Seismic Risk Assessment for Production Scenario “Basispad Kabinet” for the Groningen field - June 2018
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the use of the L-gas resources in its portfolio and the deployment of the Groningen field to allow the L-gas market
to function.
The dataset provided in the Expectation Letter has been worked by GasTerra to establish the utilisation of the
Groningen System, and determine volumes produced from UGS Norg, PGI Alkmaar and Groningen field. It assumes
the underground gas storages UGS Norg and PGI Alkmaar to be volume neutral over the gas-year, because it is filled
with gas from the Groningen field in summer which gets produced during cold periods in winter. Furthermore it is
assumed that the Alkmaar facility is filled with pseudo-G-gas, and can compensate for 0.5 N.Bcm/year of gas
production from the Groningen field.
The applied methodology to determine the utilisation of Groningen system assets is based on perfect insight on
future temperature profile (e.g. weather conditions are upfront known for every single day in future). This perfect
insight assumption is a deterministically approach and is similar to the methodology applied by GTS. This Groningen
system assets utilisation outcome is therefore to a degree theoretical, and does not cater for certain market
uncertainties.
Figure 2-2
Groningen field production profiles for cold, average and warm temperatures as outcome of GasTerra
analysis. Top monthly production volumes, bottom annual production volumes.
The requirement to fill Norg UGS in the summer has a flattening effect on the Groningen production profile, and
actually leads to a seasonal production profile with higher production in summer than in winter for the average and
warm production profiles, Figure 2-3.
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Figure 2-3
Monthly production fluctuation by gas-year for cold (left), average (middle) and warm (right) temperatures.
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2.2
Spatial distribution of production
The Expectation Letter (Ref. 5) requires the distribution of production from the Groningen field to be reflecting the
insights from NAM’s 2017 optimisation study (Ref. 4), whilst honouring the volume restrictions as advised by SodM
in their report (Ref. 3) following the Zeerijp earthquake (8/1/2018).
Excerpt from the Expectation Letter (Verwachtingenbrief aanvulling winningsplan Groningenveld 2016,
2/5/2018)
The results from NAM’s 2017 production optimisation study for seismicity are a function of the objective for which
is optimised (e.g. event count, maxPGA, etc). However, all objective functions suggest prioritising production from
the South-East of the field (Figure 2-4).
A further observation from the 2017 optimisation study is that production from the South-Western part of the field
(clusters Kooipolder, Slochteren, Froombosch) seems to have a relatively strong non-linear effect on the analysed
seismicity metrics. Consequently, production from this area should be minimized.
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Figure 2-4:
Areal production optimization for various objective functions, based on partial dependence analysis on all objective functions. Increasing production from green
coloured controls improves the response with respect to the objective function, red colours indicate deterioration, white colours indicate a neutral effect. After
Figure 6-9 from Reference (Geurtsen & Valvatne, 1/12/2017)
2.3
Production fluctuations
It was stated in the Expectation Letter that in addition to optimising production across the clusters and regions, the
production should also reflect SodM’s “Zeerijp-advies” to avoid production fluctuations.
Excerpt from Expectation Letter (Verwachtingenbrief aanvulling winningsplan Groningenveld 2016,
2/5/2018)
The reduction of production fluctuations is addressed in the Building Block of the Operational Strategy (Ref. 7). In
this document a probabilistic approach was used to analyse the utilisation of the Groningen system assets (Groningen
field, UGS Norg and Alkmaar) for the gas-year 2018/2019, based on the 31 provided temperature profiles and the
market demand model. The production fluctuations are related to temperature profile, yearly Groningen field
volume offtake, spatial volume distribution over the field, UGS utilization and UGS work volume.
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2.4
Model implementation
This section addresses the implementation of the spatial distribution and optimisation of production over the field
as used in the modelling for the Hazard and Risk Assessment. The operational implementation in the Groningen field
for gas-year 2018-2019 is addressed in the “Bouwstenen voor Operationele Strategie Groningenveld - 2018/2019”
(Ref. 7).
In the Expectation Letter, the minister has depicted 5 regions (see table 2.1 and figure 2.5). To control the volume
off-take for the regions (spatial distribution) a production cluster start-up sequence has been implemented in the
model (see table 2.2). This is in line with both the request in the Expectation Letter to make use of the Optimisation
Study results, as well as the operational strategy. The surface network model sequentially opens-up (groups of)
clusters following the start-up sequence until the total required production demand is achieved. The Bierum
production cluster (BIR) is kept at a constant offtake level and the Eemskanaal cluster (EKL) is assumed to produce at
constant low rate from 1
st
October till 31
st
March and shut-in over summer. To reflect operational conditions (lower
number of clusters in operation when low demand) and to optimise production within the cluster groups, further
divisions have been introduced for the production clusters within regions East-Central and South-West, see table 2.2.
Region
Clusters
South-East
ZPD/SZW/EKR
East-Central
OWG/SCB/AMR/TJM/SDB
South-West
ZVN/SPI/ TUS-SAP/KPD/SLO-FRB
North
BIR
Eemskanaal
EKL
Table 2-1:
Regions and cluster overview
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