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a b s t r a c tGeological storage of CO 2 in clastic reservoirs is expected to have a variety of coupled chemical-mechanical effects, which may damage the overlying caprock and/or the near-wellbore area. We performed conventional triaxial creep experiments, combined with fluid flow-through experiments (brine and CO 2 -rich brine) on samples of poorly consolidated, carbonate-and quartz-cemented Captain Sandstone from the Goldeneye field. The main goal was to study the effect of carbonate cement dissolution on mechanical and ultrasonic properties, as well as on the failure strength of the material. Our experiments were performed under in situ reservoir conditions, mimicking reservoir depletion and injection. Although total dissolution of calcite was observed, and confirmed by microstructural and fluid chemistry analyses, it did not affect the rock mechanical properties, nor was any measurable rock strength reduction observed. This is most likely because grain-to-grain contacts were sufficiently quartz-cemented and quartz is not affected by CO 2 -rich brine. Failure data for the Captain Sandstone showed that the stress conditions under which CO 2 injection will take place remain far away from the failure envelope. Therefore, CO 2 injection is not expected to lead to shear failure of the reservoir. However, longer-term chemical reactions, involving minerals such as feldspar, clays or micas, still require more research.

Advancing production from the Groningen gas field to full depletion generates substantial, field-scale deformation, and surface subsidence. Quantifying associated risk requires understanding physical processes in the subsurface, in particular those related to deformation of the Permian sandstone reservoir. Here, we report the results of a large experimental study, using fresh core material taken from the center of the field. By subjecting the material to depletion and slight unloading, complemented with a range of rock property measurements, we determine what rock physical properties control production-induced compaction in the material. Our results show that, although a large part of the deformation can be explained by classical linear poroelasticity, the contribution of inelastic (permanent) deformation is also significant. In fact, it increases with progressing pressure depletion, i.e. with increasing production. Utilizing univariate and multivariate statistical methods, we explain the additional inelastic deformation by direct effects of porosity, packing, and mineral composition. These proxies are in turn related to the depositional setting of the Permian reservoir. Our findings suggest that field-scale subsidence may not only be related to the often-used rock porosity, but also to packing, and composition, hence the local depositional environment. This motivates alternative assessments of human-induced mechanical effects in sedimentary systems.

Investigation of the transport of reactive fluids in porous rocks is an intriguing but challenging task and relevant in several areas of science and engineering such as geology, hydrogeology, and petroleum engineering. We designed and constructed an experimental setup to investigate physical and chemical processes caused by the flow of reactive and volatile fluids such as supercritical CO(2) and/or H(2)S in geological formations. Potential applications are geological sequestration of CO(2) in the frame of carbon capture and storage and acid-gas injection for sulfur disposal and/or enhanced oil recovery. The present paper outlines the design criteria and the realization of reactive transport experiments on the laboratory scale. We focus on the spatial and time evolution of rock and fluid composition as a result of chemical rock fluid interaction and the coupling of chemistry and fluid flow in porous rocks.

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