Project Experience
The following engagements represent a selection of Fleissen’s completed work. Each entry reflects an assignment that was technically demanding, operationally grounded, and consequential for the client’s commercial or regulatory position.
FIRST E&P — Offshore FPSO Emissions Assessment
PML 83 & 85, Nigeria · GHG Assessment
Lack of a comprehensive, defensible emissions inventory across offshore FPSO operations. The client required a rigorous baseline to support regulatory obligations, decarbonisation strategy, and investor reporting.
Approach
- Compiled and validated production data, fuel consumption records, flare volumes, and equipment specifications
- Applied IPCC 2006 Guidelines, API Compendium, EPA AP-42 factors, and NUPRC methodologies
- Developed emissions models for combustion, venting, flaring, and fugitive sources
- Conducted Tier 1 uncertainty analysis to assess data reliability
- Prepared detailed assessment report with visual summaries and sector benchmarking
Outcome
- Complete, methodology-verified GHG emissions inventory established
- Emissions reduction roadmap aligned with national climate goals and NUPRC requirements
Client positioned for regulatory submissions and ESG reporting
Waltersmith Petroman — LDAR Survey & GHG Management Plan
Ibigwe Marginal Field, OML 16, Nigeria · GHG + LDAR
Unquantified fugitive and process emissions across the Ibigwe marginal field, with no structured framework for ongoing management or reduction reporting.
Approach
- Conducted baseline emissions quantification using engineering calculations and published emission factors
- Executed field-based LDAR survey using direct measurement — leak detection and quantification
- Applied U.S. EPA and API methodologies to assess venting, flaring, and fugitive emissions
- Developed structured GHG management plan with prioritised reduction strategies
Outcome
- Emissions profile established for the Ibigwe field
- Practical reduction strategies covering methane recovery, flare minimisation, NGL vapour recovery, and equipment optimisation
GHG management plan in place for ongoing compliance and reporting
Cabinda Gulf Oil Company (Chevron) — Fiscal Metering Audit
Installations · Measurement Audit · Retainer
Potential revenue exposure due to measurement inaccuracies across multiple offshore and onshore installations. Fleissen was engaged on a retainer basis through SMIC Angola.
Approach
- Deployed hydrocarbon measurement expert across 7 offshore and onshore installations
- Inspected fiscal meters, secondary measurement devices, production data integrity, and documentation
- Assessed calibration status and measurement gaps against international standards
- Produced audit report with prioritised recommendations for each installation
Outcome
- Improved measurement accuracy across all audited installations
- Recommendations issued to minimise financial exposure from measurement deficiencies
Ongoing retainer engagement — annual audit reports produced since 2023
World Bank — Nigeria Downstream Petrochemicals Opportunity Assessment
Abuja · Lagos · Port Harcourt · Market & Investment Advisory
The World Bank required a rigorous, data-driven assessment of the downstream petrochemicals opportunity in Nigeria to guide investment decisions and policy recommendations.
Approach
- Mapped Nigerian and regional petrochemical downstream value chains
- Assessed regional and global demand for intermediate and end-products
- Identified highest-potential value chains based on local inputs, production costs, capex, demand, and infrastructure
- Defined development requirements and investment roadmap for priority value chains
Outcome
- Clear identification of the highest-potential downstream petrochemical value chains
- Investment roadmap grounded in market data, cost analysis, and infrastructure assessment
Findings presented across Abuja, Lagos, and Port Harcourt
EGPP — LDAR for Gas Processing Facility
Ebedei, Ukwuani, Delta State · OML 30 · LDAR
The client required site-level emissions quantification and a practical emissions reduction plan for a gas processing facility.
Approach
- Conducted site-level emissions quantification using field data, process simulation, and engineering calculations
- Applied U.S. EPA and API methodologies to assess venting, flaring, and fugitive emissions
- Identified key emission sources and loss pathways across the facility
Outcome
- Practical emissions reduction plan developed — methane recovery, flare minimisation, NGL vapour recovery, equipment optimisation
Quantified emissions baseline established for regulatory and reporting purposes
Midwestern Oil & Gas — Gas Flow Rate Validation
OML 56, Umusadege Field, Nigeria · Field Measurement
The client required gas flow measurement for 8 gas lift wells as part of the biannual NUPRC MER Test. No fixed metering infrastructure existed.
