Seismic Characteristics of Mud Diapir in Song Hong Basin, Offshore Vietnam

Seismic characteristics of mud diapir has been investigate over an area of 3900 km2, located in the central part of Song Hong basin, using four 2D seismic lines. There are six mud diapirs and three mud pipes have been documented. The core of the diapir is characterized as a zone of chaotic, disrupted seismic reflection, with the amplitude reflection ranging from low the high. High amplitude reflections are distributed in the top of the some diapir, which is possibly related to the gas accumulation. They are in different sizes, shapes, and the relationship with surrounding rock. They are characterized as deep sourced, high energy rooting from Oligocene/early Miocene shale layers. This organic rich shale rocks are in the oil and gas windows, thus their hydrocarbon generation combining with the tectonic inversion during Miocene make the overpressured shale and therefore rising the diaipirs. The area has experienced several phases of eruption in Middle Miocene, Late Miocene, Late Pliocene and Present day. The discovery and identification of the occurrence of mud diapirs implied a great potential for prediction of structural traps in the central part of the Red River Basin.

Shear margin moraine, mass transport deposits and soft beds revealed by high-resolution P-Cable three-dimensional seismic data in the Hoop area, Barents Sea

High-resolution seismic data are powerful tools that can help the offshore industries to better understand the nature of the shallow subsurface and plan the development of vulnerable infrastructure. Submarine mass movements and shallow gas are among the most significant geohazards in petroleum prospecting areas. A variety of high-resolution geophysical datasets collected in the Barents Sea have significantly improved our knowledge of the shallow subsurface in recent decades. Here we use a c. 200 km2 high-resolution P-Cable 3D seismic cube from the Hoop area, SW Barents Sea, to study a 20–65 m thick glacial package between the seabed and the Upper Regional Unconformity (URU) horizons. Intra-glacial reflections, not visible in conventional seismic reflection data, are well imaged. These reflections have been mapped in detail to better understand the glacial deposits and to assess their impact on seabed installations. A shear margin moraine, mass transport deposits and thin soft beds are examples of distinct units only resolvable in the P-Cable 3D seismic data. The top of the shear margin moraine is characterized by a positive amplitude reflection incised by glacial ploughmarks. Sedimentary slide wedges and shear bands are characteristic sedimentary features of the moraine. A soft reflection locally draping the URU is interpreted as a coarser grained turbidite bed related to slope failure along the moraine. The bed is possibly filled with gas. Alternatively, this negative amplitude reflection represents a thin, soft bed above the URU. This study shows that P-Cable 3D data can be used successfully to identify and map the external and internal structures of ice stream shear margin moraines and that this knowledge is useful for site-survey investigations.

Unambiguous reconstruction of the complex amplitude reflection coefficient of a laterally homogeneous crystal using analyser-based phase-contrast imaging

A theoretical approach is developed to invert analytically a hard X-ray analyser-based phase-contrast image of a known weak object to recover the complex amplitude reflection coefficient (ARC) of a laterally homogeneous crystal. Numerical simulations test the method to recover the ARC from two systems of interest: a thick perfect crystal and a linearly strained thin film. For the latter model, a kinematical diffraction approximation was used to recover the one-dimensional deformation profile from the ARC.

Stratigraphic Trap in the Permian Unayzah Formation, Central Saudi Arabia

ABSTRACT The recent discovery in Central Saudi Arabia of Arabian Super Light oil in 'Usaylah-1 confirms stratigraphic trap potential of the Permian Unayzah Formation. The trap is an updip pinch-out of an upper Unayzah sandstone along the eastern flank of the north-south trending Hawtah anticline. The seal is the basal shales and siltstones of the Khuff and Unayzah formations and the source rock is the Lower Silurian Qusaiba Shale. The well encountered an oil column of 31 feet in an upper Unayzah eolian dune facies. The areal distribution of the prospect was mapped with a 3-D seismic survey. Seismic horizon slices and relative amplitude maps at the target reflection clearly delineate the trap. The oil-productive Unayzah sandstone is imaged as a high-amplitude reflection in an isolated area of approximately 8 square kilometers. Seismic isochron maps are proving effective in focusing future exploration to areas of similar stratigraphic trap potential in the region.

Two-dimensional patterns in Rayleigh-Taylor instability of a thin layer

We study experimentally and theoretically the evolution of two-dimensional patterns in the Rayleigh—Taylor instability of a thin layer of viscous fluid spread on a solid surface. Various kinds of patterns of different symmetries are observed, with possible transition between patterns, the preferred symmetries being the axial and hexagonal ones. Starting from the lubrication hypothesis, we derive the nonlinear evolution equation of the interface, and the amplitude equation of its Fourier components. The evolution laws of the different patterns are calculated at order two or three, the preferred symmetries being related to the non-invariance of the system by amplitude reflection. We also discuss qualitatively the dripping at final stage of the instability.