Design and Optimisation of a Steam Assisted Gravity Drainage (SAGD) Facility for Improved Recovery from Canadian Oil Sands

As conventional oil production becomes limited, transportation fuels are being produced from other unconventional fossil resources such as oil sands. Oil sands are a combination of clay, sand, water and bitumen. Vast quantities of oil sands resources have been found worldwide. The largest known reservoir of oil sands in the world is located in the province of Alberta (Canada). Several techniques for the extraction of the oil from oil sands have been developed in recent decades. Steam-Assisted Gravity Drainage (SAGD) is the most promising approach for recovering heavy and viscous oil resources. In SAGD, two closely-spaced horizontal wells, one above the other, form a steam-injector and producer pair. The reservoir oil is heated by the injected steam and drains to the producer under the effect of gravity. The general aim of this dissertation is a detailed study of optimisation of an hypothetical industrial scale facility (named LINK), located in Alberta. All data relating to LINK plant have been obtained from a review of the existing literature references or have been assumed. The facility employs SAGD technology to recover bitumen and deliver a multiphase mixture of bitumen, water, Doctoral School on Engineering Sciences Universita Politecnica delle Marche steam and gas to the CPF (Central Processing Facility). The main purpose of this work is to present a detailed technical optimisation of the pipeline system based on the Flow Assurance discipline. Flow Assurance analysis has been carried out by the multiphase flow simulation tool OLGA by SPT for four systems: emulsion, steam, natural gas and source water pipeline systems. An additional underground pipeline has been considered to connect the CPF to a private station (called NGS Metering Station) in order to supply natural gas for the facility. On the basis of the collected data and assumptions, the Flow Assurance study has been carried out by performing simulations in steady state and transient conditions. They have been performed after a detailed thermodynamic characterization of the different fluids carried out by PVTsim, by Calsep. Results have been obtained in terms of systems configurations and selected diameters, thermal, chemical and hydraulic behaviors, operability characteristics, design and operating parameters, mechanical integrity, system deliverability, systems performance, possible uncertainties and criticalities that can occur. The second aim of this Thesis is an economic optimisation and evaluation of the hypothetical system studied. Discounted Cash Flow Analysis of LINK Facility has been performed in a MS Excel spreadsheet. Costs (capital and operating) of existing projects have been found in literature. The results show that the hypothetical plant LINK is a good investment. Third and last purpose of the present work is an environmental analysis of the LINK plant: in order to evaluate GHG emissions from LINK plant, an Excel spreadsheet has been developed for the LCA analysis. The calculated emissions from oil sand production by SAGD technology have been compared with values relating to conventional crude oil pathways and to recovery and extraction of bitumen through surface mining from literature. The comparison demonstrated that SAGD is a promising technology also from an environmental point of view.