In a corresponding article from 2015, I quoted the title of Brant Bennion’s 1999 article “Formation Damage—The Impairment of the Invisible, by the Inevitable and Uncontrollable, Resulting in an Indeterminate Reduction of the Unquantifiable.” I would like to think that, given the considerable effort spent on drilling- and completion-fluid development since the article was written, we have a much better control of the “inevitable and uncontrollable.” Likewise, with respect to a “reduction in the unquantifiable,” much of the uncertainty can be minimized by performing representative corefloods using plugs of different permeability value to reflect the values expected downhole. It is permeability that is often the most difficult to quantify; therefore, focusing on permeabilities in coreflooding to cover the span of those likely to be encountered can improve our understanding of the potential formation damage that could be expected.
In this short article, I would like to focus on “the impairment of the invisible” because it is here that the greatest uncertainty exists with regard to formation-damage evaluation. One of the challenges for those involved with understanding an unexpected decline in well performance is identifying the exact causes for the reduced productivity because we cannot see downhole what type of damage has occurred and where. Production engineers can use significant amounts of time in attempting to identify a cause for poor productivity. This process involves evaluating all that has happened in the well, which includes the fluids used, losses during drilling and completion, lower-completion type and potential for plugging, and how effective well cleanup was. Consideration of all data available can eventually point toward one factor that could explain productivity decline. Coreflooding can also be used to simulate the sequences performed in the well, to try to identify the damaging mechanism. Regardless of those factors, the key take-home message is that prevention is much better than cure.
SPE 178963 Laboratory Simulation and Damage in Openhole Water Injectors by Michael Byrne, LR Senergy, et al.
SPE 178018 Evaluation of Damage Mechanisms in Tight Gas Reservoirs: Field Example From Perth Basin by Nick Bahrami, SGS Netherlands, et al.
SPE 179007 Ability of a Filter-Cake Breaker To Diffuse Into Completion Brine and Packed Gravel by Clotaire-Marie Eyaa Allogo, Schlumberger, et al.
Niall Fleming, SPE, Leading Adviser, Well Productivity and Stimulation, Statoil
01 February 2017