The physical chemistry processes most likely to improve oil recovery are well known in theory, but their implementation to oil reservoirs in real conditions is an extremely complicated balancing act. This makes PERL’s expertise in physical chemistry a crucial asset for Total. As a strategic area for the future of the oil industry, it lays the foundation for energy-saving and cost-saving industrial processes to help improve oil recovery in the future.
Chemical boosters to push the limits of oil recovery
Conventional production techniques only allow us to recover 35%, on average, of the oil stored in reservoirs. If we want to push this limit, we will need to deploy advanced recovery improvement techniques. Gaining expertise in the chemical take on this (CEOR, Chemical Enhanced Oil Recovery), with an additional 5-20% recovery at stake, is a considerable challenge.
CEOR relies on the injection of chemicals that can help boost recovery. For example, adding polymers to the injection water to make it more viscous improves its “piston action” effect on mobile oil. This more efficient flushing of the oil reservoir on a macroscopic level can deliver an increase of five recovery points, even more for highly viscous oils. However, to improve performance even further, we need to start taking action at the microscopic level of physical chemistry processes. This is where surfactants and alkalis come in, as they target the trapped oil in the smallest pores of the rock matrix that is unreachable by conventional means. To overcome the capillary pressure that keeps this oil trapped, surfactants must trigger a dramatic drop in interfacial tension - by a factor of around 1,000 - between the oil and the injected fluid.
World-class expertise to overcome all the challenges of CEOR
At the Platform for Experimental Research at Lacq (PERL), we have some strong assets to help towards mastering these physical chemistry levers for oil extraction.
- Our expertise in physical chemistry is a launch pad for innovation, a capacity for which we are renowned within the oil industry and academic world alike. As such, in 2015 we partnered up with the ESPCI (the École Supérieure de Physique et de Chimie Industrielles in Paris), an internationally reputed authority in the field, to establish the joint research laboratory for the Physical Chemistry of Complex Interfaces (PIC). Here, we are working to deepen our understanding of what happens at oil-water-solid interfaces, the metaphorical front-line of CEOR.
- Our “homemade” analytical techniques put us front of the pack in terms of analyzing complex systems that mix water, salts, oil and additives. The development of proprietary equipment enables us to closely examine polymers in solutions, or to identify and quantify the chemical species involved in balancing multiphase systems.
- Our integrated physical chemistry approach to the CEOR workflow, from the development of molecules to the design of injection and post-treatment pilot projects, is unique for our industry. It is a decisive factor in boosting technical and economic performance, and is part of a major effort to model and assess technical and economic challenges, which we are carrying out in collaboration with the CSTJF labs in Pau, France, the development team behind our future reservoir simulator, and the EOR team for the onshore product line.
CEOR: tailor-made chemical formulations
In the field of CEOR, there is no such thing as a molecular master key. Products are designed based on a tailor-made approach, adapted to the specific conditions at each target reservoir.
- Ruled by salinity and temperature, the viscosifying power of a polymer also depends on its resistance to mechanical degradation once it has been injected, and on its ability to withstand spending a number of months or years in the reservoir.
- As for the surfactant, it needs to create the strongest possible interactions (and with equal energy) between the oil and the water. It’s a complicated equation. The surfactant’s affinity with the water and oil depends on the salinity (the nature and concentration of salts present) and temperature. However, its relationship with the oil is also subject to other parameters - the length and structure of the oil’s carbon chain, the amount of dissolved gas, or the hundreds of other species of surfactant molecules that are potentially present naturally in the crude - that are often very difficult to detect.
- Alkalis can be precious allies in reducing the need for synthetic surfactants. By basifying the water, they limit the adsorption of surfactants on the rock and convert the crude oil naphthenic acids into naphthenates (which are themselves powerful surfactants).
The terms of the equation are economic too. Against a backdrop of low prices per barrel, the industrial roll-out of CEOR will only be possible if the additional costs of doing so are low. This is where the multidisciplinary nature of our expertise in physical chemistry truly shines. Because it’s not enough to simply develop chemical formulations and injection strategies to minimize the volume of products used - the entire production chain needs to be optimized, offering cost-effective surface processes for treating oil and water that are suited to the chemicals produced in the well.
Technological advances that have set the bar for the oil industry
Pioneers of CEOR since launching pilots in the 1980s, we are continuing to push the boundaries of this strategic business area.
- Our polymer injection pilot on Dalia (Angola, 2008-2012) was a world-first in a deep offshore field. It allowed us to make significant progress in controlling polymer injectivity and in our understanding of polymer mechanical degradation. The latter, in particular, enabled us to patent innovative non-shear valve technology that preserves polymer integrity during injection. The ground-breaking nature of this development has attracted other companies to start collaborating with Total, in a JIP, to help industrialize it.
- In 2013, a surface transport pilot for polymers in a solution (United States) assured us there was no mechanical degradation of the polymers during turbulent-flow operations. The addition of an innovative deoxygenation solution for the transported solution also protected the polymers from iron-induced chemical degradation.
- With the injection pilot for ABK surfactants (Abu Dhabi, 2014) we pushed the limits of salinity allowing the use of surfactants, which at that time was between 40 and 60 g/l. The formulation produced in our laboratories was able to withstand a hot (83°C) and highly saline (230 g/l) reservoir, and achieve an increase in oil recovery around the pilot well of approximately 35% in a poorly permeable (5 mD) reservoir.
- With the Petrocedeño pilot currently underway in Venezuela, we are now pushing the limits of polymer usage by injecting them, for the first time, on a heavy crude (2,000 cP). Our goal is to double current recovery levels to achieve rates of around 16-20%.
This strategic CEOR offensive is set to continue, with new pilots targeting the challenges faced by our Middle East & Africa portfolios. In our sights, we have the injection of polymers into viscous oils (>200 cP) and the injection of polymers and surfactants into very hot (120°C) and highly saline (200-250 g/l) carbonate reservoirs.
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