Successful Combination of an Organically Crosslinked Polymer System and a Rigid-Setting Material for Conformance Control in Mexico

Abstract

Summary The Cantarell field, a mature reservoir offshore Mexico, presents significant water-management problems because the hydrocarbon production comes from a naturally fractured carbonate reservoir. Controlling water production in the Cantarell field becomes more critical because of its limited water-handling facilities. This paper presents the field application of two systems widely used in the petroleum industry for water control: (1) an organically crosslinked polymer (OCP) system and (2) a rigid-setting-material (RSM) system. The OCP system is based on a copolymer of acrylamide and t-butyl acrylate (PAtBA) crosslinked with polyethyleneimine (PEI). To date, more than 100 jobs have been performed in Mexico with this system to address conformance problems such as water coning/cresting, high-permeability streaks, gravel-pack isolation, fracture shutoff, and casing-leak repair. This system can penetrate deep into the matrix of the rock or fractures to provide a more efficient water shutoff. The RSM system is a rigid "cement-like" setting material that has a right-angle set. Unlike cement, the RSM system is capable of rapidly developing highly compressive strength to avoid losing the treatment to the formation before setting and will not invade the formation. The RSM system is for near-wellbore applications. Several case histories are presented in this paper to show the application of these two water-shutoff systems together. The OCP system was used for deep matrix/fracture penetration, while the RSM system was used as a tail-in because of its fast-setting properties (to avoid overdisplacement of the OCP system) and its capability to stop gas migration. These advanced water-control technologies have extended the well life and profitability of the treated wells. In the past, many of these wells were abandoned because of the limited water-handling facilities.