Karibu msomaji wa Petroleum field ambapo  today I am going to share with you Asili ya mafuta na Gesi (origin of Petroleu).

Where does Petroleum Come from? (Nini asili ya Mafuta na gesi)

Well,  Kabla hatujaua jinsi mafuta na gesi yanavyotengenezwa lets  discribe the word Petroleum its self.

Karne kadhaa zilizopita Rock outcrop kwenye  uso wa Dunia ilikuwa ikizalisha mafuta.na hayo mafuta yaliitwa Oil Rock because oil was seep out the rock itself

 Kati kati mwa Karne ya 19 watafiti walikuja na idea mpya mbapo walisema, Neno Petroleum Linatokana  na maneno mawili neno la kigiriki Petro ambalo mana yake kwa kingereza ni Rock, na Neno Leum  ambalo ni neno la kilatin ambalo maana yake kwa kingereza ni Oil

Summary.

Petro means Rock

Leum means Oil.

Now, Mafuta na gesu yanatengenezwaje? Lets go

Kuna theory kuu 2 zinazozungumzia origin of Petroleum (asili ya Mafuta na gesi).Nazo  ni hizi zifuatazo.

1.Organic theory
2.Inorganic theory


Lest first descuss about Organic Theory.

Theory hii inaeleza kuwa Petroleum (mafuta na gesi) ilitokana na mabaki ya mimea na wanyama walikoufa miaka million kadhaa iliyopita.

Baadhi ya Wadudu wadogo (microscopic animals) ambao wanaishi baharin(ocean) Kama Planton na Algae hufa na n kujifukia chini ya bahari kwa kingereza wanasema(they burried into bottom of the ocean). Mabaki yao ndio huwa chanzo cha mafuta na gesi.

SPECIAL CASE
Kama unavyojua mnyama yoyote akifa wanyama wengine na bakteria huja na kula yale mabaki. (when animal died, other Animals and bacteria comes to consume remains).

Kwa hiyo kwenye maji ya kina kifupi (Shallow water)ambapo  wadudu hawa huishi,mkondo wa maji huja na kuwasukuma chini ya maji ambapo hakuna hewa safi(oxygen) ya kutosha na hivyo kupelekea wao kufa.

Wanyama hao husukumwa na mkondo wa maji kutoka kwenye mazingira yenye oxygen ya kutosha (Aerobic environment) na kuwapeleka kwenye mazingira ambayo yaNA ufinyu wa hewa safi ya Oxygen(Anaerobic enviroment) hivyo hufa mara moja.

Kumbuka kwenye anaerobic environment (mazingira yenye hewa finyu ya oxgen) hakuna wanyama wala bakteria wengine wanaoweza kuja kula mabaki ya viumbe hivyo vilivyokufa.

So, Mabaki ya wanyama hao yatabaki hapo mpaka yatakapouja kufunikwa na mchanga na udongo (get burried by Particles of sand and silt)

Cycle hii itajurudia mara kwa mara.Baada ya mika kadhaa this particle of sand and silt ambazo zilifunika wanyama hao waliokufa zinakuwa zinapata mkandamizo wa  layer nyingi zaidi hadi ile layer ya kwanza inakuwa imezama chini kwenye kina kirefu.

Hii inasababisha kuongezeka kwa Presha na heat mpaka sediment zina badilika kwenda kwenye sedimentary rock,na zile remains hubadilika kuwa hydrocarbon.

Note
Kwa theory hii ya mafuta na gesi yanavyotengenezwa hata makaa ya mawe (coal) pia hutengenezwa kwa mtindo huu. Isipokuwa,

Mafuta (Oil) hutengenezwa kutokana na mabaki ya wanyama kama Plankton.

Makaa ya mawe (Coal) Hutengenezwa kutokana na mabaki y mimea mbali mbali.

Gesi hutengenezwa baada ya mabaki ya wanyama kufukiwa kwa muda wa mrefu zaidi.

