Overpressure

About: Overpressure is a research topic. Over the lifetime, 3236 publications have been published within this topic receiving 34648 citations.

Shock Wave from a Four-Meter Spark

Abstract: The shock wave emitted by a 4‐m spark of energy 2×104 J has been measured at distances from spark midgap of between 0.34 and 16.5 m. Close to the spark, a single dominant shock wave is observed; farther from the spark, a number of significant shock waves (generally 3 or 4) are observed. For distances less than 2 m, both the shock overpressure and the duration of the overpressure are between a factor of 1.5 to 5 less than predicted by cylindrical shock‐wave theory. The discrepancies between the experimental data and cylindrical shock‐wave theory are partially explained by consideration of the spark channel tortuosity.

Formation and destruction mechanism as well as major controlling factors of the Silurian shale gas overpressure in the Sichuan Basin, China

Abstract: Taking the Well JY1 and Well PY1 in the Eastern Sichuan Basin as examples, the formation mechanism of shale gas overpressure was studied by using the cross plot of acoustic versus density logging data. During the processes of hydrocarbon generation and the uplifting, the pressure evolution of fluids in shale gas layers was reconstructed by fluid inclusions and PVTSIM software. The major factors controlling the evolution of shale gas overpressure were established according to the study of fracture, the timing of the uplifting, and episodes of tectonic deformation. Our results showed that the main mechanism of overpressure in the Silurian shale gas reservoirs in the Sichuan Basin was the fluid expansion, which was caused by hydrocarbon generation. Since the Yanshanian, the strata were uplifted and fluid pressure generally showed a decreasing trend. However, due to the low compression rebound ratio of shale gas reservoir rocks, poor connectivity of reservoir rocks, and low content of formation water and so on, such factors made fluid pressure decrease, but these would not be enough to make up the effects of strata erosion resulting in a further increase in fluid pressure in shale gas reservoirs during the whole uplifting processes. Since the Yanshanian, the Well PY1 zone had been reconstructed by at least three episodes of tectonic movement. The initial timing of the uplifting is 130 Ma. Compared to the former, the Well JY1 zone was firstly uplifted at 90 Ma, which was weakly reconstructed. As a result, low-angle fractures and few high resistance fractures developed in the Well JY1, while high-angle fractures and many high resistance fractures developed in the Well PY1. In totality, the factors controlling the overpressure preservation in shale gas reservoirs during the late periods include timing of late uplifting, superposition and reconstruction of stress fields, and development of high-angle fractures.

How to Accurately Measure Low Sonic Boom or Model Surface Pressures in Supersonic Wind Tunnels

Abstract: R 3/4 scaling. Methodology being developed for general acoustic (linear) ray spreading was applied to sonic boom and (non- linear: required for large initial sonic boom overpressure) aging was applied separately. Acoustic conical ray spreading meant a slower amplitude decay that varies with R ½ scaling; therefore, the rest of the observed amplitude decay was due to non-linear aging or stretching of the signature. Measurement distance in a wind tunnel is affected by both aging and acoustic propagation concerns.