Geology Questions?
BASIC CONCEPTS OF GEOLOGY
1. How long ago was the oil being extracted today formed?
The oil was roughly formed between 30 to 500 million years ago
2. Where do you find oil or gas in rock underground?
We find them in pore or fracture of rocks
3. What are the common reservoir rocks?
There are sandstone, limestone and dolomite
4. What sort of rocks are they?
They are mostly sedimentary rocks
5. What is meant by a trap?
A trap is a underground formation which prevent the escape of oil and gas contained in reservoir rock.
6. What is a cap rock?
Cap rock is non-porosity and impermeable to the fluids bellow
7. Do you think overburden pressure can force the reservoir fluids through the cap rock and up to surface if a hole is drilled through the cap rock?
Yes
8. How do oilmen know where to drill?
Generally speaking, that is the job for the petroleum geologist.
9. how can petroleum geologist locate the position where oilmen are to drill?
Petroleum geologist can use the result of seismic surveys (or even aerial surveys) to get information about rock features beneath the surface
10 when and how was the earth originated?
The earth is though to have originated some four to five billion years ago by condensing out of a cloud of cosmic dust.
11.what is the origin of igneous rocks?
Igneous rock is solidified from molten form called magma.(molten melt)
12.how many kinds of rocks have been considered so far?
Three kinds
13.what are they ?
they are igneous rock, sedimentary rock and metamorphic rock.
14.if metamorphic rocks are subjected to even more heat, they may be melted and become magma rocks, do you agree?
Yes ,I agree. (ignore and igneous inflame)
15.among igneous rocks, metamorphic rocks and sedimentary rocks, which one is more important to petroleum geology?
Of course,the sedimentary rock is more important than the rest.
16.why?
because most oil and gas accumulations occurs in sedimentary rock.
phenomenon appearance phenomena
17.where can we see some samples originally deposited in an ancient sea?
Some remains of marish shells can be found in some hightest mountains and in deepest oil wells.
18.what is the most common kind of deformation?
The most common kind of deformation is the buckling of the layers into a fold.
.are folds the most common structure in mountain chains
yes ,folds are the most common structure both in present and former mountain chains.
20.what are anticlines?
Anticlines are upfolds or arches structure of the mountain chains.
21.and synclines?
Downfolds or troughs are synclines.
22．Folds, usually,have only one form, is that right?
No. folds have many forms.
23.folds are often symmetrical, are not they?
yes and no. they may be symmetrical or asymmetrical
24.how do you describe faults?
Faults are described according to their present attitude by various names.
25.how many kinds of faults are classified?
There are four kinds of faults.
26.what are they ?
they are normal,reverse,thrust and lateral.
27.what are rotational faults and upthrusts?
Rotational faults and upthrusts are variations of normal and reverse faulting.
28.how many kinds of oil seeps are there in petroleum geology?
There are two general kinds.
29.what are these two kinds of oil seeps?
Seepage up --dip and seepage along fractures.
30.are there any other geophysical methods used to find suitable structure for petroleum accumulation?
Yes ,there are.
31.could you tell me what these methods are?
We can find favorable structures for petroleum accumulation using gravimeter and magnetometer .
32.what is porosity?
Porosity is a measure of the pore space in the body of reservoir rocks, usually expressed as a percent of a void space per unit volume of rock.
33.what is permeability?
Permeability is a measure of ease with which a fluid flows through the connected pore spaces of a reservoir rock.
34. is it important to predict sand trends in exploiting sandstone reservoirs?
Yes ,but not only the prediction of sand trends but also the prediction of pore space distribution.
35．What is needed to get a petroleum accumulation ?
there are three points in dealing with the question.
36.what is the first point,please?
Firstly ,there must be a source of oil and gas.
37.and your second point?
Secondly,the existence of a porous bed which is permeable enough to permit the oil and gas to flow through it the reservoir rock.
38.and the last one .
a trap ,which is a barrier to flow fluid so that accumulation can occur against it
39.where did oil and gas originated ?
oil and gas originated from decayed organic matter in sedimentary rock.
40．What does the word “migration”mean in petroleum geology?
After generation ，the dispersed hydrocarbons in the fine grained source rocks must be concentrated by migration to a reservoir。Such a process is called migration 。
41．How are the driving forces behind migration ？
the driving forces behind migration are provided by the weight of the overlying rocks，circulating of groung water and gravity。
42．What are those forces behind migration?
The driving forces are the forces necessary to expel the hydrocarbons and to move them through the more porousbeds or fractures to regions of lower pressure.
