Summary
Daqing oil field is one of the earliest to develop displacement technology
by polyacrylamide (HPAM). One tonne of polymer can increase 100 to 120 tonnes
of oil; the recovery increases from 40% (OOIP) to 50% (OOIP). In view of the
geological and physicochemical characteristics, a series of technologies have
been developed, such as polymer-flooding mechanism, productivity forecasting,
proposal optimization, domestic excellent-quality polymer production, surface
injection, downhole separate-layer injection, and separate-layer testing during
injection. The oil field is characterized as a heterogeneous multilayer
sandstone reservoir. During polymer flooding, separate-layer injection
technology is also needed to mitigate the interlayer differences, enhance oil
recovery, and improve the whole development effect.
After polymer flooding in main oil layers, polymer flooding in Daqing oil
field turned to lower-permeability layers. To obtain a better displacement
effect, the injected-polymer molecular weight is usually determined according
to the injectivity of high-permeability layers. However, if polymer solution
with the same molecular weight is injected in each layer, it will cause
blockage in low-permeability layers. In order to solve this problem, a new
technology is developed that can control both separate-layer polymer molecular
weight and injection rate; the injection profile was improved greatly in later
field applications.
This paper introduces the development and practice of separate-layer
polymer-injection technologies, and presents the principle, string structure,
and parameters of eccentric different-molecular-weight polymer-injection
technology and its field applications in Daqing oil field.
© 2011. Society of Petroleum Engineers
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History
- Original manuscript received:
26 January 2010
- Meeting paper published:
12 April 2010
- Revised manuscript received:
6 January 2011
- Manuscript approved:
1 March 2011
- Published online:
25 May 2011
- Version of record:
10 August 2011