Dr. Hilmi S. Salem Porosity and Lithology Modeling From Well Logs for Reservoirs-libre

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Computer Modeling of

Porosity and Lithology forComplex Reservoirs UsingWell-Log MeasurementsHilmi S. SalemVersion of record first published: 29 Oct 2010.

To cite this article: Hilmi S. Salem (2000): Computer Modeling of Porosit y andLit hology for Complex Reservoirs Using Well-Log Measurement s, Energy Sources,22:6, 515-524

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E nergy Sou rces , 22:515 ] 524, 2000Copyright Q 2000 Taylor & Francis0090-8312 r 00 $12.00 q .00

Computer Modeling of Porosity and Lithologyfor Complex Reservoirs Using

Well-Log Measurements

HILMI S. SALEM

Atlantic Geo-Technology, Halifax, Nova Scotia, Canada

The high degree of heterogeneity, saturation of multiphase fluids, and presence of (clays in com plex reser v oirs m ake each of the three porosity logs sonic, density, and )neutron , if used independently, generally record inaccurate porosity. For such

reser v oirs, combining different logs gi v es accurate results of porosity. The reser v oirs( )of Terra No v a an d H ibernia Jeanne dArc Basin , offshore of the eastern coast of

Canada, are saturated with m ultiphase fluids, enriched with clays, and m ade of compacted and heterogeneous rocks, in terms of the lithological and mineralogicalcomposition, and the size and shape of the grains and pores. In this study, the porosity and the rock constituen ts were determ ined for both reser v oirs using acomputer technique in which the iteration process was applied. That was done byde v eloping and using v arious computer programs and models, and utilizing numer -ous data from se v eral logs analyzed at 0.2-m sampling-depth inter v als. T he m ore thenumber of logs and iterations u sed in com putation, the higher the degree of accuracyof results obtained. The reser v oirs are m ade of shalestone, sandstone, siltstone,lim estone, marlstone, and conglomerate. Th e porosity v aries widely, because of v ariations in the rock composition and o v erburden pressure. The modeled porosity

( )was compared to the porosity m easured by the com pensated neutron log CN L . T heresults indicate that the CNL-measured porosity is generally higher than the modeled porosity by abou t 50 %. The CNL-measurements are greatly affected by the highamoun t of hydrogen that is chem ically bound in the shales, hydrocarbons, and water. Therefore, CN L records higher v alues of porosity when porosity is actuallylow, and lower v alues of porosity when it is actually high.

Keywords computer m odeling, lithology, porosity, well logs

The Terra Nova and H ibe rnia reservoirs of the Je anne dArc Basin, offshore of theeastern coast of Canada, are complicated mosaics made of multilithological compo-nents, with different mineralogy of grains. They are characterized by poor sortingof grains and enriched with clays. The y have complicated pore-channel networks,

( )and are saturated with multiphase fluids oil , gas , and brine . The rocks in bothreservoirs are anisotropic and ge nerally characterized by fine to medium size of grains and high spe cific surface are a. The reservoirs are located at different de pthsand, hence , affected by various degree s of overburden pressure. Further informa-

Received 9 March 1999; accepted 15 April 1999.(Sincere thanks are e xtended to Prof. G. V . Chilingarian School of Petrole um Enginee r-

)ing, University of Southern California for his critical review of the manuscript.

Address correspondence to Dr. Hilmi S. Salem , Atlantic Geo-Technology, 26 AltonDrive , Suite 307, Halifax, N.S. B3N 1L9, Canada. E-m ail: hilmisalem@ canada.com

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( )t ion and references about these reservoirs are given by Salem 1994, 2000 and( )Salem and Chilingarian 1999 , 2000a , 2000b .

The high degree of heterogeneity and presence of clays and multiphase fluidsmake the petrophysical evaluation for such reservoirs complicated. For he teroge-

( )neous shaly c layey formations , these charac te r is tics make e ach of the threew ( ) ( )porosi ty logs sonic log SON , density log DEN , and compensated ne utron log

( )x ( ) (CNL , if used independe ntly, generally record inaccurate porosity f Asquith,)1991; Tiab & Donaldson , 1996 . In this case , d iffe rent logs are combined to

determine f and lithology.The sonic log me asures the compressional-wave t ransit t ime , which is the

