K18-Golf Field seismic and reservoir modelling challenges
J.C.P. Pipping, A. Wever, R. Bachmann, V. Smirnov and S. Deneuvillers
Journal name: First Break
Issue: Vol 37, No 5, May 2019 pp. 59 - 65
Info: Article, PDF ( 1.08Mb )
The Wintershall Noordzee operated K18 Golf field is located ca. 50 km WNW of Den Helder in the middle of a restricted military area (Figure 1). 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 well K18-8 showed a maximum gas rate of 200,000 Nm3/d at 25 bar FWHP before hydraulic fracking while K18-7x was tested at 56,000 Nm3/d at a 12 bar FWHP. A hydraulic frac in the K18-7x top interval increased the production to 370,000 Nm3/d at 128 bar FWHP. 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’s production was lower than expected. The latter showed pressure build-up after one-year shut-in, indicating poor connectivity. 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. Given the current expected production decline of the three producers, a fourth producer might be required soon. A better understanding of the seismic data is therefore required and will be first explained in the following sections.