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Tarim Basin 50 years of
exploration in
It has been 50 years
since
the first oil and gas discovery was made, yet much of China’s Tarim
Basin is
still a petroleum frontier. Fewer than 1,000 exploration wells have
been
drilled despite the discovery of seven fields each with recoverable
reserves of
500-3,000 million boe. The great size and remoteness of the basin
contribute to
its under-exploration. It covers 216,000 sq mi, or about 80% of the
area of
Texas, and is located almost 2,000 mi from Beijing in extreme western
China
bordering Kazakhstan, Kyrgyzstan and Tajikistan (see figure). The main
reason
for limited drilling, however, is that exploration has not been opened
for
international participation except during limited periods of time and
under restrictive
operating agreements.
The Tarim Basin has
a
world-class petroleum system with a resource potential of 78 billion
bbl of oil
and 296 Tcfg. Every interval from Cambrian to Holocene is charged
except
Devonian and Triassic. Rich source rocks are found within Cambrian,
Ordovician,
Permian, Jurassic and Triassic strata, and seven active petroleum
sub-systems
have been identified. Ordovician carbonate, Carboniferous clastic, and
Cretaceous and Tertiary clastic reservoirs are the chief producing
intervals.
Most oil fields are concentrated in the northern part of the basin on
the Tabei
uplift and in the Kuqa fold belt (pronounced “koo-cha”), though the
super-giant
Tazhong Field Complex is located on the Central uplift.
The tectonic and
stratigraphic evolution of the basin was complex. In the early
Paleozoic epoch,
the Tarim Block was probably separate from Pangaea. As much as 10,000
ft of
mostly shallow marine and coastal plain strata accumulated during the
Cambrian
and Ordovician. Ordovician platform carbonates and dolomitized shallow
water
successions comprise the most important petroleum reservoirs today.
Late
Ordovician uplift resulted in widespread exposure of the platform. Deep
erosional valleys and canyons formed, with as much as 6,000 ft of
relief, and
were later filled with clastic sequences. Karsting, erosion and
subsequent fill
produced classic buried hill and complex stratigraphic traps that
account for
most of the petroleum accumulations in the basin in combination
structural-stratigraphic traps.
Platform carbonate
deposition in the Carboniferous was interrupted during the Late
Paleozoic
Orogeny when the Tarim Block and Tian Shan Block to the north
converged. Marine
sequences were uplifted, and deep paleosols formed across the basin.
Eolian and
shallow marine tidal and shoreface sands of the Donghe Sandstone
were
deposited. The Donghe Sandstone is the other important Paleozoic
reservoir in the
Tarim.
During the Triassic
and
Cretaceous periods, convergence from both north and south resulted in
foredeeps
(northern and southern depressions) on both margins of the basin
separated by a
broad flexural arch (Central uplift). These foreland basins were
dominated by
nonmarine clastics shed off the adjacent highlands. The middle Tertiary
collision of India and Eurasia produced compression and strike-slip
faulting
that formed many of the structural traps in the Kuqa fold belt, and on
the
Tabei and Central uplifts. Continental deposits continued to dominate
the basin
fill, and reservoir intervals at Dina, Kela and Dabei Fields in the
Kuqa fold
belt consist of both Cretaceous and Tertiary nonmarine
sandstones.
About 8.5 billion
bbl of
oil and 30 Tcf of gas have been produced to date, and the five largest
fields
have been discovered in the last 10 years. Regional seismic data was
first
acquired in 1983. Many discoveries were made in Ordovician carbonate
and
Carboniferous clastic reservoirs, including the Tazhong (1,465 MMboe,
1989) and
Tahe (3,300 MMboe, 1998). More recent exploration in the Kuqa fold belt
resulted in gas discoveries at Dina (2,474 MMboe, 2001) Kela (1,564
MMboe,
2004) and Dabei (813 MMboe, 2007). The 2,600-mi West-to-East Pipeline
now carries
Kuqa gas to Shanghai on the east coast of China.
