Ann: Rafael Flow Test Update, page-196

The other indication from the interpretation of the pressure data is that there is apparent near wellbore formation damage from invasion by drilling and completion fluids that has reduced the flow capacity of the tested zone. Experience in similar reservoirs indicates that this form of reservoir effect can be remedied by standard workover operations. This will form part of the recommendation to the joint venture for re-testing of the well in addition to the yet to be tested upper interpreted pay zones behind casing.



Formation Damage

• Formation damage is most commonly caused by wellbore fluids used during drilling and completion

Formation damage is a condition most commonly caused by wellbore fluids used during drilling, completion and workover operations. It impairs the permeability of reservoir rocks, thereby reducing the natural productivity of reservoirs. Formation damage can adversely affect both drilling operations and production, which directly impacts economic viability. Although the severity of formation damage may vary from one well to another, any reduction in recovery potential is unwanted. From the initial drilling operation and completion of a well to reservoir depletion by production, the effects of formation damage can negatively impact oil and gas recovery.
Although formation damage may affect only the near-wellbore region of a well—reaching only a few centimeters from the rock face of the bore-hole wall—it can also extend deep into the formation. The damage may be caused by solids that migrate and block pores or by drilling fluids that alter the properties of reservoir fluids. Reservoir engineers must be vigilant about the potential for formation damage and they can mitigate the impact of formation damage by understanding its mechanisms and how various types of damage might impact production. Assessment, control and remediation of formation damage are crucial to ensuring efficient use of the world's hydrocarbon resources.


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https://www.slb.com/resource-library/oilfield-review/defining-series/defining-formation-damage