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Recognizing and describing processes in producing and abandoned oil- and gas reservoirs that may cause environment footprints and identifying technologies to impair these

Ursin J. R.

AGH Drilling, Oil, Gas

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2016

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Vol. 33, no. 2

291--305

EN

The content in this report was presented at the 3rd MUSE steering committee meeting at UoS, in Stavanger, December 10th, 2015. The project report consists of five individual reports, each focusing on various themes: 1. Hydrocarbon Reservoir Behaviour during the Process of Abandonment and Thereafter by Victor Chukwudi Anokwuru, IPT/TN/UoS 2. Monitoring Techniques Applied to CCS-EOR by Intergrity Obara, IPT/TN/UoS 3. Risk Assessment by Emil Gazizullin, IPT/TN/UoS 4. Environmental Considerations of CO2 Projects by Oduro Takyiwa Susanna, IKM/TN UoS and Yen Adams Sokama-Neuyam, IPT/TN/UoS 5. How to Reduce the Likelihood of Environmental Impacts During Plug and Abandonment by Alexander Steine Johnsen, Preben Emil Haugen and Jann Rune Ursin, IPT/TN/UoS The reports are all written under supervision of the WP2 project leader. All reports are based on open sources; local (UoS) reports, publications available on the internet, official publications and journal papers, and communications with a great number of individual resource persons in the Norwegian oil and gas industry. The relevance of the work presented in the above mentioned reports, in relation to the MUSE project objectives is, as far possible, promoted through carefully following the project description (part of the AGH–UoS partnership agreement) and with reference to a preliminary WP1 progress report from mid February 2015; WP1-Selecting reservoirs for application of CO2 storage with IOR technology and feasibility studies. The work in the MUSE project is accomplished through the willingness and skills of UoS department master students, hired as project assistants. Fortunately for the project there are quite a few high class student, capable of writing high quality technical reports at UoS. The five reports are presented sequentially and all reports are the responsibility of the author and all reports are approved by the WP2 project leader.

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Gas-condensate banking and well deliverability : a comparative study using analytical- and numerical models

Ursin J. R.

AGH Drilling, Oil, Gas

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2016

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Vol. 33, no. 2

259--289

EN

Reservoir condensate blockage in the reservoir and in particular in the close vicinity of the wellbore may result in significant loss of well deliverability for medium to tight gas reservoirs. The dynamics of fluid flow in these types of reservoirs are investigated by way of analytical description and by numerical simulation of radial two phase flow behavior. The analytical model is based on a single phase semi steady-state solution, being revised for two phase flow of gas and condensate oil. As the liquid is dropping out of the gas, a saturation distribution of immovable oil is seen to develop radially in the reservoir with time. Condensed oil not being part of this saturation distribution is produced to the surface. The numerical model is a cylindrical, single well, fine gridded, simulation model run on the Eclipse E300 compositional simulator. The base case study comprises a rich gas condensate fluid (GOR ~ 1000 Sm3/Sm3), an initial gas-in-place volume of 750 MSm3, and reservoir permeability of 10 mD. A gas flow rate of 0.5 MSm3/day is leading to a production period of about 4 years. A comparative study is performed by varying parameters such as pressure development, development of bank of immovable oil both radially and as function of time, condensate blockage effects, and gas and condensate oil production and onset of reduced well deliverability. Sensitivity analysis are performed by studying variation in the productivity index, non-Darcy and mechanical skin, and sensitivities related to permeability. It has been confirmed in this study that condensate blockage has a direct and negative impact on well deliverability, where both the plateau period and the bottom hole pressure are reduced. We also show that the analytical model compares well with the numerical models and that many features describing gas-condensate banking and well deliverability are adequately described in the model. The analytical model also offers insight into the process of reservoir liquid storage in gas condensate reservoirs.

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Experimental and theoretical investigations of CO2 injectivity

Sokama-Neuyam Y. A., Ursin J. R.

AGH Drilling, Oil, Gas

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2016

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Vol. 33, no. 2

245--258

EN

Laboratory sandstone core flooding experiments were conducted to investigate the impact of brine desaturation and salt precipitation on CO2 injectivity. An attempt was then made to reduce the impact of salt precipitation on CO2 injectivity by injecting a slug of diluent prior to CO2 injection. The effect of brine salinity, CO2 injection rate and initial core permeability on the efficacy of this mitigation technique was investigated. Decrease in diluent brine salinity improved injectivity but there exist a critical brine salinity below which CO2 injectivity was further impaired. It was also observed that, above a certain CO2 injection rate, alternating CO2 injection with the diluent brine could not enhance CO2 injectivity. Injectivity improvement also depends on initial permeability of the porous medium. Up to about 30% injectivity improvement was observed in the experiments.