class reservoir simulation

7/29/2019 CLASS Reservoir Simulation

1/50

RESERVOIR SIMULATION

The will discuss all of the important facets of the reservoir modeling process.

Important factors that can dramatically impact the model results are emphasized.Specific topics include Data Acquisition, Fluid Properties, Rock-Fluid Interaction,

Grid Construction, History Matching and Prediction Cases.

These and other topics will help the attendees better understand how to plan and

conduct a reservoir simulation study and how to review a study conducted by

someone else.

Although there will be no direct computer related activities, time throughout the

two-days is reserved for discussion of case studies that were previously models

conducted by the teacher.

Attendees are also encouraged to bring materials and data (non-confidential)

relating to a potential project that they may be involved with in the future; and as

time permits, the class as a group (or groups, guided by the teacher) will brainstorm

and discuss the approach to be taken to achieve the desired study objectives.


2/50


3/50

Why We Do Reservoir Simulation

Typical Problems

How many wells

What rate

Infill Drilling Perforation

Work-over

Pressure Maintenance

Water or Gas Injection

Pattern Flood


4/50

Reservoir Drive Mechanisms1. Rock and fluid expansion2. Solution-gas drive

3. Gas-cap drive4. Water drive5. Gravity-drainage drive

6. Combination drive

412/19/2012 Maximizing Oil Recovery


5/50

Solution Gas DriveLiberation, expansion of solution gas.



6/50

Solution Gas Drive (Cont.)Typical Production Characteristics



7/50

Solution Gas Drive (Cont.)

Reservoir pressure trend



8/50

Gas Cap Drive

8

Expansion of the original reservoir free gas.



9/50

Gas Cap Drive (Cont.)Typical Production Characteristics



10/50

Water Drive

Influx of aquifer waterTypes :

Edge-Water Bottom-Water



11/50

Water Drive (Cont.)Typical Production Characteristics



12/50

Gravity DrainageGravitational forces and reservoir fluids density difference.



13/50

Combination Drive



14/50

Average Recovery Factors



15/50

SIMULATION:

"To Give the Appearance Of


16/50


17/50

Reservoir Simulation

106-108 cells

Engineering/Simulation

Model


18/50

Outlines

Brief of simulation

Introduction of Eclipse

Eclipse demo


19/50

Brief of simulation

What is simulation?

What would be simulated usually?

Imitation or representation, as of a potential situation or in

experimental testing


20/50

What is Reservoir?

Trapped HC, same pressure gradient

Tops

Layer

zone

Faults

Boundary


21/50


22/50

What we shall know from a well?

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


23/50

Formation

Tops

Layer

Zone

Dz (Thickness)

Dznet (Net Thickness)

Faults

Boundary

Permeability

Porosity

Fluid Property

Relative permeability

Saturation

Density, Gravity (API)

Viscosity

Formation Volume factor

Compressibility

How to describe reservoir?


24/50

The reservoir is divided into a number of cells

Basic data is provided for each cell

Wells are positioned within the cells

The required well production rates are specified as a function of time

The equations are solved to give the pressure and saturations for each block

as well as the production of each phase from each well

Reservoir Simulation Basics


25/50

Reservoir Simulation (1)

9 16

4 10 1 7 23

1 5 11 18 24 27

2 6 12 19 25 26

3 7 13 20 26

8 14 21

15 22

Numerical model of reservoir made up of an

array of cells. Equations are solved to calculate

pressures and flows.

Fluid flow - underlying concepts Conservation of mass

Darcys law

PVT model

Partial differential equations are written infinite-difference form and solved numerically


26/50


27/50

WHAT BENEFITS ?

Golden Rule:

You can only produce once

You can simulate many times


28/50


29/50


30/50

Overview of Modeling Procedure

History

match

Describereservoir

reservoir structure(seismic,logs)

gross and net thickness(logs)

well location and perforatd intervals

Design

reservoir grid

porosity, permeability(logs, cores)

fluid analyses(lab data)

pressure and contacts(logs, well tests, etc.)

Select simulator

model

black oil or compositional

fractured, condensate,etc

horizontal wells, EOR, thermal, etc.

