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UNITED STATES DEPARTMENT OF THE INTERIOR

GEOLOGICAL SURVEY

Assessment of undiscovered conventionally recoverable petroleum resources in offshore Tertiary sedimentary basins of The People's Republic of

by

Keith Robinson!/

Open-File Report 84-329

This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards and stratigraphic nomenclature,

1984

^Denver, Colorado CONTENTS

Page

Assessment of energy resources 1 Acknowledgments 1 Introduction 2 Comments 14

ILLUSTRATIONS

Figure 1. Location map showing major Tertiary offshore basins 3 2. Location map of offshore China assessment area and discovery wells 4 3. Northern area, offshore China, undiscovered recoverable oil, Yellow , Subei, Sea, and Taiwan Basins 7 4. Northern area, offshore China, undiscovered recoverable total gas, , Subei, , and Taiwan Basins 8 5. Southern area, offshore China, undiscovered recoverable oil, Pearl River, Beibu , Yinggehai and southeast Hainon-Qiong Basin 9 6. Southern area, offshore China, undiscovered recoverable total gas, Pearl River, Beibu Gulf, Yinggehai and southeast Hainon-Qiong Basin 10 7. Offshore China, aggregate undiscovered recoverable oil 11 8. Offshore China, aggregate undiscovered recoverable total gas 12

TABLES

Table 1. Offshore China fields and discoveries - 2. Assessment of undiscovered conventionally recoverable petroleum resources in offshore Tertiary sedimentary basins of The People's Republic of China 3. Supplementary and comparative data supporting the resource assessment in offshore Tertiary sedimentary basins of China - 13 Assessment of undiscovered conventionally recoverable petroleum resources in offshore Tertiary sedimentary basins of The People's Republic of China

by

Keith Robinson

ASSESSMENT OF ENERGY RESOURCES

This report was prepared as part of the World Energy Resources Program of the U.S. Geological Survey (USGS). The objective of the study is to assess the undiscovered conventionally recoverable resources remaining within petroleum- producing provinces. The study utilizes geological and petroleum engineering data, in conjunction with statistical techniques, to estimate undiscovered resources by a process involving a team of geologists and statisticians. The geologic investigation leading to the assessment was conducted by Keith Robinson. The estimates represent the views of the U.S. Geological Survey estimation team and should not be regarded as an official position of the Department of the Interior.

Other U.S. Geological Survey publications relating to the assessment of undiscovered conventionally recoverable petroleum resources include the following:

Open-File Reports 81-0986 - Basin and Zagros fold belt (Arabian-Iranian Basin) 81-1027 - Volga- Basin 81-1142 - Indonesia 81-1143 - Northeastern Mexico 81-1144 - Southeastern Mexico, northern Guatemala, and Belize 81-1145 - Trinidad 81-1146 - Venezuela 81-1147 - West and Basins, USSR 82-0296 - Middle Caspian Basin, USSR 82-1027 - East Siberian Basin, USSR 82-1056 - North 82-1057 - Timan-Pechora Basin, USSR, and Barents-northern Kara shelf 83-0598 - Northwestern, central, northeastern Africa 83-0801 - Onshore China 84-0094 - Northwest European 84-0158 - New Zealand

ACKNOWLEDGMENTS

The resource assessment for this report was prepared in collaboration with the Resource Appraisal Group of the Branch of Oil and Gas Resources. INTRODUCTION

The location of the major Tertiary offshore basins of The People's Republic of China is shown in figure 1. Figure 2 shows the two areas of assessment, northern and southern, which include, respectively, the North and South Yellow Sea, Subei, East China Sea, and Taiwan Basins; and the Pearl River, Beibu, Yinggehai, and Southeast - Qiong Basins. Figure 2 also shows the location of the natural gas producing region in Taiwan and crude oil discovery wells in the Beibu and Pearl River Basins, together with the unsubstantiated Longjing discovery well in the East China Sea Basin. The discovery wells are identified in table 1, as are the locations, discovery date, type of discovery and status. Table 2 lists estimates by the USGS appraisal group of oil and gas resources for Tertiary sedimentary basins in offshore areas of China, separated into northern and southern and aggregated. Figures 3 through 8 are computer generated graphs showing the probability of occurrence relative to specific amounts of oil and gas resources. Data supplementary to these estimates are given in table 3.

