seismic ingenious

بسم الله الرحمن الرحيم

how do you know about subsurface

these technology of seismic survey simplify this proplems , incredible increase in the success rate of locating natural gas reservoirs and knowledge of the properties of underground natural gas deposits, to gather data that can later be interpreted and used to make educated guesses as to where natural gas deposits exist

It was discovered in the mid 1800's that anticlinal slopes had a particularly increased chance of containing petroleum or gas deposits

the study of this begin with study of surface geology

search for places that petroloum and gas might be exist

like

outcroppings of rocks on the surface or in valleys and gorges

rock cutting and samples from oil and water digs

fluid content, porosity, permeability, age, and formation sequence of the rocks

when they know the possiplility of area to have oil and gas , tests can be performed to gain more detailed data about the potential reservoir area to give more accurate map of underground formations that done by geophysicisits

study of how energy, in the form of seismic waves, moves through the Earth's crust and interacts differently with various types of underground formations

this seismogram study (earthquakes )the vibration of seismic waves through earth

in 1921 this technology was applied to petrolum industry

as the earth crust composed of layers , seismic energy that emit from source and travel through crust interact with layers differently , reflect from some layers , this reflection data give more info about the subsurface geology

geophysicsits are to create vibration on the earth surface to penetrate the earth and how this reflect to the surface again

rubber ball that is dropped on concrete will bounce in a much different way than a rubber ball dropped on sand

like this seismic waves donot reflect at the same way from different layers

seismic waves sent underground will reflect off of dense layers of rock much differently than extremely porous layers of rock

that give info about what is in the earth subsuface at which depth

involves seismic artificial source and sensetive detectors

geophones

data detected by geophones are transmitted through recording trunk

to be processed and interpreted by geophysicsit , geologists and engineers

while seismograms was designed to detect earthquakes , there is also more sources of vibration like dynamite that used in early survey

seismic waves were created using dynamite. These carefully planned, small explosions created the requisite seismic waves

now they almost donot use explosive sources , use non explosives

like that use large impacts series of vibrations These impacts or vibrations create seismic waves similar to those created by dynamite

When exploring for natural gas that may exist thousands of feet below the seabed floor

small different type of survey was done

use ship instead of trunk

hydrophones instead of geophones

use air gun instead of dynamites or impacts biston

hydrophones designed to detect vibration in water , towed behind the ship in various configurations depending on the needs of the geophysicist

air gun release bursts of compressed air under the water and then cause seismic vibration

be continued

make tests during and after drilling , to allow geologists and drill operators to monitor the progress of the well drilling and to gain a clearer picture of subsurface

there are many types , more than 100 logs can be performed ,and then make comparison and and know about different layers

Various types of tests include standard, electric, acoustic, radioactivity, density, induction, caliper, directional and nuclear logging

standard log give infomation about physical aspects of well

the drill cuttings

These cuttings and cores are often examined using powerful microscopes, which can magnify the rock up to 2000 times to examine the porosity and fluid content in subsurface rocks

this data alone would be useless without careful and methodical interpretation

seismic interpretor use all available data to interpret and put model , Some techniques, including seismic exploration, lend themselves well to the construction of a hand or computer generated visual interpretation of underground formation , other data that come from core samples and logs are important to determining the subsurface geological structures

develop a cross-sectional picture of the underground rock , using them to develop a conceptual model of the composition and thickness of the various layers of rock underground. This process is normally used to map underground formations, and to make estimates based on the geologic structures to determine where it is likely that deposits may exist.

'direct detection'

white bands or bright spots often appeared on seismic recording strips

this indicate deposits of hydeocarbons

The nature or porous rock containing natural gas could often result in reflecting stronger seismic reflections than normal, water filled rock

Many of these 'bright spots' do not contain hydrocarbons, and many deposits of hydrocarbons are not indicated by white strips on the seismic data. Therefore, although adding a new technique of locating petroleum and natural gas reservoirs, direct detection is not a completely reliable method

use of computers to compile and assemble geologic data into a coherent 'map' of the underground. Use of this computer technology is referred to as 'CAEX', which is short for 'computer assisted exploration'

it is easy for computer to collect data from field that allow much processing of data on it and increase reliability to put seismic model

There are three main types of computer assisted exploration models

2d

3d

4d

now possible to incorporate the data obtained from different types of tests, such as logging, production information, and gravimetric testing which can all be combined to create a

'visualization' of the underground formation

used to estimate the probability of formations existing in a particular area , raising the success rate of exploration efforts

cost anywhere up to $1 million per 50 square mile area

it is usually used in conjunction with other exploration techniques , geophysicist may use traditional 2-D modeling and examination of geologic features to determine if there is a probability of the presence of natural gas

and then used 3d

In fact, 3-D seismic can increase the recovery rates of productive wells to 40-50 percent, as opposed to 25-30 percent with traditional 2-D exploration techniques

Two dimensional computer assisted exploration includes generating an image of subsurface geology much in the same manner as in normal 2-D data interpretation

and also may use color graphics to show geologic structures

less complicated and less detailed than 3d , much cheaper and more easier ,quickly performed

the latest technology of seismic exploation and modeling

This type of imaging is an extension of 3-D imaging technology , static image of the underground, in 4-D imaging the changes in structures and properties of underground formations are observed over time , the time is the 4 dimension

is called 'time lapse

The different images are amalgamated, to create a sort of 'movie' of what is going on under the ground. Through studying how seismic images change over time

through this geophysicsit can give abetter good image about the state and properties of rocks including underground fluid flow, viscosity, temperature and saturation and evaluate the properties of a reservoir

can increase recovery rates above what can be achieved using 2-D or 3-D imaging. Where the recovery rates using these two types of images are 25 to 30 percent and 40 to 50 percent respectively, the use of 4-D imaging can result in recover rates of 65 to 70 percent

hey it's very nice really

i am so happy for collecting as much as u can these data

thanks again

very very nice