An Effective Technique of Estimating Drainage Shape, Magnitude and Orientation in a Low-Permeability Gas Sand

摘要

This study presents a methodology to determine the optimalrninfill location for the Mesaverde Field in the San Juan Basin,rnNew Mexico. Evaluation techniques include: (1) Log-derivedrncumulative distributions to develop producing interval limits,rn(2) Seismic analysis to identify fractures, (3) Type-curvernanalysis to generate reservoir properties, (4) Productionrndecline analysis for establishing inter-well relationships, (5)rnGeostatistical modeling to distribute reservoir characteristics,rnand (6) Flow simulation for verification and formationrncontribution. The result of incorporating these evaluationrnmethods is a map that provides limits to the drainage area.rnSpecific information obtained is degree of anisotropy,rnaspect ratio, and the magnitude and orientation of thernpermeability. In the study area, the dominant fracturernorientation was N30oE as indicated by seismic curvaturernanalysis and confirmed with production decline analysis.rnType-curve analysis resulted in an average well permeabilityrnfrom 0.10 md to 7.75 md. It was demonstrated that arnminimum permeability ratio (kmax/kmin) 13.7:1 was sufficient tornmatch the interfering production response exhibited betweenrnwells. Limited infill drilling was identified on the drainagernmaps, as the existing wells exhibit an average drainage area ofrnapproximately 160 acres. Potential recovery was estimated tornbe 800 MMscf per well for the selected locations with the bestrnchance for success.rnA common problem in infill drilling projects is to decide torntarget prolific areas or low reservoir quality areas in thernMesaverde Group. This study area consists of high equivalentrnpermeability as a function of naturally occurring fracturernnetworks, when compared to the rest of the basin. Thernlikelihood of widespread drainage to occur is high. Therefore,rnthe potential for infill drilling may be limited. This workrndemonstrated that although limited potential, exists, properrnevaluation methods established in this work might be useful tornidentify the best location.