A STUDY ON THE SAFETY OF THE CO2 INJECTION WELL 2019. 02. 21 JONG-RYEOL YOON

CONTENTS 1 2 3 4 Review of Standards Well Design Safety Assessment Summary

1 Review of Standards CHAPTER 1 1-1. EPA 1-2. API

1-1. EPA (Environmental Protection Agency) ■ EPA (USA) ▷ Operating UIC (Underground Injection Control) Program ▷ Regulation of the construction, operation, permission and closing of injection wells ▷ Classification according to the type and the depth of injected fluid ▷ Addition of CO2 injection well (Class VI) at 2010 Classification The Characteristics of the Injection Well Class I Used to inject hazardous and non-hazardous wastes into deep, isolated rock formations Class II Used exclusively to inject fluids associated with oil and natural gas production Class III Used to inject fluids to dissolve and extract minerals Class IV Shallow wells used to inject hazardous or radioactive wastes into or above a geological formation Class V Used to inject non-hazardous fluids underground and dispose of wastes into or above underground sources of drinking water Class VI Used for injection of CO2 into underground subsurface rock formations for long-term storage, or geologic sequestration(GS)

1-1. EPA (Environmental Protection Agency) ■ Definition of Class VI wells 『 Class VI wells are used to inject carbon dioxide (CO2) into deep rock formations. 』 ■ Requirements for Class VI wells ① Extensive site characterization requirements ② Injection well construction requirements for materials that are compatible with and can withstand contact with CO2 over the life of a GS project ③ Comprehensive monitoring requirements that address all aspects of well integrity, CO2 injection and storage, and ground water quality during the injection operation and the post-injection site care period ④ Financial responsibility requirements assuring the availability of funds for the life of a GS project  ⑤ Reporting and record keeping requirements that provide project-specific information to continually evaluate Class VI operations and confirm USDW protection 

1-2. API (American Petroleum Institute) ■ API (USA) ▷ Developing petroleum equipment and operating standards ▷ Defining standards of the drilling materials for oil and gas fields ▷ Certificating and supervising of manufacturer maintenance Certification Code Objects API Spec 2B Structural Steel Pipe API Spec 5CT Casing and Tubing API Spec 5D Drill Pipe API Spec 5L Line Pipe API Spec 6A Wellhead and Christmas Tree Equipments API Spec 6D Pipeline Valves (Steel Gate, Plug, Ball, and Check Valves) API Spec 6H End Closures, Connectors and Swivels API Spec 10A Well Cements

CHAPTER 2 2 Well Design 2-1. Overview 2-2. Casing Design 2-3. Cementing Design

2-1. Overview Basic Data Mud Design BHA Design Select Casing Sizes ■ Major Design Factor Basic Data Mud Design BHA Design Geological properties Exploratory drilling Rock properties Fluid type / Density Additives Quantity calculation WOB design Stabilizer BHA assembly Select Casing Sizes Cement Design Drilling Parameter Annular volume G-Class Cement T/P condition Cementing Test Casing Setting Depth Casing & Hole Size Selector buoyancy WOB/RPM analysis Calculation of WOB, RPM Casing Strength Bit Design Well Completion Geological boundaries Pore/fracture pressure Casing type and grade Rock type and strength Bit Index Select proper bit Wellhead Rig performance Drilling schedule

2-2. Casing Design ■ Basic Well Design Multi-stage structure according to Class VI Ensuring structural safety with international standards Casing design : KS → API 5CT • Connection compatibility and sealing of well head • Connection type : welding → joint (thread ) • Corrosion resistance • Connection of FRP casing and sealing

2-3. Cementing Design ■ Basic Well Design G-class cement Cement Properties Cement Type : G-class Specific Gravity : 3.15 Composition Cement+55%Water+35%Slica +1.25%Retarder(BS200R-2) +0.5%Defoamer(BP-1A)+0.3%RPM Slurry Properties Cement slurry density : 1.9g/cm3 Yield : 1.51ft3/sack ■ Basic Well Design Total Volume (m3) Weight (ton) Total G class 35% Sand 55% Water Retarder & Deformer Amount 24.92 47.42 24.85 8.7 13.67 0.2 Excess (50%) 39.87 75.92 39.75 13.91 21.86 0.4 G-class cement Sealing the space between the outside of the casing and the rock mass Prevention of CO2 leakage and the corrosion of the casing

