Print this pageShaly Behaviors Revealed: Some Lessons Learned Using Microseismic Monitoring during Hydraulic Fracturing and Re-Fracturing
Significant volumes of gas are currently being produced from unconventional shale reservoirs such as the Barnett, Fayetteville, Whirlpool and Woodford Shales in the US. These plays are partly technology driven and partly economics-driven. Modern well log evaluation techniques and completion methods are required to yield economic wells. Among several, three principal geologic factors govern gas production from these formations: ultra-low matrix porosity and permeability as well as fracture-induced permeability. These shales are extremely low porosity reservoirs that must be effectively hydraulically fracture stimulated.
We present the results of several microseismic monitoring campaigns performed in these various shale environments to highlight the variability of the induced fracture systems to be expected during an initial stimulation program. We document how local stress field can sometimes vary along a lateral and how perforation strategies can be developed to ultimately maximize production. We illustrate that it is critical to integrate surface seismic data with real-time microseismic monitoring of hydraulic fracture treatments to detect potential geo-hazards unresolved by surface seismic data, verify interpreted fault geometries and allow on-the-fly changes in fracture stimulation design to maximize the reservoir volume effectively contacted by the stimulation treatment.
Following initial completion, oil and gas wells experience a production decline that results from depletion, water influx, lost conductivity, drainage interaction, equipment failure, etc. Some of the causes for lost productivity can be remedied, while others cannot. A well might also contain potentially productive zones that were bypassed either intentionally or inadvertently during the original completion. In an attempt to increase productivity, operators sometimes initiate re-fracturing programs designed to identify and re-complete underperforming wells.
We also show re-fracture stimulation case studies where a novel diversion technique is successfully applied to Barnett horizontal wells. We emphasize real-time monitoring and control decision taken to produce diversion, increase lateral coverage, influence fracture geometry and improve gas recovery.
AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009