Up-to-date geotechnologies in the development of Chiren Underground Gas Storage

Authors: Rumen Ognianov, Ph.D., Head of Storage of Natural Gas Dept. Dimitar Shterev, M.Sc., Senior Expert, Storage of Natural Gas Dept. Mariana Pavlova, M.Sc., Expert, Storage of Natural Gas Dept.

CS Kardam 2 CS Kardam 1 ROMANIA Gen. Toshevo CS Russe Montana Varna Chiren UGS Biala Levski CS Vratza YUGOSLAVIA Roman CS Polski Senovetz Turgoviste Zlatna Panega CS Lozenetz Elin Pelin Debelt Iambol CS CS Strandja Pazardjik Parvomaj Dimitrovgrad TURKEY MACEDONIA Legend: CS Main gas pipeline Gas pipeline branch Transit gas pipeline Compressor station GREECE Gas reduction station

IGRC, Paris Oct. 2008, Working Committee 2: Underground Storage (UGS) Numerical Applications for UGS – from E&P to Dispatcher

Chiren UGS basic information

● Production from Chiren gas-condensate field: 1965-1974

● Cyclical operation as UGS facility: 1974-2008

● Number of injection-withdrawal wells: 22

● Number of observation wells: 10

● Down-hole equipment of the wells: typical for packer’s operation.

● Surface equipment: commensurable to operational parameters and capacity of UGS.

IGRC, Paris Oct. 2008, Working Committee 2: Underground Storage (UGS) Numerical Applications for UGS – from E&P to Dispatcher Chiren over thrusted geologic structure

IGRC, Paris Oct. 2008, Working Committee 2: Underground Storage (UGS) Numerical Applications for UGS – from E&P to Dispatcher Chiren UGS outline

- Orientation of the geologic structure: NW-SE

- Length of the geologic structure: 14,2 km

- Width of the geologic structure: 5,7 km

- Average depth to the gas reservoir: 1790 m

- Average thickness of the pay zone: 150 m

- Geologic age: Mid.-Up.Triassic & Lower Jurassic

IGRC, Paris Oct. 2008, Working Committee 2: Underground Storage (UGS) Numerical Applications for UGS – from E&P to Dispatcher

Parts of Chiren UGS surface facilities

IGRC, Paris Oct. 2008, Working Committee 2: Underground Storage (UGS) Numerical Applications for UGS – from E&P to Dispatcher The beginning …

- Work in an environment of insufficient information;

- Study of the geologic structure;

- Chiren gas storage fractured reservoir;

- Relationship between fractures and present day in situ stress regime.

IGRC, Paris Oct. 2008, Working Committee 2: Underground Storage (UGS) Numerical Applications for UGS – from E&P to Dispatcher Evaluation of fractures’ directions from paleomagnetically oriented core

from APPLIED PALEOMAGNETICS, Inc., Santa Cruz, California

IGRC, Paris Oct. 2008, Working Committee 2: Underground Storage (UGS) Numerical Applications for UGS – from E&P to Dispatcher

The goals of paleomagnetic fracture study were, as follows:

- To determine orientation of natural open fractures that may control the permeability anisotropy of gas-bearing rocks;

- To determine angular relationship between directions of open fractures and present-day in- situ stress;

- To evaluate fracture density and apertures vs. depth and lithology;

IGRC, Paris Oct. 2008, Working Committee 2: Underground Storage (UGS) Numerical Applications for UGS – from E&P to Dispatcher Initialization of different fractures related to the formation mechanism of the local structure

IGRC, Paris Oct. 2008, Working Committee 2: Underground Storage (UGS) Numerical Applications for UGS – from E&P to Dispatcher IGRC, Paris Oct. 2008, Working Committee 2: Underground Storage (UGS) Numerical Applications for UGS – from E&P to Dispatcher Estimation of angular relationship between present-day in-situ stress & open fractures directions

(from core material) from APPLIED PALEOMAGNETICS, Inc., Santa Cruz, CA

IGRC, Paris Oct. 2008, Working Committee 2: Underground Storage (UGS) Numerical Applications for UGS – from E&P to Dispatcher Similarity between Chiren E-33 Vuggy Set 1 Fractures, Carlsbad Cavern (New Mexico), and In Situ Stress

sHmax Applied A Paleomagnetics x N i Project 30 km s from Carlsbad o

f

B

i g The open

R

o

o

m

a W t E fractures C

a

r ls

b

a

d

C contain vuggs

a

v e

r Carlsbad Cavern, New Mexico; photo from Hill (1990) S n

N

Chiren E-33

sHmax W E

S

Vuggy Set 1 fractures, Chiren E-33

Healed natural fractures Open natural fractures Induced fractures Figure 25. In both Chiren E-33 and Carlsbad Cavern (New Mexico), vugs in natural fractures probably formed by acid migration along natural fractures striking  to, and held open by, in situ stress over the past few million years.

