Quartz cementation inhibited by crestal oil charge: Miller deep water sandstone, UK North Sea

Abstract

In the Miller Field, diagenetic quartz abundance, isotopic compositions and salinities of quartz-cementing fluids display a distinct pattern which is related to the structural depth of the reservoir sandstones. Quartz cement volumes increase from the crest of the field (average 6.0±1.5%) towards the flanks of the field (average 13.2±2.1%) and directly reduce reservoir porosity. By integrating petrographic observations with results of fluid inclusion measurements and O isotope analyses of diagenetic quartz, the pattern of quartz cementation is seen to be related to the reservoir filling history. Oil filled the crest of the reservoir first and prevented extensive quartz cementation. At greater depth in the reservoir oil zone, quartz overgrowths continued to precipitate until inhibited by the developing oil column. Oxygen isotope compositions of diagenetic quartz imply that quartz cement continued to precipitate in the water zone of the reservoir up to the present day.

Pore water evolution in oilfield sandstones: constraints from oxygen isotope microanalyses of quartz cement

“…Quartz cementation is the main cause of porosity loss in the Brae Formation sandstone reservoirs of the Miller and Kingfisher Fields (Giles et al, 2000;Marchand et al, 2000Marchand et al, , 2002. The precipitation of quartz overgrowths in many sedimentary basins commonly occurs during deep burial diagenesis (>2.5 km) at elevated temperatures, typically 70 -130 jC (e.g.…”

“…The Brae Formation sandstones are Upper Jurassic submarine fan deposits presently buried to depths of 4.0 km. Porosities in the hydrocarbon reservoirs examined typically have been reduced by 5 to 15% quartz cement (Marchand et al, 2000).…”

The geological risks of exploring for a CO2 storage reservoir

“…This is shown by higher porosity in oil-bearing sections than the water-bearing equivalents in many oilfields (e.g. Marchand et al, 2000). It is here considered that the effect of relatively shallow burial depth for CO2 storage will at least partly offset the need for better reservoir quality, and the lack of porosity preservation by hydrocarbon charge in an aquifer.…”

Sandstone cementation and fluids in hydrocarbon basins

“…The distributions of quartz cement and porosity are controlled closely by the oilfield structural elevation. Rapid porosity decline in this oilfield is caused by slow oil charge with simultaneous extended cementation (Marchand et al, 2000).…”