While the production zone is typically the responsibility of the reservoir engineering team, taking proactive steps during drilling and considering the full life cycle of a well have been shown to minimize formation damage, thereby significantly enhancing potential production outcomes.
Reducing damage, or skin effect, in mechanically weak and structurally complex reservoir geologies is critical to maximizing production and enhancing the net present value of an asset. Tightening margins, however, have prompted the universal strategy to reach the payzone and put the well on production as quickly and as economically as possible.
Typically, that approach includes the application of standalone drilling or reservoir drill-in fluids (RDF), which can intrude into the formation, diminishing permeability and production flow of often intrinsically depleted reservoirs. The resulting formation damage may extend a few centimeters or deep into the payzone, jeopardizing maximum reservoir drainage.
One option drilling and reservoir teams have is to include a wellbore-shielding additive in the fluid system, which blocks whole fluid filtrate losses into the production zone. Compatible in all types of drilling, RDF or completion fluids and comprising only 2% of the total fluid content, the technology also requires no acid cleanup to remove the deposited filter cake.
As confirmed in the results of a number of third-party return permeability studies, the use of wellbore-shielding technology consistently minimizes production-restricting formation damage. One independent study demonstrated that mixing the standard 2% concentration of the shielding technology within a 12.5-lb/gal oil-based RDF slashed the damage ratio from 64.3% to 4.5%.
Reservoir damage mechanics
In-fill development of mature fields and the young sedimentary rocks in many offshore plays represent the challenges operators face in maintaining permeability in often highly depleted and mechanically weak reservoirs. To that end, minimizing natural and induced formation damage to enable unobstructed production flow takes precedent when designing the reservoir drill-in and completions strategy.
Uncontrolled fluid invasion can further destabilize what is often inherently unstable geology, thereby laying down a thick and difficult-to-remove filter cake. The thicker filter cake, coupled with the increasing depth of filtrate invasion, can severely and often permanently restrict reservoir drainage.