Applied Paleomagnetics, Inc.

IGRC, Paris Oct. 2008, Working Committee 2: Underground Storage (UGS) Numerical Applications for UGS – from E&P to Dispatcher Chiren UGS,

Wyoming, USA 40°

from APPLIED

IGRC, Paris Oct. 2008, Working Committee 2: Underground Storage (UGS) PALEOMAGNETICS, Inc., Numerical Applications for UGS – from E&P to Dispatcher Santa Cruz, California Fracture Relationships in Cores from Well Chiren E-33 Open & Healed Natural Fractures vs Induced Fractures N

1692

1694 Core 1 Histogram of open 1696

1698 and healed natural 1728 1730 Core 2 fractures 1732

1734 1782 vs. Core Depth (meters) DepthCore 1784 Core 3 1786 induced fractures, 1822

1824 Core 4 i.e. vs. present-day 1826

1828 in-situ stress 0 5 10 0 1 2 3 4 Fracture Density Total Open Fracture Apertures S (# of fractures/0.31 meters) (millimeters)

Open Natural Healed Natural Tectonic Stylolite Induced from APPLIED PALEOMAGNETICS, Figure 6. Summary histograms illustrating open vs. healed natural fracture and induced fracture relationships in well Chiren E-33. Note that the most open natural fractures occur near the top of Core 1 and the bottom of Core 4. Note also the inverse correlation between induced vs. natural fracture density: most induced Inc., Santa Cruz, CA fractures occur in Core 2, which has the lowest natural fracture density. Key point: most open natural fractures are within 19° of striking parallel to present-day in situ stress, as revealed by induced fractures.

Applied Paleomagnetics, Inc.

IGRC, Paris Oct. 2008, Working Committee 2: Underground Storage (UGS) Numerical Applications for UGS – from E&P to Dispatcher Results from the paleomagnetically oriented core material: - The present-day in-situ stress direction is: N 880 E (N 80-1000 E, estimated by us before paleomagnetic study)

- 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;

- Those fractures that strike perpendicular to present-day in-situ stress are completely healed;

- Fracture permeability anisotropy in Chiren UGS structure revealed by open fractures determined in the core material exhibit a remarkable similarity to fracture permeability anisotropy at Little Sand Draw Field, Wyoming, USA.

IGRC, Paris Oct. 2008, Working Committee 2: Underground Storage (UGS) Numerical Applications for UGS – from E&P to Dispatcher Drilling of the first deviated injection-withdrawal well using MWD-equipment

+300 m +300 Aptian + m Neogene 0 0

- Hauterivian - -300 300 Barremian

- -600 600 Upper Jurassic - - Valangian -900 900

-1200 Dogger - Toarcian 1200

Pliensbachian -1500 - 1500 Lower Middle – Upper Triassic Triassic -1800 Hettangian - - Sinemurian 1800 DUAL POROSITY – DUAL PERMEABILITY

RESERVOIR SIMULATION

IGRC, Paris Oct. 2008, Working Committee 2: Underground Storage (UGS) Numerical Applications for UGS – from E&P to Dispatcher 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;

- Periodic assessment of possible gas losses (Technical Losses Monitoring);

- Assessment of CUSHION and WORKING GAS for possible expanding of the UGS at new bigger levels.

IGRC, Paris Oct. 2008, Working Committee 2: Underground Storage (UGS) Numerical Applications for UGS – from E&P to Dispatcher Structural maps of the gas-bearing horizons used for the reservoir modelling

from GeoFrame

IGRC, Paris Oct. 2008, Working Committee 2: Underground Storage (UGS) Numerical Applications for UGS – from E&P to Dispatcher History matching by wells in different regions (tectonic blocks) of the gas storage reservoir

from Eclipse History matching by wells during cycling operation

from Eclipse

IGRC, Paris Oct. 2008, Working Committee 2: Underground Storage (UGS) Numerical Applications for UGS – from E&P to Dispatcher Gas saturation in the fractures at the end of 1974

