Abstract
Heavy oil in Middle East fractured carbonate reservoirs account for 25-30% of the total oil in place in the region. Production of heavy oil from such reservoirs is thought to play an important role in the future of the ever-growing world\'s energy consumption in which Iran\'s recoverable heavy oil is more than 85 billion barrels. The offshore Ferdows field in Iran is reportedly on the order of 30 billion barrels of oil and holds perhaps the greatest promise to add significant future carbonate heavy oil production within the region. With depletion of conventional petroleum reserves and increase of hydrocarbon fuel demand, there is no doubt that there will be a tremendous demand on the development of heavy oil reservoirs in the coming decades. Despite its strategic importance, recovery of heavy crude from fractured carbonate reservoirs has found limited applications due to the complexity of such reservoirs. As most of the oil is stored in matrix due to its higher storage capacity than fracture network, reservoir development plans will aim at maximizing the matrix oil recovery. For reservoirs with high recovery factor, minimizing matrix residual oil saturation is a critical issue to extend the life of the reservoir. For reservoirs with low recovery factor, accelerating the production rate is more vital. For each of these reservoir types, different Enhanced Oil Recovery (EOR) methods should be considered and implemented accordingly. In this study, a comprehensive review is conducted to figure out the feasibility of heavy oil recovery from fractured carbonate reservoirs by use of Cyclic Steam Stimulation (CSS), Steam injection, In-Situ Combustion (ISC), Steam Assisted Gravity Drainage (SAGD), Vapor Extraction (VAPEX) and Expanding Solvent-Steam Assisted Gravity Drainage (ES-SAGD).
Highlights
Carbonate reservoirs introduce great challenges due to their complex fabric nature and unfavorable wettability
The viscosity effect here is most important, improving Gas-Oil Gravity Drainage (GOGD) rates to commercial values. Another steam based enhanced oil recovery (EOR) method that used in fractured carbonate reservoirs is Thermally Assisted Gas-Oil Gravity Drainage (TA-GOGD)
In TA-GOGD process, steam is injected into the reservoir and heats the rock matrix blocks through the higher permeability fracture network and improves oil recovery principally by reducing the oil viscosity and increasing the rate of gravity drainage through the matrix
Summary
Carbonate reservoirs introduce great challenges due to their complex fabric nature (low matrix permeability, poor effective porosity, fractures) and unfavorable wettability. These challenges are further displayed when combined with increased depth and low grade oil (high density and viscosity). Thermal methods (steam injection or in-situ combustion) and nonthermal methods (VAPEX) may be cited as examples of such processes Some processes involve both vertical and horizontal wells, as demonstrated by recent progress on certain technologies, such as measuring while drilling (MWD), which improved the success of horizontal wells, reducing any drilling navigation problems. Example of the technologies that use horizontal wells are: steam assisted gravity drainage (SAGD), expanded solvent with gravity drainage (ES-SAGD) and vapor extraction (VAPEX)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
