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8738181 
Meetings & Symposia 
Coiled-tubing reverse circulation - An efficient method of cleaning horizontal wells in a mature, pressure-depleted field 
Kumar, PS; Al-Amri, B; Kouli, P; Van Gisbergen, S; Shidi, S; Ferdiansyah, E; Mowat, P 
2005 
81-87 
English 
Several methods of cleaning deviated and horizontal wells have been developed over the years. One of the most common methods is running in with coiled tubing and circulating the solids out with a liquid or multiphase fluid. Solids tend to settle at the bottom or low side of the wellbore in highly deviated or horizontal wells. This makes the cleanout process inefficient in bringing the solids to the surface. In this field, most of wells are horizontal. One of matured fields in the northern directorate of Petroleum Development Oman manily produces from horizontal wells. The produced water is injected back into the reservoir. Scale is found in injectors and producers. The acid insoluble materials in these scales vary from 4% to 22%. Hence, cleanout of the horizontal hole is required in this field to keep the wells producing/injecting at their potentials. Various methods of cleaning like coiled tubing cleanout and reverse circulation through workstring during hoist/rig operations were tried in cleaning the horizontal wells. However, they were not successful in cleaning the horizontal hole. One of the main reasons is the loss of kill/completion fluid into the formation during well operations. In order to establish an effective cleaning method in this environment, it was decided to experiment the coiled tubing reverse circulation process in cleaning horizontal openhole injectors so that the same process could be extended for cleaning out horizontal producers. This paper presents the results of coiled tubing reverse circulation trials carried out in three horizontal openhole injectors. The cleanout method was a combination of venturi junk basket and reverse circulation, with an initial venturi run being made to identify the top of fill and to remove the larger fill particles, followed by reverse circulation to remove the smaller particle out of the wellbore. Post cleanout injection rates increased on an average of 15% over the pre cleanout rates. Further to evaluate the effectiveness of this method, spinner runs were made along the horizontal openhole section before and after the cleanout jobs. The results revealed that injection was more uniform along the horizontal openhole section after the reverse circulation when compared to the few points of injection before the cleanout. Implementation of this reverse circulation process is now planned for producers in which it is not possible to remove acid insoluble materials by normal cleanout methods. Copyright 2005, Society of Petroleum Engineers Inc.