( )shortest t ime required for the acoustic sonic wave to travel through a unit length( )meter or foot of a format ion. The acoust ic-wave ve loc ity depends on manyfactors, including lithology and mineralogy of rocks, density of minerals composing

the rocks, nature of pores and fluids saturating the pores, magnitude of porosity,grain s ize , e lastic propert ies of rocks, temperature , pressure , e tc. V ariations inthese factors affect the acoustic-wave velocity conside rably. The presence of shales,fractures , and g as complicates the SON-me asurements. The sonic transit t ime is

( )high for shaly clayey formations and low for sandstones and carbonates . Forformations be aring oil or gas, the calculated f from SON is higher than the actual

(f , and therefore SON yie lds unre liab le values of f Timur, 1982 ; Tiab &)Donaldson , 1996 .

The bulk density, me asured by DEN, ref lects changes in rock composit ion,

mineralogy of grains , s ize and shape of grains and pores , and k ind of f lu idsaturating the pores. The density log reflects the electron density rather than the

(true density. The refore , f determined from DEN is general ly inaccurate Savre ,)1963 . The influence of c lays on DEN is sole ly a func tion of the c lay density

( ) ( 3 )Hilchie , 1982 . For instance , montmorillonite , which has a density 2.33 g r cm( 3 )lower than that of sandstone 2.65 g r cm , causes f determined from DEN to be

(higher than the actual f . O n the o ther hand , ill ite , which has a density 2 .763 )g r cm greate r than that of sands tone , causes f de te rmined f rom DEN to be

( 3 )lower than the actual f . Kaolini te , with a density 2.69 g r cm approximate lye qual to that of sandstone , cannot be de tected by DEN , especially when kaolinite isintercalated with sandstones. I f chlori te , with density 2.77 g r cm 3 , exis ts in aformation , i ts influence on f becomes significant, particularly when f is lowerthan 10% .

The compensated neutron log, used to me asure porosity, is less effect ive in( ) ( )shaly c layey format ions Merke l , 1986 . For shaly formations , CNL records

inaccurate f , because of the high amount of hydrogen that is chemically bound in( )shales, hydrocarbons oil and gas , and water. If oil and water fill the pores, CNL

records higher f than the actual f , because of the high amount of hydrogenchemical ly bound in these f luids . I f gas fi lls the pores , CNL records lower f ,because of the lower density of hydrogen chemically bound in gas.

( )For two- and th ree -phase porous med ia , Katz e t al. 1995 deve loped atechnique to estimate porosity and fluid saturation by using a predefined set of models and a system of balance equations. Their proposed m ethodology is basedon experimental and theoretical analyses of relationships among f , pore satura-tion , density, and velocitie s of compressional-and she ar-seismic wave s. The veloci-tie s were obtained from seismic re flection surve ys , acoustic well-log me asureme nts,

and laboratory measurements of ultrasonic waves.

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Modeling of Porosity and L ithology for Com plex Reser v oirs 517

Methodology

Iteration Process

Because the SON, DEN, and CNL logs give different values of f for the same

interval of de pth , due to variations in rock and fluid properties and changes inoverburden pressure , me asureme nts of various logs were integrated to achie ve thebest solution of porosity and lithology for the Terra Nova and Hibernia re servoirs.This was done by using the i teration process, with the trial-and-error approach ,

( )applie d for e ach sam pling-de pth interval D Z , indepe nde ntly, within the differentzones in both reservoirs. The iteration process solves a set of equations that define

( ) ( )the input data of different logs. For e xample , Eqs. 1 ] 3 were applied , respec-( ) ( )tive ly, for t he sonic tr ansit- time log SON , t he dens ity log DEN , and the

( )gamm a-ray log GR :

( )328 SH q 181 SS q 156 LS q 620 f s SO N 1

( )2 .50 SH q 2.65 SS q 2.71 LS q 1.00 f s DEN 2

( )100 SH q 30 SS q 20 LS q 10 f s GR 3

( ) ( )The above equations, which involve , for example , shalestone SH , sandstone SS ,( )and l imestone LS , as wel l as f , we re solved for each interval analyzed. These

equations require , in addition to the l ithological components and porosity that

