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New technologies applied for technological & operational

safety of Chiren UGS and before its forthcoming extension

by

Dimitar K. Shterev, M.Sc.

Storage of Natural Gas Dept.

Bulgartransgaz EAD

Chiren UGS

Legend: Main gas pipeline Gas pipeline branch Transit gas pipeline Compressor station Gas reduction station

CS Kardam 1 CS Kardam 2

CS Lozenetz

CS Strandja

Sevlievo Lovech

Zlatna Panega

Roman

Botevgrad

Elin Pelin

Pleven

Sofia

Pernik

Vratza

Montana Russe

Razgrad

Isperih Kubrat

Turgoviste

Biala Levski

Varna

Dobrich

Gen. Toshevo

Burgas

Debelt Iambol

Sliven

Rakovski

Plovdiv Pazardjik

Asenovgrad

Parvomaj

Stara Zagora

Dimitrovgrad

Haskovo CS Petrich

ROMANIA

SERBIA

GREECE

TURKEY

CS Polski Senovetz

CS Ihtiman Nova Zagora

CS Provadia

MACEDONIA

CS Valchi dol

International Gas Union, Working Committee Storage

2015-2018 Triennium, Amsterdam, March 21-24, 2016

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Chiren UGS

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Geologic structure: over-trusted zone

Orientation: NW-SE

Length: 14.2 km

Width 5.7 km

Average depth to the gas reservoir: 1790 m

Average thickness of the pay zone: 150 m

Reservoir rocks: limestones, sandstones

Basic geologic information

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Chiren UGS basic information:

Production from Chiren gas-condensate

field: 1965 – 1974

Initial pressure: 192 bar

Cyclical operation as UGS facility: since 1974 - continue

Number of injection-withdrawal wells: 23

/20 vertical + 3 deviated/

Working gas: 550 mcm

Max injection capacity: 3.6 mcm/d

Max withdrawal capacity: 4.3 mcm/d

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In the beginning… 1997 – 1998…

Bulgartransgaz was a member of the Rock

Mechanic Consortium - Integrated PoroMechanics

Institute, Oklahoma University.

Findings:

- Reservoir (gas-bearing) rocks are fractured

limestones & sandstones;

- Vertical and sub-vertical fractures;

- Fracture orientation?;

- To work in insufficient data environment…

Additional studies should be undertaken !!!

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Fracture study I:

objectives:

- to estimate and use the volumetric properties of the

gas storage reservoir in a best way;

Paleomagnetic orientation of fractures from core

material:

- to determine angular relationship between open

fractures and present-day in-situ stress directions;

- to determine orientation of open fractures;

- fractures may control the permeability anisotropy

of the reservoir rocks;

- to evaluate fracture density and fractures’

apertures vs. depth and lithology.

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Evaluation of fractures’ directions from paleomagnetically oriented core

Paleomagnetically oriented

core provides key reservoir

anisotropy information

Knowledge of reservoir

anisotropy caused by

fractures; drilling new high

production inj./w

ith. wells;

Changes in structural dip can

initiate fluid migration and

control reservoir drainage

patterns.

APPLIED PALEOMAGNETICS, INC. Santa Cruz, California

To draw up a

successful drilling

plan;

To determine the

orientation of open

natural fractures prior

to drilling;

To establish the

direction of present-

day in-situ stress;

To determine whether

the present-day in-situ

stress will hold natural

fractures open during

UGS operation ;

Predict orientation of

hydraulic fractures.

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Estimation of angular

relationship between

present-day in-situ

stress

&

open fractures

directions

(from core material)

APPLIED PALEOMAGNETICS, INC.,Santa Cruz, California

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40°

Wyoming, USA

Chiren UGS, Bulgaria

from APPLIED

PALEOMAGNETICS, Inc.,

Santa Cruz, California

Fracture permeability in Chiren UGS revealed a remarkable similarity to

fracture permeability at Little Sand Draw Field, Wyoming, USA.

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Results from the paleomagnetically

oriented core material: - The present-day in-situ stress direction is: W 880 E

- The most open and vuggy natural fractures striking on

average N 690 E, which is within 190 of the present-day in-

situ stress direction (880 – 690 = 190);

- Those fractures that strike perpendicular to present-day in-

situ stress are completely healed (closed);

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Pliensbachian

Lower

Triassic Hettangian -

Sinemurian

Middle – Upper

Triassic

+300 m

-300

0

-600

-900

-1200

-1500

-1800

+300

m

-300

0

-600

-900

-

1200

-

1500

-

1800

Hauterivian -

Barremian

Upper Jurassic -

Valangian

Dogger Toarcian

Aptian + Neogene

Drilling of deviated injection-withdrawal wells using

Measurements While Drilling (MWD) equipment

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DUAL POROSITY – DUAL PERMEABILITY

RESERVOIR SIMULATION

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Reservoir simulation objectives:

- Assessment of the INITIAL GAS in PLACE of the gas–

condensate field;

- Optimizing of wells’ injection & withdrawal regimes according

to the seasonal gas demands;

- Monitoring and prediction of Gas-Water-Contacts both in

matrix and fractures;

- Periodical assessment of possible gas losses (Technical

Losses Monitoring);

- Assessment of CUSHION and WORKING GAS for possible

extension of the UGS at new bigger levels.

