Unwanted water production from formation-related issues is always challenging during field development. In carbonate reservoirs, coning and channeling cause excessive water production from heterogeneity or fractures in the formation. In clastic reservoirs, depleted formation and water coning are the reasons for this circumstance. Excessive water production implies not only having less hydrocarbon production but also higher production costs in terms of lifting and water disposal. Identifying the cause and source of water production is important for optimizing field performance.
The initial study suggested that the water zone was far below the produced zone; however, high-water production was occurring. This contradictory result should be confirmed by using tools that can capture the recent conditions of the well while also identifying the source of the water.
For this industry, many downhole tools are used to characterize well and reservoir performance. One is a pulsed neutron tool, which captures the remaining hydrocarbon saturation behind casing in wells and is effectively used for strategic planning in workover wells. Additionally, water diagnostic analysis is used to understand well behavior.
This paper discusses planning and execution using necessary best practices to determine the appropriate tools for identifying current hydrocarbon saturation, reservoir conditions, water conformance problems, and interpretation workflows, as well as the principle of pulsed neutron logging and interpretation results.
Appraisal of formation characteristics is critical to long-term field development planning. Inaccurate appraisal will lead to increased costs for the field.