In the past, it was difficult to justify the expense of water control because it often produced poor results. The most commonly used water-control technique, cement squeezing, had only a 50% success rate. Other more exotic treatments had even lower success rates and were performed only as experiments or "last resorts." These unsuccessful treatments often resulted because the source of the problem was not correctly identified. With the tools available today, the essential element of conformance control is identifying the nature and source of the problem. Once the problem is correctly identified, the best material or solution to solve this problem must be determined. The best placement technique must also be determined to ensure that the material or solution is placed where it has the best possible chance of solving the problem.

Addressing poor sweeps, channeling, interwell communi-cation, and other water-control problems is especially important in fields where injection is used to enhance oil production. Chemical analysis and water flow logging can help operators isolate water flow, invasion, and annular leaks that destroy casing integrity and decrease profitability. A case history in-volving five wells demonstrates the use of analytical techniques to identify conformance-control problems. It also focuses on the evaluation and solution processes. In essence, the case indicates the importance of thoroughness. In this case, identification, evaluation, implementation, post-analysis, and re-evaluation were combined into a single process.

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