2013 Fractured Weathered Basement Reservoirs Best Practices for Exploration Production - Examples From USA, Venezuela, And Brazil - Tako Koning

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Fractured Weathered Basement Reservoirs: Best Practices for Exploration Production - ExamplesUSA, Venezuela, and Brazil*

Tako Koning 1

Search and Discovery Article #41250 (2013)**Posted December 9, 2013

*Adapted from poster presentation given at AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013**AAPG©2013 Serial rights given by author. For all other rights contact author directly.

1Gaffney, Cline & Associates, Luanda, Angola, West Africa ( [email protected] )

Abstract

Fractured and weathered basement rocks are important oil and gas reservoirs in various basins in the worldwide. This author has

followed this subject very closely for 30 years and hereby shares his knowledge and experience. This paper focuses on relevant fields inthe USA including the Kansas fractured quartzite "buried hill" oil fields and basement oil fields in California including the El Segundoand Edison oil-bearing schist reservoirs. Also reviewed are the La Paz and Mara basement oil fields in Venezuela and basementreservoirs in the Carmopolis oil field, onshore Brazil.

Best practices include the following: production wells should be drilled near perpendicular to the dominant fracture system. Explorationwells should also be drilled highly deviated rather than vertical in order to optimally intersect the dominant fracture systems. Highlyfocused 3-D seismic such as CBM (Controlled Beam Migration) is needed to define the fracture systems in basement. Extensive corecoverage is necessary to provide critically important information on the lithologies and reservoir parameters. Some of the cores shouldalso be radiometrically age dated in order for the geologists to understand the complexities of the basement reservoirs they are dealing

with. Development wells must be sufficiently deep to fully drain the reservoir. Wells should not just "tag" into the top of basement. Forexample, wells in the La Paz field, Venezuela were typically drilled 500 meters into the basement.

In a general sense, fractured granites and quartzites are the optimum reservoirs. Weathered "rotten" granites can also be excellentreservoirs as can be observed in outcrop in tropical areas. Rocks such as schists and gneisses are less attractive since they are ductileand tend to "smear" and not fracture when subjected to tectonic stress. The high mafic content of schists also negates the creation ofsecondary porosity by weathering. Likewise, granites and quartzites are more likely to provide attractive, highly porous "granite wash"sands whereas eroded schists do not produce such good reservoirs.

mailto:[email protected]:[email protected]:[email protected]


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Selected References

Landes, K.K., J.J. Amoruso, L.J. Charlesworth, F. Heany, and J-P. Lesperance, 1960, Petroleum resources in basement rocks: AAPGBulletin, v. 44/10, p. 1682-1691.

Beglinger, S.E., J-D. van Wees, S. Cloetingh, and H. Doust, 2012, Tectonic subsidence history and source-rock maturation in theCampos Basin, Brazil: Petroleum Geoscience, v. 18/2, p. 153-172.


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AbstractFractured & Weathered Basement Reservoirs – Best Practices for Exploration and

, . , ,

Cline & Associates, Luanda, AngolaFractured and weathered basement rocks are important oil and gas reservoirs in various basins in theworldwide. This author has followed this subject very closely for 30 years and hereby shares his

.fractured quartzite “buried hill” oil fields and basement oil fields in California including the El Segundoand Edison oil-bearing Jurassic schist reservoirs. Also reviewed are the La Paz and Mara oil fields in

Venezuela and also basement reservoirs in the Carmopolis oil field, onshore Brazil.

Best practices include the following: production wells should be drilled near-perpendicular to thedominant fracture system. Exploration wells should also be drilled highly deviated rather than verticalin order to optimally intersect the dominant fracture systems. Highly focused 3D seismic such as CBM

(Controlled Beam Migration) is needed to define the fracture systems in basement. Extensive corecoverage is necessary to provide critically important information on the lithologies and reservoirparameters. Some of the cores should also be radiometrically age dated in order for the geologists tounderstand the complexities of the basement reservoirs they are dealing with. Development wells mustbe sufficiently deep to fully drain the reservoir. Wells should not just tag” into the top of basement.For example wells in the La Paz field, Venezuela which produces from basement were typically drilled

500 meters into the basement.

In a general sense, fractured granites and quartzites are the optimum reservoirs. Weathered “rotten” granites can also be excellent reservoirs as can be observed in outcrop in tropical areas. Rocks such asschists and gneisses are less attractive since they are ductile and tend to “smear” and not fracture

.secondary porosity by weathering. Likewise, granites and quartzites are more likely to provideattractive, highly porous “granite wash” sands whereas eroded schists to not produce such goodreservoirs.


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il in B m n •

basement reservoirs by K.K. Landes et al (1960

“Commercial oil deposits in basement rocks are not ‘ ’

which obey all the rules of oil sourcing, migration

basement, oil deposits within basement should beas accumulations in the overlying sediments ”.


