New Algorithms and Integrated Workflow for Tight Gas and Shale Completions

Abstract

Abstract Multi-stage stimulation has become the norm for unconventional reservoir development. How many fracture treatment stages and perforation clusters are optimal? What is the ideal spacing between perforation clusters? Where is the best location for each fracture treatment stage? These are critical and difficult questions to answer when designing completions for tight gas and shale reservoirs and the approach to answering these questions can differ considerably for vertical and horizontal wells in different lithologies. In the past, optimizing the number and location of fracture treatment stages has been primarily a manual, time intensive process, resulting in a "cookie cutter" approach that may not properly account for vertical and lateral heterogeneity. This paper details new algorithms and an integrated workflow that could improve fracture treatment staging in both vertical and horizontal wells. The primary obstacles to optimizing completions in tight gas and shale reservoirs have been the absence of hydraulic fracture models that properly simulate complex fracture propagation which is common in many reservoirs, efficient methods to create discrete reservoir simulation grids to rigorously model the hydrocarbon production from complex hydraulic fractures, automated fracture treatment staging algorithms, and the ability to efficiently integrate microseismic mapping measurements with geological and geophysical data. One of these obstacles has been overcome with the recent development of complex hydraulic fracture models (Meyer and Bazan, 2011, Weng et al., 2011, Xu et al., 2010). However, the remaining obstacles are just now being addressed. Algorithms for efficient and rigorous design of multi-stage completions are detailed in the paper. Separate staging algorithms have been developed for vertical and horizontal wells that utilize detailed stress, rock mechanical, and image measurements (i.e. - natural fracture identification) to select stage intervals and perforation locations. The staging algorithms incorporate "fit-for-purpose" hydraulic fracture models ranging from standard planar pseudo 3D models to newly developed complex fracture models, depending on the environment. The algorithms are seamlessly integrated with microseismic measurements, a common Earth Model, and automated routines to discretely grid the complex fracture geometry for reservoir simulation. A common software platform enables the efficient utilization of multiple data sources from multiple disciplines. The application of the newly developed algorithms and integrated workflow is illustrated using examples from tight gas and shale reservoirs.