On average in the United States, more than seven barrels of water are produced for each barrel of oil.1 Worldwide, an average of three barrels of water are produced for each barrel of oil.2 The annual cost of disposing of this water is estimated to be 5-10 billion dollars in the US and 40 billion dollars worldwide.2
Many different causes of excess water production exist (see Table 1). Each of these problems requires a different approach to find the optimum solution. Therefore, to achieve a high success rate when treating water production problems, the nature of the problem must first be correctly identified.3 Many different materials and methods can be used to attack excess water production problems. Generally, these methods can be categorized as chemical or mechanical (see Table 2). Each of these methods may work very well for certain types of problems but are usually ineffective for other types of problems. Again, for effective treatment, the nature of the problem must first be correctly identified.
Four problem categories are listed in Table 1 in the general order of increasing treatment difficulty. Within each category, the order of listing is only roughly related to the degree of treatment difficulty. Category A, "Conventional" Treatments Normally Are an Effective Choice, includes the application of water shutoff techniques that are generally well established, utilize materials with high mechanical strength, and function in or very near the wellbore. Examples include Portland cement, mechanical tubing patches, bridge plugs, straddle packers, and wellbore sand plugs.
Logically, identification of the excess water production problem should be performed before attempting a water shutoff treatment. Unfortunately, many (perhaps most) oil and gas producers do not properly diagnose their water production problems. Consequently, attempted water shutoff treatments frequently have low success rates. Several reasons exist for the inadequate diagnosis of excess water production problems. First, operators often do not feel that they have the time or money to perform the diagnosis, especially on marginal wells with high water cuts. Second, uncertainty exists about which diagnostic methods should be applied first. Perhaps 30 different diagnostic methods could be used. In the absence of a cost-effective methodology for diagnosing water production problems, many operators opt to perform no diagnosis. Third, many engineers incorrectly believe that one method (e.g., cement) will solve all water production problems or that only one type of water production problem (e.g., three-dimensional coning) exists. Finally, some service companies incorrectly encourage a belief that a “magic-bullet” method exists that will solve many or all types of water production problems.
A number of excellent papers have addressed candidate selection and various aspects of treating specific types of excess water production problems.2-14 A common theme of many of these papers is a need for proper diagnosis of the excess water production problem. However, for the reasons mentioned above, such diagnosis is frequently not obtained. This report focuses on a cost-effective strategy and methodology for diagnosing and solving excess water production problems. The objective of this study is to provide a straightforward strategy and methodology for performing effective problem diagnosis so the practicing engineer does not forego problem diagnosis and, in turn, implement ineffective water shutoff treatments.