Temporal and spatial variation in diagenesis and reservoir quality: Brent sandstone, Heather field, North Sea

Conference · Wed Mar 01 00:00:00 EST 1989 · AAPG Bull.; (United States)

OSTI ID:5795700

Lundegard, P D; Glasmann, J R; Penny, B K

Brent Group sandstones in the Heather field show extreme inter- and intrafacies heterogeneity in reservoir quality as a result of diagenetic variation. Diagenetic patterns varied spatially and temporally as a result of variations in paleofluid chemistry, the time of hydrocarbon accumulation, and detrital grain composition. Important diagenetic cements are poikilotopic calcite, kaolinite, quartz, and illite. Geochemical, petrographic, and structural evidence indicate that calcite precipitated in the Late Jurassic (approximately 150 Ma) at a low temperature (40/degrees/-50/degrees/C), from reducing water of partial meteoric derivation (/delta//sup 18/O water = /minus/4 to /minus/6 /per thousand/ SMOW) that contained highly radiogenic strontium (/sup 87/Sr//sup 86/Sr > 0.71). Calcite distribution was partially controlled by local erosion of the Brent immediately following its deposition. Subsequently, a major period of kaolinite precipitation and feldspar dissolution occurred. Isotopic and tectonic/thermal history data suggest that these events were caused by thorough meteoric flushing (/delta//sup 18/O water = /minus/6 to /minus 8/ /per thousand/ SMOW) during the mid-Cimmerian sea level low (ca. 140 Ma), but not via recharge at the mid-Cimmerian unconformity immediately above the structure. Quartz precipitated as a result of feldspar dissolution, pressure solution, and fluid movement up fault zones over a long period of geologic time. In the vicinity of major faults, quartz fluid inclusions indicate invasion of hot, saline brines.

• Research Organization: Unocal Science and Technology, Brea, CA (USA)
• OSTI ID: 5795700
• Report Number(s): CONF-890404-
• Journal Information: AAPG Bull.; (United States), Vol. 73:3; Conference: AAPG annual convention with DPA/EMD Divisions and SEPM, San Antonio, TX, USA, 23-26 Apr 1989
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
NORTH SEA
PETROLEUM DEPOSITS
RESERVOIR ROCK
DIAGENESIS
BRINES
CALCITE
GEOLOGIC FORMATIONS
JURASSIC PERIOD
QUARTZ
SANDSTONES
SEA LEVEL
ALKALINE EARTH METAL COMPOUNDS
ATLANTIC OCEAN
CALCIUM CARBONATES
CALCIUM COMPOUNDS
CARBON COMPOUNDS
CARBONATE MINERALS
CARBONATES
CHALCOGENIDES
GEOLOGIC AGES
GEOLOGIC DEPOSITS
LEVELS
MESOZOIC ERA
MINERAL RESOURCES
MINERALS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
RESOURCES
ROCKS
SEAS
SEDIMENTARY ROCKS
SILICON COMPOUNDS
SILICON OXIDES
SURFACE WATERS
020200* - Petroleum- Reserves
Geology
& Exploration