Kang OQ ada 2 web yg bagus aku dapet dr website :
Keduanya berbeda melihat compaction factor dari Coal ini karena "awal" dari
pembentukan coal ini mungkin berbeda ... ada yang 10: 1 ada yang 20:1 ...
Bedanya mungkin apakah diawali dari "peat" (gambut) atau sejak masih beripa
nipah2 (rawa) ?
Saya sendiri yakin..... coal compaction ini sangat tidak linier jadi "rumus
jempol" nya musti pake jempol tangan dan jempol kaki juga :( ... rumit dah
... :p, karena semakin dalam (burial/+tekanan) akan terjadi proses kimiawi
juga yg berbeda dalam masing-2 tahapan coal rank.
Kalo soal compaction factor utk sand-shale (+ carbonate ?)... aku yakin pak
Koesoema punya rumus di software yg beliau kembangkan ... Mungkin udah ada
lisensinya (?) ....
Kalo utk Coal ini aku yakin men-temen Coal Miners lebih banyak nguplek soal
ini ...
gimana friends ?
RDP
" masih mencari analoque lowstand wedge reservoir ... :(("
===
http://www.fcii.arizona.edu/poulton/nats101/CourseContent/Mineral/t2e2.html
Energy Minerals
Coal
Coal does not fit our definition of a mineral since it forms from organic
processes. We do still consider coal to be an earth resource. Coal is
divided into five categories based on the energy content: peat, lignite,
sub-bituminous, bituminous, and anthracite. The table below represents the
classification, or rank, based on percentage of carbon, amount of gasses,
and the amount of water present.
Rank % Carbon % Gasses % Water
Peat 60 >60 75
Lignite 71 52 30
Sub-bituminous 80 40 5
Bituminous 91 14 1
Anthracite 95 2 2
Peat forms in mires or swamps where the ground water is acidic. Decaying
plant material accumulates close to the place of growth in a pile called a
"catotelm". The catotelm is a big mound of both decaying and growing
vegetation that is always waterlogged. There is little or no oxygen at the
base of the catotelm. The top of the catotlem is where most of the living
vegetation is and this is called the "acrotelm". The acrotelm contains
larges amounts of bacteria and fungi which help convert the plant material
to peat. Peat can accumulate at a rate of about 0.1 - 2 mm / year, depending
on the climate. If the peat to coal compaction ratio is about 10:1 then a 1
mm coal seam can represent anywhere from 4 to 100 years of peat
accumulation.
As the peat accumulates it eventually becomes buried and compressed and
starts the coalification process. The peat is first converted to lignite. As
part of the process, volatile gasses and water are squeezed from the peat.
As more and more of the water and gas are squeezed from the coal we get
sub-bituminous, bituminous, and finally anthracite. The coalification
process is partly biochemical and partly physico-chemical. As peat forms
lignite and lignite forms sub-bituminous coal, hydrocarbons are removed from
plant tissue, leaving material rich in oxygen and carbon. Humic acid forms
which can completely decompose the plant leaving only water and carbon
dioxide. Once buried, no oxygen is present and anaerobic (lack of oxygen)
bacteria operate on the material.
============ cut ===========
http://gsa.confex.com/gsa/2001AM/finalprogram/abstract_26215.htm
Paper No. 23-0
THE COALIFICATION PHASE OF COAL SYSTEMS
CECIL, C. Blaine, DULONG, Frank T., and NEUZIL, Sandra G., MS 956, U.S. Geol
Survey, Reston, VA 20192, [EMAIL PROTECTED]
The coalification phase of coal systems (transformation of peat to coal)
results in significant physical reduction in volume and loss of water and
organic matter. Modern peat deposits that could result in commercial grade
coal generally form in oligotrophic (nutrient poor) environments that are
free of detrital sediment influx. Oligotrophic peat-forming environments
primarily are acid (pH < 5) and, as a result, microbial degradation is
highly restricted. Oligotrophic peat (OP) is well preserved (fibric > humic
>>> sapric) and consists of 90% moisture, 9% organic matter, and up to 1%
mineral matter (by weight). Well preserved wood also may be an important
constituent. Alkaline and alkaline earth elements, Fe, and S, only occur in
minor to trace quantities because of the absence of any significant source
of these elements. Acid leaching may further reduce available alkaline and
alkaline earth elements. The mineral matter in oligotrophic peat, therefore,
is primarily composed of relatively insoluble compounds of Si and Al that
are precursors to quartz and kaolinite. Significant amounts of Fe and S may
be incorporated as pyrite during and after burial.
