Miocene and Oligocene Petroleum Reservoirs of the Santa Maria and Santa Barbara-Ventura Basins, California

Home , Santa Ynez Mountains, Sisquoc Formation

SEPM Core Workshop No. 14

Edited by:

MargaretMargaret A.A. KellerKeller and Mary K. McGowen

ISBN 978-1-56576-268-8, CD catalog 71014 Originally published in print as SEPM Core Workshop (CW) No. 14 ISBN 10-918985-84-6, catalog 70014 Tulsa, Oklahoma, U.S.A., 1990 www.sepm.org

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RELATIVE EUSTA TIC! SEA LEVEL TEC TONIC

PLIOCENE

A UPPER MONTEREY

LOWER "=- = MONTEREY= MIOCENE -

'I\\ --\,-, \,--,\;--,\,---,\,---,\,--,,---,-,-/ji,,...._\,,--- ,--../,-,,-.. /,-/,-../,-.. ..--,-\, ...... -,-,--,,,_/_\/.,,-,. .,.. --,,--\-\,-,_.,,_,,_,,,,..\,-,--,,,,.,..,,,i-,,,,. OLIGOCENE

SEPM SEPM Core Workshop No 14 San Francisco, June 3, 1990 1926

Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/3801372/9781565762688_frontmatter.pdf by guest on 30 September 2021 COVER DIAGRAM: The left column is a schematic representation of Oligocene, Miocene, and Pliocene climate and basin development.The two right columns are schematic diagrams illustrating the interaction of tectonic and eustatic processes with resulting relative sea level and lithostratigraphic evolution in Western Santa Barbara County, California by K. Bohacs, Exxon Production Research

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36°-o ONSHORE SANTA MARIA BASIN rs -6 GUADALUPE offshore SAN MIGUEL Santa Mana onshore SANTA MARIA VALLEY Santa Maria oo CASMALIA rs CAT CANYON OFFSHORE ORCUTT% Santa Barbara-Ventura SANTA MARIA \ 34° BASIN JESUS FOUR DEER ZACA MARIA 74144 INDEX MAP LOMPOC POINT BARHAM RANCH PEDERNALES LOS ALAMOS >,- BONITO o ROCK xkci,\c) o0-s 0 POI o ov 4r- cso\- O'). are. rosa rar .)V9 POINT ARGUELLO VP* A SACATEIZZ='UARTA AO A '\- 0...A.C".1;),9Y )Ik SWORD '73 SOUTH COAL 11 HONDO OIL GOVERNMENT ELWOOD POINT PESCADO POINT tel:2 PITAS POINT 00 SANTA BARBARA CHANNEL SANTA CLARA SANTA ROSA

SOCKEYE o 20 Km HUENEME C:z)

Index map of oil and gas fields in the Santa Maria and Santa Barbara- Ventura Basins.

A Core Workshop

Organized and Compiled by Margaret A. Keller and Mary K. McGowen

SEPM Core Workshop No. 14 San Francisco, June 3, 1990

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Additional copies of this publication may be ordered from SEPM. Send your order to:

SEPM (Society for Sedimentary Geology) Printed in the United States of America

Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/3801372/9781565762688_frontmatter.pdf by guest on 30 September 2021 PREFACE

This volume presents papers that have been assembled for Core Workshop

#14 of SEPM (Society for Sedimentary Geology) on Miocene and Oligocene

Petroleum Reservoirs of the Santa Maria and Santa Barbara - Ventura

Basins, California. The main emphasis of the workshop is the Miocene

Monterey Formation, the most important petroleum reservoir in both the

Santa Maria Basins and a very important reservoir in the Santa Barbara-

Ventura Basin,particularly in the offshore. In addition to the

Monterey Formation, core studies are also presented on the post-Monterey

Sisquoc Formation and on pre-Monterey reservoirs including the Sespe,

Alegria, and Vaqueros Formations.