43．Do you think gravity plays some part in the migration ？
yes ，gravity plays a role of separating gas ，oil and water。
44．What about the distribution of fluids in a reservoir rock？
The distribution of fluids deponds on their densities and on the capillary properties of the rocks。
45．If a reservoir rock contains uniform pores，and if the pore are evenly distributed，what will the distribution of fluids be like in a trap， then？
In this case ，there will be three zones of fluids in the trap。
46．What are the three zones in a trap ，please？
An upper zone( or gas cap) ,a middle zone and a lower zone .
47．What are contained in the three zones respectively？
The rock pores in the upper zone are filled mainly by gas.
48．And the middle zone and the bottom zone？
The middle is filled mainly by oil and gas in solution and the lower water
49．Is there any water in the middle zone？
A certain amount of water always occurs together with oil in middle zone。
50．What is the usual proportion of water to oil in the middle zone？
The proportion of water to oil is usually from 10 to 30 percent。
51．Does water occur in the gas cap?
Yes ,it does.but the proportion of water to gas is frequently lower than the proportion of water to oil.
52．Is there a special name for the water found in the oil and gas zones？
Yes，there is。It is called “interstitial water”or“connate”
53．Does the crude oil in a trap contain natural gas in solution under pressure?
Yes ,it does. It is the local pressure and temperature conditions that keep the gas in solution with the oil.
54．How does the natural gas come from crude oil？
It is quite simple 。（quite） simple.when the crude oil rises to the surface ,the pressure drops. And-----
55．Oh ,I see,as the crude oil rises to the surface the pressure has dropped enough, the gas comes out of solution?.
Yes ，you are right。
56．Why are gas wells and most wells initially flowing well？
The basic production mechanism in naturally flowing wells is the result of pressure differences。
57．If the bottom hole pressure resulting from the hydrostatic head is lower than formation pressure the oil will move through the pores of the reservoir rock and out into the bottom of well bore ，is that right？
Yes ，you are right。
58．How many factors affect the flow rate of reservoir crude？
Four factors。
59. what are the four factors？
Bottom-hole pressure，formation pressure，rock permeabiliy，and the viscosity of the oil。
60．What kind of reservoir has the hightest permeabilities of all?
Of course the fracture d reservoir。
61．What is a wet gas？
If natural gas contains a relatively large quantity of the other heavier hydrocabons，it is called a wet gas。
62．Is there any other name for natural gas？
Yes ，there is 。
63．What is it？then？
it is called a dry gas。
64．What comes to the top of a well together natural gas？
Lighter liquid hydrocabons，and wanter。
65．In what technical terms that an oilman would use？
In suspension。
V．2 SAMPLING
1． What is sampling ？
Sampling is collecting cuttings at a certain place on a rig。
2． What are the cuttings?
Cuttings are chips of rock cut from the formation by the bit
3． How do the cuttings come out of the bore hole？
They are carried to the surface by the mud circulating up the annulus。
4． Where do you collect cuttings on the rig？
We always collect the cuttings from the shale shaker screen。
5． Whose job is it to collect the cuttings?
Of course ,sample catcher is.but during the initial period of drilling,the mud logger often gives a hand.
6. how does he know when to collect the cuttings?
The sample catcher is told for the collection each time by a mud logger.
7. and how does the mud logger know when to collect the cuttings?
He can respond to the buzzer signal given by the on-line system or he can observe the regular depth interval shown at a panel.
8． is that all?
Of course not。It also depends on the lag time of the cutting transit in the annulus。
9． By the way，what does a sample catcher collect the cuttings with？
Well，he offen collect cuttings with trowel。
10． How much cuttings does the sample catcher collect each time？
That deponds。Normally 500 gram is enough。
11． What should he pay attention to while collecting the cuttings?
To ensure that a representative sample is taken with minimum caving.
12.what is the next step after the collection ?
washing the collected cuttings.
13.why do you have to wash the cuttings?
In order to have a better look at them under the microscope.
14. is it difficult to wash the the cuttings.
Yes and no .it all depends on the rock areas that are drilled.
15.what do you mean by this ?
I mean that the cuttings drilled in hard rock areas,usually quite easily cleaned,but it is more difficult for those in areas and zones of loose sands and shales. tight
16.by the way ,how do you often wash and clean the cuttings?
We wash the cuttings in a sieve-stack..
17.why do you clean the cuttings in sieve-stack?
Because we want to collect the required grain size of cuttings.
18.then what are you going to do with these washed cuttings?
Some of them shall go for examination under the microscope ,and the rest shall be dried in an oven. furnace
Groundwater storage is like a bank account. The balance falls when withdrawals exceed deposits. Nature makes deposits through rainfall, and withdrawals through leakage of groundwater to streams and the ocean. Our wells represent further withdrawals. If total withdrawals exceed deposits, we deplete our groundwater storage. Do we know if we are draining our account?
