Lunch & Learning: Basic Concept for Reservoir Simulation

Niu Yuqiang

2 Initials04/22/23

Overview

What you should know

•Basic hydrocarbon geology

What you can learn

•Formation property•Formation fluid property•Field production datasetTool you need

•Eyes ears and hearts

3 Initials04/22/23

Oil and Gas Wells

GASGAS

OILOILWATERWATER

sandstone gradessandstone gradesto clay sedimentto clay sediment

sandstonesandstonepinch outpinch out

lithological

4 Initials04/22/23

Multiwell Plots

5 Initials04/22/23

RTPM-GREAT Reservoir Definition

6 Initials04/22/23

What we shall know

• Lithology (reservoir rock?)• Resistivity (HC,water,both?)• Porosity (how much HC?)• What type of HC

• Formation mech. properties• Permeability / cap pressure• Shape of the structure• Geological information• Geothermal• Unconventional applications

7 Initials04/22/23

8 Initials04/22/23

Porosity - Definition

9 Initials04/22/23

Porosity (Continued)

A rock can be made up of small grains or large grains but have the same porosity

Porosity depends on grain packing, not the grain size

10 Initials04/22/23

Oolites and Oomoldic Porosity

Freedman/Sander, 1978

Ooids Oolitic limestone withoomoldic porosity

11 Initials04/22/23

Pore-Space Classification

Total porosity, t =

Effective porosity, e =

VolumeBulkSpacePoreTotal

VolumeBulkSpacePorectedInterconne

12 Initials04/22/23

PermeabilityPermeability is a measure of the ease with which fluids can flow through a formation.

Note: To be permeable, a rock must have some interconnected pores, capillaries, or fractures. Hence, there exists some rough relationship between porosity and permeability. Greater permeability, in general, corresponds to greater porosity, but this is not an absolute rule.

Shale and some sands have high porosity but the grains are small that the paths available for the movement of fluid are quite restricted and tortuous; thus their permeabilities may be very low.

Limestone may be composed of a dense rock broken by a few small fractures of great extent. The porosity can be low but the permeability of a fracture can be enormous.

13 Initials04/22/23

Darcy’s experiment

Water Tank

Rock Core with u

Height, H

Flow out, Q

Q=-K A / u * dp / L

dp = rou*g*H

Length, L

Area, A

14 Initials04/22/23

Relative Permeability

15 Initials04/22/23

Saturation Definitions

HydrocarbonWater

*Sw*(1-Sw)

(1-)

*Sw=amount of water per unit volume*(1-Sw)=amount of hydrocarbon per unit volume

16 Initials04/22/23

SaturationThe saturation of a formation represents the amount of a given fluid present in the pore

space.

The porosity logs react to the pore space.The resistivity logs react to the fluids in the pore space.The combination of the two measurements gives the saturation

Matrix

water

oil

Sw = Swirr + Sw"free"

So = Soresidual + So"free"

17 Initials04/22/23

Invasion

18 Initials04/22/23

Archie’s Equation

n

t

mw

wR

RaS

Water saturation, fraction

wSResistivity of formation water, -mwR

Resistivity of uninvaded formation, -m

tRPorosity, fraction

Empirical constant (usually near unity) a

Saturation exponent (also usually near 2)

n Cementation exponent (usually near 2)

m

19 Initials04/22/23

Formation Structure

Tops

Layer

zone

Faults

Boundary

20 Initials04/22/23

Formation

TopsLayerZoneDzDznetFaultsBoundaryPermeabilityPorosity

Fluid Property

Relative permeabilitySaturationDensity, Gravity (API)ViscosityFormation Volume factor

Compressibility

21 Initials04/22/23

Production Dataset

Time

Oil Production Rate

Water Production Rate

Gas Production Rate

Other Operation

22 Initials04/22/23

What is Reservoir

Trapped HC; One pressure gradient

How to define Reservoir

GeologyFluid

How to simulate Reservoir

Production data

23 Initials04/22/23

Eclipse Data For Simulation (Continued)

RUNSPECTITLE THIS LINE IS A RUN TITLEDIMENS 9 9 1 /OILWATERFIELDTABDIMS 1 1 20 2 1 20 /WELLDIMS 2 1 1 2 /START 1 'JAN' 1983 /

GRID DX 81*50 /PERMX 81*50.0 /EQUALSPERMX 130 206 206 205 205 1 1 /PERMX 130 205 207 206 206 1 1 /PERMX 130 206 206 207 207 1 1 //COPYDX DY /PERMX PERMY / PERMX PERMZ //

DZ 81*50.0 /TOPS 81*5000.0 /PORO 81*0.3 /RPTGRID1 1 1 1 1 0 0 0 /

24 Initials04/22/23

Eclipse Data For Simulation (Continued)

PROPS SWFN .25 .0 4.0 .7 1.0 .0/SOF2 .3000 .0000 .7500 1.0000/PVDO-- VF Vis .0 1.0 2.0 8000.0 .92 2.0/

ROCK 5000.0 .30E-05 /DENSITY 52.0000 64.0000 .04400 /PVTW .0 1.0 3.03E-06 .65 /REGIONS SATNUM 81*1 /SOLUTION EQUIL4000 4000 5028 0 0 0 0 0 0 /

SUMMARY FWIPFOIPFOPRWBHP/FWCTFPR

25 Initials04/22/23

Eclipse Data For Simulation (Continued)

SCHEDULE RPTSCHED 1 0 1 0 0 0 1 0 0 0 0 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 /WELSPECS'P' 'G' 5 5 4000 'OIL' //COMPDAT'P' 5 5 1 1 'OPEN' 0 1000000 1* 1* 0.0 //

WCONHIST 'P' OPEN LRAT 0 50 0 / /TSTEP50*0.1/ WCONHIST 'P' OPEN LRAT 0 0 0 / /TSTEP50*1/ WCONHIST 'P' OPEN LRAT 0 50 0 / /END