This paper discusses a technology for waste management and disposal through cuttings reinjection (CRI). The fully integrated process was successfully applied in the Ecuador Apaika-Nenke field, which is an area with significant oil potential located in the heart of a protected biodiverse zone. The advantage of the applied process, from candidate selection screening to the detailed implementation phase, represents a permanent drilling solution in environmentally sensitive areas. This paper presents a case study of CRI in an Apaika injection well. The well was chosen based on feasibility tests and previous injectivity test results, making it the first drilled waste reinjector well in Ecuador supported by best practices. This paper describes injection equipment used for the slurry process and injection into the formation, waste collection and transportation from the rig site to the CRI facilities, slurrification process describing how the cuttings are treated for reinjection, injection parameters given by the feasibility study, and pressure response to injection explaining how the formation will react in time to the slurry injection. Each slurry injection was performed in 12-hour cycles instead of continuous injection, allowing the formation to reach pseudoequilibrium stages while the cuttings migrated within the selected structure through fracturing conduits. From June 2014 through December 2015, 209,000 bbl of slurry from 11 drilled wells were injected into the disposal well. All the waste fluids (dewatering water, cutting pits rainwater, and rig wash) were used for the preparation of injection slurry, reducing chemical use for the dewatering process. The well was also used for disposal of produced water with more than 400,000 bbl injected. The cyclic injections were conducted in three stages: preflush, post-flush, and slurry injection pumping to displace the entire tubing volume and minimize well plugging risks. During the first stage, wellhead pressure and slurry properties were monitored to help establish accurate injection parameters. No significant changes were observed in terms of pressure performance at a maximum pressure differential of 2,000 psi during the three stages. The first CRI met all expectations of not leaving any cutting on surface. All the cuttings and drilling waste from the Apaika-Nenke pads were reinjected without any operational inconvenience. For future wells, deforestation will not be necessary for new cutting pits in this sensitive area, helping minimize the environmental impact and addressing social challenges and inherent risk present within the oil industry. The application of CRI in the Apaika-Nenke field demonstrated that drilling in a sensitive area could be performed with high environmental standards and in compliance with local environmental laws with excellent results.
Natural gas is the most environmental friendly fossil fuel with a high energy content and has a promising future within the energy consumption outlook. For this reason, its production from coal is gaining a significant interest, converting the most abundant, stable, and low price fossil fuel to synthetic natural gas (SNG). In this paper a technology outlook and a sustainability assessment of the technical, economical, and environmental factors is developed. It was found that the sustainability of the process depends mainly on the local price of coal and natural gas, as well as, emerging SNG technologies, also known as direct methanation. The conventional methanation process, the indirect methanation, has high capital costs but it is currently the only proven large scale technology. Although the emerging technology has not yet been tested at a commercial scale, it has a better technical performance with an net efficiency increase of more than 10 percent as results of the process stage reduction which should lead to lower capital costs requirements. Regarding the environmental performance, the conventional process produces large amounts of CO2, approximately 1.3 kg CO2 for each kg of coal, that has to be compressed and sequestered to meet the environmental targets.
Coal is the most interesting gasification resource in commercial application due to its wide reserves and low prices, therefore numerous commercial coal gasification technologies have been developed. The features of the most important have been studied in this paper. The gasifiers considered are the British Gas Lurgi, Siemens, General Electric, Conoco Phillips and Shell; principal parameters have been taken into account such as the cold gas efficiency, the production capacity, oxygen, electricity and steam consumption, effect of coal type, syngas produced for the desired final product, capital, operation costs, and environmental performance. From assessment of the latter features for each gasifier, one can conclude that although the BGL has the lowest production capacity with 1000 tons/day, it represents the best technology option due to its highest cold gas efficiency of 89%, the lowest oxygen and electricity consumption and the lowest capital costs with 50 million dollars per unit.
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