In retrograde gas condensate reservoirs, condensate blockage is a major reservoir damage problem, where liquid is dropped-out of natural gas, below dew-point pressure. Despite that most of this liquid will not produce due to not reaching the critical saturation, natural gas will be blocked by the accumulated liquid and will also not produce.This work investigates the effects of gas injection (such as methane, carbon-dioxide, and nitrogen) and steam at high temperatures on one of the Egyptian retrograde gas condensate reservoirs. Several gas injection scenarios that comprise different combination of gas injection temperature, enthalpy, injection gas types (CO2, N2, and CH4), and injection-rates were carried out.
The results indicated that all conventional and thermal gas injection scenarios do not increase the cumulative gas production more than the depletion case. The non-thermal gas injection scenarios increased the cumulative condensate production by 8.6%. However, thermal CO2 injection increased the condensate production cumulative by 28.9%.
It was observed that thermal gas injection does not vaporize condensate It was observed that thermal gas injection does not vaporize condensate more than conventional injection that have the same reservoir pressure trend. However, thermal injection mainly improves the condensate mobility. Appropriately, thermal injection in retrograde reservoirs, is mostly applicable for depleted reservoirs when the largest amount of non-producible liquid is already dropped out. Finally, this research studied executing thermal gas injection in retrograde gas condensate reservoirs, operationally, by considering the following items: carbon dioxide recovery unit, compressors, storage-tanks, anti-corrosion pipe-lines and tubing-strings, and corrosion-inhibitors along with downhole gas heaters.

Environmental performance criteria currently represent major decision factors in civil engineering projects, including pipeline construction. This paper presents a framework based on systems modelling and multicriteria decision analysis (MCDA) that captures different setups of pipeline installation techniques and the environmental impacts expected from different execution scenarios. A model is developed via SysML using the principles of systems modelling and engineering to capture the interactions of the pipeline as a product, the installation technique utilized, together with the environment. A TOPSIS-based MCDA module permits selecting the optimum alternative among construction alternatives. Open cut trenching and microtunneling are exemplified and a case study is provided where both techniques are evaluated in terms of environmental impacts. The contribution of this work is providing a structured and versatile framework that properly captures the interactions of different pipeline installation techniques and the environment, enabling the quantification of environmental impacts to a high degree of precision. The capacity to model different scenarios allows comparison and selection of the most suitable alternative.

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