I have worked on
projects
in the Tarim Basin since 2005, and visited the basin most recently this
May. I
have great respect for the strong technical approach that PetroChina
and
Sinopec employ as they continue to explore Tarim. In addition to using
all
available seismic and subsurface technology, their E&P teams are
involved
in rigorous programs of field geology and core interpretation. Two
companies,
however, cannot effectively evaluate and explore a basin as large and
geologically complex as the Tarim.
Beginning in 1993,
licensing rounds were held and several international companies
evaluated tracts
in the basin. While work programs were executed by foreign companies,
offered
tracts had low exploration potential, and licensing agreements were
restrictive. After a few years, most companies exited. Again in 2006, a
licensing offer was announced, and several international
companies purchased
data packages, but bid rounds never occurred.
Competition is
critical to
ensure the efficient development of petroleum resources, and Tarim is
no
exception. Vast areas are only slightly deformed, and stratigraphic
emphasis
will be critical. The number of seismic and drilling programs must be
greatly
expanded to meet China’s need for oil and gas. I do not understand why
China
doesn’t encourage more aggressive exploration and development in its
own
highest-potential basin by inviting competition from foreign companies.
IHS
provided data about
Tarim Basin plays, petroleum system, and exploration history. IHS’s
ongoing
support of this column is greatly appreciated.
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Major Oil
Fields
The
Daqing
Oil Field
Situated in a large plateau
between the Songhua
River
and Nunjiang River in Heilongjiang Province, the Daqing Oil Field is
the
largest comprehensive oil production base in China. It is also among
the
largest oil fields the world over. It was put into operation in May of
1960, soon producing two-thirds of the national total. By 1976,
the
output of its crude oil reached 50.3 million tons making it one of the
10 largest oil fields in the world. Since then on, it has well
maintained
an output of crude oil standing at 50 million tons or more. Statistics
show that Daqing's proven recoverable reserves exceed 5.3 billion tons,
and it has produced crude oil of 1.405 billion tons, accounting for
47.2
percent of the national total.
The
Shengli Oil Field
Situated in the Yellow River delta in
the north
section
of Shandong Province and on the shore of the Bohai Sea, the Shengli Oil
Field began to produce oil in 1962, serving as an important base of
oil
industry in east China. By 1993, its output of oil accounted for
one-fifth
of China's total thus becoming the second largest oil field in the
country.
The
Liaohe Oil Field
The Liaohe Oil Field, the third
largest oil
field in
China, is situated in the lower reaches of the Liaohe River. It began
to
produce oil in the 1960s. The proven recoverable reserves is over 90
million
tons and its controlled-reserves exceeds 100 millions tons.
The
Dagang Oil Field is located in the Bohai
New Area
about 50 km to the southeast of Tianjin city. It is the only land-based
oil gas field of large-scale in the coast region and under the
jurisdiction
of a large city. Discovered in 1966, the field was found to occupy a
total
land of 18,600 square km, with the proven reserves of oil being 725
million
tons and natural gas 28.719 billion cubic meters.
The Huabei (North China) Oil Field
The Huabei Oil Field is the first
buried-hill
oil field
discovered in China. Located in a plateau in the central section of
Hebei
Province, it was found in 1975.
The
Jidong
(East Hebei) Oil Field
The Jidong Oil Field is located in
the east
part of Hebei
Province, adjacent to Tangshan City. It is an offshore oil field, of
which
the industrial prospecting began in 1978.
The
Zhongyuan Oil
Field
Located in a place bounded on the
north by
Shandong and
south by Henan Province, the field was found in 1975. It has maintained
an annual output of about 4 million tons.
The Tarim
Oil Field
The China National Petroleum
Corporation (CNPC)
began
the prospecting of the Tarim Basin in April of 1989. In all nine
integrated
oil fields were found with 26 structures containing oil and gas.
Production
began since 1990. By 1996, the proven reserves of oil gas came to over
400 million tons including natural gas being 206.2 billion cubic
meters.
The
Turpan-Hami
Oil Field
Located in the Turpan-Hami Basin, the
field
occupies
a land totaling 53,000 square km, which is of great strategic
importance
for development of China's oil industry. By 1997, 14 oil gas fields
had
been discovered there with the proven reserves being 220 million
tons.