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Basic Requirements for Oil or

Gas in Basement• Reservoir – need fractured or weathered

• Source – need hydrocarbon source rockse ow, a acent or a ove t e asement

reservoir

•Closure – need structural closure

– nee cap roc s a ove ebasement reservoir


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Tako’s Preferance Scale for

in Basement

•Fractured quartzites……. Most preferred

• Fractured carbonates• • Weathered granites• Fractured gneisses

• Fractured schists• Weathered schists……….. Least preferred


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Potential of Gneisses & Schists as

Basically Bad! • Gneisses: a foliated metamorphic rocks

corresponding in composition to granite ore spat c p uton c roc sProblem: can be massive or dense or slabby with

open ractures para e to t e rect on ofoliatiation; fracturing is too planar

• Schist: a fissile metamorphic rock with closelyo a e s ruc ure cons s ng o para e p anesProblem: are generally too micaceous, thinly

e e , ss e an uc e o e prone o mega-scale fracturing


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KANSAS, USA – Precambrian Fractured QuartziteBuried Hill Basement Oil PoolsKANSAS US - Precambrian Fractured QuartziteBuried Hill Basement Oil Is

• B a s e m e n t o i l f i e l d s

N o n b a s e r n e n t o f f f i e l d s

I

R U S S E L L I

IIIIII

I

A u s s e l l ~t - I E l s ' o r t h

B a r t o n l _ : _ I

K A N S A S~

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r-

IIIII

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IT

K r a f t - P r u ,

BARTON

-

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.'.I •R i n g w a l d

E L L S W O RT H

,1

O r t h

o 1 0 k m

M a p s h o w i n g t h e l o c a t i o n o f t h e K a n s a s b a s e m e n t o i l f i e l d s ( L a n d e s l a l 1 9 6


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KANSAS, USA – Precambrian FracturedKANSAS, USA - Precambrian Fractured...,-te Buried Hill Basement Oil Pools

Depth m)150 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

00

450

600

a

· . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .· . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .· . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .· . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .· : . : . : . : . : . : . : . : . : . : . : . : . : . : . : . : . : . : . : . : Pennsylvanian· : . : . : . : . : . : . : . : . : . : . : . : . : . : . : . : . :· . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .· . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

• Top of Missouriseries

1 2

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. Precambria n

3 4

. . . . . . . . . . . . . . . . . .

• • • • •...... _ . J I . . :

5 6 7

••

Kansas basement oil production.Oil is produced from Precambrian basement(in section) mostImmonly fractt/red quartzites. Oil is sourced from fl anking Cambro·Ordovician or overl ying Pennsylvanianks . (Landes e l 01 196


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KANSAS, USA: Summary of

Basement Oil Fields

Small oil pools, approximately 150,000 barrels oilr w . r x , r ubarrels produced from 15 wells.

rv r: r - r r ur u r z• Source rocks: Pennsylvanian shales• Oil is recovered from the top of Pre-Cambrian

buried hills, depth of about 1,000 meters• Best practices: more oil could be produced bydrilling horizontal drain holes, also should be

system; 3D seismic is necessary


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. ,,

~ ~,

-

-

Pacific Ocean

o 1 km

I- , - li t- Gas and oil fields I

urassic nd oldermer morphi cs nd gr nites I

' - I' - Nevada I

' - I' -

,I ' \ J

~ r. 0

\ ~ \' - \

' - I

California

,(

I

/(l

/r

,/

_ rMEXICO

Map showing the main Californian gas and oil wells of I Segundo Santa Maria Wilmington Playa delRay, and Edison. The fields circled in green produce oil from basement reservoirs. Landes e t al. 1960).


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CALIFORNIA: Basement Oil Fields All of California’s oil production is from Tertiary

which produce from basement:

• , ,Jurassic schists

• ,• Santa Maria , Santa Barbara area, fractured

• Wilmington , Long Beach area, 22 million• Edison , Bakersfield area, 20 million barrels

CALIFORNIA El S dCALIFOR IA S d


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CALIFORNIA: El SegundoCALIFOR IA: I Seg ndoBase e t Sch-st) Oil Field

11 k i n~

AD e p t h

h T l }

]5 0

1 8 0 0

2 1 0 0

2 4 0 0

C r o s s - s e c t io n ·t h r o u g h t h e E I S e g In d o f i e l d c.a I i f o r n i i a T h e r e s e r v o i i r is i n f r a rc r u r e d J 1u r a s s i c s c h i t s~ t h ~ ~ s : a nd s c h is t and c o n g l o m e r a t e i n t h e - e a s t . T h e a V e l a g e depd . . . , 0 h e o il b a 5 e l f T l e n tp l o d u c d C l i f l l il 2 3 0 0 . l1......an d e s e t : a L 1 1 9 6 0 ) .


