Summary
Because of the geological characteristics and low permeability of Western
Siberia hydrocarbon reservoirs, hydraulic fracturing is the most effective
method for improving hydrocarbon production. During recent years, the massive
fracturing treatments in this area have led to a reduction of well candidates
for this type of production-enhancement technique. Currently, the majority of
selected wells for fracture stimulation are considered risky because of
significant water cut increase after stimulation. The question arises: How to
reduce water production while enhancing oil production?
This paper reviews 26 case histories exemplifying the use of relatively
permeability modifiers (RPMs) in hydraulic fracturing to enhance oil recovery
and control water production. Also, results of laboratory studies are included
to support the RPM-fracturing concept and -placement techniques.
Introduction
The Western Siberia Oil and Gas basin is second in the world, after the
Persian Gulf basin, in hydrocarbon reserves. The proven recoverable Western
Siberia Oil reserves are an estimated 13.8 billion t. Total area of the Western
Siberia basin is 3.5 million km2 (for example, the total area of
France and Germany together are 0.9 million km2) (Kalfayan and
Dawson 2004). Hydrocarbon production from Western Siberia makes up 70% of the
oil and 90% of the gas production of Russia (Fig. 1). The main hydrocarbon
reserves are concentrated in relatively young terrigene sediments, Mesozoic and
Cenozoic formations, which formed in the last 200 million years. However, oil
and gas production is also associated with Paleozoic formations. According to
the Russian Ministry of Energy, Western Siberia will maintain a leadership
position in oil and gas production up to year 2020, although its oil
contribution to Russia will drop to 55–58% (down from 70%) by that time. The
majority of oil fields are confined within the central part of Western Siberia
(Khanty-Mansy County) while the northern part has predominantly gas and
condensate production (Yamal-Nenetskiy County).
Development of Western Siberia oil fields began in 1950–1960 with the
discovery, in 1953, of the first oil field in the Berezovskiy region in the
lower reach of the Ob River. To date, there have been approximately 626 oil
fields discovered. At present, the majority of these fields are mature
reservoirs with high water production. In the largest oil fields that govern
total oil production, approximately 60% of total reserves have already been
extracted. Water cut has increased to 80–85% (Fig. 1, Table 1) (Karasev 2002).
This means that with every 1 t of oil produced, 5.5 t of water is produced,
with a required 7 t of water injected into the formation to maintain formation
pressure (Karasev 2002). If it is assumed that water cut will increase 1% per
year, then in 5 to 8 years, water cut in Khanty County will reach 90%, and oil
production cost will double (Fig. 2) (Karasev 2002). Significant water cut
affects not only oil cost (and, thus, net price), but it is a primary factor in
the high rate of pipeline blowouts that have a negative environmental effect on
Western Siberia. The major cause (98%) of pipeline blowouts is pipeline
corrosion. High fluid velocity and water content in pipelines reduce pipe
lifetime by half.
Nevertheless, despite the development of major fields since the middle of
the last century, hydrocarbon production is increasing every year (Fig.1). For
example, it is expected that Khanty County will produce 289–302 million t in
2007 and 294–310 million t in 2008. High production levels will be achieved
through newly drilled wells (Priobskoe field), and through applications of
production-enhancement technologies of which hydraulic fracturing is the
greatest part.
© 2008. Society of Petroleum Engineers
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History
- Original manuscript received:
27 June 2006
- Meeting paper published:
24 September 2006
- Revised manuscript received:
3 March 2007
- Manuscript approved:
7 November 2007
- Version of record:
15 August 2008
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