Introduction to Formation Evaluation: A Comprehensive Guide for Petroleum Engineers, Lecture notes of Formal Semantics

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Introduction to Formation

Evaluation

By

Abiodun Matthew Amao

Lecture Outline

• What is formation evaluation?

• Why do we evaluate formation?

• What do we evaluate?

• What data are we interested in?

• Who needs these data?

• What tools and methodology?

• Summary

• References

Why do we evaluate formation?

• We want answers to the following questions:
• Is there any oil or gas there?
• Where are they located?
• How much of it?
• How much can we produce, which answers the question, “How much money can we make?”

What do we evaluate?

• We evaluate a reservoir; a reservoir is the

“container” storing the hydrocarbon.

• A conventional reservoir will be characterized

by the following properties;

– Trap/Cap Rock

– Source Rock

– Porous and Permeable media

– Hydrocarbons (Gas or Oil)

Scale in Formation Evaluation

Order of Magnitude

(Meters)

Formation Evaluation Technique Purpose

Satellite Imagery

Gross Structure

Basin Geologic Studies

104 Seismic, gravity, magnetics

103 Borehole gravimeter, Ultra long

spacing electric logs

Local Structure

Drill Stem Tests Productivity and Reserves

101 Wireline Formation tests

100 Full diameter cores (Whole Core) Local Porosity, permeability

and Lithology

10 -^1 Sidewall cores, LWD, Wireline

Core-plug analysis, micro-logs

Cutting analysis, mud logging Local Hydrocarbon Content

Core analysis Rock Properties

10 -^5 X-ray mineralogy Rock and clay typing

10 -^6 Scanning Electron Microscope Micro-structure 7

Who Needs What Data?

Discipline Data Geophysicist Time-Depth relationship for seismic profile Geologist Stratigraphy, Structural Sedimentary features, Mineralogy, bedding planes Reservoir Engineer Porosity, permeability, fluid contacts, reservoir pressure, producibility Drilling Engineer Reservoir targets, offset log data if any Production Engineer Rock mechanical properties, reservoir pressures, flow potential, flow assurance issues, fluid types Manager Hydrocarbon in place, recoverability, cost of development, profitability Government (Regulator) Keeps a record of All data, field development plan (FDP), Profitability for the national economy

Seismic Surveys

Data from Seismic Survey

• Vertical Seismic profile of the earth

• Sedimentary and stratigraphic information

• Structure of the reservoir

• Location of traps and seals

• Depth of structures and geologic layers

• Presence of fluids

• 3 D high resolution surveys

• Time Lapse seismic ( 4 D Seismic)

Data from Mud Logging

• Typical data gotten include the following;
  • Lithology, mineralogy and their estimated depths
  • Hydrocarbon shows and type
  • Chromatographic analysis of gas
  • Hazardous gas e.g. H 2 S
  • Rate of penetration
  • Fossil record
  • Overpressure zones
  • Drill cutting porosity

MWD/LWD Tools

LWD

Wireline Logging

Logging Truck Logging Tools Skid Units Wireline Cable

Well Log

Data from Wireline Logging & LWD

• Most versatile of the formation evaluation methods, it is an indirect measurement. The following data can be gotten: Tuesday, February 21 , 2017 Well Logging PGE 492 17

Open Hole Logging (LWD & Wireline) Cased Hole Logging (Wireline only)

• Porosity
• Fluid Sample (Types)
• Water Saturation
• Hydrocarbon movability
• Lithology
• Formation dip and structure
• Sedimentary Environment
• Travel times of elastic waves
• Permeability
• Fracture and Vugs
• Rock mechanical properties
  • Flow rates
  • Fluid types
  • Pressure
  • Residual oil saturation
  • Cement evaluation (Bonding)

Data from Core Analysis

• Coring: Get unaltered formation sample, bring it to the surface with its native fluid, preserve both and transport to a laboratory for detailed analysis. - Conventional Coring- Used of core bit and BHA - Wireline Cores: Sidewall core guns and Rotary sidewall coring tool
• Data gotten from cores are; ( These are direct measurements done on the core samples )
• Routine core analysis : Porosity, Permeability, Lithology, grain density, Fluid saturation etc.
• Special core analysis : Relative permeability, pore-size distribution, mineralogy, SEM, CT-Scan, Electrical properties, mechanical properties, Capillary pressure, etc.

Telemetry Hydraulics Electronics Packer Drawdown / Pump Large Volume Pump Tank Carrier Borehole Exit V.P.C. Extraction manifold Tank Tank Formation Fluid Sampling Formation Tester from Baker Atlas