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CALIFORNIA: El Segundo

asemen e• Reservoir is a Jurassic fractured schist in

the east half

• teste up to , o eggravity crude• Average depth 2,100 – 2,180 meters

, ,


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VENEZUELA: La Paz Basement

La Paz Oil Field, Venezuela


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VENEZUELA: La Paz Basement

La Paz Oil Field, Venezuela


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VENEZUELA: La Paz Oil Field

• The main La Paz oil field was discovered in,

basement oil field was discovered in 1953which was 30 years later and has produced325 million bls oil these numbers need to beupdated; this author is seeking more reliable

La Paz and Mara basement oil fields • eservo r s racture gran tes anmetamorphics


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VENEZUELA: La Paz Oil Field

• Maximum IP (initial productivity) from, ,

IP is 3,600 BOPD• In the initial development of the basement,

into basement• ara e was scovere n ,

has produced 27 million barrels of oil frombasement (numbers need to be updated),

meters and wells has IP’s of 2,200 BOPD


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BRAZIL: Carmopolis Basement

Oil Field, Sergipe Sub-Basin-map from Beglinger et al, 2012

BRAZIL C li B


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, - X-section from Berlinger et al, 2012


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anprasil

10 bRoundMain ields

y e r s Oil Gas Bidding Rounds

Geological cross-section - Sergipe Sub Basin

Campo de Campo de Campo de Ar Carmopolis Camorim CaiobaI ~ ~ ~ ~ ~ ~ = = ~ - - - - - - -

Seq. Drifte (Cretacio SuperiorlTercicirio)

o Seq. Drlfte (Albiano/Cenomaniano)o Seq. Transicional (Aptiano)E Seq. Rift (Neocomiano/Barremiano)o Seq. Pre·Rift (Paleoz6ico/Jurassico)

Embasamento (Crosta Continental)

2

2 km


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BRAZIL C li B t


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, - v r ,

Sergipe Sub-Basine ro eum sys ems: armopo s mem er

reservoirs and fractured basement

r g na o - n-p ace m on cu c me er(1.7 billion barrels); approx 55 million cubic

approx 10 -15% is from basement or 5.5These production numbers are very

,more specific & reliable production data



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BRAZIL: Carmopolis Basement ,

Oil is of a mixed base ranging from 24.

Depth range of all reservoirs is ashallow 400 – 800 meters de th

on this field about the basement reservoirs in


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SUMMARY: Best Practices for Exploring

an ro uc ng asemen eservo rs1.) Look for oil in basement beneath existing oilfields, e.g. La Paz basement was found 30 years afterdiscovery of oil in overlying Cretaceous sediments.

2.) Wells should not just “tag” into the top of

meters.

3.) Basement should be targetted using 3D seismiclike CGGVeritas’ CBM (controlled beam migration).

4.) Wells should not be drilled vertical but rathershould be high angle wells drilled perpendicular tothe dominant fracture patterns.


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an ro uc ng asemen eservo rs5.) Basement needs to be cored to providecritically important reservoir data; with mostbasement reservoirs the oil is stored only in the

,weathered zones at the top of basement can beexcellent oil and gas reservoirs.

6.) Initial wells need to be extensively tested to besure that there is not a situation of very high IP but

then followed by a rapid decline; testing may also - bearing fracture systems.


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an ro uc ng asemen eservo rs7.) Some of these fields can be complicated. They may have

early water breakthrough, rapid production decline, very’ . ,

experience was in 1982 with the Beruk NE basement oil fieldin Sumatra which watered out after producing only 2 million

.fracture analysis based on well data and seismic. Forexample, differentiate between fractures which conduct oil or

- .may need to out-source this work to “experts” to get second

opinions about your basement field.

8.) BUT, highly prolific basement oil and gas fieldsworldwide such as Bach Ho Viet Nam Suban Indonesia LaPaz (Venezuela) and such fields in Libya, Egypt, Russia, andChina serve as a reminder: do not forget your basement!

Select Sources of Information


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Select Sources of Information

Landes, K.K. et al, 1960, “Petroleum resources in basementrocks ” , AAPG Bulletin, 44, pp 1682-1691.

Nelson, R.A. et al, 2000, “Production characteristics of the

fractured reservoirs of the La Paz Field, Maracaibo basin,” , , , - .

Talukdar et al, 1994, “ The petroleum systems of the Maracaibo , , , – .

Koning, T. & Darmono, F.X., 1984, “The Geology of the Beruk North ,

basement rocks ” , Proceedings of the 13th Annual Convention of theIndonesia Petroleum Association, Jakarta.

Koning, T., 2003, “ Oil and gas production from basementreservoirs: examples from Indonesia, USA and Venezuela” , SpecialPublication 214 – Hydrocarbons in Crystalline Rocks, Geological Society of

London.

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2013 Fractured Weathered Basement Reservoirs Best Practices for Exploration Production - Examples From USA, Venezuela, And Brazil - Tako Koning