Hasil untuk "cond-mat.quant-gas"

Julian Horton

Dan Tudball

Praveen Kumar, Ramon Rabinovitch

AbstractUsing a unique data set with detailed information on the derivative positions of upstream oil and gas firms during 1996–2008, we find that hedging intensity is positively related to factors that amplify chief executive officer (CEO) entrenchment and free cash flow agency costs. There is also robust evidence that hedging is motivated by the reduction of financial distress and borrowing costs, and that it is influenced by both intrinsic cash flow risk and temporary spikes in commodity price volatility. We present a comprehensive perspective on the determinants of corporate hedging, and the results are consistent with the predictions of the risk management and agency costs literatures.

B. Vizoso, I. R. Mat�as, M. L�pez-Amo et al.

D. R. Jones, C. E. Little

G. Bozza

David M. Leitner

Muhammad Zakwan Mohd Sahak, Maung Maung Myo Thant, Tengku Amansyah Tuan Mat et al.

Abstract In oilfield with significant gas production, either from high associated gas production or non-associated gas (NAG) wells, gas injection is often prioritized due to the aim of oil production sustainability compared to gas export, with only the remaining gas flow not taken by the injection wells is exported as sales gas. However, with gas emerging as a cleaner energy source as compared to oil and instability in oil price, higher gas demand is expected in the future. Due to this, flexibility in managing the allocation between gas injection and gas export would be an advantage, especially with the cyclical demand peak due to winter and summer seasons. A case study for optimization for a unified management and automation of the gas export and gas injection is presented in this paper, which includes the flexibility in prioritizing either utilization options and managing the impact of changes in injection gas supply accordingly via process control and automation. With the adoption of new controllers, operator would now be able to choose which priority mode would be given considering subsurface injection and gas export requirements. For example, when priority is given to the gas injection as per current operating mode, only the remaining gas balance will be used for export. However, when gas export is prioritized, operator would have the option to set the minimum gas export flow that is required, and the control system will automatically control the allocation for sales and injection, including automatically calculating and assigning the injection gas flow to each injector wells when the resulting gas injection supply is changed as a result of gas export prioritization. With the automation exercise, the operator would not need to conduct the manual adjustment of choke valves opening to regulate the gas injection and gas export flow, rather only the usage mode prioritization and the desired flow setpoints for both cases are required. The scheme allows the operator to take advantage on the opportunity of prioritizing gas export or injection depending on prevailing market demand and operational requirement needs for maximizing the value from the field.

Varuneswara Reddy Panyam, Veda Sai Kolla, Lokesh Palawat et al.

Presently, to enhance the thermal efficiency of a gas turbine power plant, turbine inlet air cooling (TIAC) is the widely used technique. The conventional refrigeration methods like vapor compression refrigeration and evaporative cooling need electric power, hence absorption and adsorption refrigeration systems are attractive options as they can be powered using the waste heat energy of the exhaust gases. Adsorption system has advantages over absorption system like scalability, requirement of lower heat source temperature, absence of corrosion and crystallization. This paper focuses on the thermodynamic analysis of waste heat powered adsorption chiller used for the cooling of intake air to enhance the net power output of the gas turbine power plant. This paper also presents a comparative analysis of the vapor-adsorption cycle-based TIAC system for four different refrigerants viz. HFC-134a, carbon dioxide, ethanol and ammonia with the motive of finding a substitute refrigerant for HFC-134a which has a high global warming potential (GWP). The adsorption chiller is mathematically modeled in MATLAB with activated carbon as the adsorbent and each one of carbon dioxide, ethanol and ammonia as the adsorbate. The variation of the coefficient of performance (COP) and specific cooling effect (SCE) with varying adsorption temperatures is presented for each pair. The net power output and primary energy rate (PER) improvement of the gas turbine power plant at different ambient temperatures are also discussed. It is observed that ammonia can improve the power plant performance significantly better compared to the other three refrigerants at ambient temperatures less than 40[Formula: see text]C.

E. L. Pankratov, E. A. Bulaeva

METZGER, FREDRICK W. and ROWAN, MAT

W. S.