IATMI sedang mengadakan worshop carbonate complexity : characterization,
modeling and simulation di Yogyakarta dari 22-25 April 2008. Workshop dihadiri
sekitar 80 orang dari berbagai institusi pemerintah, oil companies, service
companies, dan perguruan tinggi.
Workshop didahului oleh kursus satu hari tentang aspek geologi dan reservoir
engineering karbonat dibawakan oleh Alit Ascaria (Premier Oil) dan Doddy
Abdassah (ITB).
Workshop dibuka pada 23 April 2008 oleh Ketua IATMI Kuswo Wahyono,
dilanjutkan dengan pidato sambutan oleh John Sinulingga mewakili Pertamina
Eksploitasi (panitia workshop adalah IATMI Komda Cirebon Pertamina), dan
pidato/presentasi kunci dari Handoyo Eko Wahono (BPMIGAS) tentang
lapangan-lapangan karbonat yang dikembangkan dalam lima tahun terakhir, Bob
Yulian (BPMIGAS) tentang kemajuan eksplorasi target karbonat di Indonesia, dan
Gatot Kariyoso Wiroyudo (Shell) tentang investasi teknologi Shell dalam
mengerjakan karbonat.
Makalah teknis yang dipresentasikan sebanyak 16 makalah. Workshop diselingi
dengan fieldtrip ke Gunung Kidul mengunjungi singkapan karbonat Wonosari.
Pembicara mendapatkan kesempatan berbicara cukup tenang karena waktu yang
diberikan antara 20-30 menit, pertanyaan 5-10 menit. Workshop ini jelas
bermanfaat menambah wawasan aspek GGRE karbonat. Karbonat merupakan objektif
sangat penting karena menyusun sekitar 50 % reservoir lapangan2 produksi di
Indonesia. Bahkan dalam lima tahun terakhir, 54 % recoverable reserve
lapangan-lapangan baru berasal dari reservoir karbonat, maka karbonat tak
kalah penting dari reservoir silisiklastik, bahkan bisa lebih.
Saya diundang IATMI berkontribusi makalah tentang geologi regional karbonat
di Indonesia. Di bawah ini adalah abstraknya, semoga berguna.
Mahasiswa tidak banyak yang hadir. Karena merasa ada yang kurang kalau saya
hanya mempresentasikan makalah saya kepada para profesional di workshop, maka
pada hari yang sama saya ke UGM dan mempresentasikan materi yang sama di
hadapan para mahasiswa tetapi dalam format penyampaian kepada mahasiswa.
Setelah itu, masih di UGM, saya melanjutkan mempresentasikan makalah
Sandhyakala ning Jenggala dan Majapahit : Hipotesis Kebencanaan Geologi
kali ini jauh lebih tenang tak seperti saat mempresentasikan makalah ini di PIT
IAGI 2007 Bali yang mesti berpacu dengan waktu yang terbatas. Waktu yang
terbatas atau terburu2 akan menyulitkan pendengar mencerna materi yang
disampaikan. Sebagai informasi, hipotesis ini telah ditangkap National
Geographic Channel untuk menjadi tayangan (pengambilan gambar sudah dilalukan)
di dalam film dokumenter LUSI.
Demikian, laporan singkat.
awang Grand Mercure 24/4/2008, 02.15
LAMPIRAN
Geologic Controls on Carbonate Reservoirs in Indonesia :
Regional Overview
Awang Harun Satyana
(BPMIGAS)
Carbonate reservoirs are characterized by extreme heterogeneity of porosity
and permeability. This is related to the complexities of the original
depositional environment and the diagenetic influences that can modify the
original textures. Wide variety of environmental facies and diagenetic changes
express controls of geologic factors. Therefore, in characterizing carbonate
reservoirs, it is important to evaluate geologic controls which influence
carbonate sedimentation and diagenesis.
Being located at warm humid tropical shallow water, in Indonesia carbonates
are geographically and temporally widespread. They occur in a range of ages and
depositional settings which were often affected by coeval tectonism,
siliciclastic input or volcanism. The carbonates developed in various tectonic
settings of back-arc, intra-arc, fore-arc, and foreland basins; island arc;
micro-continents; and continental passive margins. They developed as patch
reefs of land-attached platform such as Baturaja buildups in South Sumatra and
West Java, fringing reefs such as Kais buildups on Arar High, the Birds Head
of Papua, barrier reefs such as Ujung Pangkah reefs in East Java, and pinnacle
reefs overlying offshore isolated platforms such as reefs of the Cepu High,
East Java and Arun reefs in North Sumatra. In each a variety of carbonate
depositional systems, the reefs often developed on structural highs.
Subsidence, uplift, active faulting, tilting or associated
silici/volcaniclastic input strongly affected facies variability,
stratal/platform geometries, sequence development and carbonate termination.
These geologic factors influence distribution and continuity of the carbonate
reservoirs.
Ages of carbonates influence the basic ingredients of carbonates. Diversity,
abundance, dominant mineralogy, and relative importance of sediment-producing
marine invertebrates are various through the geologic periods. This will
influence the response of carbonates when they are changed by diagenesis.
Producing carbonate reservoirs in Indonesia range in ages from the Jurassic
Manusela fractured oolitic carbonates in Seram Island, Eastern Indonesia to
Pliocene globigerinid limestones of the Madura Strait. Paleogene carbonates in
Indonesia are commonly dominated by larger foraminifera. These carbonates
typically form large-scale platforms or isolated shoals. Good poroperms can be
preserved in shoal or redeposited carbonates lacking micrite. Secondary
porosities developed due to fracturing, chemical dissolution during burial, or
as karstic cavities. However, the opportunities for leaching were limited.
Neogene carbonates often contain abundant aragonitic bioclasts, such as
corals. They typically develop as reefal buildups, shelfal deposits or as
isolated platforms. Compared with Paleogene carbonates, poroperms are generally
higher in Neogene carbonates, various porosities all occur. The most important,
common and economic carbonate reservoirs in Indonesia are the Miocene buildups
such as Arun in North Sumatra, Baturaja in South Sumatra and West Java, Kujung
I or Prupuh in East Java, and Kais in Salawati, Papua.
Petrographic studies of carbonate reservoirs in Indonesia have shown that
they have been subjected to a number of diagenetic processes including
compaction (stylolization), dissolution, cementation, neomorphism,
silicification, dolomitization and fracturing. Most of these processes are
common to all depositional facies types (reefal, near reef, shallow shelf and
outer shelf open marine). Original particle types of the sediments inherited
from the deposition play an important role in this respect. Interconnected
corallites commonly suffer dissolution resulting in porosities. Neomorphism is
especially common in micritic carbonates reducing their porosities.
Dolomitization has a varied distribution and in many cases is associated with
clay minerals. It may affect reservoir poroperms and be a factor in generation
of undesirable non-hydrocarbon gases. Stylolization and silicification are
localized features. Study of sequence of diagenetic events is important for
knowing the
preservation or occlusion of porosities.
An understanding of the geologic controls on carbonate depositional
environments, spatial and temporal facies distributions and controls on
deposition and diagenesis is essential in order to characterize carbonate
reservoirs and to evaluate their considerable economic potential.***
---------------------------------
Be a better friend, newshound, and know-it-all with Yahoo! Mobile. Try it now.