Pia kumbuka napozungumzia wanyama wanaotengeneza mafuta na gesi hapa sizungumzii kila mnyama  hapa nazungumzia wanyama wadogo (microscopic animals) like Plankton and algae.

Now lets move on second theory.

 2. Inorganic theory




Kwenye theory hii mafuta hutengenezwa kwa kufanya reaction between Minerals.

Wanasayansi wamejaribu kutengeneza gesi ya methane kwa  kwa kuapply heat na pressure into minerals.

Lakini hata hivyo ni ni kiwango kidogo sana cha mafuta siku hizi kinachotengenezwa kwa njia hii.

FINAL WORDS

Najua kuna mengi sana kuhusiana na origin of Petroleum ambayo sijayazungumzia hapo,kama unachochote cha kuongezea kuhusiana na Origin ya Petroleum,please share with us

Oil and Gas Traps

All oil and gas deposits are found in structural or stratigraphic traps.  You
may have heard that oil is found underground in “pools,” “lakes,” or
“rivers.”  Maybe someone told you there was a “sea” or “ocean” of oil
underground.  This is all completely wrong, so don’t believe everything
you hear.

Oil Moving Through Pore Space In Sandstone

Most oil and gas deposits are found in sandstones and coarse-grained
limestones.  A piece of sandstone or limestone is very much like a hard
sponge, full of holes, but not compressible.  These holes, or pores, can
contain water or oil or gas, and the rock will be saturated with one of
the three.  The holes are much tinier than sponge holes, but they are
still holes, and they are called porosity.

The oil and gas become trapped in these holes, stays there, for
millions of years, until petroleum geologists come to find it and
extract it.

When you hold a piece of sandstone containing oil in your hand, the
rock may look and smell oily, but the oil usually won’t run out, and you
can’t squeeze sandstone like a sponge!   The oil is trapped inside the
rock’s porosity.

Oil Formation and Oil Movement

The very fine-grained shale we talked about previously is one of the
most common sedimentary rocks on earth.  In many places, thousands upon
thousands of feet of shale are stacked up like the pages in a book, deep
underground.  It is not unusual to have layers in the earth’s crust
made up mostly of shale that are 4 miles thick.  These shales were
deposited in quiet ocean waters over millions of years time.

During much of the earth’s history, the land areas we now know as
continents were covered with water.  This situation allowed tremendous
piles of sediment to cover huge areas.  The oceans may have left the
land we now live on, but the great deposits of shale and sandstone
remain deep underground….right under our feet!

The Tiny Gigantic Kingdom

In the deep ocean, far from land, about the only sediment deposited is the fine-grained clastic rock known as shale.But
what about the oil and gas?  For the answer, we need to move to the
ancient oceans that once covered almost all of the earth.

Tiny Microfossils Make Up the Sea-Floor Ooze

A lot of other material is deposited along with the clay or mud-sized
sediments.  We often think of sharks and whales as being the kings of
the deep oceans.  Actually, there are other animals that have
established giant kingdoms in the sea…the largest and most impressive
kingdoms of all!  These animals are the various kinds of microscopic
creatures….both plant and animal.  Most of them would fit on the head of
a pin. They are tiny, but there are uncountable trillions of them.  
When these creatures die, they sink to the bottom and become part of
the  sediments there that will eventually turn into shale.

The animals die by the trillions and rain down on the ocean floor all
the time.  And since the beginning of life on earth, they have been
living their exciting lives in the ocean, dying, sinking to the bottom,
and becoming part of the once-living matter that is part of most shale
rocks.

It is the trillions of tiny animals that make up most of the gunk
(the scientific name for this gunk is “ooze”) deposited on the ocean
floor.  It’s a very fine-grained goop containing a lot of organic
material mixed with the clay-sized particles that form shale.  It is
called organic-rich shale.

Later, when thousands of feet of organic-rich shales have piled up
over millions of years, and the dead animal bodies are buried very deep
(more than two miles down), an amazing thing happens.   The heat from
deep inside the earth “cooks” the animals, turning their bodies into
what we call hydrocarbons……oil and natural gas.

