Seismic Coffecent Rock And Rock Density Analysis Biology Essay

The general theory of seismal contemplation and transmittal of moving ridges that incident sidelong at an interface between two fluid-filled porous stones is similar to that for two elastic not dissipative media. Harmonizing to Biot ‘s theory, an isotropic homogenous porous stone and its pore-filling fluid are treated in the mode of two permeating elastic continuance, ( Dutta, et al.

, 1983 ) .The first usage of amplitude information as hydrocarbon indexs was in the early 1970s when it was found that bright-spot amplitude anomalousnesss could be associated with hydrocarbon traps ( Hammond, 2011 ) . Increasingly quantitative work after Ryseth et al. , ( 1998 ) who used acoustic electric resistance inversions to steer the reading of sand channels, and Zeng, et al. , ( 1996 ) used frontward patterning to better the apprehension of shallow Marine facies from seismal amplitudes.

We Will Write a Custom Essay Specifically
For You For Only $13.90/page!


order now

Neri, ( 1997 ) used nervous webs to map facies from seismal pulse form.Planar and 3-dimensional seismal studies are the current primary geographic expedition tool used for deepwater sandstone reservoir word picture Sandstone and shale belongingss vary widely in assorted countries of universe. Reservoir sandstones have speeds that may be higher and lower than incasing shale, which can bring forth a positive, negative or no contemplation ( Batzle, et al.

, 2000 ) .A multiplicity of factors influences seismal contemplation and transmition coefficients and the ascertained gravitation of typical sedimentary stones. Contemplation and transmittal coefficients can be defined in several ways, one of which is the ratio of energy fluxes. Another manner is to specify these coefficients as the ratio of matrix displacement amplitude of the appropriate Boot ‘s moving ridge and the incident amplitude ( Nietzsche, 2005 ) .

The speed and denseness of the Rocks depend upon the mineral composing and the farinaceous nature of the stone matrix, cementation, porousness, fluid content and environmental force per unit area. Depth of burial and geologic age besides has an consequence. Lithology and porousness can be related through empirical observation to speed by the time-average equation. This equation is most dependable when the stone is under significant force per unit area and is saturated with seawater and contains well-cemented grains.

For really low porousness stones under big force per unit areas, the mineral composing can be related to speed by the theories of Voigt and Reuss ( Gardner, et al.,1974 ) .The chief purpose of this chapter is to construe the petrologies of Miocene sequence in the subsurface. Geologically significance of seismal contemplation is merely an indicant of an acoustic boundary where we want to cognize that whether this boundary makes a stratigraphic contact with any other boundary.

This chapter describes the seismal belongingss ( such as acoustic electric resistance, contemplation and transmition coefficient ) every bit good as determines the petrologies of the Miocene sequence. The seismal belongingss and petrologies are determined with the aid of Gardner ‘s ( 1974 ) of velocity-density relation in stones of different petrology.

4.

2 METHODOLOGY AND RESULT

The research methodological analysis and consequences includes the acoustic electric resistance, seismal coefficients, formation speeds and densenesss computations that are discussed as follows ;

4.2.1 Acoustic Electric resistance

The acoustic electric resistance of a stone is the merchandise of its denseness ( I? ) and its moving ridge speed ( V ) , which is a basic physical belongings of stones ; mathematically it is given as under ;aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦ . 4.1Where, Z is acoustic electric resistance, I? is denseness ( g/cc ) and V is speed ( m/s ) .

Contemplations arise at boundaries where the acoustic electric resistance alterations, electric resistance does non alter even if lithology alterations. The greater the difference in the acoustic electric resistance the stronger is the contemplation.To happen the acoustic electric resistance, the speeds from the selected seismal subdivisions were calculated. These speeds were so used in contouring plan Surfer 10.0 for mold, the concluding end product from the surfboarder 10.0 plan is given in Figure 4.1.

The fluctuation in colour indicates high acoustic electric resistance values occur largely on South-Western part of the survey country, while most of the studied country comprises stones holding acoustic electric resistance value scope from 7000 to 9000 g/m2.s which are the moderate values and normally consequences from loose stuffs such as dirt, alluvial sediment and sand.In a comparing of 2D theoretical account ( Figure 4.1 ) with 3D theoretical account ( Figure 4.