( )nee d to be modeled , the observed sonic travel t ime SON , read from the sonic logw ( )x ( ) 3in ms r m Eq. 1 , the observed densi ty DEN , read from the densi ty log in g r cm

w ( )x ( )Eq. 2 , and the observed gamma ray GR , read from the gamma-ray log in APIw ( )xEq. 3 , which were used as inpu t data. The coe ffic ien ts o f the equations

w ( )x w ( )xrepresent the sonic trave l t ime Eq. 1 , the density Eq. 2 , and the gamma rayw ( )x ( )Eq. 3 for each of the calculated li thological components SH , SS, and LS and

( )porosity f . These coefficients vary with variations of the ove rall response of e ach( )log SO N, DE N, and GR , depe nding on variations of the lithological compone nts,

mineralogy of the grains, size of the grains and pores , nature of the fluid saturatingthe pores, etc. Accordingly, each log generates an independe nt equation with i tsown coefficients, which differs from interval to interval.

The mass balance equation was also used in the ite rat ion process , whichimplies that the sum of any number of the l ithological components and porosityinvolved in the computat ion must be uni ty. For example , the mass balanceequation for shalestone, sandstone, limestone, and porosity is

( )SH q SS q LS q f s 1 .00 4

Accuracy of Iteration Process

The iteration process, used for the porosity- and lithological-components determi-nation for each D Z analyzed , was adjusted by the following factors that help toobtain a higher degree of accuracy.

1. The number of the iterations and logs used in the computation was as manyas possible . The more iterat ions and logs were used , the higher was the

quality of the porosity and lithology results obtained.

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( )2. The thickness of the sampling-depth interval D Z considere d in the analy-( )sis was as small as possible 0.2 m . The smaller the thickness of D Z chosen

for the analysis, the greater was the accuracy of the results. Considering asmaller thickness of D Z he lped to keep the number of the l itho logicalcomponents and the coefficients to minimum. The fewer the componentsand the coefficients were used, the better were the results obtained. Thus,overestimation or underestimation of the real situation was avoided.

3. The coefficients used in the computat ion were carefully chosen, and thelithological c omponents were appropriately identified from analog logs andcut records . This , in turn , he lped grea tly to improve the porosity andlithology re sults.

4 . The input data of the logs were carefully checked. This helped to avoidm any inconsistencies that m ay result from bad log registrations, bad hole

conditions, and log miscalibration.5. The numerical diagnostic process was also applied , which helps to assesswhether the final results were adequate or not. This process was controlledand evaluated by the following.

The sum deviation which showed how far the analysis departed fromthe mathem atically ideal solution. A zero-sum de viation indicated ahigh degree of accuracy.

The proportional variance and the error factor, which were applied toimprove the degrees of the solutions accuracy and the agreeme ntbetween the porosity-lithology model and the input data. The errorfactor, if other than zero, indicated an overestimated case.

The proportional variance which indicated the degree of heterogeneityof the various l ithological components involved in the proposedmodel for each interval analyzed, relative to the input log data.

Application of Iteration Process

Digital and analog data of sonic transit-time log, density log , gamm a-ray log, andvarious resistivity logs, along with data of cut measurements, were analyzed for 14we lls pene trating the Terra Nova and H ibernia reservoirs. The total thickness of

( )the investigated intervals ranges from ; 140 to 600 m within a total depth Z ranging from ; 3 to 5 km. Computer programs were used and others developed , inwhich the iteration process was applied to determine the lithological componentsan d f o f the Terra Nova and Hibern ia reservoirs. Numerous models weregenerated in order to achieve the highest degree of accuracy of the l ithological

components and f . The thickness of each of the reservoirs was d ivided in todifferent zones , depe nding on the lithological and physical propertie s. The analyses( )we re carried out at very de scriptive approach D Z s 0 .2 m within the different

zones.wExamples of the input data and the results for two wells Terra Nova K-07 ,

( )with an interval thickness of 300 m 3 ,114 ] 3,414 m , and Hibernia P-15, with an( )xinterval thickness of 140 m 4 ,114 ] 4 ,254 m are given in Table 1 at D Z o f 10 m.

