Production Acceleration and Injectivity Enhancement Using Steam-Propane Injection for Hamaca Extra-Heavy Oil

Abstract

The largest known hydrocarbon deposit in the world, the Orinoco Belt in Venezuela, contains oil with a gravity ranging from 9 to 14 ° API. The Hamaca project encompasses more than 400 square miles of the Orinoco Belt and is believed to contain more than 30 billion barrels of extra-heavy oil (9 ° API). Production of the project started in November 2001 and the target is to produce some 30,000 m3 (190,000 barrels) a day over a life span of more than 35 years. This study found that using propane as a steam additive can accelerate oil production and improve the effect of steam injectivity in the Hamaca field. In our laboratory study, steam-propane injection accelerated the start of oil production by 21% compared to that with pure steam injection. In the field, this could translate into significant gains in discounted revenues and a reduction in steam injection costs. Second, steam injectivity with propane as an additive was up to three times higher than that for pure steam injection. Third, accelerated oil production and increased injectivity were practically the same for all of the runs using propane as a steam additive (irrespective of the propane-steam mass ratios). Propane appears to be a viable steam additive at propanesteam mass ratios as low as 2.5:100. Introduction The effects of injecting steam with other gaseous additives have been tested experimentally on several occasions. Redford(1) showed that the addition of CO2 or ethane to steam improved oil recovery. Naphtha increased recovery even further. Harding et al.(2) showed that the co-injection of CO2 or flue gas with steam yielded higher recoveries than pure steam injection. Stone and Malcolm(3) achieved higher production rates with steam-CO2 injection. Using their method, Stone and Ivory(4) found that under certain conditions, CO2 presoaking increased oil recovery above conventional CO2-steam injection. Nasr et al.(5) increased bitumen recovery by injecting CO2, N2, and flue gas with steam in both continuous and cyclic injection. The use of CO2 resulted in higher oil recoveries than that with N2 and flue gas injection. Frauenfeld et al.(6) showed that for oils without an initial gas saturation, co-injection of CO2 with steam could improve oil recovery. On the other hand, when an initial non-zero gas saturation was present, co-injection of CO2 was not beneficial. Metwally(7) showed that injecting a CO2 slug prior to the steam improved injectivity in cores from the Lindbergh field. However, the presence of a noncondensible gas with steam did not improve steam drive recovery and resulted in higher residual oil saturation than with pure steam injection. Gumrah and Okandan(8) performed linear and 3D displacement experiments to evaluate the performance of CO2-steam injection on the recovery of 24 ° API, 12 ° API, and 10.6 ° API oils. The 1D tests indicated that the oil recovery increased with increasing CO2- steam ratios until an optimum value was reached. The addition of CO2 did not produce a significant increase in the recovery of the lighter oil.