Well SEATH-1 is a perpendicular offshore wildcat good drilled to measure a chance. The evaluated interval was 4800-5490ft and it consists of claystones interbedded with sandstones. The position of the well is oil find. The entire deepness drilled is 6718ft and the well lifts above mean sea degree are: Kelly Bushing ( KBE ) 89.00ft ; Drill floor 88.00ft ; Water depth 196.00ft. All the log deepnesss were measured from the drill floor lift.

The mark reservoir was drilled with an 8.5 inches bit utilizing an oil based clay ( OBM ) system with mud weight 9.100lb/gal. The deliberate underside hole temperature is 206 & A ; deg ; F and that of the surface/seabed is 50 & A ; deg ; F. The downhloe temperature gradient is 2.42 & A ; deg ; F/100ft ( Table1 ) .

The Gamma beam, Sonic, Photo-Electric Factor, Array Induction Resistivities, Density and Neutron logs were used for the rating. Five 30ft nucleus were cut at intervals 4851-4881ft, 4881-4911ft, 4911-4941ft, 5195-5225ft and 5225-5255ft with recovery of 100, 100, 73, 100 and 90 % severally. Routine nucleus analysis was carried out on the nucleus stopper cut at about 1ft interval. No Particular nucleus Analysis measuring has been made on the nucleus stopper to day of the month, nevertheless, formation electric resistance factor at ambient research lab status in nearby Wellss indicates a cementation factor ( m ) of 1.8, presuming Archie ‘s invariable ( a ) is 1.0. The drill root trial consequences at intervals 5202-5225ft, 5232-5236ft, and 5002-5046ft gave a consequence of the gas rate, the oil rate, the fluid belongings and the interval permeableness ( Table 3 ) No electric resistance index informations are presently available, but the regional formation Waterss are comparatively fresh with a salt & A ; lt ; 10,000ppm NaCl equivalent but are known to change within littorals.

The oil H2O contact ( OWC ) interpreted from the log secret plan ( fig. 1 ) is at a deepness of 5350ft. The force per unit area versus deepness secret plan ( fig. 5 ) indicates that the free H2O degree ( FWL ) is at a deepness of 5364ft. From the force per unit area V deepness secret plan, there are two oil columns with different gradients ( they are non in communicating ) .

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1.2 Aims of the rating

The petrophysical rating of good SEATH-1 was undertaken to reexamine available informations, place petrologies and compare consequences obtained from nucleuss with that obtained from logs, good trial ; measure the clay volume, porousness and impregnation ; supply the mean reservoir belongingss of porousness, impregnation and net thickness of all major sand organic structures ; place hydrocarbon bearing zones and contacts, find the hydrocarbon type ( oil or gas ) , and supply a sum-up on the well consequences bespeaking possible issues that the direction needs to be cognizant of when measuring the chance.

2.0 Data Review

The undermentioned informations were available for the rating of good SEATH-1.

2.0.1 Well Data

The well informations is a sum-up of the well information it includes the name of the well, the field, the type of good, the position, the reservoir formation and entire deepness of the well. Besides included in the well informations tabular array are the entire deepness of the well, lift data point inside informations, the clay physical belongingss ( clay weight, unstable base, and components ) , the size of the drill spot and the borehole temperature ( Table1 ) .

2.0.2 Raw Log Data

The natural log informations is the existent informations prepared in the field by the contractor. It includes the mensural deepness of the well, the hole size in inches as measured by the caliper tool, the litholgy/porosity logs ; Gamma beam ( GR ) , Sonic ( DT ) , Density ( RHOB ) , Neutron ( NPHI ) , and Photo-Electric Factor ( PEF ) . Besides included in the natural informations are the Entire Vertical Depth Subsea ( TVDSS ) of the well in pess and the Array Resistivity Logs.

2.0.3 Formation Pressure Data

Formation force per unit area is the force per unit area in the pore fluid that occupies the pore infinite, at any deepness the pore unstable force per unit area should be the same across the accretion. Formation force per unit area informations of 36 points were acquired utilizing a wireline Repeat Formation Tester ( RFT ) tool ( Table 2 ) and were plotted against the true perpendicular deepness obtained from the natural informations. From this secret plan the Oil and H2O gradient along with the place of the Free Water Level ( FWL ) were obtained ( fig. 5 ) .

2.0.4 Core Data

The nucleus information is based on the driller ‘s deepness ; it includes the nucleus deepnesss, tantamount log deepnesss and their corresponding permeablenesss, porousnesss and grain densenesss. A displacement of -5ft was applied to the nucleus deepness to fit it with the wireline log deepness.

2.0.5 Drill Stem Test Data

The trial consequence obtained from the drill root trial is shown in the tabular array below.

