits seismic cue, which covers oth the shelf nd slope res, hs however still een useful for direct seismic ttriute interprettion. Seismic chrcteriztion (Seismic Fcies Anlysis nd ttriute computtion) hs thus een performed on the rw seismic volume. NE 4000 m SW NE 2000 m SW Figure 5: Good well-to-seismic clirtion results t the Annpolis-G-24 nd Crimson-F-81 wells on Verits seismic. The effect of the AGC is clerly visile on the clirtion tles: mplitudes re oosted in the lower prt, elow K94, in comprison with Mrthon 3D seismic dt. Figure 6: Comprison etween seismic section through the Annpolis-G-24 well from the Mrthon () nd Verits seismic cues (). An AGC hs een pplied on this cue during processing, seismic mplitudes re not preserved, coustic inversion cnnot provide relile results. Verits coustic inversion PL. 5.3

5 ISMIC RERVOIR CHARACTERIZATION Centrl Scotin Slope Study CANADA June 2016 Seismic chrcteriztion t H Snd level on the Mrthon seismic dt: Both supervised nd unsupervised seismic fcies mps were generted t the H Snd level on the Mrthon 3D cue (Figure 8). The unsupervised seismic fcies mp ws uilt with three clsses (red, lue nd green), which present cler N-S trend comptile with snd deposit direction. The Annpolis-G-24 well, in which the thickest snd ws found, is locted in the red clss, wheres the Crimson-F-81 well, with lower snd thickness (Figure 11 in plte 5.5), is locted in the lue clss. Root trces present much lrger mplitudes for green nd red clsses. Anlogies with the RMS mp presented in Figure 9 re evident, with the red clss clerly linked with high RMS mplitudes. A first interprettion is then to define green nd red clsses s snd clsses. Supervised clssifiction hs een guided y trces extrcted round the two wells, ssigning them to two clsses; the first or red clss is linked to Annpolis-G-24, the sndier well. The other (lue) clss should reflect the chrcteristics of Crimson-F-81. Oservtions given for unsupervised clssifiction re confirmed here, with the red clss ssocited with the presence of more snd, nd the lue clss with lessor mounts of snd. Figure 7: Seismic section in the Mrthon cue through Annpolis-G-24, showing the loction of the H, L nd M Snd interpreted horizons on which seismic chrcteriztion ws performed. Figure 8: Unsupervised () nd supervised () seismic fcies mps clculted t the H Snd level (48ms elow top H Snd) on Mrthon seismic reflectivity from inversion. The supervised pproch is composed of two clsses guided respectively y Annpolis-G-24 nd Crimson-F-81. The two mps re well correlted; the circled pttern, which is present on oth mps, my correspond to snd infilling. Figure 9 : RMS mp clculted t H Snd (48ms elow top H Snd). The circled energy nomly corresponds to topogrphic high ounded y fult. The fetures of this mp re well correlted with those of the seismic fcies mps. PL. 5.4 Seismic fcies nlysis t H Snd

6 ISMIC RERVOIR CHARACTERIZATION Centrl Scotin Slope Study CANADA June 2016 Seismic chrcteriztion t H Snd level on the Verits seismic dt: An unsupervised seismic fcies mp ws generted on Verits seismic t the H snd level (Figure12). Becuse of the post-processing pplied to these dt (AGC), the seismic fcies nlysis ws conducted on the rw seismic trces insted of reflectivity trces. In the zone covered y oth Verits nd Mrthon surveys, the unsupervised seismic fcies mp ppers much noisier thn Mrthon s (Figure 8), ut presents the sme glol fetures, with cler N-E trend. The root trces re lso very similr to those otined with Mrthon cue. On the pltform re where Cheucto nd Glenelg wells re locted, the supposed red snd follows more costl trend; this ehvior is consistent with Dionisos modeling (PL. 6.2). 1D seismic modeling test: A 1D modeling test ws performed t Annpolis-G-24: the AI log ws modified to mimic thickening of the snd intervl t the H Snd level, from 3 m to 12 m, to evlute its impct on the seismic response (Figure 10). Synthetic nd reflectivity trces (RC) were then generted from the modified AI log. The snd lyer thickening leds to chnge of the seismic response: the originl reflectivity trce in green evolves to the red trce presenting lrger negtive mplitude. This is wht is oserved on root trces, indicting tht the red clss my correspond to thickening of the snd lyer. Therefore, the red res evidenced y the seismic fcies mps, mostly locted round Glenelg-J-48 nd Cheucto-K90, which present thicker H Snds (Figure 11), nd t the est of Annpolis-G-24 nd Crimson-F-81, my correspond to sndier res. Poor seismic dt qulity Figure 10: () Modeling on the AI log t Annpolis-G-24 of n increse of snd thickness from 3 to 12 m. () Synthetic nd reflectivity logs generted from the originl (green) nd modelled (red) AI. A chnge of the seismic trce cn e oserved due to the thickening of the snd lyer. H Snd 48ms Figure 11: Lithology logs t Glenelg, Cheucto, Annpolis nd Crimson, 48ms elow H Snd. Glenelg nd Cheucto hve more snds t the H Snd level. Figure 12: Unsupervised seismic fcies mp clculted t the H Snd level (48 ms elow top H Snd) on Verits seismic. Bsed on the 1D modeling results, the red trces my correspond to snd thickening. The red zones on the mp might therefore correspond to sndier res. Seismic fcies nlysis t H Snd PL. 5.5