( )Table 1 shows some of the logs SON , DEN , and GR used in calculation , as well( )as the me asured porosity f obtained from the compensated neutron logCN L

( ) ( )CNL . I t also shows the modeled porosi ty f and the modeled lithologicalm

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( )c om po ne nts SH , S S , SI , an d LS for both we lls. A c om pariso n be twe e n f man d f is given in Figures 1 and 2 , in the form of stack histograms. Each of theseCN L

(histograms assembles a total number of readings of 495 275 for 8 Terra Nova we lls)and 220 for 6 Hibernia wells , obtained at D Z of 10 m. The readings for the 16

( )we lls, pene trating both reservoirs, represent a range of depth Z from 2,888 to4,978 m. It is important to mention that porosity measurements from cores are not

( )available to be correlated to the modeled porosity f .m

Results and Discussion

Modeled Porosity and Lithology

( )The modeled porosity f and lithology indicate that the rocks of the Te rra Novamand Hibernia reservoirs reflect highly heterogene ous system s with vertical andlateral lithological and petrophysical complexities. The rocks in both reservoirs are

( )composed m ainly of SH , SS, SI , and LS. Minor amounts of marlstone MA and( )conglomerate CO exis t only in the Terra Nova reservoir, obtained f rom the

analyses of three Terra Nova wells. Both reservoirs have the following ge neral( )ranges and ranges of averages given in parentheses of the modeled porosity and

lithological components, determined at D Z of 1 m for the 14 wells investigated:( ) ( ) ( )modeled porosity f f 0.0 ] 60% f 7 ] 18% ; S H f 0 ] 65% f 20 ] 32% ; SS fm

( ) ( ) ( )0 ] 80% f 20 ] 35% ; SI f 2 ] 98% f 20 ] 30% ; LS f 0 ] 55% f 14 ] 27% ; MA f( ) (2 ] 34% f 15% , for only one Terra Nova well ; and CO f 5 ] 43% f 24 ] 30% , for

)only two Terra Nova wells .

( )Figure 1. Histogram showing the range and count of the modeled-porosity f for them( )Terra Nova and H ibernia reservoirs; 495 re adings obtained at s ampling-depth intervals D Z

of 10 m within 16 wells penetrating both reservoirs and ranging in depth from 2,888 to 4,978

m. The average value of f is 13.4% .m

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Modeled Porosity and Measured-Compensated Neutron-Log Porosity

( )The modeled porosity f , obtained at D Z of 10 m and presented in Figure 1,m( )ranges from ; 0 to 45% average ; 15% for the Terra Nova reservoir, and from

( ); 0.5 to 28% average ; 12% for the Hibernia reservoir, with an overall average

( )value of 13.4% . The CNL-measured porosity f , obtained at D Z of 10 m forCN Lthe same sampling-depth intervals and presented in Figure 2, ranges from ; 5 to

( )55% ave rage ; 29% fo r the Te r ra Nova re se rvo ir, and from ; 7 to 55%( )average ; 23% for the Hibern ia reservoir, with an overall average value of 26.3% . Figure 1 shows that the majority of the re adings of f is gene rally lowe rmthan 20% . Meanwhile, Figure 2 shows that the majority of the readings of f isCN Lgenerally greater than 20% . This is also indicated by the overall average values of

( )f and f 13.4% and 26.3% , respe ctive ly . It is obvious that f is gene rallym CNL CNLgreater than f by about 50% . For compacted , consolidated , and highly cem e ntedm

( )shaly reservoirs as in the present case , porosity is most fre quently lowe r than 20%( )Tiab & Donaldson , 1996 . As mentioned ear lier, the CNL-measured porosity( )f is general ly inaccurate , because of the influence of hydrogen of theCNL

( )hydrocarbons, water, and shales . The compensated neutron log CNL recordshigher f than the actual f when the pores are saturated with oil and water, andlower f when the pores are saturated with gas. Also , when the form ations areshaly, f is gene rally highe r than the actual f .CNL

Modeling of Porosity and L ithology for Com plex Reser v oirs

Figure 2. Histogram showing the range and count of the me asured-compensated neutron( )porosity f for the Terra Nova and Hibernia reservoirs; 495 re adings obtained atC NL

( )sampling-depth intervals D Z of 10 m within 16 wells penetrating both reservoirs and

ranging in depth from 2,888 to 4,978 m. The average value of f is 26.3% .C NL

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Variations of Modeled Porosity with Lithology, Depth, and O verpressure

The results indicate that the Terra Nova reservoir contains gre ater amounts of (shalestone than the Hibernia reservoir see gamm a-ray readings in relation to the

)shale content in both reservoirs; Table 1 . The Terra Nova reservoir also contains

some amounts of marlstone and conglomerate , which m ake it more he terogene ousthan the Hibernia re servoir. On the other hand , the Hibernia reservoir is affectedby a greater degree of overburden pressure than the Terra Nova reservoir due to