We thank the many people from the United States Geological Survey, the

oil industry, academia, and SEPM (Society for Sedimentary Geology), who

helped make this core workshop possible,especially ARCO,Chevron,

Exxon,Shell, Texaco, and Unocal who donated either or both core and

staff time.

Margaret A. Keller

Mary K. McGowen

Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/3801372/9781565762688_frontmatter.pdf by guest on 30 September 2021 LIST OF CONTRIBUTORS

Organizers and Editors Margaret A. Keller Mary K. McGowen U. S. Geological Survey ARCO Oil and Gas

Authors Bonnie Bloeser University of Southern California

Kevin Bohacs Exxon E.P.R.

Mary Lou Cotton-Thornton Unocal

John Dunham Unocal

Nuel Henderson Unocal

Nancy Hinman University of Montana

Greg Miles Exxon, U.S.A.

Peter Ramirez University of California Santa Cruz

Phil Rarey Chevron U.S.A.

Cathy Rigsby Long Beach State University

Kumbe Sadler Chevron U.S.A.

Dan Schwartz Shell Western E & P

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ONSHORE SANTA MARIA BASIN 36

offshore Santa Maria 8 MUSSEL 5 SANTA MARIA VALLEY ROCK CASMALIA OFFSHORE 9ti4 Santa Barbara-Ventura SANTA MARIA 34 BASIN INDEX MAP

496 #1 8 4 POINT PEDERNALES CAPITÁN 3 6 POINT ARGUELLO

SANTA BARBARA CHANNEL

SOCKEYE 1 20 Km czr:)

Location map of cores and outcrop studies in this volume; numbers are keyed to the Table of Contents.

vii

Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/3801372/9781565762688_frontmatter.pdf by guest on 30 September 2021 TABLE OF CONTENTS

INTRODUCTION TO STRATIGRAPHY AND HYDROCARBON OCCURRENCE IN OLIGOCENE AND MIOCENE ROCKS OF THE SANTA BARBARA-VENTURA AND SANTA MARIA BASINS OF CALIFORNIA

by M. A. Keller 1

SEDIMENTOLOGICAL AND RESERVOIR CHARACTERISTICS OF THE UPPER SESPE FORMATION AT SOCKEYE FIELD, OFFSHORE CALIFORNIA

by P. J. Rarey 12

LITHOSTRATIGRAPHY AND DEPOSITIONAL ENVIRONMENTS OF THE VAQUEROS AND UPPER SESPE/ALEGRIA FORMATIONS, HONDO FIELD, SANTA BARBARA CHANNEL, CALIFORNIA

by G. A. Miles and C. A. Rigsby 39

LITHOSTRATIGRAPHY AND DEPOSITIONAL ENVIRONMENTS OF THE VAQUEROS FORMATION, CAPITAN FIELD, CALIFORNIA

by C. A. Rigsby and D. A. Schwartz 88

SEQUENCE STRATIGRAPHY OF THE MONTEREY FORMATION, SANTA BARBARA COUNTY: INTEGRATION OF PHYSICAL, CHEMICAL, AND BIOFACIES DATA FROM OUTCROP AND SUBSURFACE

by K. M. Bohacs 139

LITHOLOGY OF THE MONTEREY FORMATION IN THE WESTERN SANTA MARIA VALLEY FIELD, SANTA MARIA BASIN, CALIFORNIA

by J. B. Dunham and M. L. Cotton-Thornton 202

THE RELATIONSHIP OF LITHOLOGY AND TECTONICS TO FRACTURING IN THE MONTEREY FORMATION, POINT ARGUELLO FIELD, OFFSHORE CALIFORNIA

by R. K. Sadler. 245

7 LITHOLOGIC AND DIAGENEITC SEQUENCES OF THE MONTEREY FORMATION, MOLINO FIELD, OFFSHORE SANTA BARBARA, CALIFORNIA

by N. W. Hinman and D. E. Schwartz 271

viii

Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/3801372/9781565762688_frontmatter.pdf by guest on 30 September 2021 DEPOSITIONAL RHYTHMICITY IN THE MONTEREY FORMATION -- THE NATURE AND TIMING OF CYCLIC PATTERNS by B. Bloeser 337 CONTROL EXERTED BY LITHOLOGIC VARIATIONS AND PEBBLY UNITS ON PETROLEUM OCCURRENCES IN THE PLIOCENE UPPER SISQUOC FORMATION, CASMALIA HILLS, SANTA MARIA BASIN, CALIFORNIA by N. C. Henderson, Jr. and P. C. Ramirez 339

