41st Gas-Lift Workshop Houston, Texas, USA June 3 - 7, 2019 Expanding Artificial Lift Initiatives in a Mature Field: Case Study of “Zeta” Field in the Niger Delta Adeyemi Ganiyu, Ochi Achinivu, Adebayo Olufemi, Oluwabiyi Awotiku, and Chijioke Ibeh (Petroleum Engineers) 2019 Gas-Lift Workshop June 3 - 7, 2019

Introduction Outline Overview Unlocking Value from Old Completions Candidate Selection Process Operational Considerations Unconventional Gas Lift (GL) Installation Procedure Case Histories Results and Conclusion Challenges / Lessons Learned / Best Practices 2019 Gas-Lift Workshop June 3 - 7, 2019

Zeta Field Overview Background: Problem statements: Location is Offshore Niger Delta Production started in the 1960s and peaked at 77,000 bopd Main production facilities and satellite stations Gas compression and water injection facilities Problem statements: Initial completions have no conventional gas lift mandrels Most of the completion fluids/mud are of high density Limited gas lift network coverage in the field 2019 Gas-Lift Workshop June 3 - 7, 2019

Unlocking Value from Old Completions Opportunities Significant reserves opportunities in stacked reservoirs Completion re-design for artificial (gas) lift Rigless intervention for potential cost saving Unconventional GL installation - Orifice insert, Pack-off Assembly Production restoration to arrest field decline Low cost strategy for marginal reserves addition 2019 Gas-Lift Workshop June 3 - 7, 2019

Candidate Selection Process Nodal Analysis Model wells IPR/VLP before and after initiation of gas lift. Screen out wells that do not benefit from gas lift initiation Remaining Oil Reserves Focus on marginal reserves that are not economical with new drills or Major Rig Workover (MRWO) Availability of Sustainable Lift Gas Source availability of lift gas (dry) with adequate lift pressure Completion Fluid Type Operational challenges of unloading completion fluid based on fluid type Mechanical Integrity Pre-work activities prior to mobilization to ascertain well-casing integrity 2019 Gas-Lift Workshop June 3 - 7, 2019

Unconventional Gas Lift Installation Types Orifice Insert Involves direct installation on tubing wall Applicable for wells with brine as completion fluid Workaround for wells without gas lift mandrel Pack-off Assembly with Pre-installed Orifice Insert Orifice insert is pre-installed on a spacer pipe Applicable for wells with mud as the completion fluid Multiple Slickline runs for future wireline intervention 2019 Gas-Lift Workshop June 3 - 7, 2019

Checklist Wellbore Configuration Pack-off assembly may not be suitable for small tubing especially 2-3/8” Installation Design Designed injection depth must be adjusted for blast joint/tubing collar Ensure adequate lift pressure available at the depth of injection Flowline availability Consider potential bottlenecks resulting from higher fluid conveyance Surface flow rerouting Completion Fluid Evacuation Make provisions for evacuating mud in annulus for zero discharge offshore 2019 Gas-Lift Workshop June 3 - 7, 2019

Unconventional GL Installation Procedure Typical Installation Procedures Valve Integrity Test Gauge Cutter Run Data Acquisition Tubing Plug Isolation Integrity Test / Set Catcher Orifice Installation Unloading of Annular Fluid Retrieval of Tubing Plug 2019 Gas-Lift Workshop June 3 - 7, 2019

Case Histories: Well AA-01 Well AA-01 was spudded in 1960 as an oil producer Well quit production due to low reservoir pressure Nodal Analysis suggest reactivation with gas lift Estimated remaining reserves was 0.5MMBO which could not support Major Rig Workover (MRWO) 2019 Gas-Lift Workshop June 3 - 7, 2019

Case Histories: Well AA-01 Well modeled with latest reservoir and well test data Gas lift designed based on available lift gas pressure 16/64” Orifice size and injection depth of 4669 ft-MD Static gradient survey showed fluid level at 3326 ft-wlm 2019 Gas-Lift Workshop June 3 - 7, 2019

