Summary
The while-drilling environment poses several potential challenges to
acquiring representative formation-fluid samples; in particular, sampling times
are expected to be restricted (perhaps severely) and dynamic filtration
conditions are expected to predominate. With the aim of formulating effective
strategies for sampling-while-drilling (SWD) operations, it is natural to seek
answers to at least the following questions: When should samples be
acquired--immediately after drilling the formation when invasion is shallowest,
or after some time when the mudcake is more mature? What is the effect of
circulation rate on sample quality? What levels of sample quality are
achievable under while-drilling conditions?
The first part of the paper describes the SWD tool used to investigate the
questions posed. The tool is composed of the following components: a probe
module; a pump-out module, which contains within it fluid-property sensors,
including a resistivity cell and a 10-channel optical spectrometer;
sample-capture modules; and a power-generation module consisting of a dedicated
mud turbine and alternator that provide the required pumping power to the
sampling tool.
The second part of the paper is devoted to the description and analysis of a
series of tests performed to characterize SWD operations. In particular, the
following aspects were studied for their effect on sampling efficiency and
sample contamination: time after drilling, mud-circulation rate, ceasing and
resuming pumping operations as a means of mitigating sticking risk during
protracted pumping operations, and the integrity of samples captured under
drilling conditions. All tests were performed in water-bearing formations
drilled with a water-based mud. A wireline sampling (WLS) tool was run after
the while-drilling tests were completed in order to compare the performance of
the two sampling tools.
The principal conclusions derived from the tests conducted are that
present-day sampling technology can be made to survive and operate effectively
under drilling conditions, and that there appear to be substantial advantages
to acquiring samples soon after drilling a formation.
© 2012. Society of Petroleum Engineers
View full textPDF
(
5,234 KB
)
History
- Original manuscript received:
23 November 2009
- Meeting paper published:
2 February 2010
- Revised manuscript received:
15 March 2011
- Manuscript approved:
9 May 2011
- Version of record:
29 February 2012
View Cart
