Engineered Approach to Isolate Intervals Invaded by Water or Gas in Naturally Fractured Carbonate Formations

摘要

An excessive water cut or high gas/oil ratio in a production interval presents a major concern in sustaining oil production, often requiring fast and efficient workover solutions to enhance the oil recovery process. Wells in the Cantarell field, a mature depleted field in the Bay of Campeche in the Gulf of Mexico, are facing drastic decreases in their production and, depending on producing zone, an increase in either water cut or gas/oil ratio. Other developed fields in Mexico's Region Marina, such as the Ku-Maloob-Zaap, have constantly increased their hydrocarbon production through the years with an incipient increase in water and gas increments. The high water cut and gas increments have had a strong impact on the production strategy, opening the opportunity for application of non-conventional, innovative, and engineered solutions to isolate or abandon production intervals invaded by gas or water and continue production from upper or deeper zones. The pay zones consist of naturally fractured, vugular carbonates with permeability as high as 5 Darcies, from Paleocene, Cretaceous, and Jurassic formations. Their characteristics present the following challenges that need to be overcome to succesfully achieve the required isolation: Loss of fluid circulation, which is necessary for well control and also negatively affects the fluid placement in the workover jobs. High gas presence, gas cap driven, which is a major concern on surface. Lack of primary zonal isolation, resulting in migration of water or gas to the productive intervals. This paper summarizes the non-conventional technologies and techniques applied to isolate the water and gas producing intervals and their synergistic performance: reticulated gel, lost circulation fiber tecnologies and gas- tight slurries integrated in an engineered solution. Results from field cases demonstrate the design, execution, and evaluation of these applications.