Techniques (Operational)

"The equipment used to take the measurements consists of a device for introducing a pressure profile into the well and a high frequency pressure transducer connected to suitable recording equipment. In its simplest form, the pulse generator may be a ball valve connected to the wellhead and exhausting to atmosphere, which can be rapidly opened and closed by hand. Alternatively, mechanically controlled devices may be used which generate shorter, reproducible pulses. The pressure transducer may be attached to the wellhead, avoiding the use of any downhole equipment."2

Numerical modeling is possible. Baseline conditions must be first considered. "The numerical model used to predict pressure oscillations included the annulus, internal tubing, and rathole below perforations. It also accepted variable fluid viscosities."5

The field procedure consisted of initiating free oscillations by suddenly opening and closing a bleed-off valve at the wellhead on the annulus, and then digitally recording the pressure oscillations until they were fully damped. Analysis consisted of propagating the identical impulse down the annulus of the numerically modelled well, and then computing oscillation. Additional information on field equipment is available at Pinnacle Technology's web site in Delft http://home.wxs.nl/~pinndelf/hit.htm.

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