The assessment of undiscovered petroleum resources is confined to areas of Tertiary sedimentation underlying marine territorial waters claimed by The People's Republic of China and restricted to areas with water depths of less than 1,000 meters. This report is not authoritative with respect to the delineation of international maritime boundaries, and those shown are only approximate for the convenience of the assessment. SEDIMENTARY BASINS A. YELLOW SEA BASIN B. SUBEI BASIN C. EAST CHINA SEA- TAIWAN BASIN D. PEARL RIVER'BASIN E. GULF OF - BEIBU BASIN F. YINGGEHAI BASIN G. S. E. HAINAN - QIONG BASIN

MIDLINE COUNTRY BOUNDARY

PEOPLE'S REPUBLIC OF CHINA

> 1 kmThickness (Tertiary sediments) > 3 kmThickness (Tertiary sediments) 1000 m Bathymetric Contour______CHINA OFFSHORE TERTIARY SEDIMENTARY BASINS

BOUNDARIES NOT AUTHORITATIVE Figure 1.--Location map showing major Tertiary offshore basins. PEOPLE'S REPUBLIC OF CHINA

SOUTH AREA

1000 m BATHYMETRIC CONTOUR GAS FIELDS AND DISCOVERIES OIL DISCOVERIES

ASSESSMENT AREA

LOCATION MAP CHINA OFFSHORE AREAS

BOUNDARIES NOT AUTHORITATIVE Figure 2.--Location map of offshore China assessment area and discovery wells, Table 1. Offshore China fields and discoveries

Number Field name or Discovery Type field (see fig. 2) discovery well Location date or discovery Status

1 Wan Beibu Gulf 1977 Oil Shut in

2 Wushi do 1981 do Do

Pearl River 3 Zhu 5 Basin 1979 do Do

Ying 9 Yinggehai Basin 1981? do Do

All Taiwan oil, gas 4 fields Taiwan 1904-81 and condensate Producing

5 Longjing East China Sea 1981 Oil? ? Table 2. Assessment of undiscovered conventionally recoverable petroleum resources in offshore Tertiary sedimentary basins of The People's Republic of China.

Resource assessment by USGS as of Feb. 17, 1983; see also figures 3 through 8.

Natural gas Crude oil in trillions of cubic feet (Tcf) in billions of barrels and billions of barrels of oil (BB) equivalent (BBOE) @ 6,000 cuft/bbl,

Region Low High Mean Low High Mean

Northern Area

North Yellow Sea, Subei-South Yellow Sea, East China Sea, and Taiwan Basin 0.33 5.00 2.05 Tcf 3.45 43.36 19.43

BBOE 0.58 7.23 3.24

Southern Area

Pearl River, Beibu Gulf, Yinggehai, and S.E. Hainan-Qiong Basins of Sea and 2.10 15.80 7.85 Tcf 10.73 83.27 40.99

BBOE 1.79 13.88 6.83

Total of offshore China provinces:.?/

3.46 20.97 9.90 Tcf 21.25 127.64 60.42

BBOE 3.54 21.27 10.07

1?95 denotes the 95th fractile; the probability of more than the amount is 95 percent. F5 is defined similarly.