2 ) it is noted that the high acoustic electric resistance occurs in the South-West part of the survey country ( xanthous colour part, acoustic electric resistance ranges from 1,000 to 12,000 g/m2.s ) this indicates the presence of compacted petrology deposited, in the incline fan depositional scene. The presence of sand organic structures ( as obvious from the speeds of seismal lines calculated in chapter 03 ) represented by dark bluish colour in Figure 4.1, farther strengthens the reading of possible reservoir interval in the survey country.

4.

2.2 Reflection Coefficient

For a specific instance of normal incidence there is a simple equation associating the incident amplitude to the reflected amplitude. The ratio of reflected amplitude to incident amplitude is called the “ contemplation coefficient ” and it is given as under ;aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦ 4.

2Where V1 is the interval speed and I?1 is the stone denseness of the first studied reflector ( top of Miocene ) , and V2 is the interval speed and I?2 is the denseness of 2nd studied reflector ( underside of Miocene ) , R is reflection coefficient between top and underside of Miocene age. There are three types of interfaces which are as follow ;Solid + solidSolid + perfect fluidFree surfacee. image map.jpg

Figure 4.

1 Acoustic electric resistance 2D map of the survey country

demoing high, moderate and low zones of acoustic

electric resistance in the survey country.

3 vitamin D wire frame.jpg

Figure 4.2 3D map of survey country demoing high acoustic electric resistance

on south-west part in the survey country.

Reflection coefficient can besides be described as the ratio of amplitude of reflected and incident moving ridges. Now if Z1 is the acoustic electric resistance of first bed and Z2 acoustic electric resistance of 2nd bed so the contemplation coefficient is positive provided Z1 & lt ; Z2 and negative if Z1 & gt ; Z2. Generally values of the contemplation coefficient scope from -1 to +1, alternatively of depicting contemplation in term of positive and negative.

Society of geographic expedition Geophysics ( SEG ) defines the normal mutual opposition as: “ A positive signal produces an upward initial gesture on the geophone and recorded as a negative figure on the tape, a negative warp on the proctor record and a trough ( white ) on the seismal subdivision, so reflection boundary appears to be trough for Z1 & lt ; Z2 and extremum for Z1 & gt ; Z2 ” .

For Dynamite

( B ) ( C ) ( D )

For Vibroseis

( A ) ( B ) ( C ) ( D )

A = Normal mutual opposition C = Normal mutual oppositionB = Reverse mutual opposition D = Reverse mutual oppositionIn order to construe the contemplation phenomenon in the survey country, seven migrated stack seismal subdivisions were interpreted and the contemplation coefficient of studied Miocene sequence stone was noted.The consequences indicated that in the West and north side of the survey country at that place was highcontemplation map.jpg

Figure 4.3 2D map of contemplation coefficient demoing the high contemplation

zone in west part of the survey country.

Nitrogen

3D wire fram.jpg

Figure 4.4 3D contemplation coefficient map of survey country which demoing centrist

zone in south- west part of the country.

values of contemplation coefficient occurs while eastern side the values of contemplation coefficient were comparatively low but on traveling towards the south-west part largely values of contemplation coefficient is comparatively low. The fluctuation in the value of contemplation coefficients is diagrammatically shown in the right side of the Figure 4.3.In order to construe the behaviour of Miocene stones in the subsurface of the survey country 3-D theoretical account of contemplation coefficient was generated, ( Figure 4.4 ) .

This theoretical account clearly shows that the value of contemplation coefficient is low on south-west side of the survey country which indicates that there is soft stone ( shale ) , where as in the west part of the survey country shows the high values of the contemplation coefficient, which indicates the compacted bed ( compacted such as limestone ) .

4.2.3 Transmission Coefficient:

An equation for transmittal coefficient is similar to that for the contemplation coefficient, and is derived by utilizing the same premises, gives the normal incidence transmittal coefficient.The ratio of familial energy in a P-wave ( Et ) to incident energy ( Ei ) is:Et / Ei = { ( 2V1* I?1 ) / ( V2* I?2 + V1* I?1 ) } 2 aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦.. 4.3The square root of equation 4.

