Recovery Processes of Extra Heavy Oil - Mechanistic Modelling and Simulation Approach

Abstract

Heavy/ extra heavy oil has captured the global attention as an unconventional hydrocarbon resource which may satisfy the ever-increasing energy demand in the future. Heavy/ extra heavy oil is often characterized as viscous and immobile fluid with high content of impurities and heavy metals, such as Nickel and Vanadium. These inherited characteristics impose great challenges not only to oil recovery optimization, but also various costs pertaining to downstream processing. Due to this fact, reservoir modelling and simulation are commonly conducted to evaluate the performances of enhanced recovery processes at early project stage. In this paper, the conceptual models for Oilfield Alpha are developed using CMG STARS reservoir simulator. They are grouped into 3 categories, i.e. (I) Horizontal wells, (II) 5-spot pattern vertical wells and (III) Horizontal well pairs, based on the nature and well configuration of the recovery techniques. These techniques are Horizontal Well (HORZ), Steam Flooding (SF), Cyclic Steam Stimulation (CSS), Steam Assisted Gravity Drainage (SAGD), Vapour Extraction (VAPEX) and some of their variations. Performance indicators, typically the Recovery Factor (RF) andCumulative Steam-Oil-Ratio (CSOR), for each model are evaluated and compared within the category. The simulation results generally show that, after 20 years of production, the thermal methods have prevalently higher oil recovery factor, i.e. 7 -37 % of OOIP, compared to that of cold methods, i.e. 8 -13 % of OOIP. Further sensitivity analysis on Expanding Solvent-SAGD (ES-SAGD) and VAPEX are also conducted in order to investigate the effects of injected fluid composition imposed on the process performance. From the results, 95 % of steam and 5 % binary components of C 3 and C 6 presents as the optimum injected fluid composition for ES-SAGD method. On the other hand, injected fluid comprising 60 % of C 1 and 40 % of C 3 delivers the best oil recovery factor for VAPEX method.