Gas Permeability Change With Deformation and Cracking of a Sandstone Under Triaxial Compressiongas Permeability Change With Deformation and Cracking of a Sandstone Under Triaxial Compression

In this paper, a THMC (Thermal-Hydrological-Mechanical-Chemical) multi-field coupling triaxial cell was used to systematically study the evolution of gas permeability and the deformation characteristics of sandstone. The effects of confining pressure, axial pressure, and air pressure on gas permeability characteristics were fully considered in the test. The gas permeability of sandstone decreases with increasing confining pressure. When the confining pressure is low, the variation of gas permeability is greater than the variation of gas permeability at high confining pressure. The gas injection pressure has a significant effect on the gas permeability evolution of sandstone. As the gas injection pressure increases, the gas permeability of sandstone tends to decrease. At the same confining pressure, the gas permeability of the sample during the unloading path is less than the gas permeability of the sample in the loading path. When axial pressure is applied, it has a significant influence on the permeability evolution of sandstone. When the axial pressure is less than 30 MPa, the gas permeability of the sandstone increases as the axial pressure increases. At axial pressures greater than 30 MPa, the permeability decreases as the axial pressure increases. Finally, the micro-pore/fracture structure of the sample after the gas permeability test was observed using 3D X-ray CT imaging.

EP.WE.824Effect of bariatric surgery on gut permeability in humans: a systematic review

Aims Altered intestinal permeability (“leaky gut”) is associated with obesity. Several mechanisms have been suggested to explain the harmful sequalae that follow permeability change such as inflammation, alteration to the microbiome and onset of insulin resistance. Studies describe bariatric surgery as having varying effects on intestinal permeability. We aim to summarise and review the literature. Methods A systematic review was performed using MEDLINE, EMBASE, and Scopus to identify studies in humans that investigated permeability change after bariatric surgery. Results 5 studies were identified, all cohort. Heterogeneity precluded meta-analysis. All calculated permeability change following oral intake of different sugar solutions. Two studies described a reduction in gastroduodenal permeability post sleeve gastrectomy (SG), one from an increased baseline compared to lean controls. Two described an increase in small intestinal permeability after “malabsorptive” operations (biliopancreatic diversion and duodenal switch). Two found decreased small intestinal permeability at one month post Roux-en-Y gastric bypass and six months post SG. One including only SG had opposite findings of increased small intestinal permeability at 6 months. The only colonic change reported was increased permeability also 6 months post SG. Conclusion Research found both increased and decreased permeability of the small intestine. Two studies found reduced gastroduodenal permeability post operatively. Evidence regarding the effect of bariatric surgery on the permeability of the gastrointestinal tract and specifically the colon is limited and follow up, operation type and small numbers limit meaningful comparison. Further study into this crucial aspect of obesity both before and after surgery is needed.

Experiments and Simulation on Integrated Approach of CO2 EOR and Storage in Mature Reservoirs

CO2 storage mechanisms in an EOR process in mature reservoirs are measured to determine three types of storage factors, which are introduced into compositional numerical simulation. The hybrid objective function coupli ng the oil recovery factor and the CO2 storage ratio is proposed to optimize the injection and production parameters in CO2 flooding. Three storage factors of the oil and water partition coefficient, the permeability change coefficient and the CO2 retention factor are measured in a laboratory, which is utilized to modify the grid properties of oil, brine, rock in compositional numerical simulation. The restart procedure is automatically adopted to consider these storage mechanisms in CO2 EOR. The bi-objective function of the oil recovery factor and the CO2 storage ratio is used to optimize the injection and production parameters for CO2 EOR, which concludes the design principles on CO2 EOR and storage. The oil and water partition coefficient defined as the ratio of the CO2 solubility in the oil phase and the brine phase is a constant for a specific reservoir condition. The permeability change coefficient caused by the mineral dissolution effect of carbonate water decreases slightly in the early stage and increases gradually with the long term injection. The CO2 retention factor that is induced by the relative permeability hysteresis decreases with the pressure and the permeability. These equivalent treated methods that modify fluids and rock in the real-time are inserted into the procedure of compositional numerical simulation to take into account the storage mechanisms in CO2 EOR. The results show that the effect of the storage mechanisms on EOR is evident. Furthermore, the bi - objective optimization indicates that the injection rate should be reduced largely in the medium and the later stages to control gas channeling as the EOR scenario is focused. And the bottom wellhole pressure of producers should be decreased to the lower level to maximize oil recovery. As the storage scenario is concentrated, the injection rate is required to be slightly controlled. As the producers are shut off, the injection rate must be increased significantly to maximize CO2 storage. The storage mechanisms in the CO2 EOR process have not been understood thoroughly. The methodology of numerical simulation coupling CO2 EOR and storage is not mature, which is still not taken into account in commercial software. The results above provide a way to optimize CO2 EOR and storage simultaneously, which is significant for the large scale storage after CO2 EOR in mature oilfield.

Spatial permeability variations of aquifers in North China Plain derived from large magnitude earthquake signals

<p>Permeability changes induced by earthquakes have been widely studied. The question remains of how multiple large earthquakes influence permeability at different depths in the far-field and permeability changes could possibly be employed for hydraulic characterization of the aquifers has not yet been investigated. We study the change in permeability in fractured aquifers of the North China Paraplatform based on 11 years of groundwater hydrographs of 7 wells and 62 earthquakes. From 2008 to 2018, the permeability changes varied from well to well, all aquifers showed a consistent and distinct magnitude of change in permeability (decrease, increase and no change) following each earthquake. From the perspective of a single well to multiple shocks, the permeability variation of the JN well is the most sensitive to seismic events. From the perspective of multiple wells to one single earthquake, there were no cases of simultaneous permeability changes in all 7 wells induced by a single earthquake. Permeabilities varying within a wide range at a given depth implies that it could be considered as a dynamically self-regulating value, while permeability changes indicate great differences at varying depths. We found that the correlations between permeability changes and seismic energy density or depth are weak, however, the azimuths of seismic waves could greatly impact the changes in permeability, i.e., from 25° to 295°, and the most significant span is 250° to 295°, and fault distribution around the monitoring wells may also contribute to this result. Employing a seismic waves-pressure amplitude model, the mobilization of colloids driven by the oscillation of pressure head as a possible mechanism of permeability change. Distant, large magnitude earthquakes can alter the permeability, also can accelerate or slow down the rate of permeability change of the aquifer material.</p>