3 is termed as transmittal coefficient ( T ) . The transmittal Coefficient besides expresses the comparative amplitude of the transmitted to the incident moving ridges.T = At / Ai = { ( 2V1* I?1 ) / ( V2* I?2 + V1* I?1 ) } aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦ . 4.4For supplanting and atom speed, it is equal to 1-R, while for force per unit area it is equal to 1+R.

Transmission coefficient can hold values from 0 to 2. For any value greater than 1 the familial amplitude is larger than the incident amplitude.From the Figure 4.5 drawn for the transmittal coefficient it is noted that values of the transmittal coefficient were comparatively high in the south west part of the survey

Figure 4.5 2D map of transmittal coefficient which demoing the moderate and low zone in south-west part of the survey country

transmision map.jpg3 vitamin D wire fram.

jpg

Figure 4.6 3D map of transmittal coefficient demoing high value in

South-west part of the survey country.

country and really low values occur in west part of the survey country ( bluish colour indicates the low transmittal coefficient zone ) .

The high values of transmittal coefficient might be given to be the soft surface ( such as shale or sandstone ) beds while low values indicate the surface might be difficult ( limestone or sandstone ) . The comparing of 2-D and 3-D theoretical account of the transmittal coefficient shows same consequence.The relationship between 2D and 3D theoretical accounts ( Figure 4.5 and 4.

6 ) , shows that south-west zone comprises comparatively high values of transmition coefficient as compared to the values of north-west and south- east part of the survey country.

4.2.4 INTERVAL VELOCITY:

If two reflectors at depths ‘d1 ‘ and ‘d2 ‘ give contemplations holding several one manner times of ‘t1 ‘ and ‘t2 ‘ , the interval speed ‘Vint ‘ between the ‘z1 ‘ and ‘z2 ‘ is defined merely as:aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦.4.

5The single bed speeds are called interval speeds because they indicate the specific reflectors.In order to construe the thickness of Miocene sequence in the studied country the interval speed values were calculated and these values were modeled two dimensionally and three dimensionally to place the zone of high speeds and low speeds which gave the thickness of the Miocene petrologies. On the north-western part, the 2-D theoretical account indicates the presence of high interval speed zone and on the western border it shows low interval speed values which indicate that at the western border largely difficult bed were present. On the other side, the north east part of the survey country has low speed values which are compared with 3-D theoretical account of the interval speed shown in Figure 4.

7 and 4.8.

4.2.5 Density Determination

Density of stone is a major belongings which describes the sum of solid portion of the stone organic structure per unit volume.

Simply aggregate per unit volume is called denseness. The fadingV interval map.jpg

Figure 4.7 2D map of interval speed demoing high speed

in south-west zone of the survey country.

Figure 4.

7 3D map of interval speed demoing high speed in south-west

zone of the survey country.

N3 vitamin D wire frame.jpgin dense stone is comparatively high. The instance is reverse for the less heavy stones. Seismic speed is reciprocally relative to denseness.

Direct appraisal of denseness from seismal speeds has been done by utilizing the undermentioned expression ;I? = 0.31 * ( Vint ) 0.25 aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦ . 4.

7WhereI? = DensityVint = Interval speed in m/sec.The speed is reciprocally relative to the square root of denseness, but it is common observation that speed appears to increase with denseness. The ground is that compression ( denseness ) reduces porousness and increases snap in such a manner that it offsets the consequence introduced by denseness addition.Figure 4.

8 shows the denseness theoretical account with basal map of the country. In this figure, the less heavy stone beds were identified in the south-western part of the survey country shown by bluish colour and on the other manus north-west and south-east part of the survey country comprises comparatively more heavy stones shown by picket xanthous colour in the Figure 4.8. From the old survey it was besides cleared that the zone of low denseness is best for hydrocarbon accretion ( Galpenergia, 2011 ) .The comparing of 2D and 3D theoretical accounts ( Figure 4.

9 ) shows that south-west zone comprises comparatively low dense stones as compared to sway present in north-west and south- east part of the survey country.density+ base map1.jpg

Figure 4.8 3D density- base map of the survey country demoing

high denseness on north-east part of the survey country.

