Joachim Tremosa

Two‐phase flow properties of a sandstone rock for the CO2/water system: Core‐flooding experiments, and focus on impacts of mineralogical changes

The two-phase flow characterization (CO2/water) of a Triassic sandstone core from the Paris Basin, France, is reported in this paper. Absolute properties (porosity and water permeability), capillary pressure, relative permeability with hysteresis between drainage and imbibition, and residual trapping capacities have been assessed at 9 MPa pore pressure and 28°C (CO2 in liquid state) using a single core-flooding apparatus associated with magnetic resonance imaging. Different methodologies have been followed to obtain a data set of flow properties to be upscaled and used in large-scale CO2 geological storage evolution modeling tools. The measurements are consistent with the properties of well-sorted water-wet porous systems. As the mineralogical investigations showed a nonnegligible proportion of carbonates in the core, the experimental protocol was designed to observe potential impacts on flow properties of mineralogical changes. The magnetic resonance scanning and mineralogical observations indicate mineral dissolution during the experimental campaign, and the core-flooding results show an increase in porosity and water absolute permeability. The changes in two-phase flow properties appear coherent with the pore structure modifications induced by the carbonates dissolution but the changes in relative permeability could also be explained by a potential increase of the water-wet character of the core. Further investigations on the impacts of mineral changes are required with other reactive formation rocks, especially carbonate-rich ones, because the implications can be significant both for the validity of laboratory measurements and for the outcomes of in situ operations modeling.

Estimating thermo-osmotic coefficients in clay-rocks: II. In situ experimental approach

Water flow in compacted shales is expected to be modified by thermo-osmosis when a thermal gradient exists. However this coupled-flow process is poorly characterized since no experiments on non-remoulded clay-rocks are found in the literature. This paper presents a set of thermo-osmosis experiments carried out in an equipped borehole installed in the Liassic argillite at the Institut for Radiological protection and Nuclear Safety (IRSN) underground research laboratory (URL) of Tournemire (southeastern France). A numerical model - including coupled-flow equations, mass conservation laws, thermal expansion and changes of water properties with temperature - was developed for the interpretation of these experiments. A thermo-osmotic response was deduced from the pressure evolution in the test interval after temperature pulses (+2.5, +5.1, and +9 degrees C). The values of thermo-osmotic permeability determined during the experiments range between 6x10(-12) and 2x10(-10)m(2)K(-1)s(-1), depending on the pulse temperature and uncertainties on the model parameters. A sensitivity analysis on several model parameters was performed to constrain these uncertainties.

Well integrity assessment under temperature and pressure stresses by a 1:1 scale wellbore experiment

A new in situ experiment is proposed for observing and understanding well integrity evolution, potentially due to changes that could occur during a well lifetime. The focus is put on temperature and pressure stresses. A small section of a well is reproduced at scale 1:1 in the Opalinus Clay formation, representative of a low permeable caprock formation (in Mont Terri Underground Rock Laboratory, Switzerland). The well-system behavior is characterized over time both by performing hydro-tests to quantify the hydraulic properties of the well and their evolution, and sampling the fluids to monitor the chemical composition and its changes. This paper presents the well integrity assessment under different imposed temperature (17–52°C) and pressure (10–28 bar) conditions. The results obtained in this study confirm the ability of the chosen design and observation scale to estimate the evolution of the well integrity over time, the characteristics of the flow along the well-system and the reasons of the observed evolution. In particular, the estimated effective well permeability is higher than cement or caprock intrinsic permeability, which suggest preferential flow pathways at interfaces especially at the very beginning of the experiment; the significant variations of the effective well permeability observed after setting pressure and temperature stresses indicate that operations could influence well integrity in similar proportions than the cementing process.