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Stimulation of the Lower Pennsylvanian (Atoka-Morrow) sands in Southeast New Mexico has presented a number of particularly difficult problems since the earliest treatments attempted. problems since the earliest treatments attempted. History of the area indicates that these sands are especially fluid sensitive and some damage most always occurs during drilling and completion operations. Treatments in the past very often reduced rather than improved flow characteristics, even those jobs involving very small breakdown volumes. Usually, production was never restored to the "natural" level.
Recent advances in treating systems for these ultra-sensitive gas sands have made a significant contribution to the successful development of gas reserves in the area.
Changes in the Morrow completion stimulation approach are discussed in this paper. In addition, a general description of job design is given along with a brief results cross-section.
Over the past 12 to 15 years, the Morrow Sand has been the object of considerable industry interest and exploratory drilling has indicated an extensive area of potential production. This area encompasses most of Eddy and parts of Chaves and Lea Counties in Southeast New Mexico (Fig. 1). During this time, however, completion difficulties encountered in the Morrow have resulted in the abandonment of numerous promising prospects. Most of these were tested during drilling operations and yielded good shows of gas or gas-condensate. Once completion attempt was underway on those projects where tests seemed to warrant the risk, subsequent production rates were frequently never as good as were indicated from DST information.
Completion - stimulation programs employed in the Morrow Sand for removal of skin damage and far reservoir improvement have for years provided inconsistent if not generally unsatisfactory results. A success ratio of 35 to 40 percent might even have been considered good but percent might even have been considered good but for those instances (at least 40 percent) where flow rate was reduced substantially as a result of treatment. This poor overall treatment response gave rise to the philosophy that the best way to complete from the Morrow was to avoid, where possible, treatment of any kind. Consequently, possible, treatment of any kind. Consequently, many completions were natural with the final flow rate being significantly less than the reservoir in an undamaged state was capable of delivering.
