For the past 30 years, matrix stimulation treatments offshore Mexico have involved pumping large volumes of fluids using a “bullheading" technique, which comprises multiple stages of preflushes, acids, and solvents without adequate control of placement. The objective of these treatments in the carbonate formations of the Ku-Maloob-Zaap field is to remove drilling-induced damage and maximize well productivity. However, the heterogeneous permeability profile created by natural fractures is a challenge to effective stimulation. The “bullheading" technique has proven to be inefficient, with evaluation logs showing nonuniformly stimulated intervals.

Coiled tubing (CT) operations adopted a new procedure to improve the stimulation treatment placement. To determine if the chemicals had correctly stimulated the target zones, radioactive tracers were pumped with the chemicals during the stimulation and an additional CT run was subsequently performed to record a gamma ray (GR) log. However this procedure proved to be inefficient and time-consuming.

For the first time offshore Mexico, coiled tubing equipped with optical fibers (CT-EOF) and distributed temperature surveys (DTS) were used to record pressure and temperature data in a cased hole oil-producing well in Campeche Bay. The information was compared with petrophysical data in real time and used to design the selective placement of chemical fluids in target zones. This innovative technique reduced operational time and eliminated the additional CT run, while optimizing placement of the stimulation fluids for improved well productivity. Analysis of the DTS data was also used to evaluate the effectiveness of the matrix stimulation treatment, and to make informed decisions on alternative lifting methods to further improve productivity.

Details of the design, execution, and post-treatment evaluation of the stimulation show how the operation was optimized, and the benefits this new technique offers in the Ku-Maloob-Zaap carbonate formations.