Water flooding is a secondary recovery process to displace oil that has not been recovered by the primary recovery method. Water flood is often associated with a problem of unwanted water production resulting from unfavorable displacement caused by channeling through high-permeable layers. The existence of high-permeability zones (thief zones) can cause early water breakthrough and excessive water production, thus, leaving a significant amount of oil bypassed in heterogeneous reservoirs. Most mature water flooding oilfields show 80-90% injected water was taken by these thief zone. Excess water production leads to many problems such as additional water treatment and disposal costs, corrosion, scaling, increased environmental issues, etc. (Pritchett et al., 2003). Therefore, it is important to improve the sweep efficiency of the waterflooding, not only to have more oil but also to reduce operating costs.
Nano-spheres are very small particles of proprietary composition that are used to enhance the recovery of oil within a wide range of reservoir conditions. This is accomplished by adjusting the permeability of the reservoir. Nano-spheres are much less susceptible to geological conditions when compared to other chemical technologies. Nano-spheres can be used in reservoirs with very high temperatures (up to~130°C) and high salinity (up to ~300,000 mg/L). Nano-spheres are designed to be used in heterogeneous reservoirs where permeability are very low (0.1mD).
Nano technology is generally used to describe technology and processes that occur on a scale not visible by the naked eye. Technology that operates on this scale can be as small as a single molecule up to several micrometers. One nano meter (nm) = 1000 micrometers (µm). ZL’s Nano-spheres particles begin with initial diameter ranging between 20-200 nm and are capable of passing through the near well born area. Over a predetermined time and reservoir conditions, the Nano-spheres will hydrate, expand and contract, constantly adjusting the permeable of the channels deep within the reservoir.
The pre-cross-linked polymer Nano-spheres with small initial nano sized, moves in deep formation as oil displacement agent, is able to pass through the near wellbore area, and dilate slowly in the formation water. Moving by Brownian motion in the deep reservoir, The Nano-spheres will provide a flowing resistance for the seepage flow of water in the high permeability channels, lower the permeability of the high permeability channels, decrease the effect of injection water fingering and channeling effects, enables more volume of the injection water to be stored in the reservoir which will increase the energy of reservoir, thus displace the oil out from the relatively low permeability channels, which will result in increasing oil production and decreasing the water cut.
Nano-sphere application is unlike other chemical treatments that need to be fed on a continuous basis. Our technology should be approached more like a treatment method that uses multiple slugs at different application rates, depending of the permeability of the thief zone. The Nano-sphere application program is tailored to meet the requirements of the client and reservoir conditions.
Oil reservoirs with relatively low oil viscosity can also obtain significantly higher oil output using this strategy. Currently, fully commercial applications have resulted in 60-500 tonnes of crude oil per tonne of Nano-sphere applied over a 2 years effective period. Some of ZL’s oil field Nano-sphere applications have increased the oil output up to 50%.
ZL’s microspheres technology are composed of polymeric spheres in the size of micrometers, it is normally combined with ZL’s nanosphere technology to improve water sweep efficiency.
ZL'S PPG is composed of pre-crosslinked polymer, particle size ranged from several micro meters to tens of micro meters. After adsorbing water, its size will expand to several milli meters. It can be injected easily and form blockage once reached formation.
Please contact ZL Technical team for more information.