( )i ts gre ater depth Table 1 . The wide variations of porosity in both reservoirs areattributed to the wide variations in mineralogical composition and grain size of thevarious lithological c omponents. A decre asing relationship betwee n porosity anddepth was obtained for both reservoirs , with low coefficients of correlat ion.There fore , the traditionally acce pted smooth porosity ] depth decreasing curve maynot strongly represent the actual re lationship for the reservoirs inve stigate d. Theporosi ty sometimes decre ases at interbedded permeable zones and increases atimpermeable beds or zones. A simple explanation for this phenomenon, within theshalestone and r or sandstone zones, may be attributed to variations in the lithologyan d r or mineralogical composition. O n the other hand , significant variations of porosity we re obtained for the same zone , e ven though it is made of one lithologi-

( )cal component of the same mineralogical composition. Maghara 1986 explainedsuch phenomenon for different reservoirs as a result of the subsurface drainageand pore pressure. The results also indicate the presence of porous zones, withrelatively high porosity values, at gre ater depths. This observation may be at-tributed to the fact that the continuous deposition and burial cause the deep rocksto be overpressured, which leads to expansion and enlargement of the pore spaces.

( )Mudford 1990 pointed out that the relat ively rapid sedimentat ion rates in theAtlantic re servoirs , in p ast ge ological time s , lead to the gene ration of overpressure.

Variations of Modeled Porosity with Physical Characterization

An incre ase in the degrees of he te rogeneity and compaction resu lt s in morecomplicated passages for the hydraulic flow, e lectric current, and acoustic wavepropagation in both reservoirs. Heterogeneity in the rock composition and var-iat ions of the porosi ty are reflected in wide variat ions of the me asured logs.

( )The gene ral r anges and r anges o f ave rages given in paren theses o f some o f the me asured logs, obtained at D Z o f 1 m , are as follows: sonic t ransi t time( ) ( ) ( )SO N f 133 ] 660 ms r m f 235 ] 280 ms r m compressional-wave velocity v p

( ) ( ) 3f 1,500 ] 7,500 m r s f 3,650 ] 4 ,270 m r s ; de nsity D EN f 1.35 ] 3.72 g r cm( 3 ) ( ) ( )f 2.24 ] 2.64 g r cm ; gam ma ray GR f 8 ] 160 API f 40 ] 90 API ; and deep

( ) ( )induction l ateral resistivity ILD f 0.2 ] 2,060 V m f 2 ] 67 V m .( )The wide ranges of the modeled porosity f and lithological components ,mwhich vary considerably from well to well in the same reservoir and from reservoirto reservoir are cle ar ly reflected in the wide ranges of the me asured logs. The

( )lower values of f Table 1 are gene rally correlated to lower SON readings andm( )vice ve rsa lower travel time ; higher compressional-wave ve locity; lower porosity .

( )Also, by reading the gamma-ray log GR and the deep-induction resis tivity log( ) ( )ILD for different wel ls , a GR reading of 150 API for example , represent ing apure clayey zone , corresponds to an ILD reading of about 4 V m. On the o ther

hand , a GR reading o f about 12 API , r ep re sent ing a pure s andstone zone ,

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corresponds to an ILD reading of about 0.8 V m. The relatively high resistivity of ( )the clayey zone 4 V m , indicating re latively low conductivity , in comp arison to the

(relatively low resistivity of the sandstones zone 0.8 V ? m , indicating re lative ly high)conductivity , suggests that by increasing the ove rburden pressure , the reservoir

rocks become affected by a greater load through the grain-to-grain contact points.This, in turn, causes re alignme nt of the grains to a close r spacing, resulting in morecompacted rocks with lower values of porosity. In this case, the low porosity zonesbecome fully saturated with saline water. The high content of water in highlypressured , or some time s abnormally pressured formations, tends to incre ase the

( ) ( )he at c apacity of rocks Bourgoyne et al. , 1986 . This causes shaly clayey forma-(t ions to be weakly conduct ive or even nonconductive i .e . , highly resistive to

)ele ctric curre nt . This indicate s that highly comp acted clays in the shaly formationssaturated with sal t water do not have a considerable influence on the electric

curre nt conduction. Therefore , the e lectric current in the Terra Nova and Hiberniareservoirs is conducted via the saline water filling the pores.

