SPIDR used for Completion evaluation & shot detection of perforating guns

By Rod Kelly | Wed, 6 Feb 2008

Having worked in field operations for many years running Tubing Conveyed Perforating (TCP) equipment for both DST, temporary and permanent completion applications, one issue that always plagued us was determining if the guns fired or not.  We routinely carried “shot detection” equipment to the wellsite, which consisted of a tape recorder and an accelerometer block, and was attached to the drill pipe or production tubing.  The accelerometer measured any movement of the pipe and recorded it for playback to determine if the TCP guns did indeed fire.

On shallow vertical land wells, we typically had positive detection more than 90% of the time but soon learned that as the well became deeper, located offshore or the wellbore was deviated or horizontal that it became much harder to make an accurate determination of shot detection with the accelerometer.

If shot detection for TCP or wireline conveyed guns is not available, or if it is but detection of the guns firing is deemed “critical” the SPIDR can be rented and utilized as a stand alone shot detection system.  The high resolution (0.01 psi) and the high frequency data gathering (1 sample per second) can quickly determine if the perforating run was successful or not by detecting the minute pressure changes that occur if gun detonation has been accomplished, even if the well goes on a vacuum, that will be recorded.  In addition, the SPIDR has the capability to measure production tubing pressure as well as annular pressure, if required.

The SPIDR can be utilized for completion evaluation once the gas or gas condensate well has unloaded liquids in the tubing and sufficiently cleaned up.  Normal procedures for gas and gas condensate well completions are to stake a flow line to a flare pit, perforate, unload liquids in production tubing and flare gas.  Flare gas until liquid yield has stabilized or is approximately 1-2 BBLS/MMSCFD, then shut in for a pressure build-up (PBU).  The time to reach radial flow is a direct function of permeability (the lower the permeability the longer the shut-in time and vice-versa).

Because the SPIDR is acquiring pressure data at the wellhead, the PBU can be monitored with a laptop and cable connection.  Once it has been determined that radial flow has been reached the well is opened to Sales.

Performing a PBU at the initial completion will provide the operator with valuable information as to the skin, permeability and reservoir pressure.