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Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/3801372/9781565762688_frontmatter.pdf by guest on 30 September 2021 INTRODUCTION TO STRATIGRAPHY AND HYDROCARBON OCCURRENCE IN OLIGOCENE AND MIOCENE ROCKS OF THE SANTA BARBARA-VENTURA AND SANTA MARIA BASINS OF CALIFORNIA

Margaret A. Keller U.S. Geological Survey 345 Middlefield Road M.S. 999 Menlo Park, California 94025

ABSTRACT

TheSanta Barbara-Ventura and Santa Maria basinsof southern California have been of great interest to the oil industry because oil or gas has been produced from nearly all the sedimentary units ranging in age from the Cretaceous to the Pleistocene. In particular, the Neogene section of these basins is oil-rich, containing eight giant oil fields (greater than 100 million barrels) in the onshore and at least five in the offshore.

In the Santa Barbara-Ventura basin the sedimentary sequence includes marine beds ranging in age from Cretaceous to Pleistocene and two nonmarine sequences of Eocene-Oligocene and Pleistocene ages. The main reservoir for hydrocarbons in this basin is the thick deep-sea sand sequence of the Pliocene and Pleistocene Pico Formation. The other important production in this basin is from reservoirs in the Miocene and,to a lesser extent, the Oligocene sequences. These reservoirs, including the nonmarineSespeFormation andthe marine Alegria, Vaqueros, Monterey, and Sisquoc Formations,are the emphasis of this core workshop.

In the Santa Maria basins to the north and northwest of the Santa Barbara-Ventura basin, the Paleogene sequence is absent for the most part, and the upper Neogene sequence does not include the thick Pliocene and Pleistocene Pico Formation. In both the onshore and offshore Santa Maria basins the fractured rocks of the deep-marine Miocene Monterey Formation are the main reservoir for hydrocarbons. Another important reservoir is the upper Miocene and Pliocene marine Sisquoc Formation; both Monterey and Sisquoc cores from the Santa Maria basin are shown in this workshop. As in the Santa Barbara-Ventura basin, the pre-Monterey sedimentary sequence of the Santa Maria basins also contains minor petroleum accumulations.

INTRODUCTION AND GEOLOGIC SETTING

The Santa Maria and Santa Barbara-Ventura basins are located in southern California at the junction of the western Transverse Ranges and southern Coast Ranges geomorphic provinces (Figs. 1, 2, 3). This junction is an area of complex and controversial geology, structure, and tectonics, exemplified by the contrasting structural grain of the west- trending Transverse Ranges and northwest-trending Coast Ranges (Fig.2). The mechanism of origin of the late Oligocene or early Miocene deep- marine basins at this junction, whether by pull-apart in a strike-slip regime, rotation of the Transverse Ranges, extensional tectonics, or another mechanism,is an open question (Hall, 1981; Hornafius and others, 1986; McCulloch, 1987). The Santa Barbara-Ventura basin

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\ BASIN AND RANGE 9 \ \ GREAT e \ 0 ,,' VALLEY SIERRA -9t..P \\ NEVADA T ... Bakersfield' \ 0 4) A SaillAns Iv e" t,IlittiHI 0,,,,, \