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Structural maps of the gas-bearing horizons

used for the reservoir modelling

from GeoFrame

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History matching by wells in different regions

(tectonic blocks) of the gas storage reservoir

from Eclipse

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from Eclipse

History matching by wells

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Reservoir simulation at a pressure of 150 bars

Gas saturation in fractures – Capabilities of

the geologic structure:

from Eclipse

Reservoir pressure up to 150 bars

Total gas – 1.8 bcm

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Implementation of specialized well-logging

measurements

Objectives:

- Fracture study II - (type, orientation, density & aperture);

- Wells’ technical status assessments;

- Wells’ injectivity parameters;

- Petrophysical analysis.

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2½” 5¾” 85/8"

6 m

1806

101.15 m

1638.72

artificial

bottom hole

1921 m

1715

1921

1792

1774

1751

1735

11¾” 16¾”

1661.14

1359.92 m

* 1118.5

1132 *

**1417.5

1431

pe

rfora

tion

packer

cracks in

the casing

co

rros

ion

cement

box

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Evaluation of wells’ technical status

• Gas leakage behind casing • Well completion

from RST, GRIT

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• Channeling in cement

• Tracking out of gas migration using

Krypton 85 as a radio-tracer

• Cement bonds status evaluation

Assessment of the wells’

technical status

• Casing

deformations

from GRIT, USIT, RST, PMIT

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Fracture study - results from FMA loggings in deviated

well

3D view from logging tools: FMI , UBI, HALS

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Specialized well-logging measurements in the newly-dilled

deviated wells

/fracture orientation, porosity, aperture and density/

3-D view from FMI

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Juxtaposition of open

fractures registered by

well-logging

measurements

with

fracture study of a core

material taken from the

same depth

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(Petrophysical analysis

vs. gas saturation)

Composite display form

well-loggings made in

newly-drilled deviated well

from GeoFrame, ELANPlus

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New surface facilities modules installed

in Chiren UGS

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Separation of the liquid phase unit (condensate from water)

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Compressor’s oil filtering unit

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Individual separation of wells

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Manifold

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Gas dehydration unit

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Gas metering ultrasonic unit

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System for automated control data monitoring and archiving

Oil filtering unit

Gas dehydration

Power supply

0,4 – 20 kV

Individual

separation

New manifold

Compressor

workshop

Dispatching

hall Wells’ telemetry

Dispatching system

WPS32

SCADA Honeywell EXPERION

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Scheme of wells’ telemetry system

EXPERION SCADA

in Chiren UGS

Server in Chiren UGS

Working station

Working station in Sofia’s Headquarter

150 МНz 2,4 GНz

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Extension of Chiren UGS – to increase storage capacity

- Active gas volume – from 550 to 1000 mcm;

- Daily capacity – from 4.25 to 10.00 mcm/d;

- Drilling of 12 new deviated inj./with wells (2

observation wells will);

- New compressors;

- Additional manifold unit;

- Additional individual separation units;

- New dehydration unit;

- New linking gas flow-lines and new metering units.

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Extension of Chiren UGS - Preliminary studies:

1. Geo-mechanical modelling & simulation - done;

2. Surface gas survey - done;

3. 3-D Seismic survey – is coming

Objectives:

To evaluate the integrity (tightness) of the

geological structure and equipment up to certain

levels of increased reservoir pressures.

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Geo-mechanical modelling and simulation

- Mechanical properties of reservoir and cap

rocks;

- Stress, strain estimation;

- Fault modelling and simulation;

- Simulation to 130, 150 and 180 bars.

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The study has been completed by UMG Engineering LTD, a

part of University of Mining and Geology, Sofia, Bulgaria.

UMG Engineering LTD.

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Geo-mechanical assessment of strain deformations

- coupled modelling by the use of PETREL and

VISAGE, Schlumberger products

130 bars

150 bars

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Fault simulation and stress estimation using

VISAGE of Schlumberger

Simulation (BARS)

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130 180

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Permeability changes - Simulation at 130 bars

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Permeability changes - Simulation at 150 bars

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Permeability changes - Simulation at 180 bars

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- 620 samples in grid 500 x 500 m on the Chiren structure;

- 300 samples located on faults;

- 320 samples located on the existing wells sites.

No surface gas flow was identified !

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The study has been completed by UMG Engineering LTD, a part

of University of Mining and Geology, Sofia, Bulgaria.

Surface Gas Survey on the Chiren UGS structure

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Surface Gas Survey - Sampling locations

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Surface Gas Survey - Field works and laboratory

measurements

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Surface Gas Survey – Gas content map

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Upcoming activities of significant importance:

- 3D seismic acquisition survey of 200 sq. km; 3D

seismic survey received funding from EC;

- The bidding process for 3D seismic survey is still

going on;

- After processing and interpretation of the results

from the 3D seismic survey, updating of geo-

mechanical model is possible.

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A sunset view from Chiren UGS area

APPLIED PALEOMAGNETICS, INC. Santa Cruz, California

UMG Engineering LTD.

Thanks to:

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