Анализ технологий ограничения водопритока в добывающих скважинах, вызванных

Background andPurpose 
 
Oil bypassing is a significant problem in U.S. reservoirs. Of the 582 billion 
barrels of oil in-place in discovered fields in the U.S., 208 billions have been 
already produced or proven, leaving behind 374 billion barrels of oil [4] 
(Advanced Resources International, 2006), or 64.3% of the oil in place. Water 
invasion [4]is known to be a major contributor to this problem. On average in the 
United States, more than seven barrels of water are produced for each barrel of oil 
[4]. 
The problem of oil bypassing by water invasion can be caused by different 
reasons in different wells and reservoirs. Displacement of oil by water is controlled 
by viscous forces, gravity forces, capillary forces and heterogeneities. These 

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mechanisms or forces may interact with each other during displacements and 
natural water influx. The water originates from the formation of multiple fingers, 
water channeling, gravity underrunning (formation of a water tongue) and/or water 
coning. The two most typical geological scenarios of abnormal water sweeping in 
homogeneous reservoirs are horizontal or anticline structures with oil underlain by 
bottom water (bottom-water systems) and dipping reservoirs with attic oil and side 
water drive (edge-water systems). Water coning is the main source of abnormal 
sweeping in the structures with bottom-water, whereas the combined effect of 
water under-running (formation of a water tongue) and coning plays a significant 
role in the abnormal sweeping of side water reservoirs. Water under-running and 
coning also have an important effect in the abnormal sweeping of heterogeneous 
reservoirs. The existence of permeability barriers, channels, and other 
heterogeneities, however, may aggravate the bypassing of oil. Understanding the 
mechanisms ofwater invasion and oil bypassing in edge and bottom water-drive 
reservoirs is, therefore, of capital importance since it would allow identifying 
potential solutions. 
Knowledge of the motion of the oil-water interface is needed in reservoir 
engineering in order to determine the amount of oil that will be recovered by the 
end of the well’s operation. For low flow velocities, gravity forces tend to 
dominate the displacement and a stable (constant slope) interface occurs. A stable 
interface is desirable because it results in high recovery factors. However, the 
required flow velocity may be so low that the corresponding critical production 
rate would not be economical. Generally, production rates needed for economic 
recovery exceed the critical rates. Therefore, the interface becomes unstable and a 
cone and/or water tongue develops, causing early water breakthrough and oil 
bypassing. Also, most of the well’s production life is plagued by very high water 
cut. When instability occurs, the less viscous water creates paths into the more 
viscous oil, leaving zones with original oil bypassed. Determining the volume of 
oil that may be bypassed in unstable displacements is of paramount importance. 

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This is because a secondary recovery method and/or a technology for the control of 
the produced water can be planned as a result of suchdetermination.