Abstract
The J Sand formation is a main pay zone in the extensively developed Wattenberg field of Colorado. Until recently, operators deemed the reservoir in the northeast part of this field uneconomical due to significant production of formation water in this low permeability and sub-pressured gas zone. By modifying the conventional completion techniques of the J Sand, an operator relatively new to the area has been able to economically exploit this reservoir. Key factors that have contributed to the success include improvements in stimulation design and production techniques. Typically, hydraulic fracture stimulation treatments for the J-Sand utilize a low viscosity, guar based, zirconium crosslinked fluid pumped at injection rates up to 24 bbl/min. The above operator differs in stimulation design by incorporating a higher viscosity, low polymer carboxy methyl guar fluid pumped at a relatively low injection rate (e.g. 12 bbl/min). Well performance evaluations utilizing the Reciprocal Productivity Index (RPI) production analysis method in conjunction with log analysis quantify stimulation effectiveness. Treatment pressure history matching with 3D fracture simulators also identify advantages in achieved fracture geometry and proppant placement with the modified treatment design.
