Use of MCR with Absorbance Curves to detect perforation gun operation
Publication Date: 2005-Sep-23
The IP.com Prior Art Database
Description of Invention: Until recently the detection of perforation guns having fired was limited to pulling the gun out of the hole. For in place perforations little was available to determine if a gun or set of guns had fired. It has been suggested that fluorescence can be used to fingerprint with the necessary precision whether a gun has fired or not if a fluorescent dye is released into a fluid system when a gun fires. Stated with that art is the detection limit of 10 parts per billion. In addition it has been suggested that fluorescence is necessary to selectively determine difference dyes. In our laboratory we have recently used MCR to measure absorbing dye concentrations down to a limit of detection of 17 parts per billion with very good selectivity. It is suggested that the combination of MCR and or other multivariate techniques of calibration may open up the opportunity for non fluorescing dyes and or pigments to trace such phenomena. This can greatly simplify the detection scheme since excitation step is required. As such this method could be more suitable for down hole fiber optic measurements than that of fluorescence measurements. Alternatively one can flow the fluid to the surface and detect the absorbance and determine which guns have fired. Down hole a multivariate optical element could be used to detect the absorbency without computer computation with a cheap pin diode or other suitable detector and have a single signal sent to the surface if the gun has fired. In these embodiments an encapsulated absorbing but not necessarily fluorescing dye or pigment would be released into the fluid of a bore hole upon the firing of a gun by the breaking of the capsule. The dye or goups of dyes would then be detected in the fluid by absorbency only. A multivariate calculation on the obtained spectra would provide the detection of each dye. The presence of each dye would determine whether a gun had fired or not. The calculation could be performed with a multivariate optical element. Sample preparation for the compositional and characterization of liquids (oil and water) VIA Laser-Induced Breakdown Spectroscopy Process: 1) In lab record absorption spectra for series of dyes intended for down hole use. 2) Pack different dye into each charge that it is wished to monitor. 3) Run guns, attempt perforation. Dyes should be released from each successfully exploded charge into down hole fluids (most likely completion fluid). 4) Flow fluid to surface, analyze fluid at surface either continuously, or batch often enough. 5) Apply MCR to absorbance curves. Note: Absorption apparatus is simpler than fluorescence apparatus and possibly more suitable to down hole. Absorbance however lacks the sensitivity and selectivity of fluorescence however MCR mitigates this once limitation. Also there are more dyes that absorb than fluoresce, and therefore more candidate dyes to choose from. In general absorbing dyes are cheaper.