Table: 3 Drill Stem trial


Time interval

Gas rate

Oil rate

Water Rate

Fluid Properties

Interval Permeability




0.1 mmscf/day

665 bbls/day


Oil 27.6 & A ; deg ; API

176 mendelevium



0.03 mmscf/day

306 bbls/day


Oil 32.9 & A ; deg ; API

1070 mendelevium

2.1 Techniques and Parameters

2.1.1 Clay volume

The clay/ shale volume was estimated utilizing individual log technique the ( Gamma Ray log ) and cross secret plan techniques from Neutron- Density cross secret plan ( fig. 3 ) , Neutron – sonic cross secret plan ( figure 4 ) and GR X secret plan ( fig. 2 ) where non clay matrix is homogenous. The 5th zone ( Table 4 ) in the lithological unit was used to specify the clay parametric quantities, from this the GR X-plot, the matrix gamma beam and shale belongingss were determined. The cleanest sand has a gamma beam of 25API while the moisture clay has the undermentioned belongingss ; Gamma ray 168.16API, Sonic 108.5µs/ft, Density 2.45g/cc and Neutron 0.36v/v ( fig. 2 ) . These values were matched with the Neutron -Density ( fig. 2 ) and Neutron-Sonic ( fig. 3 ) cross secret plans to see if it is consistent with the tendencies and were imputed in the parametric quantity tabular array ( Table 4 ) .

2.1.2 Porosity

An synergistic matching of the nucleus porousness against different porousnesss obtained from the Sonic, Density and Neutron logs ( with or without shale rectification ) was made, the concluding porousness used was the Density derived porousness without shale rectification because it is the more consistent with the nucleus porousness informations as indicated in the consequence secret plan ( fig. 8 ) .

2.1.3 Water Impregnation

To gauge the H2O impregnation, the Archie and Indonesia theoretical accounts were compared, the concluding H2O impregnation theoretical account used was the Archie theoretical account because it gave the best consequence. To obtain the H2O impregnation parametric quantities, the formation electric resistance factor measurings at ambient research lab status in nearby Wellss indicated a cementation factor ( m ) of 1.8, if Archie constant ( a ) is assumed to be 1.0. Besides the regional formation H2O are known to be comparatively fresh with salt & A ; lt ; 10,000ppm NaCl equivalent. These values were used along with a temp value of 173.9 & A ; deg ; F to gauge the best fit line ( H2O line ) in the lookout ( electric resistance vs porousness ) secret plan ( fig. 5 ) . And the values imputed in the parametric quantity tabular array ( Table 4 ) . There is an consequence of clay on the lookout secret plan shown by the tendency traveling downwards.

2.1.4 Definition of Parameters Used

The parametric quantities use to specify the matrix belongingss are from Log responses to sway organizing mineral tabular array. Since the matrix is known to be quartz, the Density Neutron and Sonic values of vitreous silica were imputed in the parametric quantity tabular array ( Table4 ) . The matrix belongingss and some other parametric quantities used are illustrated below ;

Matrix belongingss from basic log response to sway forming mineral

GR of 25 API for clean sand

Density 2.65g/cc

Neutron -0.02 v/v

Sonic 55.5µs/ft

Wet Clay belongingss from the GR X-plot ( figure 2 )

GR 168.16 API

Density 2.45g/cc

Neutron 0.36

Sonic 108.5 µs/ft

Pore fluid belongingss The impute values were based on that of fresh H2O

Density 1

Neutron 1

Sonic 189 µs/ft

Impregnation parametric quantities of nearby Wellss were used

Cementation facto ( m ) 1.8

Archies constant ( a ) 1.0

Impregnation advocate ( n ) 1.8

Rw Temperature 173.9 & A ; deg ; F

Rw 0.7ohm-m

2.1.5 Net Reservoir wage

Three instance scenario ‘s were established ( high, most likely and low ) to find the net reservoir. However, some sets of cut -off ( clay volume, porousness and H2O impregnation ) were defined for all three instances. The porousness cut -off for the three instances was obtained from the nucleus porousness vs horizontal permeableness ( kh ) secret plan ( fig. 7 ) .The Vclay cut-off was used to specify the reservoir, the porousness cut-off was used to specify the permeable zones and the impregnation cut-off was used to place the hydrocarbon productive zone ( net reservoir ) . The cut -off values for the clay volume and H2O impregnation were obtained from the consequence secret plan ( fig. 8 ) .

3.0 Discussion of consequences

3.0.1 Petrology

The interval consists of medium – monolithic ruddy claystones interbedded with sandstones. The claystones are by and large ruddy brown, dark ruddy or on occasion dark brown, blockish to stand in blockish, difficult to really hard. These sandstones are chiefly composed of amalgamate vitreous silica grains with no seeable cement. They are average to coarse grained and just to ill sorted with some interstitial clays described in some littorals. Five nucleuss were cut within the evaluated interval ( Table 5 ) . A conventional suit of wireline logs including gamma beam, Density, Neutron and Sonic logs were used to map out and specify the lithological units ( Table 6 ) . Mud log gas shows were reported for three intervals ( Table 7 ) .

