Search

Fault slippage threatens the structural integrity of buried pipelines. In this work, we adopted a 3D thermo-hydro-mechanical coupling numerical model for investigation of a warm steel pipeline crossing active tectonic fault in permafrost, focusing on two pipeline-soil interactions: fault slippage in the course of the thawing of the permafrost and pipeline mechanical behavior. Effects of pipeline fluid temperature, thawed soil permeability as well as faulting regime to longitudinal strain along the pipeline were examined. This study shows that the relatively warm pipeline heats the surrounding soil-ice bonded permafrost, thawing of the permafrost leads to diffusion of the pore fluid surrounding the warm pipeline, and the accumulated pore water near the impermeable freezing front could cause a drastic pore pressure change, which would affect the destabilization of previously stable faults in critically stressed regime. The fault slippage and the corresponding longitudinal strain along the pipeline increase with pipeline fluid temperature and thawed soil permeability, while a relatively larger longitudinal strain takes place in the strike-slip faulting regime. [ABSTRACT FROM AUTHOR]

Nowadays, a great deal of petroleum geology and engineering projects associated with underground fluid injection and production (FIP) are widely conducted around the world. The FIP engineering may cause complex stress perturbation and trigger seismicity, which have been extensively reported and studied. In this paper, we investigated the fault slippage characteristics influenced by FIP. It reveals that for a fault (normal or reverse) that penetrating through the reservoir into the caprock and underburden, the footwall reservoir is the relatively stable one for fluid injection in a fluid FIP engineering. No matter it is a normal or a reverse fault, injecting fluid into footwall reservoir and producing fluid from the hanging wall reservoir can induce smaller fault slippage. After having determined the better fluid injection-production pattern, we studied the influence of three key factors of fault, i.e., dip, offset and depth, on fault stability. We found that, in our range of study, the influence of single action of fault dip, offset or depth on fault slippage in a FIP engineering was small. However, the influence of the combined effects of the factors may be large. Finally, we studied the effect of different pressure management scenarios on fault responses based on the specific fluid injection-production pattern. The results revealed that appropriate pressure management could effectively reduce fault slippage in a FIP engineering. However, inappropriate pressure management may cause much larger fault slippage. Given these concerns, it is therefore vital that the effect of pressure management scenario to be modeled prior to FIP. [ABSTRACT FROM AUTHOR]

CO 2 geological storage combining with deep saline water (or brine) recovery (CO 2 -EWR), which is a novel geoengineering approach of CO 2 geological utilization and storage, is presented to solve the dilemma between increasing carbon emissions and water scarcity in China. The major idea of CO 2 -EWR is to use the pressure buildup from CO 2 injection to enhance the recovery of deep saline water. However, avoiding all the buried faults in the reservoir at CO 2 -EWR sites is impossible. Some faults may penetrate through the reservoir into the caprock and basement. Both the fault zone's architecture and the related permeability structure affect the fluid flow in the reservoir and fault zone. In this paper, we investigated the influences of faults at different stages of evolution on reservoir management and induced fault slippage. The results indicate that CO 2 injection can effectively enhance the recovery of deep saline water when the fault zone acts as a conduit. In addition, the induced fault slippage can be significantly reduced when the production-injection ratio is appropriately controlled. However, when the fault zone acts as a barrier, CO 2 injection can no longer enhance the recovery of deep saline water. The production of water may play a negative role in the stability of the fault. Moreover, surface uplift from fluid injection may cause the region above the fault to undergo a potentially serious tilt, which may be very harmful to infrastructures on the ground. [ABSTRACT FROM AUTHOR]

Injection or withdrawal of fluid at depth may trigger felt seismicity. At a site with natural faults or artificial fracturing cracks, understanding how to avoid triggering felt earthquakes plays a crucial role in the success of underground anthropogenic activities, such as subsurface energy storage and CO geological sequestration. With the application of a hydromechanical coupling finite element model, we examine the potential of injection-induced pore pressure change and the responding fault slippage along the fault surface in two injection scenarios: multi-layer injection (MLI) and single-layer injection (SLI). The results indicate that fault slippage buildup is mainly located along the portion of the fault intersecting the reservoir. MLI leads to a relatively lower level of induced seismicity compared with SLI. In the fault zone, the external zone and core of the fault exert a connection effect and barrier effect on the hydraulic connectivity, respectively. After 20 years of injection, the pore pressure in the core presents a smaller change than that in the internal and external zones. Furthermore, an uncertainty analysis was performed to evaluate the statistical significance of permeability in the caprock, reservoir, and fault (core, internal zone, and external zone), and only the permeability in the reservoir significantly affects the level of fault slippage based on the fault zone hydromechanics associated with subsurface energy storage and CO geological sequestration. [ABSTRACT FROM AUTHOR]