Modeling of the Mesaverde Formation in the San Juan Basin, northwestern New Mexico, shows the importance of using realistic drainage patterns in a naturally fractured reservoir. Fractures not only enhance the overall porosity and permeability of these reservoirs, but fractures also create significant permeability anisotropy. Permeability anisotropy causes the drainage area around the wells to be elliptical. Directional permeability is best found with multiple well interference tests. Predicted potential for infill drilling depends on the modeling approach, because elliptical drainage creates more overlap and undrained sections than a more radial drainage in an isotropic permeability case. Modeling with permeability anisotropy increases the potential for infill drilling and identifies optimum locations for new infill wells.

This approach has been applied in the Mesaverde Formation to determine economic optimization of infill drilling in these reservoirs and demonstrates that field development based on elliptical drainage areas can lead to a reduction in drainage overlap of adjacent wells and prevent leaving undrained areas. From multiple well interference testing a strong permeability anisotropy was found. Reservoir simulations were performed in two pilot areas of different fracture intensity to quantify the potential for infill drilling, reducing the well spacing from 320 to 160 acre. Simulation results indicate areas of effective drainage, the optimum locations for infill wells, and the additional recovery from infill wells.

AAPG Search and Discovery Article #90937©1998 AAPG Annual Convention and Exhibition, Salt Lake City, Utah