The Hugoton Field located in the Texas Panhandle is one of the largest gas producing fields in the lower 48 states. Up until now, these shallow reserves have been exploited by drilling either vertical wells with air or long reach horizontal wells with conventional overbalanced techniques. Due to the low formation pressures, in the range of 600 psi, depletion is a major issue and wells drilled in conventional overbalance have not exhibited a consistent productivity trend. These low pressures have also resulted in severe lost circulation problems during drilling with resultant formation damage and productivity deterioration. An additional challenge has been the close proximity of water to the productive formation, which effectively eliminates the use of fracturing as a stimulation option.
Previously, wells were drilled vertically using underbalanced techniques (UB) but the limited kh that resulted had little positive effect on productivity. Nevertheless, the operator decided to drill three horizontal wells using UB, as a case study to make a definitive evaluation of its effectiveness in the Hugoton Field. All three wells were successfully completed and achieved a significant increase in production when compared to offset wells drilled conventionally. The results achieved were of added significance considering the low cost environment in which the wells were drilled, where use of conventional techniques typically resulted in marginal economics.
In this paper the authors will detail the well design and the UB model considerations, which took into account the geological, reservoir depletion and water proximity challenges. They will present a detailed evaluation of the incremental production rates of the order 300 – 400% that were achieved when compared to offset wells drilled and completed conventionally. They will conclude that the use of Horizontal-UB techniques in the Hugoton Field is indeed a highly viable means of achieving significant production improvement and may well provide a powerful tool for the continued exploitation and prolonged economic life of the field.