Interpretation of Permanent Well Monitoring Data to Improve Characterization of a Giant Oil Field
By Hans Walker, NOV
This material was first presented at the SPE Europec Conference,
Amsterdam, The Netherlands, October 2021
Abstract:
The Johan Sverdrup field located on the Norwegian Continental Shelf
(NCS) started its production in October 2019. The field is considered
as a pivotal development in the view of sustainable long-term
production and developments on the NCS as well as creating jobs and
revenue. The field is operated with advanced well and reservoir
surveillance systems including Permanent Downhole Gauges (PDG),
Multi-Phase Flow-Meters (MPFM) and seismic Permanent Reservoir
Monitoring (PRM). This provides an exceptional basis for reservoir
characterization and permanent monitoring.
This study focuses on reservoir characterization to improve
evaluations of sand permeability-thickness and fault transmissibility.
Permanent monitoring of the reservoir with PDG / MPFM has provided an
excellent basis for applying different methods of Pressure Transient
Analysis (PTA) including analysis of well interference and time-lapse
PTA. Interpretation of pressure transient data is today based on both
analytical and numerical reservoir simulations (fit-for-purpose
models). In this study, such models of the Johan Sverdrup reservoir
regions have been assembled, using geological and PVT data, results of
seismic interpretations and laboratory experiments. Uncertainties in
these data were used to guide and frame the scope of the study.
The interference analysis has confirmed communication between the
wells located in the same and different reservoir regions, thus
revealing hydraulic communication through faults. Sensitivities using
segment reservoir simulations of the interference tests with different
number of wells have shown the importance of including all the active
wells, otherwise the interpretation may give biased results. The
estimates for sand permeability-thickness as well as fault leakage
obtained from the interference analysis were further applied in
simulations of the production history using the fit-for-purpose
reservoir models.
The production history contains many pressure transients associated
with both flowing and shut-in periods. Time-lapse PTA was focused on
extraction and history matching of these pressure transients. The
simulations have provided reasonable match of the production history
and the time-lapse pressure transients including derivatives. This has
confirmed the results of the interference analysis for
permeability-thickness and fault leakage used as input for these
simulations. Well interference is also the dominating factor driving
the pressure transient responses. Drainage area around the wells is
quickly established for groups of the wells analyzed due to the
extreme permeability of the reservoir. It was possible to match many
transient responses with segment models, however mismatch for some
wells can be explained by the disregard of wells outside the segments,
especially injectors. At the same time, it is a useful indication of
communication between the regions. The study has improved reservoir
characterization of the Johan Sverdrup field, also contributing to
field implementation of combined PTA methods.
Bio:
Hans Christian has a master's degree in petroleum technology from
University of Stavanger with a specialization in natural gas
technology with some reservoir background. He is currently working at
NOV as an offshore operations engineer for wired drill pipe. In his
professional career he has mainly worked with analyzing subsurface
data, and data analytics. The content of this paper stems from further
work of his master thesis he wrote with Lundin Energy Norway.