Experimental study of rock-fluid interaction using automated multichannel system operated under conditions of CO2-based geothermal systems

PROCEEDINGS, Thirty-Eighth Workshop on Geothermal Reservoir Engineering Stanford University, Stanford, California, February 11-13, 2013 SGP-TR-198 EXPERIMENTAL STUDY OF ROCK–FLUID INTERACTIONS USING AUTOMATED MULTI-CHANNEL SYSTEM OPERATED UNDER CONDITIONS OF CO 2 -BASED GEOTHERMAL SYSTEMS Miroslav Petro 1 , Jim Zesch 1 , Norine Chang 1 , Alan Bell 1 , Ashutosh Kole 1 , Alexandra Rodkin 1 , Patrick F. Dobson 2 , Yoojin Jung 2 , Tianfu Xu 2 Palo Alto Research Center (PARC) 3333 Coyote Hill Road, Palo Alto, CA 94304 Lawrence Berkeley National Laboratory (LBNL) 1 Cyclotron Road, Berkeley CA 94720 e-mail: mpetro@parc.com ABSTRACT INTRODUCTION Rock–water–CO 2 interactions play a significant role in various hydrothermal systems that often produce carbonated waters, at CO 2 sequestration in aquifers, during CO 2 enhanced oil recovery and, finally, when considering an enhanced geothermal system with CO 2 replacing water as the working fluid. As reported previously (Petro et al., 2012), PARC’s multichannel rock-fluid interactions system can produce a wide range of mineral solubility and dissolution data on diverse minerals under the conditions relevant to geothermal underground processes, mostly in support of the modeling activity using TOUGHREACT at LBNL (Jung et al, 2013). To mimic these processes and accurately quantify the corresponding rock-fluid interaction, PARC has built a multichannel experimental system equipped with several batch reactors confined in a large oven and each connected on-line to a sophisticated analytical system that monitors dissolution profiles of individual minerals. The system has been recently upgraded by adding a flow-through circulation channel that allows us to simulate the reservoir injection-production loop and study additional factors related to the complex interaction kinetics. Synchronized high-throughput operation in both batch and flow-through modes provides numerous data on thermodynamic and kinetic parameters of the interaction for modeling and additional studies at LBNL. In addition to mapping out mineral solubilities under high pressure and high temperature conditions in supercritical CO 2 – water environments, we have studied in more detail the dynamic effects of surface area and changes in other parameters during the course of the interaction. Along with better understanding of generic issues with hot rock-water- CO 2 interactions, we obtained samples from relevant fields, such as from the Southeast Regional Carbon Sequestration Partnership test site in Cranfield, Mississippi. Our goal is to evaluate potential impact of rock-fluid interactions on large scale underground processes triggered by the injection of CO 2 . The multi-channel experimental system has been used to map-out behavior of diverse minerals in a variety of CO 2 /water environments and under a range of pressures and temperatures. The resulting findings are complementary to the efforts focusing on certain aspects of the rock-fluid interactions in specific geological settings. The recent studies address a wide range of relevant topics, from the role of supercritical CO 2 in a granite-based geothermal system (Re et al, 2012), through an acidizing effect of dissolved CO 2 on evolution of a volcanic hydrothermal system (Rina, 2012), or a long-term reaction of injected CO 2 with a caprock (Rochelle, 2011), up to a CO 2 -assisted mineral re-precipitation and fluid immiscibilities in several active geothermal reservoirs (McLin, 2012). Several other experimental systems were built in the last decade to study various aspects of high- temperature/pressure rock-fluid interactions (Ueda, 2005; Rosenbauer, 2005; Magliocco, 2011; Bai, 2012), with at least one of the reports revealing a significant effect of CO 2 on dissolution kinetics of carbonates at various pressures and temperatures (Pokrovsky et al, 2009). In order to better understand