Nitrogen

3D wire fram-1 copy.jpg

Figure 4.9 3D denseness map of the survey country demoing low denseness

stone in south-western part of survey country.

Nitrogen

4.3 IDENTIFICATION OF LITHOLOGY OF DIFFERENT FORMATION

Every stone or stuff has a scope of denseness, so by ciphering the denseness, we can place the type of stone. In this manner the petrology of reflector can besides be identified.

Density OF COMMON ROCKS

Rock

Density Range ( g/cc )

Shale1.95-2.40Limestone and dolomite2.20-2.85Sandstone2.

10-2.60Dirt and alluvial sediment1.65-2.20

Table 4.1 general values of the densenesss of different stone

Robinson, 1988 ) .

4.3.

1 Lithology designation a general process

There are two chief parametric quantity require to place the petrology of different formation.Interval speed ( Vint )Density ( I? )These two parametric quantity were used to construe the petrology by simple correlativity of the mean interval speed and mean denseness of the formation on a standard modified graph of Gardner, et al. , ( 1974 ) , in which majority densenesss versus speed for different petrology were plotted in Figure 4.

10.

4.3.2 Velocity-Density-Lithology Correlations

In the present survey interval speeds were calculated in feet/sec and denseness in gm/cm3. By utilizing standard graph of Gardner, et al. , ( 1974 ) , a perpendicular line on the footing of norm calculated value of denseness and a horizontal line on the footing of norm calculated interval speed value are projected for each contact. The point of intersection

Figure 4.10 Generalized graph of Velocity-Density relation in stones of different petrology modified after Gardner, et Al, ( 1974 ) .

theoretical account.jpgof these two lines gives the appropriate type of petrology which is shown in Figures4.11 to 4.17.An illustration of the broad scope of P-wave speeds and lesser scope of majority densenesss for the more prevailing sedimentary stone types through a broad scope of deepnesss is given in figure 4.

10In the present survey the petrology of Miocene sequence is interpreted utilizing seven seismal lines. The top and bottom clip, deepness of pronounced reflector gives the mean interval speed and utilizing interval speed the mean denseness valued is calculated which is so used to happen the denseness at the top and underside of the reflector. In this mode the petrology was identified by supper enforcing the lines drawn corresponds to denseness and interval speed on graph developed by Gardner, et al. , ( 1974 ) . The Lithological reading of seismal lines is given below.

4.

3.3 Lithology designation of Line No 86-9007

The interval speed in feet/sec and majority denseness in gm/cm3 were calculated for each shooting point of reflector, the norm of the majority denseness and interval speed were so obtained for studied reflector which is 10199 feet/sec and mean bulk denseness is 2.3 gm/cm3.

Then a perpendicular line was drawn matching to the denseness value of 2.3 gm/cm3 and a horizontal line drawn corresponds to the interval speed 10199 feet/sec on standard graph of Gardner, et al. , ( 1974 ) .

The point of intersection of these two lines gives the type of petrology of reflector, shown in Figure 4.11. The petrology identified for the reflector might be shale. The consequences were verified signifier good data located in the studied country ( Appendix 3 ) .

4.3.4 Lithology designation of Line No 86-9013

The mean interval speed calculated from seismal subdivision line figure 86-9013 is 10397 feet/sec and mean bulk denseness is 2.4 gm/cm3. A perpendicular and horizontal line was drawn matching to 2.4 gm/cm3 and 12532 feet/sec severally in the similar manner as done for the old line on standard graph of Gardner, et al. , ( 1974 ) .

The points of intersection of these two lines lie near to shale line and byline # 86-9007.jpg

Figure 4.11 Lithological reading of line # 86-9007 demoing the shale is present in this part.

line # 9013.jpg

Figure 4.12 Lithological reading of line # 86-9013 is demoing the presence of shale on the footing of speed and denseness.

correlating with good log informations ( Appendix 3 ) , the Miocene stone comprises largely shale in this line, ( see Figure 4.12.

)

4.4.5 Lithology designation of Line No 86-9029

A similar method was applied for this line as stated above.