_2/ Totals are derived by statistical aggregation; only the mean total equals the sum of the component parts . O Assessment date - Feb. 17, 1983 «p 1

2: ESTI MflTES EE"Q£ ^ MERN - 2.05 I-« o \ MEOIflN - 1.69 LJ 95X. 0.33 i»-or \ 75X 0.98 1.69 o \ 50X L_ 25X 2.70 O 5X 5.00 £V MODE - 1. 10 \ S.O. 1.56 PROBflBILI \ 0.00.20 1 ,,<,., \ V ^ ^ . - - . " . II »l 0.0 1.2 2.4 3.6 -1.8 6.0 7.2 8. 4 9,6 10.8 12-0 BILLION BflRRELS RECOVERflBLE OIL

Figure 3.- Northern area, Offshore China, undiscovered recoverable oil, Yellow Sea, Subei, East China Sea, and Taiwan Basins. RSSESSMCNT DflTE » FEB 17, 1983 o _ IflTES" ~z. ESTII ccin ««-, - MEflN 19.43 E-. o~ \ MEDIRN - 17.08 LJ 95X 3.45 g»-C£ 75X 10.40 17.08 o BOX CO L- 25X 25.83 0 \ 5X 43.36 £ < " \ 12.91 f-« _ \ MODE - ^-i 0 S.D. 12.74 _J » i CO CC rsi " CD ^!~ \ s. 0 ° oc: Q_ ^ 0 . ^- _

o - . 0.0 9.0 18.0 27.0 36.0 45.0 54.0 63.0 72.0 81.0 90.0 TRILLION CUBIC FEET RECOVERflBLE GflS

Figure 4.--Northern area, offshore China, undiscovered recoverable total gas, Yellow Sea, Subei, East China Sea, and Taiwan Basins. RSSESSMENT DfVIE i FEB 17, 1983 O

:zr ^ ESTI MflTES DC m. ' MEflN 7.85 f-« o \ MEDIflN - 7.20 LJ 95X 2.10 §«-o: 75X. 4.78 \l 507. 7.20 o LL. 25X 10.20 O 5X 15.80 MODE 6.00 »-« 0 S.D. 4.29 _J \\ 1 1 CO CC CM * GO 0 ° \ Q_ ^- o' . ^__ o -^- . 0.0 3.0 6.0 9.0 12.0 15.0 18.0 21.0 21.0 27.0 30.0 BILLION BRRRELS RECOVERflBLE OIL

Figure 5.--Southern area, offshore China, undiscovered recoverable oil, Pearl River, Beibu Gulf, Yinggehai and southeast Hainon-Qiong Basin. RSSESSMENT DHTE » FEB 17, 1983 o WES ' ^ ESTII l» : MEflN 40.99 h-« o~ \ MEDIflN - 37.45 LJ 95X 10.73 g«rC£ \ 75X 24.73 o \ 50X. 37.45 LL. 25X 53.31 0 5X 83.27 ^~* ^« fr-* _ MODE - 30.91 ^-* 0 \\ S.D. 22.79 _J i « 00 01 CM ' CD - 0 ° ^v C£ CL o . ^^~~-~_

o_ ~ 0.0 15.0 30.0 45.0 60.0 75.0 90.0 105.0 120.0 135.0 150.0 TRILLION CUBIC FEET RECOVERRBLE 6RS

Figure 6.--Southern area, offshore China, undiscovered recoverable total gas, Pearl River, Beibu Gulf, Yinggehai and southeast Hainon-Qiong Basin. flSSESSMENT DflTE i FEB 17, 1983

\ ESTI MflTES MEflN 9.90 1C f-« o \ MEDIflN - 8.52 OJ 957. 3.46 757. 5.89 0 507. 8.52 OP \ 257. 12.33 \ 57. 20.97 £-. \ MODE 6.32 i o S.D. 5.85 _] « orOO oj go oc: OL ^" ^-^ o ~ o. " - ... , 0.0 4.5 9.0 13.5 18.0 22.5 27.0 31.5 36.0 40.5 45.0 BILLION BflRRELS RECOVERflBLE OIL