CHAPTER 3 3 Safety Assessment 3-1. Casing 3-2. Cementing 3-3. Wellhead 3-4. Foundation of Storage Tank

3-1. Casing ■ Casing Size ■ Safety Factor of API ■ Casing Strength Section Original design Modified design Drilling Casing Grade Conductor (0~30 m) 16″ 14″ KS D3562 Surface (0~535 m) 12″ 10″ 12¼″ 10¾″ K-55 Intermediate (0~803 m) 8″ 9⅞″ 8⅝″ Monitoring (803~1100 m) - Open hole 7⅞″ 3.5” Strength Design safety factor Burst (from internal pressure) 1.1 Collapse (from external pressure) 1.125 Tension and Joint strength 1.8 ■ Casing Strength Depth 10 ¾ inch K-55 8 5/8 inch K-55 3.5 inch FRP Burst Pressure (psi) Collapse Pressure Weight (1000lb) Surface (0~535m) 3,130 1,580 629 - Intermediate (0~800m) 2,950 1,370 381 inner (790~1,090m) 2,500

3-1. Casing Not considering the buoyancy : Designing casing strength with worst condition Burst Pressure=Max. Pore PressureⅩSafety Factor(1.1) Collapse Pressure=0.052ⅩMW(13 ppg)ⅩDepth(ft)ⅩSafety Factor (1.125) FRP Casing : Collapse Pressure 17.9 Mpa ← Satisfying designed pressure (14 Mpa) K-55 grade : Yield strength 379~552 MPa / tensile strength > 655 MPa (minimum elongation: 15%) ■ Corrosion Upper steel casing :13 CR Lower FRP casing : Aliphatic Amine Cure Epoxy

Bottom Hole Static Temperature (BHST) 3-2. Cementing ■ Gravel Packing Collaboration with Canada Veriperm Co. ← Satisfying Class VI regulation Temperature monitoring using fiber optic sensor Cementing Depth : 913 m ■ Cementing Test Cementing test according to API Standard Water sampling from nearby rivers that are actually used for cementing Determining test condition considering actual physical conditions of injection well UCS of hardened cement slurry after 72 h : 23.6 MPa Bottom Hole Static Temperature (BHST) 45 ℃ Bottom Hole Circulating Temperature(BHCT) 30 ℃ Bottom Hole Pressure(BHP) 2,308 psi Mud Weight 1.16 g/cm3 Item Cement Density [g/cm3] 1.9 72h UCS (MPa) 23.6 Initial consistency (Bc) 12 100Bc Thickening time (min) 150

3-3. Wellhead ■ Completion and Pressure Test Control of Pressure and Sealing Pressure Welding Standard (API 2B) and Manufacturer’s welding standard (StreamFlo EB 01-004) Casing Pressure Test (max=14 Mpa] : test of sealing status Sealing of the control Line after installing the casing hanger • Stainless Line : Swagelok fitting • Polyurethane Line : Conax fitting Wellhead Pressure Test

3-4. Foundation of Storage Tank ■ Mat Foundation of Storage Tanks Seismic Design of Foundation: Korea Building Code (Ministry of Land, Infrastructure and Transport, 2016) Designed Foundation : Resistant to Intensity VII and Magnitude 6.1 ← Occurred Mag. < Designed Mag. Visual inspection and Level Survey : No Abnormality Sign Level survey of CO2 Tank Anchor Visual inspect of foundation crack Structure Front Level Back Level Difference Result Foundation 113 cm 113.5 cm 0.5 cm For rainwater drainage – Clear Tank Anchor 106 cm 0 cm Clear

4 Summary CHAPTER 4

4. Summary ■ Application of international standards for safety and reliability of the injection well ▷ No standardized domestic regulation related to the CO2 storage ▷ No domestic standard of the aseismic design for the CO2 injection well ▷ Design and completion according to the EPA Class VI and the API standards ■ Casing and cementing designs applied conservative standards and safety factor ■ Confirming sealing status of the wellhead by pressure test ■ Foundation construction based on the domestic standard of seismic design (KBC) ■ The status of the Janggi CO2 storage site after the Pohang Earthquake ▷ No detailed crack or settlement of mat foundation ▷ No pressure change of DTS sensor → borehole stability ■ Additional investigation for the completed monitoring well

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