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Abstract

One of the major issues that comes with the development of unconventional ultra-tight shale gas reservoirs is related to under-displacing or over-displacing hydraulic proppant fracture treatments in multiple zone completions in horizontal wells. Multi-stage hydraulic proppant fracture treatments in horizontal well completions in tight gas reservoirs are, in general, under-displaced to ensure that a highly conductive path exists between the reservoir and the wellbore. In recent years, a large amount of multi-stage propped fracture treatments in horizontal wells in ultra-tight shale gas reservoirs are being over-displaced in order to get a clean wellbore and avoid problems with the hardware used for rapid multi-zone completions. Clean-out treatments are not required and therefore multiple treatments can be performed quickly, saving time and money. This practice may result in a poor connection between the ultra-tight reservoir and the wellbore. On the other hand, if the rock strength is sufficient, over-displacing a treatment could result in a very high conductivity region at the wellbore. This mechanism is similar to what has been seen in some wells with proppant flowback, where well productivity has increased following proppant flowback, which creates channels in the proppant pack near the perforations. This paper discusses these practices and, based on a combination of finite element modeling and fine gridded reservoir simulation, will try to answer if and when over-displacing fracs in shale or tight gas reservoirs should have a positive or a negative effect on production.

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/content/papers/10.3997/2214-4609-pdb.293.F019
2012-06-04
2024-03-28
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