Geochemical and Thermodinamic Modeling of Segara Anak Lake and the 2009 Eruption of Rinjani Volcano, Lombok, Indonesia

DOI: 10.17014/ijog.v5i4.106Rinjani is the second highest volcano in Indonesia with an elevation of 3726 m above sea level. The steep and highest cone of Rinjani consists mainly of loose pyroclastic ejecta and contains a crater with a few solfataras. The West of this cone is Segara Anak caldera. The western side of the caldera is occupied by a 230 m deep lake, covering an area of 11 km² and its volume was (before the 2009 eruption) estimated 1.02 km3. This is probably the largest hot volcanic lake in the world.The lake water is neutral (pH: 7-8) and its chemistry dominated by chlorides and sulfates with a relatively high TDS (Total Dissolved Solids: 2640 mg/l). This unusual TDS as well as the lake surface temperatures (20 - 22°C) well above ambient temperatures (14 - 15°C) for this altitude, reflect a strong input of hydrothermal fluids. Numerous hot springs are located along the shore at the foot of Barujari volcanic cone. Bathymetric profiles show also several areas with columns of gas bubbles escaping from the lake floor indicating a significant discharge of CO gas into the lake. The mass and energy balance model of Rinjani Crater Lake produce total heat lost value on the average of 1700 MW. Most of the heating periods of the lake occurred when the heat released by the surface of the lake to the atmosphere was lower than the heat supplied from the hydrothermal system. Peaks of heat losses correspond to period of strong winds. Crater lake monitoring can provide a basic information about deep magmatic activity and surface processes that occur in the volcano. The monitoring also contributes to predict the next eruption in order to improve mitigation of volcanic eruption. Precursory signals of the May 2009 eruption can be seen from significant changes in the temperature and chemistry of some of the hot springs, the increase of Fe concentrations in spring #54, chemical plume of low pH and dissolved oxygen, acidification of Segara Anak Lake, and increasing of lake surface temperatures. The new lava flow from May - August 2009 eruption covers an area of 650,000 m2. The shoreline was significantly modified by the entry of lava into Segara Anak Lake. The area of the lake is reduced by 460,000 m2

The HPx software for multicomponent reactive transport during variably-saturated flow: Recent developments and applications

Abstract HPx is a multicomponent reactive transport model which uses HYDRUS as the flow and transport solver and PHREEQC-3 as the biogeochemical solver. Some recent adaptations have significantly increased the flexibility of the software for different environmental and engineering applications. This paper gives an overview of the most significant changes of HPx, such as coupling transport properties to geochemical state variables, gas diffusion, and transport in two and three dimensions. OpenMP allows for parallel computing using shared memory. Enhancements for scripting may eventually simplify input definitions and create possibilities for defining templates for generic (sub)problems. We included a discussion of root solute uptake and colloid-affected solute transport to show that most or all of the comprehensive features of HYDRUS can be extended with geochemical information. Finally, an example is used to demonstrate how HPx, and similar reactive transport models, can be helpful in implementing different factors relevant for soil organic matter dynamics in soils. HPx offers a unique framework to couple spatial-temporal variations in water contents, temperatures, and water fluxes, with dissolved organic matter and CO2 transport, as well as bioturbation processes

Assessing impacts to groundwater from CO2-flooding of SACROC and Claytonville oil fields in West Texas

Comparison of groundwater above two Permian Basin oil fields (SACROC Unit and Claytonville Field) near Snyder, Texas should allow us to assess potential impacts of 30 years of CO2-injection. CO2-flooding for enhanced oil recovery (EOR) has been active at SACROC in Scurry County since 1972. Approximately 13.5 million tons per year (MtCO2/yr) are injected with withdrawal/recycling amounting to ~7MtCO2/yr. It is estimated that the site has accumulated more than 55MtCO2; however, no rigorous investigation of overlying groundwater has demonstrated that CO2 is trapped in the subsurface. Mineralogy of reservoir rocks at the Claytonville field in southwestern Fisher County is similar to SACROC. CO2-EOR is scheduled to begin at Claytonville Field in Fisher County in early 2007. Here we have the opportunity to characterize groundwater prior to CO2-injection and establish baseline conditions at Claytonville. Methods of this study will include: (1) examination of existing analyses of saline to fresh water samples collected within an eight-county area encompassing SACROC and Claytonville, (2) additional groundwater sampling for analysis of general chemistry plus field-measured pH, alkalinity, and temperature, stable isotopic ratios of hydrogen (D/H), oxygen (18O/16O), and carbon (13C/12C), and (3) geochemical equilibrium and flowpath modeling. Existing groundwater data are available from previous BEG studies, Texas Water Development Board, Kinder Morgan CO2 Company, and the U. S. Geological Survey. By examining these data we will identify regional groundwater variability and focus additional sampling efforts. The objective of this study is to look for potential impacts to shallow groundwater from deep CO2-injection. In the absence of conduit flow from depth, we don’t expect to see impacts to shallow groundwater, but methodology to demonstrate this to regulators needs to be established. This work is a subset of the Southwest Regional Partnership on Carbon Sequestration Phase 2studies funded by the Department of Energy (DOE) in cooperation with industry and government partners.Bureau of Economic Geolog

Prediction of the lifespan of cement at a specific depth based on the coupling of geomechanical and geochemical processes for CO2 storage

The injection of carbon dioxide (CO2) captured from combustion-based processes into underground formations is one of a number of plausible methods to reduce its release into the atmosphere and consequential greenhouse gas warming. Once the gas has been captured efficiently and effectively, depleted oil and gas reservoirs are seen as high potential candidates for carbon storage projects. However, legacy issues associated with a high number of oil and gas wells abandoned during the last few decades put the carbon capture and storage projects (CCS) at risk. These include any defects within the cement surrounding the well casing or for capping an abandoned well that can become unwanted CO2 leakage pathways. To predict the lifespan of these cements due to exposure to CO2-bearing fluids at the conditions found underground, the geochemical processes need to be coupled with the geomechanical changes within the cement matrix. In a viable CCS project for sequestering CO2, the cement matrix should be capable of withstanding acidic environments formed by dissolution of CO2 in brine for more than ten thousand years. This work aims at providing a framework to predict the behaviour of cement due to CO2 exposure under reservoir conditions. The results show that the chemical reactions and geomechanical changes within the cement matrix can result either in its radial cracking or radial compaction. Both of these behaviours are investigated as possible phenomena which may affect the CO2 leakage, and therefore the viability of the site for long term carbon storage

Expert-based development of a standard in CO2 sequestration monitoring technology

Bureau of Economic Geolog

Changes in hydrodynamic, structural and geochemical properties in carbonate rock samples due to reactive transport

Reactive transport plays an important role in the development of a wide range of both anthropic and natural processes affecting geological media. To predict the consequences of reactive transport processes on structural and hydrodynamic properties of a porous media at large time and spatial scales, numerical modeling is a powerful tool. Nevertheless, such models, to be realistic, need geochemical, structural and hydrodynamic data inputs representative of the studied reservoir or material. Here, we present an experimental study coupling traditional laboratory measurements and percolation experiments in order to obtain the parameters that define rock heterogeneity, which can be altered during the percolation of a reactive fluid. In order to validate the experimental methodology and identify the role of the initial heterogeneities on the localization of the reactive transport processes, we used three different limestones with different petrophysical characteristics. We tracked the changes of geochemical, structural and hydrodynamic parameters in these samples induced by the percolation of an acid fluid by measuring, before and after the percolation experiment, petrophysical and hydrodynamic properties of the rocks.Peer ReviewedPostprint (published version