Conclusions

The sonic log, density log, or neutron porosity log, if used independently, does notgive accurate results of porosity. The porosity and the lithological components weremodeled for the Terra Nova and Hibernia reservoirs, using multilog measurements

and a computer technique in which an iteration process was applied. As a result ,(the porosity and the l ithological components of the reservoirs made of heteroge-)neous rocks, with complicated li thology and pore-channel networks , were deter-

mined with a high degree of accuracy. The Terra Nova and Hibernia reservoirs arecomposed of a variety of lithological components, including shalestone , sandstone ,s ilts tone, limestone , marls tone, and conglomerate . E ach of these componentsexercises an important influence on the magnitudes of the various physical proper-tie s that govern the hydraulic flow, electric current conduction , and seismic-wave( )acoustic signe d propagation. He teroge ne ity in the rese rvoirs lithology, and varia-

t ions in the porosi ty and s ize and shape of the grains and pores , as wel l as theinfluence of ove rburden pressure , are reflected in wide variations of the electricresistivity, acoustic signal velocity, gamma ray, density, e tc. V ariations in theselithological attributes and physical properties result in wide variations of water andhydrocarbon saturations, perme ability, tortuosity, specific surface are a, form ationresistivity factor, Archies cem e ntation factor, Kozeny-Carman coefficient, com-pressibility, various elastic moduli, etc.

Nomenclature

CNL compensated neutron-porosity log , %CO conglomerate component , % or f rac tionalDEN dens ity log , g r cm 3G R gam m a- ray lo g , A PIILD induction dee p lateral resistivity log, V mLS limes tone component , % or f rac tional

MA marlstone component , % or fractional

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SH shales tone component , % or frac tionalSI si lt stone component , % or frac tionalSON sonic t ransit- time log, ms r mSS sandstone component , % or f rac tionalv compre ssional wave ve locity, m r s p Z depth, mD Z sampling-de pth interval, mf porosity, % or fractionalf me asured porosity from compensated porosity log, %CN Lf mode led porosity, %m

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saturations using multiple sources of geophysical data. J . Pet . Sci. Eng . 13:103 ] 111.Maghara, K. 1986. Compaction and fluid migration , Practical Petroleum Geology, Develop-

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Mudford, B. S. 1990. A one-dimensional, two-phase model of overpressure generation in theVenture gas field, Offshore Nova Scotia. Bull. Can . Petrol . Geol . 38:246 ] 258.

Salem , H. S. 1994. The ele ctric and hydraulic anisotropic be havior of the Je anne dArc Basinreservoirs. J . Pet . Sci. Eng. 12:49 ] 66.

Salem , H. S. 2000. Interrelationships among water and hydrocarbon saturations, perme abil-ity, and tortuosity for shaly sandstone reservoirs in the Atlantic Ocean. Energy Sources

( )22 3 :333 ] 345.

Salem , H. S., and G. V . Chilingarian. 2000a. Physical and m athematical aspects of tortuosity (in regard to the fluid flow and electric-current conduction in porous media on theexample of the Hibernia and Terra Nova reservoirs, offshore of the eastern coast of

) ( )Canada . Energy Sources 22 2 :137 ] 145.Salem, H. S., and G. V. Chilingarian. 2000b. Influence of porosity and direction of flow on

( )tortuosity in unconsolidated porous media. Energy Sources 22 3 :207 ] 213.Salem , H. S., and G. V . Chilingarian. 1999. Determination of specific surface are a and me an

grain size from well-log data and their influence on the physical behavior of offshore( )reservoirs. J . Petrol Sci . Eng . 22 4 :241 ] 252.

Savre , W. 1963. De termination of a more accurate porosity and m ineral composition incomplex lithologies with the use of the sonic, neutron, and density surveys. J . Pet .Technol . 15:945 ] 959.

Tiab, D., and E. C. Donaldson. 1996. Petrophysics . Theory and practice of measuring reser v oir rock and fluid transport properties . Houston, TX: Gulf.

Timur, A. 1982. Open hole logging. Int. Petroleum Exhibition and Technology Symp.,Society of Petroleum Engineers, Beijing, China, 10037, 639 ] 674.

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Dr. Hilmi S. Salem Porosity and Lithology Modeling From Well Logs for Reservoirs-libre