The Orinoco heavy oil belt in Venezuela is one of the largest extra-heavy oil resources in the world. It has become a major goal for the unconventional oil exploitation in these years. Now, the most common production method is to use the horizontal well cold production without sand. It is an economic and commercial process, and with the reservoir of this area have high initial gas to oil ratio (GOR), porosity and permeability with unconsolidated sand. However, after several years' production, the oil rate draws down quickly caused by the reservoir pressure drops; the key challenge of cold production is that the recovery factor (RF) tends to be only between 8% and 12%, implying that the majority of the oil remains in the oil formation. It is necessary to develop viable recovery processes as a follow-up process for cold production. Generally, steam based recovery method was widely used as a follow-up process for cold production. In this paper, steam fracturing (dilation) Cyclic Steam Stimulation (CSS) operation and Non steam fracturing (No dilation) CSS operation by using reservoir simulator is examined for a post cold production in extra heavy oil reservoir, in order to analyze the performance of the oil rate, cumulative steam-to-oil ratio (cSOR), steam depletion zone, greenhouse gas emission and some necessary parameters. The key component of the steam fracturing (dilation) is the ability to inject high temperature and pressure steam into the formation to fracture the reservoir rock which in turn raises the rock permeability and mobilized the oil by lowering the visocisity. To compare the results of the dilation and no dilation CSS operation, this study reveal that due to the steam is injected into the reservoir by using the same cumulative cold water equivalent (CWE), the steam condensate; pressurized by steam vapour, fracture the formation. Dilation operation achieves higher oil rate, lower cSOR. The result also show that fraturing (dilation) of the reservoir during steam injection relieves the pressure which in turn lowers the steam injection pressure below the case where No dilation operation ouccurs.

Primary production using horizontal wells has been successfully applied in extra-heavy oil reservoirs, heavy oil belt, Orinoco, Venezuela. During drilling period, formation damage due to drilling fluid invasion lowers the effective permeability around the well, leads to higher pressure drop and has detrimental impact on well productivity in such pressure depleted reservoirs. In this study, laboratory experiments of drilling fluid invasion are conducted to identify damage mechanism. The oil sample used in the test is taken from Block J, Orinoco Belt and the formation temperature is restored in the lab to mimic the process of drilling fluid mixing with crude oil in horizontal drilling. The stable emulsion is formed by mixing the crude oil with drilling fluid in different proportions. Furthermore, damage level is quantified by well test interpretation. Skin factor, wellbore storage and other formation parameters are estimated by deconvolution method based on three build-ups. Finally, acid washing and well bottomhole electric heating, two methods of remedy are applied in oilfield. Experiment results show that low productivity of the horizontal wells is due to the presence of highly viscous emulsion system stabilized by large amount of calcium carbonate in drilling fluid. The emulsion system restricts reservoir fluid flowing from the formation to the slotted liner. In Block J, constrained by the operational problems, the effective shut-in time is commonly short. Conventional well test method can hardly give the reliable results. Compared with the conventional method, deconvolution method can solve the data limitation, minimize the initial distortion caused by wellbore storage and get more reliable results. The production can be improved temporarily after the acid washing while declines rapidly. Electric heating can obviously improve the oil mobility near wellbore and maintain stable production. This paper combines both lab studies and well test interpretation to characterize the formation damage, provides guidance for the remedial operations to improve well productivity.