Shut-ins on water injectors will help to: Detect waterfront and support relative permeability curves with waterflooded fields.Detect a gas breakout in an oil well or a liquid drop out in a gas condensate well, support the value of saturation pressure and understand the influence of multiphase region spreading away from the well.Assess a well intervention with pre and post PBU tests.Quality control rate measurement and allocation,.Some applications in surveillance Some other applications in surveillance for producing fields include: This would be understood by a combination of well testing and production logging, and could result in the need for well treatment so as to maximize the well’s production life. A performance deviation, such as a change in rate of decline, may be caused by changing wellbore damage (skin) or/and by pressure support problems. Then periodic tests (often opportunistic thanks to permanent downhole gauges) are performed to adjust the reservoir description (average reservoir pressure), monitor well properties (effective KH and skin) over time and predict possible water breakthrough. This initial test defines the initial well productivity and will be used as the reference response, against which later tests could be compared to. These results should be reviewed in a post well review to assess the drilling and completion performance. In addition to initial reservoir pressure data, the interpretation will provide information on the average permeability thickness (kh) and initial skin after drilling and completing the well. On a production/injection well, initial PBU/PFO tests are performed a few days after start-up as baseline tests. On an exploration and appraisal well, this surveillance activity is used to confirm an oil/gas reservoir discovery, well productivity, initial pressure, reservoir heterogeneities and boundaries, hydraulic connectivity, etc… Bottom-hole fluid samples are also taken for PVT laboratory analysis and sand production could be tested. It plays a central role in reservoir and petroleum engineering. In that sense, well testing is one of the keys to understand well & reservoir performance and could be seen as the link between the different subsurface disciplines. Geological, geophysical and petrophysical views would reduce the range of possible solutions. It is a non-unique process, which leads to a range of possible interpretations that are consistent with the pressure data. Well test interpretation is a process of recovering this information by exploring the pressure data with special tools and techniques. Information gained from well test By measuring flow rates at surface and pressure with a downhole gauge, a well test provides information on well productivity and reservoir performance over a large scale of investigation (skin, permeability, connected volume, reservoir pressure…). This is called a Pressure Fall-Off (PFO) test.
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