Tertiary recovery techniques

Water injection from seawater or fresh water sources contributes to the souring of oil fields with H2S usually resulting in an increase in the corrosion rate, which sometimes requires a complete change in corrosion strategy. These water sources may necessitate biocide injection and will require deaeration to avoid introducing a new corrosion mechanism into the existing system. Tertiary recovery techniques are often based on miscible and immiscible gas floods. These gas floods invariably contain a... 

A consequence of the use of advanced technology in oil production from a reservoir results in increase in the corrosivity of the oil production environment. The extent of corrosion increases because (i) oil, water, and gas are present in the field. Seawater or fresh water is injected downhole to drive oil out of formation. As time passes, the amount of water to the amount of oil increases and the degree of internal corrosion increases. Water injection from seawater or fresh water sources causes souring of oilfields with H2S and increases in corrosion rate. These water sources require biocide injection and deaeration to avoid the introduction of new corrosion pathways into the existing system. Tertiary recovery techniques involve miscible and immiscible gas floods that may contain as much as 100% CO2. This leads to high corrosivity of the fluids. 

Conventional oil and gas oil available using recovery techniques known up to 1980. Thus, oil from tertiary oil recovery coal shales etc., is referred to as unconventional oil. 

As the production lives of secondary methods lose their efficiency, further techniques have been tested and found to continue to release additional amounts of oil. These methods are considered tertiary methods and are generally associated with chemical or gaseous recirculation methods of recovery. Some instances of in-situ thermal recovery have been used but not on a large extent. 

When this pressure drops, it can be built-up again by water flooding. Unfortunately, after these primary and secondary processes, there still remains up to 70% of the oil adsorbed on the porous clays. Consequently, in recent years, there have been tremendous efforts made to develop tertiary oil recovery processes, namely carbon dioxide injection, steam flooding, surfactant flooding and the use of microemulsions. In this latter technique, illustrated in Fig. 1, the aim is to dissolve the oil into the microemulsion, then to displace this slug with a polymer solution, used for mobility control, and finally to recover the oil by water injection ( 1). 

Other Useful Applications. It is well known that there are many other important applications of surfactants and organized surfactant assemblies in separation science. Many specific separation processes such as secondary and tertiary oil recovery (500-502), tar sand extraction (503). gas scrubbing and purification (504) and different electrophoretic techniques utilize surface active agents (505). However, space limitations and the existence of several recent review articles preclude further discussion of these applications in this particular overview. 

Tertiary or enhanced oil recovery (FOR) incorporates a variety of techniques involving more elaborate injection schemes than employed in secondary recovery. The treatment of EOR-produced emulsions must be approached independently from any primary or secondary production from the same field or reservoir. Standard demulsifiers and treatment methods used during primary and secondary recovery operations may not handle EOR-produced emulsions. 

Polymers that have been suggested for mobility control in oil reservoirs include polyacrylamides, hydroxy ethyl cellulose, and modified polysaccharides which are produced either by fermentation or by more conventional chemical processes. In this paper the solution properties of these polymers are presented and compared for tertiary oil recovery applications. Among the properties discussed are non-Newtonian character for different environmental conditions (electrolytes and temperature), filterability, and long term stability. The behavior of these water soluble polymers in solution can be correlated with the effective molecular size which can be measured by the intrinsic viscosity technique. A low-shear capillary viscometer with a high precision and a capability of covering low shear rates (such as 10 sec - - for a 10 cp fluid) has been designed to measure the viscosities. The measurement of viscosities at such slow flow conditions is necessitated... 

The same type of dissociation technique may be used to recover N-permethylated polyamines from their metal-salt complexes. The solvent is the major factor to be considered in designing such a procedure. The solvent chosen should boil near or slightly above the thermal dissociation temperature of the particular polyamine salt complex. With N-permethylated polyethylene polyamines, the final recovery of a polyamine from the extraction solvent is best done by distilling the hydrocarbon solution. Recovery by phase separation is not possible with the tertiary polyamines since these compounds generally are miscible with most hydrocarbon solvents. 

The evaluation of solute-micelle binding constants has important implications outside the field of chromatography, such as micellar catalysis, tertiary oil recovery, and enzyme and membrane modeling. MLC is a powerful technique for the determination of these constants, in comparison to classical methods. The use of MLC in this field has several advantages ... 

---