Laboratory evaluation of filtercake cleanup techniques and metallic-screens plugging mechanisms in horizontal wells

Abstract

Tests were conducted to evaluate the plugging mechanisms of metallic screens after cleaning up the altercate developed on an unconsolidated core by two exiting drill-in fluids (DIF's). Two simulated drill solids, clay or 75-[]m reservoir sand were added as drill solids to these DIF 's. Poroplus[] metallic screens developed by Purolator Products Company were used to simulate the sand control device. The DIF's tested included a sized-calcium carbonate (SCC) and a sized-salt (SS). Drill solids added to the tested DIF's simulate tiny formation particles. The presence of these drill solids was found to affect the particle size distribution as well as the mean size (D[]) of the particles of the bridging and weighting material (BWM) and loss control material (LCM) that make up a fundamental part of the DIF's. BWM solids containing calcium montmorillonite clay showed that the median size of the particles was substantially decreased and the ultrafine material content (particles smaller than 45 []m) was increased. BWM solids containing 75-[]m sand as drill solids showed an increase of the median size of the particles with a decrease in the ultrafine material. After the filtercake clean-up treatment and subsequent backsaw, screen plugging evaluated in terms of regained-flow capacity was much more severe in the presence of the whole altercate (after 3% KCl treatments) than in the presence of the degraded filtercake (after HCI acid treatments). On the basis of the previous observations, it can be concluded that when SCC filtercakes were backflowed, the smaller the particle size of the altercate, the higher the minimum dislodging pressure (MDP) and screen plugging, and consequently the lower the regained-flow capacity. Coarse particle size of the filtercakes tended to result in minimum MDP, leading to higher regained-flow capacity and lower plugging of the screen. In contrast, these effects in SS filtercakes were masked by the presence of a polymer, xanthin gum, in the filtercake. The polymers act as glue on the sized particles forming a strong, tough, and rigid filtercake. Therefore, these filtercakes required high pressure to be backfired, decreasing the regained-flow capacity highly and causing severe plugging of the screens. Also, the results indicated that the hydrochloric acid treatment was more effective in removing the filtercakes than the 3% KCI treatment. Also, it was demonstrated that the use of HCI is much more effective in removing the filtercake formed by SS than in removing the one formed by SCC.