Figure 7.--Offshore China, aggregate undiscovered recoverable oil. RSSESSMENT DRTE i FEB 17, 1983 o

w 4 ESTII 1FITES \ MERN 60.41 f^ MEDIflN - 52.08 LJ 95X 21.25 or 75X 36.06 tjp 50X 52.08 0 \ 25X 75.21 O 5X 127.64 MODE 38.69 CD \ S.D. 35.53 enGO QQ \ O CD N 0_ 0 . ^ ^- O... . 0.0 30.0 60.0 90.0 120.0 150.0 180.0 210.0 240.0 270.0 300.0 TRILLION CUBIC FEET RECOVERRBLE GflS

Figure 8.--Offshore China, aggregate undiscovered recoverable total gas. Table 3. Supplementary and comparative data supporting the resource assessment in offshore Tertiary sedimentary basins of ChinaA'

Crude oil Natural gas (BB) (Tcf) Cumulative production to 1/83

Northern Area North Yellow Sea, Subei-South Yellow Sea, East China Sea, and Taiwan Basin 0.018 I/ + £3/

Southern Area Pearl River, Beibu Gulf, Yinggehai, and S.E. Hainan-Qiong Basins of and Gulf of Tonkin

Subtotal 0.018 1.0+ (est.)

Measures reserves to 1/83

Northern Area North Yellow Sea, Subei-South Yellow Sea, East China Sea, and Taiwan Basins 0.008 0.7

Southern Area Pearl River, Beibu Gulf, Yinggehai, and S.E. Hainan-Qiong Basins of South China Sea and Gulf of Tonkin 3/ 3/

Subtotal 0.008+ 0.7+

Undiscovered Resources (mean) Northern Area 2.05 19.43 Southern Area 7.85 40.99

Original recoverable Resources (or Total).!/ 10.00 62.00

_L/ Cumulative production and reserves are composited estimates from various sources,

_2/ Mostly condensate in Taiwan, minor Subei Basin crude oil.

2J Quantity positive, but data unavailable. Total estimate, this paper.

ZJ Does not include an estimate of inferred reserves.

13 COMMENTS

Offshore Tertiary sedimentary basins of China can be classified as continental rifted basins. Fault block, horst and graben structures form the traps for most oil and gas fields. The fault blocks also controlled Paleogene sedimentation. Environments of deposition were mainly nonmarine, fluvio-deltaic to lacustrine, with occasional incursions of coastal plain and brackish marine sediments.

Commercial discoveries of crude oil, natural gas, and condensate have been made in the Pearl River, Yinggehai, Beibu, Taiwan, and Subie-South " Yellow Sea Basins. The Longjing discovery well drilled in the East China Sea has not been substantiated. Relatively very few exploratory wells have been drilled in any of the basins, and information is scant.

Adequate maturation may be a problem in the Yellow Sea region; geothermal gradients appear to be low, generally less than 2 F/100'. Adequate source rock, reservoir rock, and maturation may be problems in the East China Sea.

In the Beibu Gulf, northwest of Hainan Island, thick sequences of nonmarine Eocene-Oligocene sediments are restricted to the deeper grabens. In this region Neogene sediments are generally less than 1 kilometer thick.

In the Pearl River Basin, the main source, reservoir, and sealing rocks are thought to be of Oligocene to early Miocene age. Lower Paleogene oil shales have been rated as having excellent source potential, but thermal maturity may be a problem. The top of the oil generating section has been put at 8,500 feet. Oil possibly migrated laterally from adjacent deep synclines.

If future discoveries of petroleum are confined to the deeper graben areas, the assessed mean estimate of 7.1 billion barrels undiscovered recoverable crude oil for the South China Sea and Beibu Gulf may be too high. A resource assessment of the area, by the author, based on a play analysis approach and assuming oil restricted to the deeper grabens with more than 2 kilometers of Tertiary sedimentary section, suggests 4 billion barrels of undiscovered recoverable crude oil.

14