## Enhanced HRAM Anomalies Correlate Fault s between 2

- 

## D Seismic Lines Serguei A. Goussev, Lisa A. Griffith, John W. Peirce and A ndreas Cordsen GED C O, Calgary

Summa ry Co rrela t ion o f faults b e tween 2

- D seismic line s u s ing enhan ced m agne tic anoma lies is illustra ted b y this e x ample from a High

- Re solu tion Ae roMagne tic (HRAM) su rve y nea r the W e ybu r n o i l fie l d in sou t h

- easte rn Saska t ch ewan a s pa rt o f the IAE W e ybu r n CO 2 Sto r age and Mo nitoring Pro j e c t. Se ismic fault picks, in te rp re ted on 2

- D seismic se ctio n s , close l y co rrela t e with linea r magne ti c ano malie s on the filtered HRAM map

. These f ault-associa t ed magne tic anoma lie s can be co rrela t ed within the 2

- D seismic cove rag e a r ea and beyond its limits.

Introdu cti on It is a l ways a challenge to co rre la te faults be tween 2

- D seismic lines which a r e widely spa c ed

. This task beco m es e v en mo re complica ted when the fault of fse t s a r e small and seismi c lines ha ve dif f eren t vin t ages and proce ssing quality

. The amb i guity o f this correla t ion can be si gnifican t ly reduced by in teg r a t ion with HRAM data

. Structu r al discon tinu ities such a s faults, lith ological con t a c ts, and depositional edges can crea te la teral co n t ra sts in magne tiza tion o f ro cks. La te ral magne tiza tion con tr as t s o f

ten gene ra te de te ctable magne tic ano malie s (Gle nn and Badge ry , 1998 , Goussev e t al, 2003 , Grauch e t al, 2001 , Peirce et al, 1998 ), man y of wh ich a r e sou r ced in the sedime nta r y section

. Ad van c ed HRAM filtering techniq ues can enhan ce the s e subtle fault-a sso cia t ed magnetic ano malie s to make them coheren t and correla t able o v e r area s co vered by 2

- D seismic p r og rams and also be tween 3

- D se ismic p r og rams.
HR AM Da ta The S.E. Saska t ch ewan HRAM Su rvey was flown along o r thogona l flig h t line s o f 500 m x 1 500 m spacing

. This ne two r k p r ovides a den se and even da ta sa mpling o v e r the surve y a r ea

. The proce ssing o f ob served da ta in cluded standard corrections (diu rnals and IGRF), cultu r al editing , le velling an d gridding a t 150 m g r id ce ll size

. The g r idded da ta we re Wie ner filtered to re move extrem e hi g h

- frequency noise an d then redu ced to the p o le to co mpensate fo r lo cal inclina t ion and de clina t ion o f the Ea rth’ s magne tic fie l d an d center the magne tic anoma lies ove r their sou r ces.
The e nhance m en t o f sub t le magne tic ano malie s a sso cia t ed with the fault-like structu r al d i sconti nuitie s was achieved by applica t i on of the ca scaded Goussev filte r (Goussev e t a l , 1998 , 2003 ) a s it p r ov ides a supe rio r supp ression o f n o ise and impro v ed coheren cy o f filte r ed a nomalie s. For our stud y , this filte r wa s designed a s a 1

. 6-3

. 2 km bandpa ss o f a dif f eren ce be tween the to tal and h o ri zon t al g r adien ts calcula t ed a f ter app lying the dep th sepa ra tion (Ja c ob sen , 1 987) to the to tal ma gne tic field

. Se ism i c Da ta Th ree nearly pa ralle l SW -NE o r ien t ed 2

- D seismic lin es (# 1

, #2 and # 3 ) we re ch osen in the IEA W e yburn CO 2 study a r ea with ~12 km spacing be tween lines #1 and # 2

, and ~14 km be twee n line s # 2 and #3

. Seismic lines are from 48 km to 50 km le ngth. Th e in te rp re ted faults ha ve sma ll o f fse t s an d a r e rela ted to both e x te nsiona l and co mpre ssional r egional stress reg i me s a t dif f eren t t i mes. T

w o faults on line s # 2 and # 3 ha ving apparent seismic signa tu res typical o f strike-slip faulting are ma rke d a s PFS - “Po s itive Flo w er Structu r e” and NFS - “Ne gative Flower Struct ur e ” (F i g . 1 ) . I n th e a b s e n c e of co m p l e m e nt ar y i n f o r m at i o n, t h e c o r r e l a ti o n o f i n t e rp re ted fault picks fro m se ismic da ta onl y is very amb i guou s, espe cially for the strike-slip fault picks.

C o rre la tion Fig

. 2 shows the enhanced HRAM anomalies o v erlain with 2

- D seismi c line s , in te rprete d fault picks and correla t ed faults. No te h ow close l y the enhan ced magne tic anomalies corre l a t e with fault picks A, B, C, D and “str ike-slip” fault picks PFS and NFS. Ba sed on the geologica lly plau sible assump tion tha t a co n t inuou s (coheren t) magne tic anoma l y repre s en ts the sa me type o f stru ctura l discon t i nuit y o v er the area of its co rrela t ion

, we can co rre late the fau l t “ A ” be tween and be yond all three seismic line s

. The same approa ch can be followed in co rrela t ing th e fau l ts “B” and “C” be tween lines # 1 and # 2

. Co rrela t ion o f the fault picks PFS and NFS wi tho u t re ference to the HRAM ano malies is ha rdly po ssible a t all. Separated by just 14 km, these faults see m to be a sso cia t ed with the opposite de fo rm a t ion style s : exten s ional NFS and comp ressional PFS. Both fault picks a r e in perfect correla t ion with enhan ced HRAM anoma lie s whic h clea rly show tha t the s e f ault picks repre s en t o r thogonall y trending strike-slip faults: the PF S fa ult trends WSW

- ENE and the NF S fault trend s SSE-NNW (Fig. 2 )

. Con c lu si on s 1. En hanced HRAM ano malies can be u s ed to co rre la te fa ults be tween 2

- D se ismic line s

. 2. HRAM da ta comp lemen t s 2-D se ismic p r og rams, bo th loca lly and regionally

. 3. HRAM da ta can help to estab l ish the stru ct u r a l d e f o r m at io n sty l es ov er l a r g e ar e a s , espe cially when combine d with seismic da ta

.

Gr e a t Explor a t ions – Ca nada and Be yond 1Fig. I 

### Line I

Line#



### Line #3



# •

2-D se i s mic lines, fault picks an d inl erpre l e d fault s

o n top o f the filtered HR AM map



### F l g .2 This work is a pa rt of GEDCO’ s con t ribu tion to the IEA W e yburn CO 2 Monito ring and Sto r age Proje c t wh ich is coo r dina ted b y th e Pe troleu m T echnolo gy Re search Cen t re (PTRC). Acknowledg ments GE D C O t h a n k s th e I EA W e y b ur n CO 2 Monito ring and Sto r age Project, and Encana Co rpo r a t ion

, a major spo nso r o f this Proje c t, fo r pe rmission to show the seismic image s.

Great Explorations – Canada and Beyond 2Great Explorations – Canada and Beyond 3 References

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