Summary
Most existing production of waxy oils occurs in high-permeability
formations, and wax issues are mostly a problem in the production tubing or
pipeline. Large reserves also exist in low-permeability formations that require
hydraulic fracturing for economic production. Such a reservoir was recently
discovered in Rajasthan, northwest India, overlying a more typical
high-permeability formation, both with high-pour-point waxy oil. Because a very
large amount of oil in place is present in the low-permeability formation, two
fracturing campaigns were performed in two different horizons to assess the
potential for successful well stimulation. The first fracturing campaign (on
four wells) showed limited success. A study was performed to determine the
reason for the failure, and significant changes were made for the second
campaign. This paper documents the second campaign. This campaign featured the
first successful use in India of heated fluids to stimulate a shallow,
low-permeability, massive oil reservoir containing high-pour-point waxy
oil.
Introduction
Numerous exploration and appraisal wells have been drilled in the RJ-ON-90/1
Block in Rajasthan, northwest India, targeting primarily the prolific Fategarh
reservoir (Zittel et al. 2008). Many of these wells have encountered
hydrocarbon-bearing-potential reservoir-quality rock in the shallower Barmer
Hill formation. Fig. 1 shows the field locale, which is situated just east of
the border with Pakistan.
The Barmer Hill formation is a shallow (700 to 800 mTVDSS), rich to
very-rich source rock and has been described generally as siltstone and
claystone, with gas peaks and frequent oil shows. Because the source rock is
lacustrine in origin, it has generated waxy oil. Fluid analysis from the Barmer
Hill reservoir shows high pour points (>45°C), wax appearance temperature
(WAT) several °C less than reservoir temperature (≈70°C), and in-situ
viscosities of tens of centipoises.
The in-place hydrocarbon may be large, especially in the north of the basin
because of the Barmer Hill's high porosities (25–30%). Producing these
hydrocarbons, however, is not easy. Natural-flow openhole tests in three
separate wells in the northern fields showed mixed-to-poor results and very low
permeability (1–10 md), as estimated from slug-flow-well test analysis. To
prove the commercial potential of the Barmer Hill reservoir, a
hydraulic-fracturing campaign was conducted.
© 2009. Society of Petroleum Engineers
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History
- Original manuscript received:
28 February 2007
- Meeting paper published:
30 May 2007
- Revised manuscript received:
18 February 2008
- Manuscript approved:
16 August 2008
- Published online:
2 March 2009
- Version of record:
26 February 2009
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