Schlumberger / Client Confidential 2015 International Perforating Symposium Europe IPSE-15-28 Laboratory Assessment of Perforation Tunnel Stability and Sanding Propensity, Using Reservoir Wellcore Schlumberger / Client Confidential Graham Fraser, Tullow Oil Chris Chow, ProDuce Consulting Brenden Grove, Duncan Sanford, Schlumberger

Schlumberger / Client Confidential Agenda Field development objectives Technical challenges & risks Laboratory program Program design Results Conclusions Implications to field development Schlumberger / Client Confidential IPSE-15-28

Field Development Objectives Deepwater asset, offshore West Africa Completion strategy = cased & perforated ~Vertical wells Large HSD guns, DP charges No mechanical sand control (region where SC is common) Goals = Maximize productivity & ultimate recovery Critical to ensure wells will produce: Sand-free With low skin Reliably (including depletion, water encroachment, etc.) Also consider water injectors (shut-in, stimulation, etc.) Schlumberger / Client Confidential

Technical Challenges & Risks Tunnel stability and sand production During perforating: Mechanical shock loading during jet penetration Wellbore dynamics & large drag forces in first ~second During production: At expected field rates At depletion stresses With watercut Address both single-perf behavior and system effects Schlumberger / Client Confidential

Schlumberger / Client Confidential Laboratory Program Launched to address & quantify risks Perforate & flow, using actual reservoir wellcore Downhole stress, dynamics, and flow conditions 2 phase program: Phase I: 3 tests (tunnel stability, sand production, injector shut-in) Phase II: 3 tests (quantify long-term sand production, to ensure within facilities constraints) Schlumberger / Client Confidential

Perforating Laboratory – Brief Introduction Field Wellbore In-situ stress Reservoir Rock type, strength, Porosity, permeability Etc. Pore fluid type & pressure Perforating gun system Casing(s) Cement Schlumberger / Client Confidential Laboratory Reservoir Pore fluid pressure Wellbore Confining Stress Perforating Objective: establish a highly productive flowpath between reservoir and wellbore

Test Program Design (1/2) Use reservoir wellcore Trim/square ends Stack similar strength pieces to assemble each target Encapsulate for load transmission Stress & perforate at downhole conditions Schlumberger / Client Confidential

Test Program Design (2/2) Production flow at > field rates Simulate depletion Increase stress Introduce water cut Monitor tunnel stability and sand production real-time Rate Stress Flow & Diagnostics Schematic Schlumberger / Client Confidential Water Cut

Test Program Execution & Results – Phase I 3 tests Tests 1 & 2 – 39g charge (12SPF) Test 3 – 20g charge (27SPF) Formation properties: Turonian sandstone UCS ~ 2,442 - 3,400psi Permeability ~ 200mD Porosity ~ 18% All tests shot on static balanced conditions Dynamic underbalance ranging from 2,000-2,400psi Static effective stress = 3,200psi Dynamic effective stress (DES) ~ 5,200 – 5,600psi Test #3 (as example) summarized on following slides Schlumberger / Client Confidential

Phase I: Test #3 Build up core assembly Displace crude with OMS Perforate Production flow (multiple rates) – establish stable PI Q, dP vs. time Q vs dP

Water hammer transient Phase I: Test #3 5. Lifecycle sanding risk Stage 3: water cut Stage 2: stress Stage 1: rate 6. Water hammer (injector shut-in) 3 cycles conducted (1 shown) Flow: Q,dP vs time Flow: Q vs dP Water hammer transient 7. Injector stimulation treatment Acid Injected at T~145F OMS post-flush Solvent pre-flush

Phase I: Test #3 – Sand Detection & Collection Equipment & Set-up Results Real-time Sand Indicator Density spike in downstream flowmeter: early time sanding event Physical Sand Capture Blue dots: sand mass collected (grams)

Phase I: Test #3 – Tunnel Integrity Screenshot of video during high rate flow Casing hole viewed from wellbore View from ~10-15” inside tunnel Stable Intact Tunnel Confirmed

Test Program Execution & Results – Phase II 3 tests Test 1 – 39g charge (12SPF) Test 2 – 20g charge (27SPF) Test 3 – drilled hole Reservoir wellcore Extended flow @ field rates, to establish sanding concentrations (pptb – lb sand / thousand bbl oil) Depletion stress Watercut (10%, 20%, 30%) Test #1 (as example) summarized on following slides Schlumberger / Client Confidential

Phase II: Test #1 Build up core assembly Displace crude with OMS Perforate Sanding flow (extended duration) – rate, dP, watercut, density 2.8 lpm Oil flow Cleanup flow (2-3 lpm) 1.4lpm oil flow 1.4 lpm Oil+watercut

Phase II: Test #1 10% watercut; sand production equivalent to < 5 pptb & decreasing 4. Sanding flow (extended duration) – rate, sand collection 1x-2x field rates: sand production equivalent to < 2 pptb Cleanup flow (2-3 lpm) 1.4lpm oil flow 2.8 lpm Oil flow 1.4 lpm Oil+watercut

Phase II: Test #1 – Tunnel Integrity Stable Intact Tunnel Confirmed

Schlumberger / Client Confidential Summary & Conclusions Laboratory program conducted to assess sanding risk during and after perforating Realistic downhole environment reservoir cores, field charges, stress, flow Life-of-well scenarios replicated Scaled rates, depletion stress, water cut Findings: Minimal risk of tunnel collapse and catastrophic sanding Minimal sand produced over extended flow durations <1-2 pptb at twice nominal field rate <5 pptb at field rates with watercut Conclusion: Cased & Perforated is a viable option Schlumberger / Client Confidential