7 ISMIC RERVOIR CHARACTERIZATION Centrl Scotin Slope Study CANADA June 2016 Seismic chrcteriztion t the L Snd level : NE 1000 m SW Both supervised nd unsupervised seismic fcies mps hve een generted t the L Snd level on Mrthon nd Verits (Figures 15 nd 16), using the sme techniques s for the H Snd. The seismic fcies re less orgnized thn t the H Snd level; this could e due to the poor seismic dt qulity nd the resulting less ccurte horizon picking. L Snd Figure 13: Lithology logs t Annpolis nd Crimson, 48ms elow L Snd. Annpolis hs more snds t the L Snd level. 48ms Figure 14: Seismic section in the Mrthon cue going through the 2 structures highlighted in Figure 15. Figure 16: Unsupervised seismic fcies mp clculted t the L Snd level (48ms elow top L Snd) on Verits seismic. The N-S trend is still visile in the sin t this level. Figure 15: Unsupervised () nd supervised () seismic fcies mps clculted t the L Snd level (48ms elow top L Snd) on Mrthon seismic reflectivity from inversion. The supervised pproch uses two clsses guided y Annpolis-G-24 nd Crimson-F-81 wells. The drk line in Figure () indictes the loction of the seismic section shown in Figure 14. Figure 17: Similrity mp t L Snd with isolines. PL. 5.6 Seismic fcies nlysis t L Snd

8 ISMIC RERVOIR CHARACTERIZATION Seismic chrcteriztion t the M Snd level: Both supervised nd unsupervised seismic fcies mps were generted t the M Snd level on Mrthon nd Verits (Figure 20 nd 21). No cler orgniztion of the seismic fcies cn e oserved t this level; this could e due to the poor seismic dt qulity nd the resulting less ccurte horizon picking. NE Centrl Scotin Slope Study CANADA June 2016 SW M Snd Figure 18: Lithology logs t Annpolis nd Crimson, 48ms elow M Snd. Annpolis hs more snds t the M Snd level. Poor seismic dt qulity 48ms Figure 19: Seismic section in the Mrthon cue through the two structures highlighted in Figure 20. Figure 21: Unsupervised seismic fcies mp clculted t the M Snd level (48ms elow top M Snd) on Verits 3D seismic dt. There is no cler orgniztion of the seismic fcies. Figure 20: Unsupervised () nd supervised () seismic fcies mps clculted t the M Snd level (48ms elow top M Snd) on Mrthon seismic reflectivity from inversion. The supervised pproch is composed of two clsses (green nd lue) guided y Annpolis-G-24 nd Crimson-F- 81 wells. The drk line in Figure () corresponds to the seismic line shown in Figure 19. Figure 22: Similrity mp t M Snd with isolines. Seismic fcies nlysis t M Snd PL. 5.7