Solve for

pressures and

saturations historical production data

Predict and

optmize future

production

investigate different scenarios

visualize results

economic calculations


31/50


32/50

WINPROP PVT-Analysis & Simulation


33/50

PVTi

Simulating

Experiments

Match

Creating

a Fluid System

Fitting

an Equation of State

FVF

Viscosity

EOS PVT Analysis & Simulation

Reseroir Simulation Grid

Export

Single Point

Pressure Depletion

Separator

Injection Study


34/50

Schedule

Defines simulation wells, connections, vertical performance,artificial lift, controls and limits.

Defines groups, controls and limits.

Defines networks, compressors, etc. Specifies time dependent data.


35/50

Wells- Path

-Tubulars

- Chokes

- Completions

- Workovers

- Production

- Injection

OCS

GGS

CTF

OCS

Network

Groups

-Capacities

-Demands

Simulation GridCell Properties Geological Model

Schematic of Data Handling in Schedule


36/50


37/50


38/50

Numerical Grid

The reservoir was sub-divided into a 10x10x4 grid.

The numerical layers correspond to the geological

layers.

The x-y dimension of the grid blocks is 500 m by500 m.


39/50

3-D Structure of Reservoir


40/50

Structure and Geology

Layer

Number

Porosity Horiz. Perm

(mD)

Thickness

(m)

1 0.35 1000 5

2 0.3 5 10

3 0.25 300 15

4 0.2 100 30


41/50

Layer 2 has numerous shale components.

The geologists best guess of the average

permeability of the mix of sand and shale is 5 Md.

The average Kv/K h ratio is 0.1. The top of the structure is approximately 2989 m

SSL.

The lowers edge of the reservoir in the aquifer is

approximately 3090 m SSL.

Structure and Geology


42/50

Aquifer

There is a aquifer attached to the edge of thereservoir that provides an edge water drive.

The geologist has estimated that the aquifer has a

volume of approximately 9 x 108 Sm3 of water and

the aquifer productivity index is approximately 500

sm3/day/bar.

A analytical Fetkovich aquifer has be used to

represent the aquifer.


43/50

PVT Data, Fluid Contacts, and Initial Fluids

in Place

A PVT description has been generated with the

Eclipse PVT program.

A live oil and dead gas system has been defined.

The bubble point pressure was determined as331.65 barsa.

The Rs at the bubble point was 477.91 sm3/sm3 ,

and the Rs at a depth of 4000 m SSL was

measured to be 486.60 sm3/sm3.


44/50

The datum depth is the GOC = 3000 m SSL where

the initial reservoir pressure is 331.65 barsa.

The water-oil contact was measured to be 3085 m

SSL.A small gas cap exists at the top of the structure.


in Place


45/50

The reservoir has a

Pore Volume of 360.8 x106 Rm3

Initial Oil In Place of 51 x106 Sm3Initial Water in Place of 173.6 x106 Sm3

Initial Free Gas in Place of 77.56 x106 Sm3

Initial Solution Gas in place of 24.4 x109 Sm3


in Place


46/50

July 03 7

x-y View of 4 Layers with Initial Water Saturations

Layer 1

Layer 2

Layer 3

Layer 4

July 03 9

x-z Cross-section with Initial Gas Saturations

July 03 8

x-z Cross-section with Initial Water Saturations


47/50

Relative Permeability and Capillary

Pressure

The relative permeability and capillary pressure

were measured in the laboratory and are plotted in

attached slides.

The connate water saturation is 0.22. The critical/residual oil saturation in water is 0.35.

The critical oil saturation in gas with connate water

is 0.2.

The critical gas saturation is 0.04.


48/50


49/50

Wells, Completions, Injection and

Production Rates

Two production wells were drilled at locations 8,5

(called P85) and 3,5 (called P35)

Both completed in layers 2 and 3.

The producers operate, during the history, at aconstant oil production rate of 1300 Sm3/day.

A water injection well and gas injection well were

also drilled.

The water injection well was shut during the history.


50/50

The gas injection well called INJG was located in

position 5,5 and completed in layer 1 in the gas cap.

The gas injector re-injects 1,000,000 Sm3/day of

the produced gas. This was designed to help maintain the reservoir

pressure.

Wells, Completions, Injection and

Production Rates

class reservoir simulation

Documents