Our work analyses the historic Enhanced Oil Recovery methods(EOR) applied in the Ayacucho block of the Huyapari area in Venezuela's Orinoco Oil Belt (OOB) and the Quifa field in Colombia. Both study areas have oil recovery factors around 12% - considered low compared to the other reservoir performance in the same basins.
Profitable exploitation of heavy and extra heavy crudes is a challenge. Identifying the critical elements for improvement in reservoir performance to make it economically viable requires an application of the appropriate technology for production efficiency.
Our collaborative team has analyzed various technological alternatives for production optimization. We have compiled reservoir characteristics from publications and have defined the screening criteria for the selection of EOR methodology in Venezuela and Colombia.
The Orinoco Oil Belt (OOB) is the most significant hydrocarbon accumulation presently assessed worldwide, with a STOIP of 1181 BBO. It covers more than 50000 km2 along the southern edge of the Eastern Venezuela Basin (EVB). Structural and stratigraphic traps are compartmentalized holding reservoirs formed in a fluvial-deltaic depositional environment. Trapping mechanisms include normal fault blocks and lateral pinch outs of channelized Oligo-Miocene fluvial sandstones deposited in a braided and meandering-fluvial system. The OOB has been subdivided into the areas of Boyaca, Junin, Ayacucho, and Carabobo. We have selected Huyapari block in Ayacucho area because of the similarities in fluid's viscosity property (1000 cp) with Quifa Field in Colombia. Also, in both areas' reservoir properties such as temperature, pressure, API gravity, permeability, trapping mechanism, and net sand thickness are similar.
Rubiales-Quifa complex, operated by Ecopetrol, is the largest oil producer in Colombia. There are Original Oil In Place (OOIP) is nearly 7.7 billion STB (7.5E9 STB) with an average oil gravity of 13 degrees API. The combined production of these two fields is approximately 180000 barrels per day as of 2021. Quifa Field was added to the operations and started production in 2008. It is located on Rubiales structure with a monoclinal dip of to the northwest. The main reservoir of the complex consists of an unconsolidated sandstone formation with high permeability and an oil density API of 14.4°. Normal faults compartmentalize sand bodies and control the distribution of the hydrocarbon accumulations with a strong aquifer supported production.
Lateral facies variations add to the complexity of the trapping mechanism of hydrocarbons. Braided rivers depositional system define the facies distribution of sands laterally interbedded with fine overbank sediments. (Flores et al., 2014). Some wells show more than on oil-water contact that confirms the existence of different reservoir flow units. The uppermost section of the stacked reservoirs is developed using horizontal wells. (Da Silva et al., 2014).
The petrophysical properties of the Huyapari block and Quifa Field are similar. Reservoirs have more than 30% porosity and permeabilities of more than 4000 millidarcys. The differences are related to the fluid composition and production mechanism. In the case of the Huyapari block, there is a fluid with high gas content (foaming gas) in the reservoir, which expands during the oil production. In the case of Quifa and Rubiales, the production mechanism is hydraulic. In both cases, sand reservoirs have good porosity, high permeability, and sand packages that facilitate the drilling of deviated, horizontal and multilateral wells. However, there are essential differences in production mechanisms, crude oil, and rock-fluid interaction.
International experience in EOR application worldwide and definition of screening criteria for selecting the EOR process, such as CO2 Miscible, Chemical, In-situ Combustion, Polymer, Steam flooding, and Gas Immiscibility - are frequently discussed among members of the collaborative team of U3 Explore Venezuela Project.
We offer an analysis of geologic and technical drivers in EOR methodology selection and ranking of the applicable EOR methods considering the following conclusions on local conditions:
Quifa's case:
- Aquifer support generates maintainable reservoir pressure.
- Water entry in the channel sands because of high permeability results in 90% Basin Sediment and Water (BS&W) in some cases.
- The steam injection test was inefficient in Quifa due to water entry into the oil zone, generating premature cooling without lowering the viscosity.
Huyapari's case:
- Weak aquifer support causes a decline of the reservoir pressure, and currently, it is below the bubble point in this block. Hence gas-oil ratio is high at 100SCF/STB, and the primary EOR driving mechanism is a solution gas.
- An inactive aquifer may lower the risk of water flooding in the steam injection area.
- We can infer that the steam is more efficient in high viscosity oil (higher 800 cp) cases.
Another consideration of this study is the CO2 emission related to EOR methods such as steam injection, which could reach more than 700 Kg/bbl.(Gordon et al., 2016). These gases have not yet been disposed of as part of an EOR method in the Orinoco Oil Belt because, currently, CO2 injections are not economically viable in the region. Each case of the CO2 injection or other EOR application in Colombian or Venezuelan basins requires a geologic-engineering assessment of the local geotechnical conditions and economic drivers for the selected solution.
U3 Explore geologic-engineering team with local and international expertise is available for consulting or expert boards using the results of this analysis in the application of best fitted EOR in the producing fields of northern South America.
U3 Explore Venezuela project team of local and international experts has collaborated on this and two other related studies published by U3 Explore. You can read more at:
- Learning from production from the Alberta Oil Sands - Dependencies between Geology and Petroleum Engineering Solution
- Comparison of Venezuela’s Faja Petrolífera del Orinoco and the Alberta Oil Sands challenges in EOR method selection
U3 Explore geologic-engineering team is available for consulting or expert boards sessions using the results of this and other two studies in applying the best fitted EOR method in the producing fields of northern South America.
REFERENCES
- Flores, A., and M. Osorio. 2014, "A Successful Gravel-Packing Technique in Vertical and Deviated Wells with Enlarged Open Hole in Cased Completions: A Case Study, Rubiales and Quifa Fields." Paper presented at the SPE Heavy and Extra Heavy Oil Conference: Latin America, Medellín, Colombia, September 2014. doi: https://doi.org/10.2118/171094-MS
- Lopez, A., R. Sanchez, and J. Pacheco. 2017, Injection Completion and Well Integrity Performance of First Cyclic Steam Stimulations to Horizontal Wells in the Huyapari Field. SPE Latin American and Caribbean Petroleum Engineering Conference held in Buenos Aires, Argentina. 2017.
- Gordon D., et al., 2015,. Know your oil; creating a global climate-oil index. Carnegie Endowment for International Peace. http://carnegieendowment.org/2015/03/11/knowyour-oil-creating-global-oil-climate-index/i3o
