Overpressure

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

Overview of overpressure in Bengal Basin, India

Abstract: Abnormally high formation pressures are encountered worldwide, ranging in geological age from Cenozoic to Paleozoic, within a depth range of few hundred meters to as deep as six thousand meters while carrying out exploratory drilling by E and P companies. Several causes can increase formation fluid pressure i.e. rapid loading of sediments results compaction disequilibrium, thermal expansion of fluids, compression and/or upliftment of strata by tectonic forces, generation of oil and gas from organic matter and its volume expansion due to high thermal stress within the restricted pore volume in subsurface condition. Few global examples on overpressure occurrences have been compiled in the paper with special reference to Bengal Basin. Emphasis has been given on methodology and interpretation on abnormal pressure detection in Bengal Basin with a compiled data package on generated curves (Geologs), charts, tables in a systematic way to understand the depth/stratigraphic horizons proved/interpreted as proved or likely to be within transition and overpressure regime. The integrated analysis indicates that the wells drilled in the east of Eocene hinge zone in the onshore and offshore parts of Bengal Basin have penetrated overpressure formation within Miocene in the depth range of 2800 m to 5340 m and the mud weight used to control this overpressure zone was more than 2.0 sp gr mud. The generated Geologs can be used as reference to understand the regime of transition and overpressure, as a valuable document for exploration drilling planning and monitoring. The generated model curve (modified using available data after Hottman and Johnson, 1956 curve) using sonic departure (i.e. Δtob(sh) −Δtn(sh)) from drilled wells may be used as an additional tool to find out the expected formation pressure gradient and equivalent mud weight in all future wells. The correlation of wells based on the trend of dcs and σ logs will be useful for predicting transition and overpressure top provided all the parameters required for calculating dcs and σ log recorded smoothly during drilling phase. The study has brought out the detail procedure to generate the pressure profile in the future wells. The generation of pressure profile of a well prior to drilling has got immense importance in oil industry. The drilling of the well should be done by maintaining the optimum mud weight generated from the pressure profile. In case, during drilling, formation pressure is more than the mud pressure, resulted gas kicks or worse, blowouts of the well. Excessively high mud pressure can fracture the formation and cause lost circulation. The oil and gas companies, worldwide, attributed 15% losses due to various problems associated with drilling complications, mostly related to improper pressure prediction of a well. The losses include loss of material as well as drilling process continuity, called non-productive time (NPT). The generation of accurate pressure profile reduces drilling problems, cuts exploration and development costs and allows billions of dollars now spent on losses to be better spent-building and replacing reserves.

Inverse Method for Identification of Acoustic Sources at Launch Vehicle Liftoff

Abstract: At liftoff, launch vehicles are subjected to a very severe overpressure and to an acoustic environment that can induce loads acting on payloads in the low-frequency domain (frequencies lower than 40 Hz). The overpressure starts at ignition of solid-rocket motors. This overpressure phase is followed by the acoustic phase. The liftoff acoustic environment is generated by the rocket exhausts and by their impingement on the launch pad. For a numerical prediction of the acoustic environment, the European Aeronautic Defence and Space Company has developed an inverse method via a time domain boundary integral equations approach that uses an optimal control method, with direct and adjoint equations. The corresponding discrete schemes are highly accurate and unconditionally stable. As an industrial application, the identification of acoustic sources is shown, on the liftoff acoustic environment of ARIANE 5. With the sources from acoustic pressure measurements on the upper part of the ARIANE 5 vehicle and on the pylons around the launch pad having been localized and characterized in the time domain, the complete environment is recovered. By integration of the resulting acoustic pressures over all surfaces of the launchers, the loads created by the liftoff acoustic field can be estimated.

The effect of vent size on pressure generation in explosions in large L/D vessels

Abstract: There is a need for more explosion relief data in large L/D vessels. In this paper we report an experimental investigation of the effect of vent size on the overpressure development in a large L/D, end-vented vessel. Three pressure peaks were identified: P 1 due to an initial elongated flame (characteristic of large L/D explosions); P 2 due to turbulent combustion in the middle and end sections of the vessel and P 3 due to the external explosion. P 1 was found to be the dominant overpressure for small vent areas and to increase with decreasing vent size, whereas the flame speed was reduced (as well as P 2 and P 3) due to reduction of unburnt gas flow through and out of the vessel.