Successful Through Tubing Perforation in Dual String Completion

Abstract

In a dual completed well, a through tubing perforation experience from geologic and reservoir study to job execution, is presented. Job targets have been the maximization of the production gain from one production string and the reduction of possible issues associated to charges detonation for the second string. The success of this job has been crucial for the life of a mature naturally fractured carbonate oil reservoir by opening new production opportunities.

The experience has started with a reservoir study followed by a log acquisition to confirm the geological hypotheses about the lack of production contribution from a level. Once the level potential was confirmed, a review of all the possible technologies available in the market, with related benefits and disadvantages, has been carried out in order to obtain the maximum result in terms of perforation efficiency and minimize the risk to lose integrity or accessibility in the well due to charges detonation. A complete explanation of the overall work flow is provided to clarify all the decision making process.

The first need to find an indication about the production contribution of a cased and cemented level through the hydraulic communication with a second perforated level open to production, can come from noise signals generated from a vertical flow path in formation. In fact, the vertical primary permeability or the natural system of fractures in a carbonate reservoir may represent a likely road to flow. The most suitable technology available to detect this phenomenon is the spectral noise log, which is a precise mean to discriminate about fluid movements in well or near wellbore according to its noise frequency. The second need to increase perforation efficiency and preserve one of the two strings from charges detonation in the second string, can be achieved by identifying a preferential direction at bottom hole and aligning the perforation guns to it. The analysis of real time data acquired through electric wireline from the "Magnetic Orientation Tool" coupled with a downhole electric motor controlled from surface, has allowed to fulfill this task.

The study presented offers a valid workflow to follow for through tubing perforation jobs to restore uneconomic wells life and provides a base for spectral noise log possible uses and innovative tools to add in perforation bottom hole assemblies to have more reliable information for improved job results.