Propellant-assisted perforating systems are used to stimulate the near wellbore region and to alleviate the formation compaction damage from the perforating event. This method involves combining a perforating gun with a high pressure, gas generating propellant. Detonation of the perforating gun causes the propellant to deflagrate. The resulting combustion gas enters the newly created perforations. This breaks down the compacted region and extends a fracture network from the perforation tunnels. Wireline formation testing has demonstrated the capability of this perforating method to stimulate beyond the depth of drilling and cementing invasion, especially in tight-gas reservoirs.

The wireline formation testing system is often referred to as a mini drillstem test (DST). It is conveyed into the well on wireline and it uses a dual packer assembly to isolate the perforated interval. With the pump-out capability of the tool, multiple drawdown and buildup cycles are performed. Pressure transient analysis (PTA) is applied to the measured pressure data to evaluate near-wellbore reservoir characteristics.

Depending on the formation parameters, there are two extreme responses observed in these tests: a radial composite model; or a linear fracture model. The radial composite model represents a higher permeability region in the near-wellbore area, surrounded by a lower permeability outer region representing the formation matrix. The typical radius for the inner region is up to 3 m. The linear fracture model represents a small fracture into the formation, generally with a fracture half-length of 1 to 2 m. In reality often a combination of the two models is more representative. All responses show less resistance to flow in the near-wellbore area, representing a positive cleanup and stimulation. Modeling indicates that the propellant-assisted perforation systems are capable of penetrating beyond any induced damage. This is often not the case when using conventional perforation charges.

This study comprehends 50 wireline formation tests in tight-gas reservoirs. These tests are used to demonstrate the successful application of propellant-assisted perforating techniques and to illustrate the different pressure responses created by propellant-assisted perforating in the near-wellbore area. The results are also compared to pre-job propellant stimulation modeling software analysis.

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