Gas saturation in the matrix at the end of 1974

IGRC, Paris Oct. 2008, Working Committee 2: Underground Storage (UGS) Numerical Applications for UGS – from E&P to Dispatcher Gas saturation in fractures at a pressure of 150 bars a

from Eclipse

IGRC, Paris Oct. 2008, Working Committee 2: Underground Storage (UGS) Numerical Applications for UGS – from E&P to Dispatcher Structural map on the top of the gas storage reservoir (Lower Jurassic sediments)

Initial Water Gas Contact: - 1675 m

Water-Gas Contact in fractures: - 1600 (-1650) m

Water-Gas Contact in matrix: - 1560 (-1575) m

IGRC, Paris Oct. 2008, Working Committee 2: Underground Storage (UGS) Numerical Applications for UGS – from E&P to Dispatcher Implementation of specific well- logging measurements

- Wells’ technical status assessment

- Wells’ injectivity

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

- Petrophysical analysis Evaluation of wells’ technical status

• Well completion • Gas leakage behind casing

2½” 5¾” 85/8" 11¾” 16¾”

6 m

101.15 m

cracks in the casing * 1118.5 from RST, GRIT * 1132

cement 1359.92 m box 1417.5 * 1431 1452 corrosion

packer 1638.72

1661.14

1715 1735 perforation 1751 1774 1792

artificial 1806 bottom hole 1921 1921 m

IGRC, Paris Oct. 2008, Working Committee 2: Underground Storage (UGS) Numerical Applications for UGS – from E&P to Dispatcher • Tracking out of gas migration using Krypton 85 as a radio-tracer Assessment of the wells’ technical status

• Cement bonds status evaluation

• Channeling in cement • Casing deformations

from GRIT, USIT, RST, PMIT

IGRC, Paris Oct. 2008, Working Committee 2: Underground Storage (UGS) Numerical Applications for UGS – from E&P to Dispatcher Fracture study & analysis using well-logging results from the deviated well

3D view from logging tools: FMI , UBI, HALS Determination of fracture orientation, fracture porosity, aperture and fracture density from specialized well-logging measurements in the deviated well

3-D view from FMI

IGRC, Paris Oct. 2008, Working Committee 2: Underground Storage (UGS) Numerical Applications for UGS – from E&P to Dispatcher Juxtaposition of open fractures registered by well-logging measurements with fracture study of a core material taken from the same depth Fracture study in core material taken from the deviated well

1801,30 m 1797,50 m 1830,80 m

IGRC, Paris Oct. 2008, Working Committee 2: Underground Storage (UGS) Numerical Applications for UGS – from E&P to Dispatcher Composite display form well-logging measurements in the deviated well

(Petrophysical analysis vs. gas saturation)

from GeoFrame, ELANPlus

IGRC, Paris Oct. 2008, Working Committee 2: Underground Storage (UGS) Numerical Applications for UGS – from E&P to Dispatcher

New reprocessing and interpretation of the existed seismic data

objectives:

- To outline the tectonic screen of the gas bearing rocks on the Northern boundary of the geological trap;

- To outline a new separate block by a fault with North-Southern direction on the Western part of the structure.

IGRC, Paris Oct. 2008, Working Committee 2: Underground Storage (UGS) Numerical Applications for UGS – from E&P to Dispatcher Seismic line SW – NE direction

Seismic line NW–SE direction

from GeoFrame

IGRC, Paris Oct. 2008, Working Committee 2: Underground Storage (UGS) Numerical Applications for UGS – from E&P to Dispatcher Results from the implementation of up-to-date geotechnologies in Chiren UGS:

• Adequate reservoir simulation based on authentic information about the structural features of the geological structure with space orientated porosity distribution both in matrix & fractures;

• Accurate estimation of the initial and residual reserves, technological losses and differences in the location of the Water-Gas Contacts, both in matrix and fractures;

• Right determination of location and azimuth of the forthcoming deviated wells;

• The determination of wells’ technical status with tracking out eventual behind casings gas migration (leakage) enabled us to take duly decisions for abandoning or for appropriate workovers in the defined wells;

• Reasonable increase of gas storage capacity and deliverability.

• The new reprocessing and interpretation of the old seismic data enabled us to foresee some fault barriers in the Western and Eastern parts of geological structure. A sunset view from Chiren UGS area …

IGRC, Paris Oct. 2008, Working Committee 2: Underground Storage (UGS) Numerical Applications for UGS – from E&P to Dispatcher