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This manuscript is submitted as an addendum to SPE/IADC 797971, which discussed emerging successes using a new fixed cutter bit to drill hard rock applications conventionally drilled with roller cone bits. The new bit design using thermostable polycrystalline (TSP) diamond cutters and stability enhancing features has produced results, particularly in the Carthage field in Panola County, which are revolutionizing hard rock drilling in several areas of East Texas. The paper focuses on how teamwork, selective testing programs, and product improvements have combined to create step change improvements in hard-rock drilling capabilities. The paper discusses new information on optimal operating parameters and includes case history examples.

Over the past 18 months the Gas Research Institute has initiated a restimulation study in wells in the Green River Basin, Piceance Basin and East Texas Cotton Valley Reservoirs.1 New specific diagnostic procedures have been utilized to select candidates as well as intensive laboratory studies have been conducted to select specific candidates for restimulation. This paper will report on the laboratory testing, which involved fluidizing beds of proppant from previous treatments and also report results of effects of various chemicals on specific reservoirs. Several restimulation candidates case histories will be presented and a great deal of detail will be given in reference to refrac design, type of treatment and diagnostics utilized to ascertain success or failure of the treatments as well as production data. The program has illustrated that there are available diverting techniques that can function over long sections and achieve excellent stimulation. The authors will discuss laboratory testing procedures and specific recommendations in reference to selection of candidates and specific stimulation procedures that can be followed in various reservoirs.