Abstract
Since the mid 1990s, when an ambitious program to rejuvenate the Burgos Basin was undertaken, Pemex Exploración y Producción (Pemex) has embraced many of the technologies responsible for increasing gas production in South Texas. These include 3D seismic acquisition and processing, improved drilling and hydraulic fracturing technologies, new logging tools, and comprehensive core studies. However, a critical component to the success of these new technologies is the rigorous application of workflows that integrate the myriad elements required to identify reserves growth opportunities.
Key steps in the workflow involve generating and integrating 3D seismic and well depth structures; seismic attribute tests, depositional architecture maps from logs and core, well logderived rock properties calibrated to routine core and SCAL data, volumetric mapping; comprehensive well history and completion analysis, EUR and drainage area bubble mapping; per-fault block recovery efficiency determination, offset analog comparison, and location selection, risking and ranking.
Two such integrated studies conducted by Pemex with assistance from The Scotia Group (Scotia) identified substantial future reserves potential and demonstrated the effectiveness of this integrated approach. At Corindon-Pandura, in the northwest corner of the Burgos Basin, for example, integration of the depositional systems interpretation, seismic and structural mapping and analysis of EUR bubble clusters revealed an obvious structural component to reservoir performance that is contrary to the depositional architecture. The integrated analysis also indicated that the effective drainage radius of most wells was much smaller (21-115 acres) than the existing 300 acre well spacing. Comparison to contiguous production in Texas confirmed the need for closer well spacing and indicated that improved drilling and completion practices could increase per completion recoveries by 0.5Bcf. Numerous infill and step-out locations were identified at Corindon-Pandura, with reserve growth potential totalling189 Bcf. Drilling to date includes more than 16 successful completions with initial rates averaging 2.8 MMcfd per well.
Similar results were achieved at Mojarrenas-Santa Rosalia where opportunities depended on identifying better primary porosity trends as well as resolving the complex structural influence on reservoir performance. The recent drilling results from the Corindon-Pandura and Mojarrenas-Santa Rosalia field complexes show dramatically the effectiveness of the integrated study workflows being implemented by the Pemex's Reynosa production teams. Characterization of the structural and reservoir complexities of the field areas has enabled Pemex to predict with reasonable certainty the development of target sands. More than 90% of the 72 wells drilled since completion of these studies have been completed and are producing.
