Geological Assessment of Reservoir Seals and Pay

Daily Title: Evaluating Reservoir Quality, Seal Potential and Net Pay

 Topic 1    BASIC PRINCIPLES OF CAPILLARY PRESSURE

                Learning Objectives: Understand uses of capillary principles in reservoir evaluation; fundamentals of capillarity: buoyancy vs. capillary pressure; wettability; contact angles; derivation of capillary pressure equations; definition of Free Water Level; description of the capillary pressure apparatus.

RELATED EXERCISE:

Use capillary pressure data to determine Free Water Level (FWL), oil/water contacts (OWC) and water saturations (Sw) at various heights above the FWL and at various subsurface depth

Topic 2           SEAL EVALUATION

Learning Objectives: Review concepts of top seals (caprocks) and intraformational seals (baffles & barriers); demonstrate application of integrated petrophysical and geochemical techniques in evaluation of seal potential in both equilibrated and dynamic petroleum systems (includes Case Studies from offshore Java, Indonesia and NW Shelf, Australia)

RELATED EXERCISE

Utilise a scenario of a large structure identified by seismic with a discovery well drilled at the crest.  Learn to use given rock properties, structure and capillary pressure data to evaluate reservoir quality of encountered rock types, locate fluid contacts and establish saturations with depth.  Also, learn to use these data to determine seal capacity, and based on this capacity determine depths at which each rock type becomes pay and whether discovery is viable

Daily Title: Evaluating Reservoir Quality, Seal Potential and Net Pay

 Topic 3     FAULT SEAL EVALUATION

Learning objectives: Understand and predict "sealing" vs "leaking" faults. Discuss the probabilistic approach to determining whether faults act as seals or conduits in the subsurface. Review the principle elements of fault sealing (juxtaposition, fault zone process, and reactivation) and present a risk matrix to assess these.  

Topic 4  PORE GEOMETRY

Learning Objectives: Understand the effects of pore geometry (size, shape, distribution of pores and pore throats) on relative permeability and capillary pressure.  Learn to relate these properties to amounts, types and rates of fluids produced. 

RELATED EXERCISE Learn to incorporate various data types (well-site sample descriptions, thin section photographs and petrographic descriptions) to estimate capillary pressure properties of different reservoir rock types.   

 Daily Title: Evaluating Reservoir Quality, Seal Potential and Net Pay

 Topic 5  RECOVERY EFFICIENCY

Learning Objectives: Learn to use drainage and imbibition capillary pressure data in conjunction with relative permeability data to evaluate recovery efficiency of reservoirs on primary depletion as well as to judge the distribution of remaining fluids prior to secondary production.

RELATED EXERCISE

Use available reservoir data to predict recovery efficiency for the carbonate “Bullseye” field.

  Topic 6           RESERVES ESTIMATION AND NET PAY DETERMINATION

Learning Objectives: Understand deterministic vs stochastic methods of evaluating reserves. Review conventional methods of determination of net pay in a reservoir and become aware of some improved techniques using core, sidewall core, cuttings, conventional plug measurements (porosity and permeability) in conjunction with capillary pressure and relative permeability data.    RELATED EXERCISES

1. Given basic rock and fluid properties, calculate OOIP and reserves for Landslide Field, Kern Co., California
2. Use available production data and reservoir properties to predict reserves and evaluate reservoir management options for the “Bullseye” field (worked on in previous Exercise).