The
Cainan Oil Field
Right within the
Kurban-Tonggute desert in the
Junggar
Basin, the Cainan Oil Field is the first integrated oil field found in
a desert in China. It was discovered in 1991 and put into operation in
1995. The annual output has reached 1.483 million tons.
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Major Gas Fields
The
Sichuan Oil
Gas Field
Located in the central section of
Sichuan
Province, it
is the largest natural gas production base in China. Prospecting was
begun
as early as in 1953. Its annual output of natural gas ranks first
among the 21 fields of this kind throughout the country.
The
Datianchi Gas
Field
Located in the east section of
Sichuan
Province, the
field is the third largest in China. Its geological structure falls
into
three gas layers with a total length of 200 km and width of 20 km. Its
proven reserves are over 50 billion cubic meters. It is expected its
annual
output will come to 3 billion cubic meters by 2000.
The
Changqing Gas
Field
Located in the northwestern China's
Erdous
Basin (Ordos),
the field is the largest integrated land-based gas field, being one of
the 115 large gas fields in the world. Entering its development stage
in
1995 it produced crude oil of 3.3 million tons in 1997. The
proven
reserves of natural gas is 300 billion cubic meters.
The
Offshore Oil Gas Fields in the Bohai Sea
The Suizhong 36-1 Oil Field is
located in the
Liaodong
Bay, about 50 km to the west of Suizhong County in Liaoning Province. A
large offshore oil field, it has a proven reserve being 300 million
tons.
The field was put into operation in 1995. The Chengbei Oil Field is in
the southwest part of the Bohai Sea. Put into operation in 1986, it is
the first Chinese-Japanese joint venture in this regard. The
Qinhuangdao
32-6 Oil Field is situated in the central part of the Bohai Sea. Found
in 1995, it has a proven reserve of 200 million tons.
The
Offshore Oil Gas Fields in the East China Sea
The Pinghu Oil-Gas Field
is situated on the
continental
shelf of the East China Sea, about 420 km away from Shanghai. It is the
first combined oil gas field with the natural gas being its main
product,
which was found and put into operation in the East China Sea. The
construction
work began in November 1996 and finished in the end of 1998. After
being
put into operation, the field has been providing quality natural gas of
1.2 million cubic meters for users in the Pudong New Area of Shanghai
each
day.
The
Offshore Oil Gas Fields in the South China Sea
The
Liuhua 11-1 Field is situated in the
29/04 cooperation
area, about 220 km away from Hong Kong. Jointly developed by China
Offshore
Petroleum Nanhai East Company and Amoco Oil Company of the United
States,
the cooperation area totals 317 square km with the controlled reserves
being 233 million tons. As the largest known offshore oil field in
China,
its construction was completed in March 1996. The output comes to 1.68
million tons annually during the rush period.
The
Fanyu 4-2 Oil Field was found in a basin
located in
the east part of the South China Sea in May 1998. Developed by the
American
Santa Fei Energy Resources Co. Ltd., it has been tested to have a
capacity to produce oil of 1,102 tons per day. It is estimated that the
recoverable reserves of the field stand at 20 million tons.
The
Yinggehai Yacheng 13-1 Natural Gas Field
is situated
in the meeting place of the Yinggehai Basin and Qiongnan Basin, about
96
km to the south of Sanya City, Hainan Province. Totaling 53.58
square
km, it is the largest offshore field of natural gas now found in China.
With a proven reserves of 96.8 billion cubic meters and the
production
capacity of 3.45 billion cubic meters per year, it is estimated to
maintain
a stable production for twenty years. Jointly developed by Chinese
and American corporations, it was put into operation in January 1996
and
has
supplied the Hong Kong Special Administrative Region with natural gas
of
2.9 billion cubic meters per year since then on. The contract period of
the field is twenty years. Since it began operation, the field has
supplied
Hainan Province with natural gas of 550 million cubic meters per
year.
The
Dongfang 1-1 Gas Field is also located
in the Yinggehai
Basin, having an area with natural gas totaling 229.6 square km. Found
in 1995, it is the second largest offshore gas field in China, with a
proven
reserves of 80.1 billion cubic meters.
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