Table 5 Cores cut from good SEATH-1


Time interval

Cut foot

Recovered foots

Recovery %


4851 – 4881





4881 – 4911





4911 – 4941





5195 -5225





5225 – 5255




Table 6 Petrology


Time interval


4800 -4840ft


4840 -4910ft

Claystone interbedded with Sandstone

4910 -5000ft


5000 -5050ft


5050 -5200ft


5200 -5240ft



Sandstone Interbedde with claystone



5340 -5490ft

Table 7 Mud Gas Show Intervals


( foot )


( foot )


Unit of measurements


Unit of measurements













Carbon dioxide


4990 -5045








5200 -5235

4314 -4340








5310 -5343

4394 -4420








3.0.2 Zonation

The evaluated interval ( 4800 – 5490ft ) was divided into 10 zones based on petrology and fluid content. This is represented on the log secret plan ( fig.1 ) and on the parametric quantity tabular array ( Table 3 )

3.0.3 Reservoir belongingss – Zone norms

A suited cut – off for the clay volume ( Vclay ) , H2O impregnation ( Sw ) and porousness were obtained from the consequence secret plan ( fig. 8 ) and the nucleus porousness vs horizontal permeableness secret plan ( fig. 7 ) . These values were imputed into the zone norm tabular array ( Table 8 ) to obtain the reservoir belongingss of the net reservoir and net wage. A cut -off values of 0.4 was established for the clay volume and 0.63 for H2O impregnation. Three instance scenarios ; a high instance ( Table 9 ) , a genera/most likely instance ( Table 8 ) and a low instance ( Low 10 ) were established based on the porousnesss obtained from the nucleus porousness vs permeableness secret plan and imputed into the zone norm table to obtain the reservoir belongingss and net wage for the three scenarios. The difference observed from these three scenarios was non much. A permeableness value of 1mD was used for all the instances this is the minimal cut-off for oil reservoirs.

The tantamount Hydrocarbon column ( EPC ) and Equivalent Pore Column ( EHC ) for the three instances show that the oil in the interval 4840 – 4910ft is the most fecund of all ( Table 8 ) .

3.0.3 Fluid and fluid contacts

The fluid and fluid contact were obtained from the log secret plan ( fig. 8 ) and the force per unit area V deepness secret plan ( fig. 6 ) . On the log secret plan, oil zones were mapped out utilizing the Density Sonic and Neutron logs, and the oil H2O contact ( 5350ft ) was mapped out utilizing the Array initiation electric resistance log entirely. On the force per unit area V deepness secret plan, the oil and H2O zones were mapped out based on their force per unit area gradient. The place of the free H2O degree 5364ft ( 5080ft TVDSS ) was besides mapped. From these consequences, 4 oil columns were established. Oil columns 1 and 2, have a gradient of 0.324psi/ft and is different from oil column 3 and 4 that have a gradient of 0.364psi/ft. This shows that Oil column 1and 2 are in communicating, oil in column 3 and 4 are in communicating but but are non in communicating with those in column 1 and 2. The gradient of the Water is 0.429psi/ft. The densenesss of the two oil and H2O gradients were computed and they gave 0.75g/cc ( column1 and 2 ) , 0.84g/cc9column 3 and 4 ) and 0.99g/cc ( H2O ) .

4.0 Summary and decision

The deepness interval for the petrophysical rating of good SEATH-1 was 4800-5490ft. The intervals consist of interbedded claystone and sandstone units. From the rating of the available informations, the following were observed.

Four hydrocarbon columns were delineated, that should be divided into two different units during production because of their force per unit area gradients.

From the log secret plan and the force per unit area deepness secret plan, the oil H2O contact is at 5350ft while the free H2O degree is at 5364ft this is due to threshold capillary consequence and it is normally encountered in hapless quality reservoirs.

From the drill root trial consequence it was discovered that the permeableness of the reservoirs are really good ( 176 and1070mD ) with good porousness as shown in the nucleus porousness vs horizontal permeableness secret plan, high hydrocarbon impregnation and good wage thicknesses. Well SEATH-1 can be said to be a good chance, I will urge that direction should develop the chance.

4.1 Recommendations

I will urge that a drill root trial be carried out in the oil column at interval 4830-4900 since it is the most fecund from the rating carried out.

A particular Core Analysis ( SCAL ) should be carried out on the nucleus to mensurate the stone belongingss such as porousness at overburden force per unit area, permeableness at overburden force per unit area, formation electric resistance factor ( FRF ) , Resistivity index ( RI ) , Resistivity index at overburden force per unit area, capillary force per unit area, comparative permeableness and cation exchange capacity ( CEC ) . Datas from a nearby good to gauge for the H2O impregnation could impact the consequence because salt is known to change within littorals in the country.

The oil column in 1 and 2 should be produced together, while that in column 3 and 4 should be produced together but otherwise from that in column 1 and 2 because they have different force per unit area gradient and therefore different densenesss.

I will urge the fracturing of Wellss should be incorporated into the development program to heighten the optimum production.


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