Summary
Modern wireline formation testers (WFTs) are able to collect a massive
amount of data at multiple depths, thus helping to quantify changes in rock and
fluid properties along the wellbore, to define hydraulic flow units, and to
understand the reservoir architecture. They are being used routinely in a wide
range of applications spanning pressure and mobility profiling vs. depth, fluid
sampling, downhole fluid analysis (DFA), interval pressure-transient testing
(IPTT), and microfracturing. Because of the complex tool strings and the
elaborate operational aspects involved in wireline formation testing, success
requires detailed upfront planning and procedural design as well as real-time
operational and interpretational support.
It is becoming increasingly critical for operating and service company
experts to remotely monitor and interpret WFT surveys in real time through
Web-based systems. The importance of meeting all rock and fluid
data-acquisition objectives cannot be overstated, given the high cost of
offshore operations and the implications of obtaining false or misleading
information. The main objective of real-time monitoring remains to assure that
the planned data are acquired according to pre-established procedures and
contingency plans. However, even in developed reservoirs, unexpected
circumstances arise, requiring immediate response and modifications to the
preplanned job procedures. Unexpectedly low or high mobilities, probe plugging,
unanticipated fluid types, the presence of multiple phases, and excessive fluid
contamination are but a few examples of such circumstances that would require
real-time decision making and procedural modifications. Real-time decisions may
include acquiring more pressure data points, extending sampling depths to
several zones, extending or shortening sampling times, and repeating
microhydraulic fracture reopening/closure cycles, as well as real-time
permeability, composition, or anisotropy interpretation to determine optimum
transient durations.
This paper describes several examples of formation tester surveys that have
been remotely monitored in real time to ensure that all WFT evaluation
objectives are met. The power of real-time monitoring and interpretation will
be illustrated through these case studies.
Introduction
WFT has become a standard part of the evaluation program of most newly
drilled wells, but the objectives vary from offshore deepwater exploration and
appraisal wells to old cased-hole and development wells later in the life of a
field. Given the wide range of applications and combinations, each WFT
evaluation program is unique. Some may include only a pressure-gradient survey
for reservoir depletion and communication information, whereas others may seek
information on the precise nature of the hydrocarbon fluids and water in terms
of chemical and physical properties, phase behavior, and commingling
tendencies. Cased-hole surveys might look for bypassed hydrocarbon zones or
have objectives that could not be achieved during the openhole phase.
Regardless of the type of survey performed, understanding the exploration and
appraisal or field-development objectives and translating these into
acquisition objectives is essential for success.
Figs. 1 and 2 schematically illustrate the real-time monitoring concept.
Real-time data are viewable by authorized personnel anywhere around the world,
thus allowing virtual collaboration between field staff and off-site service-
and operating-company experts throughout the operation. This paper includes
several examples of WFT surveys that were monitored and supervised in real
time. The cases presented span the entire spectrum of WFT applications
including pressures, gradients, sampling, downhole fluid analysis (DFA), IPTT,
and microfracturing. The power of real time monitoring and interpretation is
clearly illustrated by these examples.
© 2007. Society of Petroleum Engineers
View full textPDF
(
2,655 KB
)
View Cart
