Fundamentals of Rock Properties

8/2/2019 Fundamentals of Rock Properties

1/44

Department of Earth Resources EngineeringUniversity of Moratuwa

Level 4Semester 1

3 Credits

1


2/44

2

End-of-Semester Examination - 70%

Continuous Assessments - 30%

Group Assignments - 15%

Mid semester exam - 15%


3/44

Upon successfully completion of this

module, student will be able to explain geological process that produce

hydrocarbon

explain systems and significance of the timingof hydrocarbon generation

discuss properties of reservoir rock and fluid

calculate reservoir volume

3


4/44

Petroleum geology

Properties of reservoir rock

Properties of reservoir fluid Petroleum reservoir engineering

Petroleum drilling

Well controlling

4


5/44

Petroleum engineering is the science of

planning the development and the

production of oil and gas field in such away that an optimal recovery of oil and gas

is achieved with optimal economic results.

5


6/44

Intended Learning OutcomeAfter completingthis section the student should be able

to

explain the reservoir rock properties

describe the methods used to determine rock properties

calculate rock properties with given data

6


7/44

To understand and evaluate the performanceof a given reservoir it is essential to know

about

The physical properties of the rock

Existing interaction between the hydrocarbon

system and the formation

7


8/44

To determine the rock properties laboratoryanalyses are performed on cores from thereservoir to be evaluated.

Some properties of the rock may change whenthey are removed.

The effect of these changes should be evaluated

in the testing program depending oncharacteristics of the formation and property ofinterest

8


9/44

CoreAnalysis

Tests

Routinetests

Porosity

Permeability

Saturation

SpecialTests

OverburdenPressure

Capillarypressure

RelativePermeability

Wettability

Surface and interfacial

tension9

V


10/44

Porosity

Absolute

Effective 10

Vp

Vr


11/44

Effective

Porosity

11


12/44

Original

developed in the deposition of the material

Induced

developed by some geologic processsubsequent to deposition of the rock

12


13/44

Show large variations vertically

Do not show very great variations parallel to the

bedding planes

To minimize the effect of this variationaveraging techniques are used

13


14/44

Arithmetic average

= i/n Thickness-weighted average

= ihi/hi

Areal-weighted average = iAi/Ai

Volumetric-weighted average

= iAihi/Aihi

Where n = total number of core sampleshi = thickness of core sample i or reservoir area ii = porosity of core sample i or reservoir area i

Ai

= reservoir area i

14


15/44

15


16/44

Fraction or percent, of the pore volume occupied bya particular fluid

16

Total volume of the fluid

pore volumeFluid saturation =

Gas Saturation(Sg)

Oil Saturation(So)

Water Saturation(Sw)


17/44

Connate (interstitial) water saturation SwcReduces the amount of space available between oil

and gas.

not uniformly distributed throughout the reservoir

17

Critical oil saturation, SocThe saturation of the oil must exceed a certain value

to flowAt this particular saturation, the oil remains in the

pores and will not flow


18/44

Residual oil saturation (Sor

)

During the displacing process of the crude oil systemfrom the porous media by water or gas injection, there

will be some remaining oil left

larger than the critical oil saturation.

18

Movable oil saturation, Somthe fraction of pore volume occupied by movable oil

Som = 1 Swc Socwhere Swc = connate water saturation

Soc = critical oil saturation


19/44

Property of the porous medium that measures thecapacity and ability of the formation to transmit fluids.

Function of open space and its interconnection.

