Abstract
Perforation is the most common way to establish effective communication between the reservoir and the wellbore in wells completed with casing. Although perforation with shaped charges has become the dominant method for completion, conventional shaped charges do not always provide deep and clean-enough tunnels that result in the required productivity and/or facilitate subsequent stimulation treatments.
Therefore, the objectives of this work are to utilize the Perforation Flow Cell (PFC) and the Perforation Treatment Cell (PTC), both developed by GEODynamics, to investigate the impact of using reactive liner shaped charges on the outcome of matrix acidizing treatments and to compare the performance of reactive and conventional charges for different charge types and loads.
Cream Chalk cores with 7 in. diameter × 24 in. length were perforated with two weights of reactive and conventional charges (15 and 23 g) under simulated downhole conditions using two designs of charges; deep penetration (DP) and good hole (GH). All cores were initially saturated in odorless mineral spirit (OMS) and the same fluid was used to flush the core before and after the acidizing step. Porosity and pre-shot (initial) permeability were measured.
After perforation, post-shot permeability was reported and the cores were CT-scanned to visualize and measure the geometry of the perforation tunnels. 15 wt% HCl was used for the acidizing step at 200°F and the effluent samples were periodically collected to measure Ca, Mg, Fe, Al, and metal ions that are present in the core, tubulars, cement, and shaped charge material in the perforation assembly. Cumulative acid pore volume and acid injectivity were reported. CT scans were performed again after acidizing to assess the wormhole morphology obtained with various types of charges.
Experimental results showed that reactive charges create tunnels with more effective (open) length when compared to the equivalent conventional charge, especially at the tip of the tunnel. As a result, stimulation treatments were enhanced and less acid pore volume and time to breakthrough were required. These results were confirmed by chemical analysis that showed higher calcium and metal ion concentration in the effluent samples when the conventional charge was used. CT-scanning after treatment showed a dominant wormhole created from the tip of the perforation tunnel when the reactive charges were used compared to multiple and deviated/branching wormholes with the conventional charges.
