New Attempt in Improving Sweep Efficiency at the Mature Koluel Kaike and Piedra Clavada Waterflooding Projects of the S. Jorge Basin in Argentina

Abstract

Proposal Most of the mature waterflood projects at the San Jorge Basin have been affected by two main problems, poor displacement and sweep efficiencies, both have limited the recovery factor achievable. This paper presents a field trial of a new reactive particulate system in an attempt to improve this volumetric sweep efficiency. This particulate system is being used to treat selected injectors operated by Pan American Energy in the Koluel Kaike and Piedra Clavada fields, located in the southern part of Argentina. The main purpose of this field trial is to demonstrate the ability of the new system to improve oil recovery by diversion of injected water into the poorly swept zones around the thief zone or streaks. This state-of-the-art technology is able to propagate deep into thief zones and has a novel mechanism of action to overcome the observed limitations in conventional polymer flooding and gel processes. The particles are manufactured having properties which allow it to propagate through porous media with the injection water. Once in the reservoir and under the influence of heat the particle expands to a size that can block pore throats, so water injected after treatment is diverted into less efficiently swept zones. The paper will describe in detail the mechanism and selection criteria of reservoirs and wells to apply the mentioned IOR technology. Theoretical and practical issues involved at the design of the application, as well as operational and logistics aspects will be also included. Finally, it will include the updated information available from the ongoing pilot tests. Introduction Koluel Kaike and Piedra Clavada fields are located at the Southern flank of the San Jorge Gulf Basin, in the province of Santa Cruz, Argentina (Figure 1). Figure 1. Koluel Kaike and Piedra Clavada Areas Location Plat Both fields are currently being operated by Pan American Energy and together with Cerro Dragon Field form one of PAE's Business Units. These two fields were discovered in early 1960s and exploited under primary depletion up to mid 1980s. Since this date, a massive waterflooding process has been initiated to increase the relatively poor primary recovery. It has involved about 220 injectors, with an operation rate of 250 cmpd (1600 bwpd) per injector, affecting 500 producers. Through the 20 years of waterfloood operation a total of 300 million cubic metres (1900 million barrels) of water have been injected and resulted in an incremental recovery estimated as 12 million cubic metres (75 million barrels) of oil, through December 2006 (Figure 2 & Figure 3). This mature waterflood project, as any other of the San Jorge Basin, has been affected by both main problems that have limited the recovery factor achievable. These are the poor displacement and sweep efficiency, characteristic of the San Jorge Basin reservoirs.