To realize multi-purpose exploration of marine resources, a novel design consisting of a monopile offshore wind turbine and steel aquaculture cage in an integrated structure is proposed in this paper; the structure is denoted as MOWTAC. Based on the theories of the screen model, a hydrodynamic analysis module is developed in the OWT simulation tool FASTv8. Then, in combination with a seismic analysis module, the fully coupled analysis model of the MOWTAC is established in the updated FAST v8. Based on the coupled model, the dynamic characteristics and coupling mechanisms of the MOWTAC under earthquake, wind, and wave loads are investigated. A tuned mass damper (TMD) is applied to the MOWTAC under earthquakes, and the influence of the TMD parameters on the mitigation effects is studied. Furthermore, a multiple tuned mass damper (MTMD) with various tuning frequencies is applied, and comparisons with the TMD are carried out. Based on the reduction of seismic responses using the TMD and MTMD, vibration control methods and related design parameters are recommended for the MOWTAC under earthquake, wind, and wave loads.

To figure out porosity evolution mechanisms of marine shales inside and at the margin of the Sichuan Basin, South China, we measured samples selected from Lower Cambrian Qiongzhusi shales and Lower Silurian Longmaxi shales by a combination of X-ray diffraction, geochemistry measurement, focused ion beam milling and scanning electron microscopy imaging, and [ ] adsorption. It was suggested that shales of the upper Qiongzhusi Formation (a marine shallow continental-shelf setting) and the Longmaxi Formation (a marine abyssal continental-shelf setting) possessed larger pore volumes and larger pore surface areas than those of the lower Qiongzhusi Formation (a marine abyssal continental-shelf setting). Pores, in terms of pores of mineral frameworks, pores associated with clay minerals, dissolved pores, and organic matter (OM)-hosted pores, were all observed in the upper Qiongzhusi Formation and Longmaxi Formation, whereas none of the four types of pores developed well in the bottom of the Qiongzhusi Formation. Moreover, migrated OM is superior to depositional OM in the contribution of the pore space, in terms of pore productivity and pore protection. Good sealing abilities of the upper Qiongzhusi Formation and Longmaxi Formation allow more migrated OM and gaseous hydrocarbon retention than the lower Qiongzhusi Formation with an unconformity beneath acting as a channel of liquid and gaseous hydrocarbon migration, which bring about better pore properties. Finally, through the above analysis, the pore evolution mode has been established to gain insights for mechanisms of destruction, formation, and preservation of pores ranging from original sedimentary to metamorphic stage ([ ]–[ ]). Mechanisms of pore destruction contain mechanical compaction, chemical cementation, and OM carbonation. Mechanisms of pore generation comprise thermal pyrolysis of OM, transformation of clay minerals, and dissolution of soluble minerals. Mechanisms of pore preservation include mechanical stability of rigid grains, chemical stability of hydrophobic OM, and gas supporting through overpressure.

The study of tectonics is one of the important aspects of shale gas preservation. It is vital for understanding how to determine the enrichment regularity of marine shale gas in anticlines. This paper focuses on typical shale blocks in the southern Sichuan Basin and shale in the Upper Ordovician and the Lower Silurian. In this study, triaxial unloading tests, permeability tests perpendicular and parallel to the stratification plane, FIB-HIM tests, and inclusion analyses are carried out with real drilling data. The enrichment regularity of marine shale gas in anticlines is studied by considering 2 aspects: the angle of the limbs and the burial depth. For anticlines with adjacent synclines, the migration regularity of shale gas is considered by 3 aspects: the dynamics, channels, and processes of migration. This study reveals that a limb angle greater than 120° reflects relatively good conditions for shale gas preservation, while limb angles lesser than 70° indicate relatively poor conditions. This study also suggests that during the process of uplift, large-scale concentrated fractures will form at a certain depth range and horizontal stress field, resulting in the large loss of shale gas. The regression equation of the fractured depth (H) and the horizontal stress (S) is presented as H=15.404S−754.41 (with a correlation coefficient R2=0.6834). The stratification plane and the organic pores form the migration channel of natural gas that is horizontal to the stratification plane in shale. Under the condition of both anticlines and contiguous synclines, shale gas escapes through fractures resulting from extrusion along the anticline and the uplift effect. In addition, driven by differences in the formation pressure coefficients, shale gas is capable of migrating in a short-distance stair-type style from synclines to the adjacent anticlines. Thus, if the drilling costs allow, the well locations should be placed in the more deeply buried synclines.