Executive summary

This course covers formation damage problems encountered during all phases of a well’s life from drilling to abandonment. Formation damage is evaluated as permeability impairment that causes energy lost beyond that required for hydrocarbon to flow from a reservoir drainage area to surface. The near wellbore phenomena responsible for many types of formation damage, is introduced. Specific problems associated with different well’s phases that cause additional pressure drop, are covered: fluid filtration, filter cake formation, fines generation and migration, precipitation of plugging materials (asphaltenes, paraffin, sludge, hydrate, scale, salts, polymer residues, and emulsion), rock elastic/plastic deformation and compaction, liquid phase banking and blockage, water/gas coning and cresting, non-Darcy flow, liquid loading (back pressure), clays swelling, stress sensitivity, wettability alteration, and natural/induced fractures closure. Field cases presenting techniques of diagnosing formation damage and applied methods to mitigate it will be discussed.

Course Outcome

• Develop understanding of the relation between formation damage and reservoir energy loss.
• Establish realization of the concept of near wellbore phenomenon and its effect on well production from drilling to abandonment.
• Develop skills to build a radial model to simulate near wellbore flow
• Learn field practices and techniques to assess formation damage problems and the current methods to restore reservoir energy.
• Use the diffusivity equation to develop a radial model for formation damage
• Differentiate the formation damage effects and corresponding techniques to alleviate them.
• Lear hoe to design and scale-up laboratory tests to simulate field formation damage problems.

Course Outline

Near wellbore modeling

• Diffusivity equation
• Radial flow modeling
• Effect of skin damage

Types of formation damage

• Chemical: wettability, swelling, deposition
• Mechanical: failure, crushing, embedment, viscoelastic effect, stress sensitivity, compaction, flow restriction
• Thermal: stresses, dissolution, degradation
• Biological: corrosion, plugging, toxicity

Drilling damage

• Stress/strain, stress/strength, stress profile, stress magnitude and direction, effective stress
• Wellbore stability: effect of filtrate on strength, osmosis, creeping, breakout
• Skin damage: internal mud cake, constant & variable skin, Non-Darcy flow
• Filtrate leak off: mud, cement, Physico-chemical effect, modeling

Completion damage

• Perforation: underbalanced, stress cage effect, oriented, limited entry, friction, plugging
• Sanding tendency: FracPack, gravel pack, fines migration

Stimulation damage

• Fracturing: oriented fracturing, tortuosity, fracture closure, creeping,
• Leakoff: fracturing fluid, acidizing fluid
• Cooling down and temperature recovery: CRCP
• Proppant embedment and crushing

Production damage

• Hydrate formation, Asphaltene deposition, Paraffin deposition, scaling
• Water coning, water cresting, gas coning
• Multiphase pressure loss, Condensate banking, water blockage, turbulence-flow pressure loss
• Well loading, compaction, smart depletion, well shut-in
• Surface compressor/ connecting high to low rate wells

WO, injection, IOR and EOR damage

• Water injection: water hammer, skin
• Thermal stresses
• Fines migration

Measurements and surveillance

• Controlled depletion
• Pressure drawdown within a well
• Smart wells: Downhole sensing and control; ICV, ICD, flowmeters
• Wellbore pressure gradient optimization

Discuss and provide Excel Sheets for the problems:

• Use a radial model of a single model to understand the effect of skin on
• Understand the effect of near wellbore stress on perforation stability and its damage effect.
• Use Hawkins’ formula to estimate the depth of damage due to drilling in unconsolidated reservoir, then determine the required FracPack length to bypass
• Derive the skin damage due to radial convergence, then compare the effect of non-Darcy flow on productivity.
• Compare flow productivity in condensate reservoir with condensate banking for longitudinal vs transverse fractures.
• Use Darcy’s equation for a horizontal well to understand how the skin factor is related to production.