This was first defined mathematically by Henry Darcy,1856

19


20/44

The effect of fluid density &viscosity on the flow were notinvestigated

20

L

)h(hkv 21

Where; V = flow velocity, cm/sech = differences in monomeric

levels, cmL = total length of the sand pack, cmk = constant

Lhkv


21/44

Where

A = cross sectional area of the sand pack

q = total measured flow rate, Cc/sec

21

L

hkAq


22/44

22

p = g(h1-z)with respect to the prevailing

atmospheric pressure

Let pressure at theany point of theflow path isp.

h1Liquid elevation of the upper manometer


23/44

23g)(dl

d

g

khv

=

=

The pressure at any point relative to datum

pointp = g(h-z) hg =

+ gz

v=(k/g)d(p/ + zg)/dl


24/44

Potential energy per unit mass

24

gzdp

The term has the same unit as (hg)

which are; distance x force per unit mass.

gz

dp

Defined as the work required by a frictionlessprocess, to transport a unit mass of fluid from astate of atmospheric pressure and zero elevationto the point in question.

gzdp

p

atm

1


25/44

Respect to arbitrary base pressure ( pb, Zb)

Fluid flow between two points, A and B

25

)zg(zdp

b

b

p

p

)(

)()(

B

bb

B

BA

A

bB

B

bA

A

A

zzgdp

zzgdp

zzgdp

p

p

p

p

p

p


26/44

The constant k/g is only applicable for theflow of water.

Law can be generalized as;

Where is the viscosity of the fluid

26

dldkv

)(dld

gk v


27/44

27

If a liquid having a viscosity of 1 cp () flows through aporous rock of 1 cm length (L) & 1cm2 cross-section(A) at a rate of 1 cm3/sec (q) when the pressuredifferential between inlet & outlet is 1 atm (p), thenaccording to the definition, the rock permeability (k) is1 Darcy.

1 Darcy = 10-8 cm2


28/44

28

Darcys empirical law described without

considering the sign.

It being assumed that all terms in equation

were positive.


29/44

If distance is measured positive in the directionof flow, the potential gradient d/dl isnegative(-ve) in the same direction.

Therefore Darcys law is

29


30/44

If production from reservoir into the well is takenas positive,

the radius is measured as being positive in the

direction opposite to the flow, d/dr is positiveand Darcys law may be stated as

30


31/44

Find the dimensions of k

What is the conversion factor between kexpressed in Darcys and in cm2 ?

31


32/44

Tendency of one fluid to spread on or adhere to a solidsurface in the presence of other immiscible fluids

32


33/44

Can be determined by measuring the angle ofcontact at the liquid-solidsurface. (measured throughthe liquid to the solid)

Contact

angle

33

Wettingcharacteristics ofthe liquid


34/44

Affects relative permeability, electricalproperties and saturation profiles in thereservoir.

The wetting state impacts waterflooding andaquifer encroachment into a reservoir.

34


35/44

By measuring the contact angle of crude oil andformation water on silica or calcite crystals

By measuring the characteristics of core plugsin either an Amott imbibition test or a USBMtest.

35


36/44

Effect of the forces at the interface when twoimmiscible fluids are in contact

When a liquid and a gas are in contact, use theterm surface tensionto describe the forces actingon the interface.

When the interface is between two liquids theacting forces are called interfacial tension

36


37/44

37

Unit Force per unit

length E.g.,

dynes/cm,

Symbol


38/44

Fup = (2r) (gw) (cos )

38

Fdown = r2h wg


39/44

When two immiscible fluids are in contact, adiscontinuity in pressure exists between the twofluids

39

Ai

r

Water

pa2

hpa1pw1

pw

2

Pa2 =pw2=p2

pa1 =p2- ragh

pw1 =p2- rwg h

Pc =pa1 -pw1

= rwg h- rag h

= rg h


40/44

Capillary force in a petroleum reservoir is acombined effect of

surface and interfacial tensions of the rock andfluids

the pore size and geometry

wetting characteristics of the system

40


41/44

This pressure difference depends upon thecurvature of the interface separating the fluids.

This pressure difference is called as capillarypressure.

41


42/44

42


43/44

43


44/44

Date post:	06-Apr-2018
Category:	Documents
Upload:	rajitha-shehan
View:	226 times
Download:	0 times

Fundamentals of Rock Properties

Documents