Case Histories-Well AA-01 Installation procedures were carefully implemented Well put on production after the orifice insert installation FTHP/FLP/CHP = 200/100/980psi Well AA-01 was successfully restored back to production Initial oil rate was 625 bopd 2019 Gas-Lift Workshop June 3 - 7, 2019

Case Histories: Well AA-02 Well AA-02 was spudded in 1970 as an oil producer Well quit production in 2009 due to high watercut Nodal Analysis suggest restoration through gas lift Estimated remaining reserves was 0.60MMBO which could not support MRWO 2019 Gas-Lift Workshop June 3 - 7, 2019

Case Histories-Well AA-02 Well modeled with latest reservoir and well test data Gas lift designed based on available lift gas pressure 14/64” Orifice size and injection depth of 3435 ft-MD Implementation involved tubing punch for mud unloading 2019 Gas-Lift Workshop June 3 - 7, 2019

Case Histories-Well AA-02 Pumped Filtered Seas Water (FSW) into tubing to unload the mud via the casing About 310 bbl. of FSW before clean returns to surface Mud return was lined up to the mud evacuation vessel as shown below Lift Gas initiation through the casing Open lift gas to casing and received about 100bbl of crude and water into Flow Back Tank (FBT) Then the isolation plug was retrieved and pack-off assembly installed at 3440 ft-MD 2019 Gas-Lift Workshop June 3 - 7, 2019

Case Histories-Well AA-02 Installation procedures were carefully implemented Well put on stream after the pack-off assembly installation FTHP/FLP/CHP = 300/200/850psi and the wellhead sample was 100% crude Well AA-02 was successfully restored back to production Initial oil rate was 1730 bopd 2019 Gas-Lift Workshop June 3 - 7, 2019

Other Applications Current Initiatives Future Technologies Oil line conversion to gas line Jacket-centric sourcing of lift gas Use of high gas oil ratio (GOR) as gas source Cement packer zone switch from an idle wellbore to gas bearing reservoir Future Technologies Gas metering through clamp-on metering Use of unbounded flexible pipe Use of velocity string 2019 Gas-Lift Workshop June 3 - 7, 2019

Results and Discussions Project Achievements: Significant production restoration from idle wellbores (~11,600 barrels of oil per day) Cost saving with rigless intervention Six oil flowlines successfully converted to gas flowlines Improved utilization of existing assets in the field 2019 Gas-Lift Workshop June 3 - 7, 2019

Unconventional Gas Lift Installation Challenges Caked completion mud is always very difficult to unload and dispose especially those of lignosulfonate composition Need for treatment and disposal vessels of mud left in annulus Optimization in a dual unconventional gas lift system is a big challenge due to installation of orifice insert. Adequate measurement and of injected gas due to non availability of gas meters Need for a portable non-intrusive strap-on type gas meter for GL optimization. 2019 Gas-Lift Workshop June 3 - 7, 2019

Conclusions The Operator has achieved substantial production restoration from old and idle wellbores Significant cost optimization was realized using rigless intervention to restore production in old completions Artificial (gas) lift implementation is a major contributor towards arresting field production decline Movement of stranded marginal oil reserves to production Excellent job design and use of cross-functional team is a critical success factor 2019 Gas-Lift Workshop June 3 - 7, 2019

Lessons Learned/Best Practices Proper job planning and candidate selection Cross-functional team approach contributed significantly to the success Static gas pressure gradient chart must be used to determine the appropriate gas gradient. Regular lookback sessions improves future gas lift designs and execution Verifying the completion fluid type is critical to job planning and successful gas lift installation wellwork Use of Tubing Collar Locator (TCL) is very important to avoid punching hole on the collar 2019 Gas-Lift Workshop June 3 - 7, 2019

41st Gas-Lift Workshop Houston, Texas, USA June 3 - 7, 2019 Thank You/Questions 2019 Gas-Lift Workshop June 3 - 7, 2019

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