Summary
A combination of fluid-inclusion and geochemical analyses was conducted on
rocks and reservoir fluids to develop an improved understanding of downdip-oil
potential in a mature exploration play, onshore Abu Dhabi, UAE. Exploration for
oil in the region is complicated by low-permeability carbonate reservoirs, poor
seismic imaging, and complex hydrocarbon-maturation and -migration histories.
In addition, a broad range of fluid properties, including gas, condensate, and
high-°API oil, makes evaluation of the reservoir fluid phase difficult.
In this challenging environment, geochemical and fluid-inclusion techniques
are effective tools for identifying downdip oil potential from gas-cap fluids
and reservoir-rock samples. Fluid-inclusion data are used to develop a
hydrocarbon-emplacement history, which constrains the distribution of fluids
throughout the exploration area. In some areas, undersaturated gas inclusions
trapped at present-day temperatures suggest a low chance for downdip oil.
Conversely, other structures contain oil inclusions that have been displaced
recently by saturated gas, suggesting good potential for downdip oil.
Geochemical analyses of recovered fluids were used independently to predict the
likelihood of downdip oil. These combined techniques were placed in a geologic
framework to regionally risk the potential for downdip oil throughout the
exploration area. This framework enables improved resource evaluation and
prioritization of exploration efforts in areas of the play where a high
probability of downdip oil exists.
Introduction
Fields from an onshore Abu Dhabi exploration trend currently produce both
oil and gas from shallower reservoirs and primarily produce gas from deeper
reservoirs. The objective of this study is to more accurately define deeper oil
potential throughout the exploration play in fields in onshore Abu Dhabi. To do
this, we use geochemical and fluid-inclusion techniques to determine
present-day fluid distributions, evaluate downdip-oil potential, and examine
the controls on fluid-type distribution in the deeper reservoirs.
A suite of samples, including cuttings, cores, oils, and condensates, was
used to develop a model for downdip-oil potential for three fields (A, B, and
C) in the study area. Geochemical methods were used to establish oil-generation
potential by determining source facies and thermal maturity of the reservoired
hydrocarbons. Fluid-inclusion technologies were used to determine paleofluid
and present-day fluid types in each reservoir, to develop a
hydrocarbon-emplacement history, to evaluate controls on fluid distribution,
such as intraformational seals, and to infer the likelihood of downdip oil
(Fig. 1).
© 2008. Society of Petroleum Engineers
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History
- Original manuscript received:
14 September 2006
- Meeting paper published:
5 November 2006
- Revised manuscript received:
27 September 2007
- Manuscript approved:
19 October 2007
- Version of record:
25 April 2008
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