At first, the oil and gas only exist between the shale particles as
extremely tiny blobs, left over from the decay of the tiny animals.  
Then, the intense
pressure of the earth squeezes the oil and gas out of the shale, and
the oil and gas fluids gather together in a porous layer and move
sideways many miles.  On their way, they may meet up with other
traveling oil or gas fluids.

Finally, the oil and gas may become “trapped” in a rock formation
like sandstone or limestone….a hydrocarbon trap. The oil and gas stay
there, under tremendous pressure, until the petroleum geologist comes
looking for it.  Without a trap, the geologist has no place to drill.  All oil and gas deposits are held in some sort of trap.

The Two Types of Traps

Structural Traps

These traps hold oil and gas because the earth has been bent and
deformed in some way.  The trap may be a simple dome (or big bump), just
a “crease” in the rocks, or it may be a more complex fault trap
like the one shown at the right.  All pore spaces in the rocks are
filled with fluid, either water, gas, or oil.  Gas, being the lightest,
moves to the top.  Oil locates right beneath the gas, and water stays
lower.

Once the oil and gas reach an impenetrable layer, a layer that is
very dense or non-permeable, the movement stops.  The impenetrable layer
is called a “cap rock.”

Stratigraphic Traps

Stratigraphic traps are depositional in nature.  This means they are
formed in place, often by a body of porous sandstone or limestone
becoming enclosed in shale.  The shale keeps the oil and gas from escaping
the trap, as it is generally very difficult for fluids (either oil or
gas) to migrate through shales.  In essence, this kind of stratigraphic
trap is surrounded by “cap rock.”

Here are four traps.  The anticline is a structural type of trap, as is the fault trap and the salt dome trap.

Four Types Of Structural and Stratigraphic Traps

The stratigraphic trap shown at the lower left
is a cool one.  It was formed when rock layers at the bottom were
tilted, then eroded flat.  Then more layers were formed horizontally on
top of the tilted ones.  The oil moved up through the tilted porous rock
and was trapped underneath the horizontal, nonporous (cap) rocks.

Another Stratigraphic Trap

This hole  has been drilled into a sandstone that was deposited in a
stream bed.  This type of sandstone follows a winding path, and can be
very hard to hit with a drill bit!  The plus is that old stream beds make excellent traps and reservoir rock, and some of these fields are tens of miles long!

This type of sandstone is usually enclosed in shale, making this a stratigraphic trap.

Just because you drill for oil or gas does not mean that you will
find it!  Oil and gas reservoirs all have edges.  If you drill past the
edge, you will miss it !  This might explain why your neighbor has a
well on his land, and you do not!

Stratigraphic Problems When Drilling

When you drill, you may find a producing reservoir very near the surface. But many other things can happen:

You might drill into a reservoir that has been depleted (all the oil
and gas removed) by another well.  There may be a new infill reservoir
between two wells that could be developed with a third well.  Or one
that was incompletely drained.  Maybe if you drill a little deeper you
might hit a deeper pool reservoir!  You might be able to back up and
produce a bypassed compartment.  The petroleum geologist has to think of
all these things when planning a new well!

Structural Problems When Drilling

Finally, structures in the earth can give the PG many challenges.  
Look at this diagram.  Imagine you first drilled the hole on the left
into the green layer which represents a nice oil and gas-bearing rock.  YES!  You have a great well, producing lots of oil and gas!

Then you drilled your second hole to the east (right) of the first one.  What happened to that hole? (answer below)

Answer:  The oil reservoir has been split in two by the fault,
which is nothing but a place in the earth where rock layers break in
two.   The arrows on the diagram show that the rocks moved DOWN on the
LEFT side of the fault and UP on the RIGHT side of the fault.   This
created a GAP in the oil field……right where you drilled your second
hole!  Incredibly bad luck!  Or, bad seismic!  Your second hole is a DRY HOLE.

Some diagrams from “A Primer of Oil and Gas Production” and “Pennsylvanian Sandstones of the Mid-Continent”