The transformation of OP to lignite (~ 30% moisture) is primarily the result
of burial compaction and expulsion of pore water that results in a volume
loss of 70 percent. Experimental data indicate that further compaction and
thermal coalification result in additional loss of pore water and loss of
organic matter in the form of CO2, CH4, H2O, and N2. Calculations based on
the chemical composition of oligotrophic peat and medium volatile bituminous
coal (MVBC) indicate that 50% of the original organic matter and > 99% of
the original pore water is lost during transformation of OP to MVBC. The
coalification processes results in a compaction ratio of 20:1 for OP peat.
As a consequence of compaction and coalification, a mineral matter content
of 10 % in OP (dry weight basis) will be increased to 18 % in MVBC, assuming
that silicate and other mineral matter is neither added nor lost.
Experimental results and calculations indicate that most of the bituminous
coal mined in the world today has undergone a 20:1 compaction and is derived
from peat whose mineral matter content (dry weight basis) was < 10 percent.
----- Original Message -----
From: <[EMAIL PROTECTED]>
>
> Boss Oki,
> First of all, ditangan saya sekarang memang tidak ada referensi yang
> published tentang itu.
>
> Utk shale, 'rule of thumb' yang biasanya dipakai adalah 1 : 3, dalam arti
> kalau shale tsb diendapkan
> setebal 3m, maka yang akan kita jumpai setelah compaction adalah sekitar 1
> m. Saya selalu mendapatkan
> ratio ini jika berdiskusi dengan lain-lain orang.
>
> Utk coal, saya mendapatkan ratio yang menurut saya agak surprise, yaitu
95%
> - 98% !!
> Jadi kalau coal tsb setebal 10m sewaktu diendapkan , maka yang kita jumpai
> di subsurface
> adalah tinggal 1 meter !!!
> Utk masalah coal ini menurut saya 'looks reasonable', kalau kita melihat
> Mahakam Delta. Dari begitu banyak
> nipa-nipa palm dlsb, sewaktu kita shallow coring di Mahakam Delta,
> kebanyakan coal yang kita jumpai tidaklah
> tebal-tebal amat, kalau dibandingkan sourcenya yang begitu 'abundant'.
> Apalagi di Mahakam, seingat saya
> dari shallow coring tsb, kebanyakan coal ini berasosiasi dengan sand.
> Kalaupun dijumpai coal yang agak tebal ~30 cm,
> coal tsb masih banyak mengandung air dan belum terbentuk menjadi semacam
> layering tipis-tipis yang sering kita jumpai
> dari core maupun outcrop..........., dalam arti coal tsb belumlah
> ter'kompaksi' secara lanjut. Mungkin kalau di'compress'
> lagi, akan tinggal bbrp cm saja...........
>
> Sorry boss, not clear enough, but hopes it will help.
>
> Salam,
> Teguh
>
>
>
>
> "Musakti, Oki"
>
> Friends,
> Ada yang punya gambaran nggak, berapa range (I know it will be varied
> under different circumstances, but a guideline is better than nothing at
> all) dari bermacam-macam batuan sediment terutama sandstone, shale dan
> coal.
> Maksudnya, kalau kita menemukan 10 ft coal saat ini, berapa kira-kira
> ketebalannya pada saat pengendapan.
>
> Kalau lebih specific lagi, lingkungan pengendapannya adalah
> fluvio-deltaic, waktu pengendapan Permian dan sedikit ada pengaruh
> glasiasi.
>
> Ditunggu pencerahan dan atau pointernya...
>
> Trims
>
> Oki
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