Abstract

In this study, a particular hybrid process with propane and steamco-injected is simulated numerically under different operation strategies. Theroles of propane in the hybrid process are investigated. The economics of thesehybrid processes are also evaluated with a supply cost model. Results show thathybrid processes with steam and propane co-injection can have the same supplycost as that of SAGD process and propane-related cost is a small part of thetotal supply cost in these hybrid processes due to the small amount of propaneused in this study. Results also show that low pressure hybrid processes aremore cost-efficient than their high pressure counterparts.

Introduction

There are enormous petroleum resources in Canada, especially in the northernAlberta area. Unfortunately, the majority of these resources are bitumen andheavy oil, with viscosity usually over 100,000mPa•s in nature, which hinderstheir recovery. Research on the physical properties of these resources over theyears has provided effective technologies to tackle this problem. Generally twotypes of methods can reduce the bitumen's viscosity. The first is to increasethe bitumen's temperature. This can be achieved by injecting a hot fluid, suchas steam, into the reservoir, or by in-situ combustion through injectingoxygen-containing gases. The second method is to dilute the bitumen by lowviscosity hydrocarbon. This method involves injecting light hydrocarbons, suchas propane or butane, into the bitumen reservoir. The hydrocarbon dissolves andmixes with the bitumen. The viscosity of the mixture reduces from the originalviscosity of the bitumen. The diluted bitumen can then be recovered. Thecombination of the viscosity reduction method and the horizontal welltechnology has provided the technologies to recover the enormous bitumenresources in Alberta and Saskatchewan area.

Two processes, the Steam Assisted Gravity Drainage 1 (SAGD) and the VaporExtraction 2 (VAPEX) processes, have been developed for practicing oil recoveryin bitumen reservoirs using a pair of horizontal wells. The SAGD process hasbeen successfully tested in the field and has been moving towardscommercial-scale application while the VAPEX process is still at the fieldpilot stage. Both processes have their advantages and disadvantages. Theadvantages of the SAGD process are its high recovery percentage and high oilproduction rate. However the high production rate of the SAGD process isassociated with intensive energy input and excessive CO2 emission due toburning natural gas to generate steam, and costly post-production watertreatment. The VAPEX process, on the other hand, has the advantage of lowerenergy consumption, thus less CO2 emission. The major drawbacks of the VAPEXprocess, however, are its low oil production rate and the additional cost ofsolvent. In the past several years, ambitions to improve the energy efficiencyof the SAGD processes and concerns about the greenhouse gas (GHG) emission haveled to an idea of hybrid process which is to synergize the advantages of bothSAGD and VAPEX processes and minimize their drawbacks.

In this study, a particular hybrid process with propane and steamco-injection in the Athabasca-type reservoir is investigated numerically underdifferent operation strategies. The steam will act as the major heat carrierand the propane will act more like a steam additive due to its lowconcentration (mole fraction less than 5%). The performances of these hybridprocesses are compared to the SAGD processes. The effects of the co-injectedpropane in the hybrid process are revealed by the numerical simulation. Alsothe economics of the hybrid process is evaluated based on the establishedsupply cost model.

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