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BICpiflC Point Arguello 617 Point Conception MIS Santa Barbara San Gabriel TFT4NSVERSE Mountains Santa Barbara VENTURA BASIN 4, '.9 \ Channel San ,11NliglIt.1 Santa Cruz SA,,,,ON .... Island i Island Ana.," Santa Monicas AugAngeles Mts Loernarmdnoountains Island ...... ' - s 34° ,antal, Island S.. A. .e4) Santa M. 4 Barbara , V Island EXPLANATION Santa ,.-., Catalina rid Approximate location of San Nimias major fault zone Island

Boundary of geomorphic 33° San Clemt,nte province Island

o San Diego 40 40 80 MILES

I I UNITED 7,7, -7000

FIGURE 2. Index map showing major faults and geomorphic provinces of southern California. From Vedder and others (1969) as modified from Yerkes and others (1965). 122° 1200 118°

36°

Offshore Map Area Santa Maria Onshore Santa Mana o

Santa Barbara-Ventura...

34° 1 G,

FIGURE 3. Location of Santa Maria and Santa Barbara-Ventura basinsand structure section A -- A'. Adjacent basins are Huasna-Pismo in the onshore, Sur to the north, and Santa Lucia to the west.

Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/3801372/9781565762688_frontmatter.pdf by guest on 30 September 2021 contains a nearly complete sedimentary sequence of Cretaceous to Holocene age, whereas most of the Cretaceous to Oligocenesequence is missing in both of the Santa Maria basins(Figs. 4A, B; Woodring and Bramlette, 1950; Crawford, 1971; Hoskins and Griffiths, 1971; Nagle and Parker, 1971). The deep-marine Miocene deposits of these basins are the source of most of the oil as well as important regional oil reservoirs.

This paper is an introduction to Miocene and Oligocene petroleum reservoirs of the Santa Maria and Santa Barbara-Ventura basins of southern California for Core Workshop #14 of the Society of Economic Paleontologists and Mineralogists. The main emphasis of the workshop is the Miocene Monterey Formation, the most important petroleum reservoir in both Santa Maria basins and a very important reservoirin the Santa Barbara-Ventura basin,particularly in the offshore(see Bloeser; Bohacs; Dunham and Thornton; Hinman and Schwartz; andSadler; this volume). In addition to the Monterey Formation,coresare also displayed from the Sisquoc Formation of the onshore Santa Maria basin (see Henderson and Ramirez,this volume), animportant reservoir overlying the Monterey Formation, and from pre-Monterey reservoirsof the Oligocene and lower Miocene sedimentarysequence of the Santa Barbara-Ventura basin,including the Sespe,Alegria, and Vaqueros Formations (see Rarey; Miles and Rigsby; and Rigsby and Schwartz; this volume).

Compared to other hydrocarbon-producing areas in California, the oil-rich Santa Barbara-Ventura and Santa Maria basinsare among the largest in size, and the oldest and youngest withrespect to discovery and development. Many geologists have worked on these basins and the literature is diverse and extensive. For references on the Santa Maria basins,see Woodring and Bramlette (1950), McCulloch (1987),and the bibliography of Tomson (1988). For the Santa Barbara-Ventura basin, see Dibblee (1950; 1966; 1988), Vedder and others (1969),Curran and others (1971),Nagle and Parker (1971),Curran (1982),Keller (1988), and Sylvester and Brown (1988).

STRATIGRAPHY

SANTA BARBARA-VENTURA BASIN

The sedimentary sequence of the Santa Barbara-Ventura basinincludes marine beds ranging in age from Cretaceous to Pleistoceneand two nonmarine sequences of Eocene-Oligocene and Pleistoceneages (Fig.4A) (Vedder and others,1969; Nagle and Parker, 1971; Ingle, 1981). A maximum thickness of approximately 50,000 ft (15,000 m)is estimated for the sequence in the Ventura River area of the basin (Vedderand others, 1969); however, a complete section isnot exposed in outcrop or penetrated by drilling. Because of lateral changes in thickness and lithofacies of the sedimentary strata in this basin,one stratigraphic column does not accurately represent the whole basin; however,Figure 4A from the western Santa Ynez Mountains (Vedder and others, 1969) best representsthe stratigraphic sequence of the core shown inthis workshop. Figure 5 (south part)shows this sequence in a uniformly dipping homocline south of the Santa Ynez fault. Only the Oligocene through Miocene and lower Pliocene parts of thesequence, the subject of this workshop, are discussed in detail in the followingtext.

Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/3801372/9781565762688_frontmatter.pdf by guest on 30 September 2021 Series Formation Ldhology Feet Description Continued from left Colo Alluvium ( 0 Silts and gravels 200 cene j Terrace Gravels cleMdSM Pleisto Diatomaceous siltstone cene/ Claystone and diatomaceous

.-^4 mudstone SiSQUOC .-- 7 Thin bedded claystone and laminated diatomite

Porcelaneous and :-...... E55 cherty siliceous shale 8 Monterey Sr+ ------Organ. shale and thin limestone 01sa....".., o Rhyolite and basalt Tranourdon , agglomerate. tuft. o 'Cr.013 bentonite J

Bncon Claystone o

Vaqueros , Sandstone and conglomerate

...... Variegated sandstone Sespe (NI and siltstone Alegrta AI- Marine sandstone

o SPECIAL SYMBOLS Gaviota Sandstone and siltstone

11111,111,111141111111 1111 J1111111111111111111114,11

Dialornacootra mud.. Sacare .7.7 c, Sandstone and claystone

Cozy Dell ClaysIone Porcolanows

.....

Matilna ;t;.. : Aram. sandstone Mort), Nob

Anita _° Shale and claystone ..... 1, 1 rra 0-S Algal irmestone Blanca -----s\ Tut Claystone and X t t siltstone. fine. Ialama grained sand. stone at top and mrddle

7777%!;7.!%-.;%' o

o ..._r y_y Carbonaceous shale and Into sandstone . Espada o hornsbon 500 o

Igneous roc.I, ; of Froncosca % Basal pebbly - sandstone

,n Hard sandstone --:-.: and shale Franciscan : 1/7 - I Setpentine mtrusions a N-Nonmarine b Continued at right

FIGURE 4. Representative stratigraphic columns: A) from the western Santa Ynez Mountains of the Santa Barbara-Ventura basin (Vedder andothers, (1969) as modified from Dibblee (1950)] and B)from the central Santa Maria District of the onshore Santa Maria basin (Woodring and Bramlette, 1950)

Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/3801372/9781565762688_frontmatter.pdf by guest on 30 September 2021 1- CO Overlying and, in the western . o o L.,, o .._,. o C (1) RS C) w -H P 0 rtiLn Santa Ynez Mountains, interfingering .<,., u3 ,-,-- _c al tli 0 CI with Paleogene marine strata is the 1. J 4--) -H E 'CS 0 nonmarine Sespe Formation, deposited za) 0. .-::.0 O v)(ci -H a) during an episode of major, ).-1 4-) a) 4., rts,_, widespread marine regression in the Nco II E ,C1 late Eocene,Oligocene,and early 0 ,__( Li-i S-I ,C) :.:...:.-o:-: o'-p0-1 Miocene (Fig.6; Vedder and others, f > g 44n 1969; Nagle and Parker, 1971; Ingle,.:.5.::. ni>,s >1 4.4 :.'8:4:. -I-)co Tfwo 1981; Howard, 1987). TheSespe CV .:-: ' al 4-) cli Formation consists of variegated .-X.IX: co m-0m strata, including red beds, composed ..:::::: 8 :.cy) w--1..) o 7:1m chiefly of nonmarine conglomerate, .c(1) X Q, ,3.:.: 4--) w \::::::: sandstone, and claystone (Vedder and .. '-' a)41' .N cn bla)4 others, 1969; Howard, 1987). Rarey e . :::',11:::: o (.1-1 4-, --1 s4 (this volume) describes the. . o 54(4-1 o : u sedimentology and reservoir T,' a) , as characteristics of the Sespe `,..-,-(\ -0-1 .. .. , . Formation of the Sockeye oil field . +-) a)73 ---1 '-H)-4 > N, inthe southeastern partofthe ...... ,u_ - o cajzi >cl N 2 Santa Barbara-Ventura basin (Fig. -G; CI) 0 7). The vicinity of Gaviota Pass in 0 w -Hx mi''0 o n the western Santa Ynez Mountains iso e 0 a) vi CD .o ' 0 "H H the western limit of the Sespe red m, a' u 0 la_ bed sequence(Vedder and others, m o o'0 , ' o o -H 1969); paralic marine deposition, vi . m,4 .H 0m m m represented by the Alegria Formation m .0 .0 , -.-. ml $.4 rd = X (of Dibblee, 1950), continued to the 0 2 l' west of this area until at least co i c)o44 a u mL° 44 E early Oligocene time (Ingle, 1981; _i_i a) o Howard, 1987). -'wmo m 04w m o o w 4-) m Conformably overlying the Sespe wa.)m 0 -8 m Formation are shallowmarine -H 0 -Q,L) m p 04 u sandstone and conglomerate of the - E--1 .1)m Vaqueros Formation, which markm_... theo a) '-, onset of widespread marine -m 44Eo0 44 it o -1 Nco ... 3-1.0 transgression during the late D c 14-1 m-H .. Oligocene and early Miocene (Vedder E m 4J and others, 1969; Nagle and Parker, s.4 m m'E'M1 73(1.) o,Q0 m 1971; Ingle, 1981; Rigsby, 1989). K4 -H 44 CD 'C' o S' 4.4 m 71 mm .>) --1 o .,, Miles and Rigsby (this volume) and o o w .7-0. o '0 o $.4 .-1 Rigsby and Schwartz(this volume) .15 ..lopm0 o . 0X w x describe the lithostratigraphy and o *, depositionalenvironments ofthe C, ...... 0 w 0-'to 0 .,600 O U) Ili4,)'CS Vaqueros in the Hondo and Capitan 0 , P c CD (1) -H II nj Ti oil fields, respectively (Fig. 7). )-1 (r) > ci)-H Conformably overlying the shallow- 0O .0 njPi > u ..,4W.H '0 marine Vaqueros Formation are deep- cc) cp 4.i )4 -H ,-1 marine basinalrocks, which were o ° c 4--) $-1 cr5 }.4 oe° omLn (f)(0. oo deposited through the Pliocene into - x co 4, -H the Pleistocene, when the marineo°.°0°.. r0 c .N c basins began to fill and 0:0%_o co 0o _a (.)XV)..-1 nonmarine deposits. The Miocenereceiveo and o 6 w m w w .0 f24 (4,-H Xm lower Pliocene deep-marine sequence ° _c c4 04 E consists of claystone and mudstone 5 o 7:5 H E W .1 I-1 )-1 0 4 0 of the Rincon Shale, overlain by m < 44mE-1 u 0 w

Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/3801372/9781565762688_frontmatter.pdf by guest on 30 September 2021 PACIFIC SEA LAND COAST LEVEL Santa Ynez Basin MAMMAL FORAM CURVE Series Ma STAGE 4-O-WEST EAST STAGE Ma O SAUCESIAN Vaqueros Fm.

ARIKAREEAN missing secti°00/000 Magri° Fm - 30 ZEMORRIAN WHaNEYAN -30- o ORELLAN

E missing section CHADRON IAN A leg ria Fm. esloeFrn. REFUGIAN Gaviota Fm. 2 40 DUCHESNEAN-40 Ti NAMDAN Coldwater Fm. WNTAN Sacate Fm. A UctictsFm

FIGURE6. Schematic diagram showing inferred lateral facies relations in the middle Tertiary section from east to west across the Sespe basin (from the Santa Ynez Mountains east through the Los Angeles area), southern California based on marine-nonmarine correlations (T=correlation lines in Figure). From Howard(1987).

