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Pipe structures are considered as fluid conduits beneath cold seeps. These structures have been observed in many geological settings and are widely accepted as the most critical pathway for fluid migration. One of such pipe structures in the Haima cold seep region is investigated herein. The pipe structure extends from below the BSR and reaches the...
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Understanding and predicting the behavior of multiphase flows from carbonate reservoirs is of paramount importance in oil and gas exploration and production. However, the complexity of these interpretations, often due to lack of agreement and variations in parameters for consideration, present significant challenges. Traditional techniques relying...
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... These pipe structures act as fluid migration pathways; some of them extend from the seafloor to below the Bottom-Simulating Reflector (BSR). There are many gas pockets within the pipe structure and near to the seafloor, according to seismic diffraction research (Liu B et al., 2021b). Moreover, a large blanking zone exists beneath the studied site from the sub-bottom profile ( Figure 1d); this has been interpreted as a free gas zone (Liu B and Liu SX, 2017). ...
The use of ocean bottom seismometers provides an effective means of studying the process and the dynamic of cold seeps by continuously recording micro-events produced by sub-seafloor fluid migration. We deployed a four-component Ocean Bottom Seismometer (OBS) at an active site of the Haima cold seep from 6 November to 19 November in 2021. Here, we present the results of this short-term OBS monitoring. We first examine the OBS record manually to distinguish (by their distinctive seismographic signatures) four types of events: shipping noises, vibrations from our remotely operated vehicle (ROV) operations, local earthquakes, and short duration events (SDEs). Only the SDEs are further discussed in this work. Such SDEs are similar to those observed in other sea areas and are interpreted to be correlated with sub-seafloor fluid migration. In the OBS data collected during the 14-day monitoring period. We identify five SDEs. Compared to the SDE occurrence rate observed in other cold seep regions, five events is rather low, from which it could be inferred that fluid migration, and subsequent gas seepage, is not very active at the Haima site. This conclusion agrees with multi-beam and chemical observations at that site. Our observations thus provide further constraint on the seepage activity in this location. This is the first time that cold seep-related SDEs have been identified in the South China Sea, expanding the list of sea areas where SDEs are now linked to cold seep fluid migration.
Seepage gas hydrate systems are abundant around the world. However, it is very challenging to characterize this type of gas hydrate because the internal structure of a seepage structure is difficult to image by the conventional seismic exploration method. Here, a novel approach is proposed to achieve high-resolution seismic imaging of a seepage gas hydrate system related to a pipe structure. Raw seismic data with small-size bins are acquired with a harrow-like acquisition geometry that uses one long cable (up to 2000 m) and multiple short cables (less than 1000 m). A high-frequency GI gun is used as a source. During processing, velocity analysis and footprint attenuation are more focused. Seismic imaging resolution has been greatly improved. A small-scale carbonate layer that is hard to identify on the conventional profile is well revealed on the new profile. The new profiles also better depict the boundary and internal structure of the pipe structure. These improve our understanding of seepage gas hydrate systems. Our approach provides an important complement to conventional offshore seismic exploration.
