Recovery, oil

Drilling fluids or muds are other aqueous functional fluids used in oil recovery. Muds are used to cool the drill bit and to keep underground formation pressure stable. The corresponding formulations are based on thickeners such as guar, starch and modified cellulose. These compounds are easily degraded by a great variety of microbe species. The consequence is that the mud s viscosity decreases and the formulation finally loses its functionality. As the aqueous functional fluids applied in oil recovery operations are used in vast quantities, one looks for microbicides to overcome the microbial problems which are effective at very low concentrations, inexpensive and environmentally safe. 

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Keywords compressibility, primary-, secondary- and enhanced oil-recovery, drive mechanisms (solution gas-, gas cap-, water-drive), secondary gas cap, first production date, build-up period, plateau period, production decline, water cut, Darcy s law, recovery factor, sweep efficiency, by-passing of oil, residual oil, relative permeability, production forecasts, offtake rate, coning, cusping, horizontal wells, reservoir simulation, material balance, rate dependent processes, pre-drilling. 

If the mobility ratio is greater than 1.0, then there will be a tendency for the water to move preferentially through the reservoir, and give rise to an unfavourable displacement front which is described as viscous fingering. If the mobility ratio is less than unity, then one would expect stable displacement, as shown in Figure 8.16. The mobility ratio may be influenced by altering the fluid viscosities, and this is further discussed in Section 8.8, when enhanced oil recovery is introduced. 

Enhanced oil recovery (EOR) techniques seek to produce oil which would not be recovered using the primary or secondary recovery methods discussed so far. Three categories of enhanced oil recovery exist ... 

When considering secondary or enhanced oil recovery, it is important to establish where the remaining oil lies. Figure 8.21 shows an example of where the remaining oil may be, and the appropriate method of trying to recover it. The proportions are only an example, but such a diagram should be constructed for a specific case study to identify the target oil . 

Water may be injected into the reservoir to supplement oil recovery or to dispose of produced water. In some cases these options may be complementary. Water will generally need to be treated before it can be injected into a reservoir, whether it is cleaned sea water or produced water. Once treated it is injected into the reservoir, often at high pressures. Therefore to design a process flow scheme for water injection one needs specifications of the source water and injected water. 

Keywords production decline, economic decline, infill drilling, bypassed oil, attic/cellar oil, production potential, coiled tubing, formation damage, cross-flow, side-track, enhanced oil recovery (EOR), steam injection, in-situ combustion, water alternating gas (WAG), debottlenecking, produced water treatment, well intervention, intermittent production, satellite development, host facility, extended reach development, extended reach drilling. 

A considerable percentage (40% - 85%) of hydrocarbons are typically not recovered through primary drive mechanisms, or by common supplementary recovery methods such as water flood and gas injection. This is particularly true of oil fields. Part of the oil that remains after primary development is recoverable through enhanced oil recovery (EOR) methods and can potentially slow down the decline period. Unfortunately the cost per barrel of most EOR methods is considerably higher than the cost of conventional recovery techniques, so the application of EOR is generally much more sensitive to oil price. 

Proceedings of the 1992 International Conference on Microbial Enhanced Oil Recovery 40a Asphaltenes and Asphalts, I... 

An important application of foams arises in foam displacement, another means to aid enhanced oil recovery. The effectiveness of various foams in displacing oil from porous media has been studied by Shah and co-workers [237, 238]. The displacement efficiency depends on numerous physicochemical variables such as surfactant chain length and temperature with the surface properties of the foaming solution being an important determinant of performance. 

D. O. Shah and W. C. Hsieh, Microemulsions, Liquid Crystals and Enhanced Oil Recovery, in Theory, Practice, and Process Principles for Physical Separations, Engineering Foundation, New York, 1977. 

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