phosphatic, calcareous, and siliceous diatomiteand diatomaceous mudstone of the Monterey Formation, in turn overlain by mudstone and diatomaceous mudstone of the Sisquoc Formation (Fig. 4A). These Miocene and lower Pliocene fine-grained deposits are overlain by, and in part interbedded with, deep-seasands of late Miocene, Pliocene, and Pleistocene age (Nagle and Parker,1971). The Neogene sequence, which, including the Vaqueros, is as thick as approximately26,000ft(7,925m) (Vedder and others,1969),is the main emphasis of this workshop, because it contains the most important hydrocarbon source rocks as well as hydrocarbon reservoir rocks of this basin (Nagle and Parker,1971). In this volume are six papers on the fine-grained rocks of the Monterey and Sisquoc Formations including: Bloeser,on depositional rhythmicity and cyclicity of the Monterey in the offshore Santa Maria basin; Bohacs, on sequence stratigraphy in the Monterey of western Santa Barbara County; Dunham and Thornton, on lithology and reservoir quality as a function of sedimentology and diagenesis of the Monterey in the Santa Maria Valley field; Hinman and Schwartz,on the lithologic and diagenetic sequence of the Monterey in the Molino field; Sadler, on the relation of lithology and tectonics to fracturing of the Monterey and Sisquoc in the Point Arguello field;and Henderson and Ramirez, on lithologic variation and petroleum occurrence in the Sisquoc of the Casmalia field.

SANTA MARIA BASINS

In most of the onshore Santa Maria basin, to the north of the Santa Barbara-Ventura basin (Fig. 3),the Paleogene sedimentary sequence is either absent (Figs. 4B, 5) or, where itis present along the basin margins, much thinner than in the Santa Barbara-Ventura basin (Woodring

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36° ONSHORE SANTA MARIA BASIN -41 GUADALUPE offshore SAN MIGUEL Santa Maria onshore -'- - ---. SANTA MARIA VALLEY o Santa Mana CASMAUA ('r 26 CAT CANYON OFFSHORE Santa Barbara-Ventura -ORCUTTIOlplik% SANTA MARIA ',0* IIN 34° BASIN JESUS FOUR DEER ZACA MARIA lift INDEX MAP LOMPOC .." PONT BARHAM RANCH PEDERNALESk LOS ALAMOS a.0' \ON1 BONITOS tcP0!e,. ROCK GO .03 eP°P <0". . 00: - ocz? 5 oe)ov01' - 10. 0 .0** POINT ARGUELLO-6 e 0°V.5\) SACATE.P. OUARfruill v0 w t4,00 ov, SWORD Or COAL )1 Cfr:-. v..N4N.- dIllìHONDO OIL S Nt4 GOVERNMENT ELWOOD alb alp POINT PESCADO POINT alb'"---...... ,0)..\-- NI" PITAS POINT SANTA BARBARA CHANNEL SANTA CLARA v. SANTA ROSA

SOCKEYEgo o 20 Km HUENEME

FIGURE 7. Location of major oil and gas fields of the Santa Maria basins and Santa Barbara-Ventura area.

and Bramlette,1950;Crawford,1971). Paleogene strata also are apparently absent or very thin in the offshore Santa Maria basin (Hoskins and Griffiths, 1971); however, few data on this area have been published.Although the stratigraphic thickness and lithofacies vary within these basins,the stratigraphy of the central Santa Maria district from Woodring and Bramlette (1950)(Fig.4B)is the basis for this discussion. In the Santa Maria basins, the base of the Oligocene(?)-Miocene sequence is represented locally by sandstone and conglomerate of the Lospe Formation (Woodring and Bramlette, 1950).At Point Sal, which is near its type area, the nonmarine and marine Lospe Formation is of early Miocene age (Stanley and others, 1990).Overlying the Lospe Formation are early Miocene deep-marine turbidite sandstones and mudstones of the Point Sal Formation (Woodring and Bramlette, 1950).In the Santa Maria basins the middle Miocene to lower Pliocene deep-marine fine-grained deposits overlying the Point Sal Formation are similar in overall aspect to the age-equivalent sequence in the Santa Barbara-Ventura basin (Fig. 4). However,there are notable differences in thickness,silica

Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/3801372/9781565762688_frontmatter.pdf by guest on 30 September 2021 diagenesis, and lithostratigraphy of the Monterey (Bloeser;Bohacs; Dunham and Thornton;Hinman and Schwartz;and Sadler, allin this volume) and Sisquoc Formations (Henderson and Ramirez, this volume). In addition, the post-Sisquoc section of the Santa Maria basins is vastly different from that of the Santa Barbara-Ventura basin in thickness and lithofacies.

HYDROCARBON OCCURRENCE

The Santa Barbara-Ventura basin has been a highly productive area for petroleum exploration and development (Fig.7). Hydrocarbons have been produced in the province from reservoirs of all ages from Late Cretaceous to Pleistocene (California Division of Oil and Gas,1974). As many as a dozen formations provide multiple exploration prospects, which have stimulated exploration for more than 100 years and may continue to do so for many years to come (Dainty and Woltz, 1984).

In the Santa Barbara-Ventura basin approximately 99 percent of the hydrocarbon production is from the post-Eocene sequence, of which 12 percent is from the Sespe Formation,12 percent is from the lower and middle Miocene section, and approximately 75 percent is from the upper Miocene and younger sequence (Taylor, 1976, Table 2). Thus, hydrocarbon production is predominantly from the Neogenesequence, in which excellent petroleum reservoir and source rocks occur(Taylor,1976). The main hydrocarbon reservoir in the basin isthe Pliocene and Pleistocene Pico Formation in the several giant oil fields of the Rincon trend (Ventura Avenue, San Miguelito, and Rincon)(Fig. 7). However, the Monterey Formation, particularly in the offshore, and the Vaqueros and Sespe/Alegria Formations are also important reservoirs in this basin.

In the Santa Maria basins, compared to the Santa Barbara-Ventura basin, exploration prospects and reservoirs in existing fields are fewer and mainly restricted to the Miocene Monterey Formation (Dainty and Woltz, 1984). The onshore Santa Maria basin has been a productive area for hydrocarbon exploration and development since the early 1900's (Crawford, 1971). Most production is from fractured reservoirs of the Monterey Formation; however, oil has also been produced from the Sisquoc and Point Sal Formations and to a much lesser extent from the Lospe and Knoxville Formations (Woodring and Bramlette, 1950). The offshore Santa Maria basin was actively explored in the early 1980's. During that time, more than a billion barrels of oil were discovered, primarily in fractured reservoirs of the Monterey Formation (McCulloch, 1987).

ACKNOWLEDGMENTS

This paper was greatly improved by helpful discussions with C.M. Isaacs, J. G. Vedder, and R.G. Stanley and by the reviews of C. M. Isaacs, K. J. Bird, and R.J. LeCompte.

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Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/3801372/9781565762688_frontmatter.pdf by guest on 30 September 2021 SANTA BARBARA OJAI OIL FIELD, _ s c;-; po.), FIELD SUMMERLAND RINCON FIELD SOUTH MOUNTAIN FIELD (-4-4brifC-)(CePPC2 VENTURA AVE. FIELD DOS CUADRAS CARPINTERIA

O SATICOY VENTURA FIELD PITAS POINT

VVNIONTALVO , HELD .1 4"» SANTA CLARA FIELD OXNARD FIELD

Platform Gail OXNARD

HUENEME SOCKEYE FIELD FIELD

SANTA CRUZ Cl PLATFORM 44CAPA \S' (:::)OIL OR GAS FIELD .-77:77, OIL FIELD WITH SESPE FM. PRODUCTION

10 MILES

FIGURE 1. Generalized location map for oil and gasfields in the eastern Ventura Basin. The OCS-P-0205 E-1 well was a straight holebeneath Platform Gail.

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