ABSTRACT

The San Juan Basin is a low pressure gathering system with 10,000 active wells, and 5500 miles of gathering pipeline. Many of these wells have been producing for over 60 years. The overall system pressures and volumes have stabilized. In 2001 a new simulation model was built of the system. The new model's graphic capability provided an immediate benefit. For the first time operators were able to see the direction of flow, and hidden system capacity constraints were revealed. By December 2001 industry experts forecast an increase in well drilling and potential for increased system throughput. These forces lined up to create the San Juan Basin Optimization Project. Optimization of this low pressure gas gathering system was completed by applying simple engineering concepts to improve the overall system efficiency. The system was optimized by designating a high pressure backbone, the removal of contract pathing, implementing push compression, and identifying liquid traps. The steady state simulation model was used to detail existing system capacity and propose changes to increase that capacity with minimal capital outlay. The result of optimization is a capacity increase of 10% throughput, with potential economics that put this project in a 50% return bracket.

SYSTEM DEMOGRAPHICS

The Enterprise San Juan Gathering System is located in the northwest corner of New Mexico. The geological formations are shallow in nature and rarely produce a dry hole. The underlying formations exist in extremely tight sands, which allow wells to produce for many years.

SIMULATION GRAPHICS

In 2001 the first San Juan Basin graphical simulation model was built. Prior to 2001 the system modeling effort had been achieved by utilizing a home grown FORTRAN program. The output of the FORTRAN model was tabular, with columns of printed numbers on reams of paper. The value of system graphics was immediate and powerful. Pressure plots identified system connectivity and volume dynamics. It provided a tool to quickly identify which wells were flowing through which compressors. Correcting compressor well groupings affected both production revenues and recovered operational costs. The simple indication of flow direction was significant to understanding problems and potentials. It allowed the recovery of long lost pigs and provided the information necessary to revamp valve position requirements during pigging operations. Flow arrows with pressure plots highlighted areas in the system where pipeline capacity was being compromised. Originally pipelines had been designated to flow to certain compressor stations. These pathways were written into contracts to ensure that non paying producers were not allowed to benefit from newly installed compression. This contract pathing caused sub optimal pipeline utilization. This discovery helped to shape future contract negotiations. Compression contracts written today obligate the gatherer to provide an average wellhead pressure and stays away from guaranteeing a specific pipeline path.

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