Abstract
Optimized landing zone has been proven the critical decision for successful unconventional play development, and it’s also the one of the most challenging topics largely due to the complex and heterogeneities of rock mechanics and reservoir properties. To make a robust decision for landing the horizontal well in the unconventional play, a better workflowintegration of geomechanics and reservoir properties have been developed. In this workflow, a novel model has been developed in order to quickly evaluate the vertical and horizontal fracture growth in a given reservoir, this model is based on Lagrangian formulation using the Least Action Principle, which captures the elastic energy of the rock matrix, surface energy of opened fracture and viscous dissipation in fracture fluids. The workflow provides a quick screening tool for hydraulic fracture growth across mechanical and stress barriers by integration of leak off due to high permeability streaks. Finally, the potentially accessed hydrocarbon volume within the SRV will be evaluated for each landing interval, which will help to make reasonable and objective decisions for landing strategy. The proposed workflow has been demonstrated in the appraisal and development in global unconventional assets, i.e. Vaca Muerta play in Argentina, Wolfcamp play in Permian basin and secondary reservoir in CB tight gas field. After calibration with pressure data from DFITs and miniFracs, the model quickly provides scenarios of fracture height growth and length propagation as a function of time for different landing depths. The fracture growth both upward and downward that was predicted from this model for Changbei secondary reservoir have a good match with the diagnostic data (micro seismic, tracer log and temperature log interpretations). As the final outcome, the normalized accessed hydrocarbon in-place index (HCCAi) of each frac stage candidate has been computed, and this HCCAi has a positive correlation with well performance (initial production and EUR), thereby assisting landing zone optimization and stage ranking. The uncertainties of fracture geometries also have been analyzed and integrated into HCCAi for well performance evaluation.