A perpendicular and horizontal line was drawn matching to 2.2 gm/cm3 and 9880 feet/sec severally on standard graph of Gardner, et al. , ( 1974 ) . The points of intersection of these two lines besides lie near to shale line and by correlating with good log informations ( Appendix 3 ) the Miocene sequence comprises largely shale in this line, ( Figure 4.

13 ) .

4.3.6 Lithology designation of Line No 86-9072

A perpendicular and horizontal line was drawn matching to 2.37 gm/cm3 and 11374 feet/sec severally on standard graph of Gardner, et Al ; ( 1974 ) . The points of intersection of these two lines lie near to sandstone line and by correlating with good log data the Miocene stone ( Appendix 3 ) , comprises largely sandstone in this line, see Figure 4.14.

4.

4.7.1 Lithology designation of Line No 86-9052

For this line a perpendicular and horizontal line was drawn matching to 2.30gm/cm3 and 9943 feet/sec severally on standard graph of Gardner, et al. , ( 1974 ) . The points of intersection of these two lines besides lie near to shale line and by correlating with good log data the Miocene stone comprises largely shale in this line, see figure 4.15.

4.

3.8 Lithology designation of Line No 86-9068

For this line a perpendicular and horizontal line was drawn matching to 2.2 gm/cm3 and 9876 feet/sec severally on standard graph of Gardner, et al.

, ( 1974 ) . The points of intersection of these two lines besides lie near to shale line and by correlating with good log informations ( Appendix 3 ) , the Miocene sequence comprises largely shale in this line, see Figure 4.16.

4.3.9 Lithology designation of Line No 86-9033

For this line a perpendicular and horizontal line was drawn matching to 2.

31 gm/cm3 and 10052 feet/sec severally on standard graph of Gardner, et al. , ( 1974 ) . The points of intersection of these two lines besides lie near to shale line and by correlating withgood log informations ( Appendix 3 ) the Miocene stone comprises largely shale in this line, see Figure 4.

17.line # 9029.jpg

Figure 4.13 Lithological reading of line # 86-9029also

demoing shale in this part of survey country.

Figure 4.

14 Lithological reading of line # 86-9072 is demoing sandstone in this part of the survey country.

line # 9072.jpg

Figure 4.15 Lithological reading of line # 86-9052 which shows

the shale in the zone of the survey country.

line # 9052.

jpg

Figure 4.16 Lithological reading of line # 86-9068 which shows the shale in the zone of the survey country.

line # 9068.jpgline # 9033.jpg

Figure 4.17 Lithological reading of line # 86-9033

is lie near the sandstone in the survey country.

3.

4 Decisions

The seven seismal lines have been interpreted, which resulted in the building of Acoustic Impedance on the footing of denseness and speeds from seismal line of the survey country, Transmition and Reflection coefficient and interval speed maps. The petrology of the different formation has been identified by utilizing standard graph of Gardner, et al. , ( 1974 ) in survey country. All the consequences are prepared by utilizing the Vertical Seismic Profile ( VSP ) informations. From the reading of all seismal lines the consequences are:The values of acoustic electric resistance are bit by bit additions, from 2000 to 17000 in south west part. And in Reflection coefficient map their value is varies from 0.3 to -0.4 ( Figure 4.

1 to 4.4 ) . All these values form theoretical accounts, which show that the country of involvement holding soft surface might be shale or sand rock.In the transmition coefficient which demoing the values were additions from 0.7 to 1.

4 bit by bit in south west part, whereas interval speed besides the high values in south west part varies from 200 to 6200. From the values of the transmition coefficient and in interval speed it shows that this part besides holding shale of sand rock, see Figure 4.5 to 4.

8.In the present survey the petrology of Miocene sequence is interpreted utilizing seven seismal lines. Time and deepness of pronounced reflector gives the mean interval speed, by utilizing interval speed the mean denseness valued is calculated which is used to find the denseness at the top and underside of the reflector. The identified petrology from the reflector might be shale, for line Numberss 86-9013, 86-9029, 86-9052, 86-9068, 86-9033, and sandstone for line figure 86-9072.

The consequences were verified signifier good data located ( Appendix 5 ) in the studied country.

x

Hi!
I'm Ruth!

Would you like to get a custom essay? How about receiving a customized one?

Check it out