Petroleum production geology

1. Oil & Gas Production Geology
Reservoir Description – Data (Sources)
Reservoir description is the base for a most effective and efficient reservoir
Management. Here, the production geologist plays a key role and will use a variety of
data (sources), including:
• mud logging data
• core data
• sedimentology and petrography reports, studies
• outcrop analogs / modern depositional environments
• a broad spectrum of wireline log and logging-while-drilling (LWD) data
• production log data
• well test data
• fluid samples
• production data
• seismic data
Production Geologist -> Static Model of Reservoir
Reservoir Engineer ->Dynamic Model + Simulation of Flows
Common Target: maximization of production froman oil or gas field
Integrated Study (Scale/Disciplines) – Micro- to Basin Scale

2. Synthetic Deposition model
Appraisal and Development of a Reservoir
A sheet-like turbidite reservoir will need only a few wells to appraise and develop it.
Channelized turbidite reservoirs will require several wells for appraisal and development
– due to this fact they may be less profitable

3. Reservoir to Net Pay
Terminology of Fluid Contacts
Pressure Gradients while Drilling through Different Media

4. Rock Types and Their Porosities
Porosity in Carbonates

5. Permeability
Processes that reduce porosity and permeability:
• Compaction
• Cementation
• Heavy hydrocarbon residue

6. Processes that enhance porosity and permeability:
• Dissolution
• Fracturing
• Dolomitization
Carbonate rocks are often subjected to early cementation, so reservoir quality depends
very strongly on dissolution, fracturing and dolomitization. Most carbonate reservoirs are
due to secondary porosity. Reefs sometimes preserve primary porosity.
Untypical Oil-Water Contact Configurations

7. Drive Mechanisms in Reservoirs
Expansion drive (Expansion of Fluids)
• _ Volumetric gas reservoir
• _ Oil reservoir without gas cap
Water drive
• _ Natural water drive by aquifer expansion
Compaction
• _ Compaction of reservoir by overburden
Water injection
• _ Pressure maintenance in reservoir by water injection
Gas(Re)injection
• _ Pressure maintenance in reservoir gas injection

8. Graph for Gas Equation
Saturation Distribution

9. Attic Oil
Evaluation Methods
Volumetric Approach (Early Life, Performance Not Indicative, Complex
Reservoirs, Always an Essential Baseline)
• Map, Calculate OIP, Recovery Factor
• Analogy
• Reservoir Simulation
Performance Approach ( More Mature Fields, Performance Trends
Established, Limited Additional Development, Volumetrics Still Informative)
• Decline Analysis
• Material Balance
• Reservoir Simulation
• Analogy
References
From many sources