Conventional reservoir drilling fluids typically consist of xanthan-based polymers to optimize recovery of drill cuttings and reduce friction or torque during the drilling operations. Previously conducted laboratory studies have indicated that the damage produced by these types of xanthan-based drilling fluids can be easily removed. Field data, on the other hand, has indicated that substantial amounts of polymeric damage remain in the formation. Even though these psuedoplastic, non-thixotropic, xanthan-based drilling fluids exhibit low shear rheologies during the operations, they can contribute to tremendous amounts of skin damage. This insufficient degradation of filter cake may impede flow and dramatically reduce formation permeability hence well productivity.
Recent extensive research was conducted to develop a treatment which could effectively reduce this type of polymeric damage. A novel biotechnological treatment has been developed, which effectively removes xanthan-based filter cakes or skin damage at temperatures from 70°F to well over 250°F.
Core flow evaluations have shown that multi-fold improvements are achieved with this optimized biotechnological removal treatment. A detailed study of the laboratory and field case histories are presented. Average incremental production rates of the treated wells were significantly improved, clearly demonstrating the effectiveness of this removal system.