Approach
- Advised on appropriate portable metering technology
- Mobilised Emerson FLEXIM G608 clamp-on ultrasonic meter to site
- Conducted trial measurement and validated results to client satisfaction
- Measured gas flow rates across all 8 wells at varying choke settings within a 2–3 day window
Outcome
- All 8 wells measured within the required regulatory timeframe
- MER Test compliance achieved with minimal disruption to operations
Client retained Fleissen on a biannual basis for ongoing MER Test support
Addax Petroleum — Metering & Allocation Audit
Izombe Flow Station, Nigeria · Expert Witness Support
Fleissen was engaged by Letton Hall Group to provide technical support on flow metering and allocation for Addax Petroleum, to understand the cause of crude oil allocation imbalances.
Approach
- Visited Izombe flow station to study the configuration of process facility and metering stations
- Performed process simulation (UniSim Design) to determine equilibrium gas and liquid flow rates
- Assessed separator and surge vessel processing capacity against API 12J
- Assessed the impact of gas break-out on crude metering figures
Outcome
- Root cause of allocation imbalances identified and technically substantiated
- Findings used to support expert witness submission
Clear recommendations provided for system remediation
Aradel required a structured Leak Detection and Repair (LDAR) programme and quarterly GHG reporting across its upstream, gas processing, and refinery operations. The engagement was designed to align with the NUPRC Guidelines for the Management of Fugitive Methane and GHG Emissions (November 2022) and the Petroleum Industry Act 2021.
Approach
Established an auditable emissions baseline using production, flaring, fuel consumption, and equipment data.
Screened facility components using an Optical Gas Imaging (OGI) camera and Gas-Sentry detector, in line with NUPRC guidelines and US EPA 40 CFR Part 60, Appendix K.
Quantified leaks and vents using a Hi-Flow sampler and vane anemometer, applying engineering calculations or emission factors where direct measurement was inaccessible or unsafe.
Calculated emissions using the API Compendium (2021) and EPA AP-42 methodologies, with uncertainty incorporated into the results.
Prepared quarterly NUPRC-aligned reports and conducted post-repair verification, maintaining all data in a centralised, audit-ready LDAR database.
Supported the development of a GHG Emissions Management Plan using the NUPRC template.
Outcome
Established tagged, evidence-backed leak and vent records with quantified emission rates.
Developed a consolidated facility-wide emissions inventory to support Aradel’s quarterly NUPRC submissions.
Advanced a regulator-ready GHG Emissions Management Plan and MRV framework.
Established an ongoing quarterly engagement for emissions monitoring, reporting, and management.
Approach
Designed and delivered a four-day training programme supported by a comprehensive Fleissen class reference manual.
Covered production operations, process fundamentals, plant economics, maintenance, mechanical integrity, process safety, HSE, and emissions management.
Used a fictional integrated facility case study (flow station and gas plant) to connect theoretical principles with practical operating scenarios.
Delivered sessions on fluid behaviour, flow and compression, separation, flow assurance, measurement, and debottlenecking.
Covered operating costs, netback, cash-flow appraisal, and production deferment.
Addressed maintenance strategies, rotating and static equipment integrity, turnaround planning, and major accident hazards.
Examined flaring, venting, methane emissions, and defensible GHG inventory development.
Conducted daily individual exercises and group assignments on operational and business decisions, supported by Excel workbooks and a closing knowledge assessment.
Outcome
Equipped participants to explain facility process routes and develop basic operating models covering revenue, costs, contribution, cash flow, and production deferment.
Strengthened participants’ ability to use equipment failure and inspection evidence to make informed maintenance decisions.
Improved participants’ ability to assess process hazards and emissions boundaries using sound engineering judgement.
Enabled participants to develop phased improvement plans with measurable benefits, assigned responsibilities, and clear acceptance criteria.