Chapter 8 Reservoir compaction and surface subsidence in the North Sea Ekofisk field

This chapter discusses the reservoir compaction and surface subsidence in the North Sea Ekofisk field. The North Sea has presented the demanding environmental challenges encountered in offshore oil and gas-resource development. The northern North Sea Basin consists of several subbasins, platforms, plateaus, grabens, and embayments. The significant structural traps are folds and fault blocks associated with salt movement and basement faulting. The most productive of the salt-induced domes are located in the Norwegian sector of the Central Graben where the Ekofisk and other nearby fields, referred to as “the Ekofisk complex,” produce hydrocarbons from Upper Cretaceous and Lower Paleocene chalk. Salt domes and ridges pushing up from the basin floor create anticlinal structures in the sedimentary layers. Seismic maps of the area reveal many such structures with different sizes and shapes, which have increased the reservoir permeability by contributing to fracturing in the massive, brittle Danian carbonates.