PGK monthly meeting
Our guest will be Koos Pipping (Wintershall) and he will give a talk about: “Integrated approach to tackle K18-Golf gas field seismic and reservoir modelling challenges“.
17:00-18:00 hrs: Social hour
18:00-19:00 hrs: Lecture
The Wintershall Noordzee operated K18 Golf field is located ca. 50 km WNW of Den Helder in the middle of a restricted military area. The gas field was discovered by well K18-7x in 2005 and subsequently appraised by well K18-8. The reservoir consists of a 270-m thick Rotliegend (Permian) sandstone reservoir with average porosities of less than 10%. The reservoir quality is very heterogeneous and of a tight nature with average permeabilities of 0.6 mD.
The development started in 2011 with two subsea wells, one horizontal (K18-G1) with five fracs and one vertical (K18-G4) with two fracs. The gas is produced via NAM’s K15-FA platform. The horizontal well was producing above expectation and the vertical well produced lower than expected. The latter showed still pressure build up after one-year shut-in, indicating poor connectivity potentially influenced by sub-seismic faults. An additional horizontal well (K18-G2) with four fracs came into production in 2015 and showed preferential depletion of layers and blocks, which is expected in this “labyrinth” type of reservoir. Requirement for infill drilling is currently investigated.
The complex geological setting of the K18-Golf gas field calls for a truly integrated reservoir modelling approach to understand the well performance and plan additional infill wells. Tectonic deformation, resulting in complex structures, causes serious seismic illumination issues at the Rotliegend target level. Multi-azimuth depth imaging (NAZ, WAZ, MAZ) permits more reliable reservoir characterisation with identification of possible baffles and fault compartments. After treating each processed acquisition dataset as stochastically independent realisation of the earth, their relative and independent quality variations are interpreted in terms of imaging and fault position uncertainty. Reservoir simulations have included the seismic uncertainties for the fault position in a creative way. The occurrence of shale layers (flow baffles) is represented as a list of K-layers, which vertical transmissibility is varied. The dynamic modelling is hampered by the lack of reliable pressure and rate measurements per well.