9 ISMIC RERVOIR CHARACTERIZATION Centrl Scotin Slope Study CANADA June 2016 Attriute genertion t seed: The similrity mps clculted on the two seismic cues t the seed level show cler evidence of pockmrks which re lso clerly visile on seismic sections (Figure 23). These pockmrks re more visile on the shelf ut cn lso e identified on the slope. NE 7500 m Figure 23: () Similrity mp clculted t seed (48ms elow seed) on Verits seismic. It highlights the presence of pockmrks, which re lso oserved on the seismic section () long the white dotted line of Figure (). These pockmrks evidence gs rising up to the surfce. PL. 5.8 Attriute mps t Seed

10 ISMIC RERVOIR CHARACTERIZATION Centrl Scotin Slope Study CANADA June 2016 Attriute genertion t K94: The energy nomlies locted in the upper prt of the RMS mps (zones 1 nd 2 on Figures 24 nd 25) re ounded y listric fults. They re ssocited with two smll sins locted t the se of progrding wedges. Zone 3 corresponds to third smll sin locted slightly downslope from sin 2. It is limited y roll-over structures (Figure 24). In contrst to sin 1, the energy nomly is restricted to the south-west prt of the sin (Figure 24). The low energy portion corresponds to chnnel with n upslope-downslope orienttion. The high energy re is locted in the centrl prt of the smll sin. Note tht the K94 closes the smll sins (Figure 24 nd 25). Figure 24: () RMS mp clculted t K94 on Mrthon seismic showing three energy nomly zones - () Seismic section on Mrthon through zone 2 nd 3. SW NE 2 Figure 24-2: Close-up of zone 2 of Figure m 3 Figure 24-3: Close-up of zone 3 of Figure 21. Figure 25: () RMS mp clculted t K94 on Mrthon seismic showing three energy nomly zones - () Seismic section on Mrthon through zone m 2000 m Attriute mps t K94 PL. 5.9

11 ISMIC RERVOIR CHARACTERIZATION Centrl Scotin Slope Study CANADA June 2016 Attriute genertion t K101: Zone 1 (Figure 26) corresponds to fulted turtle ck. The energy is concentrted t the top of the structure (Figure 26); high mplitudes re lso present inside the structure (Figure 26). Zone 2 (Figure 27 nd section 2) lso corresponds to roll-over with high energy t the summit. It is ounded y listric fult t the southest. An mplitude nomly is present in the upper prt of the onshore-offshore chnnel defined y zone 3 (Figure 27 nd section 3). Zone 4 (Figure 27 nd section 4) is slightly inverted. The energy nomly corresponds to the top of the structure nd is ounded y fults m Figure 26: () RMS mp clculted t K101 on Mrthon seismic showing one energy nomly zone; () Seismic section on Mrthon through zone Amplitude m 4000 m Figure 27: () RMS mp clculted t K101 on Mrthon seismic showing three energy nomly zones; (2) Seismic section on Mrthon through zone 2; (3) Seismic section on Mrthon through zone 3; (4) Seismic section on Mrthon through zone m PL Attriute mps t K101

12 ISMIC RERVOIR CHARACTERIZATION Centrl Scotin Slope Study CANADA June 2016 Attriute genertion t K130: Zone 1 (Figure 28) corresponds to the sediment infill of smll sin proly relted to deep seted slt movements. The energy nomly is locted in the xil prt of the sin nd is limited to the est y north-south striking fult. This energy nomly likely corresponds to sndsheet deposit in this smll sin (Figure 28). Zone 2 (Figure 29) corresponds to the sediment infill of smll sin relted to deep seted slt movement nd growth fult structures. It is locted t the se of progrding wedge; the energy nomly is concentrted in the southwest prt of the sin. This re ppers to correspond to sndsheet deposit (Figure 29A); Zone 3 (Figure 29) corresponds to n nomly on the flnk of turtle ck structure. The K130 cps complex set of inverted chnnels. The high energies re locted t the top or on the flnk of this structure (Figure 29B). It is limited to the northest y slt dipir. 5000m Figure 28: () RMS mp clculted t K130 on Mrthon seismic showing one energy nomly zone; () Seismic section on Mrthon through zone m 2 Figure 29-2: Close-up of zone 2 of Figure m 5000m Figure 29-3: Close-up of zone 3 of Figure 26. Figure 29: () RMS mp clculted t K130 on Mrthon seismic showing three energy nomly zones; () Seismic section on Mrthon through zone 2 nd m Attriute mps t K130 PL. 5.11