Porosity and permeability variability across a chalk reservoir in the Danish North Sea: Quantitative impacts of depositional and diagenetic processes

2021 ◽  
pp. 106059
Author(s):  
Amour Frederic ◽  
Hamidreza M. Nick
Keyword(s):  
North Sea ◽  
Diagenetic Processes ◽  
Porosity And Permeability

The Ravenspurn North Field, Blocks 42/30, 43/26a, UK North Sea

1991 ◽  
Vol 14 (1) ◽  
pp. 459-467 ◽  
Keyword(s):  
North Sea ◽  
Clay Content ◽  
Gas Production ◽  
Commercial Production ◽  
Reservoir Rock ◽  
Normal Faults ◽  
Well Drilling ◽  
Variable Permeability ◽  
Porosity And Permeability ◽  
Sandstone Formation

AbstractThe Ravenspurn North Field is a gas accumulation located in the Southern North Sea, Permian Gas Basin which was discovered in October 1984. It has undergone four years of appraisal well drilling culminating in the approval of the development plan in 1988. Development wells are currently being drilled and three offshore installations are planned; first gas production began in July 1990.The Ravenspurn North Field is a combined structural and stratigraphic trap. The reservoir is fault closed along a series of anastomosing oblique strike-slip and normal faults. Seals along the faults are provided by the Silverpit Formation mudstones and Zechstein Group evaporites. The reservoir deteriorates to the northwest because of thinning, facies change and increasing authigenic clay content.The Lower Leman Sandstone Formation of the Rotliegendes Group forms the reservoir. It consists of a sequence of aeolian dune, fluvial sheetflood, fluvial channels and lake margin sabkha deposits. Non-reservoir intervals are formed by playa lake mudstone sequences. Fluvial and sabkha facies dominate in the northwest while aeolian facies dominate in the southeast parts of the Field.Reservoir quality was initially controlled by lithofacies distribution. Subsequent diagenesis further modified the reservoir rock resulting in variations in the porosity and permeability. Deliverability is a function of variable permeability with two areas identified; the high deliverability area where gas wells have tested sufficient quantities for commercial production without artificial stimulation and a low deliverability area where gaswells require hydraulic fracture stimulation before significant commercial production rates are achieved.

The Esmond, Forbes and Gordon Fields, Blocks 43/8a, 43/13a, 43/15a, 43/20a, UK North Sea

1991 ◽  
Vol 14 (1) ◽  
pp. 425-432 ◽  
Author(s):  
F. J. Ketter
Keyword(s):  
North Sea ◽  
Arid Environment ◽  
Gas Production ◽  
Alluvial Fan ◽  
Southern North Sea ◽  
Offshore Installations ◽  
Porosity And Permeability ◽  
Sandstone Formation ◽  
The Uk

AbstractThe three separate fields, Esmond, Forbes and Gordon form the Esmond Gas Complex in Quadrant 43 in the UK Southern North Sea. The Bunter Sandstone Formation is the reservoir in each of the separate, seismically defined, simple, anticlinal structures. The Bunter Sandstone correlates well across the three structures and is composed of a 400-500 ft thick interval containing individual channel sandstones deposited in an arid environment on an alluvial fan. Porosity and permeability are controlled by original texture and by subsequent diagenesis. Reservoir communication within the Bunter reservoir is good though locally tortuous.First gas production started in July 1985. Four offshore installations have allowed gas to be produced at full contract (plateau) rates of 200 MMSCFD without major interruption. Ultimate sales gas reserves are approximately 530 BCF.

scholarly journals Coupled experimental/numerical workflow for assessing quantitative diagenesis and dynamic porosity/permeability evolution in calcite-cemented sandstone reservoir rocks

2018 ◽  
Vol 73 ◽  
pp. 36 ◽  
Author(s):  
Steven Claes ◽  
Fadi H. Nader ◽  
Souhail Youssef
Keyword(s):  
Permeability Evolution ◽  
Flow Properties ◽  
New Approach ◽  
Reservoir Rocks ◽  
Pore Blocking ◽  
Diagenetic Processes ◽  
Porosity And Permeability ◽  
Sandstone Reservoir ◽  
Calcite Cement ◽  
Host Rocks

Some of the world best hydrocarbon reservoirs (carbonates and siliciclastics) are also believed to be valuable for subsurface storage of CO2 and other fluids. Yet, these reservoirs are heterogeneous in terms of their mineralogy and flow properties, at varying spatial-temporal scales. Therefore, predicting the porosity and permeability (flow properties) evolution of carbonates and sandstones remains a tedious task. Diagenesis refers to the alteration of sedimentary rocks through geologic time, mainly due to rock-fluid interactions. It affects primarily the flow properties (porosity and permeability) of already heterogeneous reservoir rocks. In this project a new approach is proposed to calculate/quantify the influence of diagenetic phases (e.g. dissolution, cement plugging) on flow properties of typical sandstone reservoir rocks (Early Jurassic Luxembourg Formation). A series of laboratory experiments are performed in which diagenetic phases (e.g. pore blocking calcite cement in sandstone) are selectively leached from pre-studied samples, with the quantification of the petrophysical characteristics with and without cement to especially infer permeability evolution. Poorly and heavily calcite-cemented sandstone samples, as well as some intermediate cemented samples were used. The results show a distinctive dissolution pattern for different cementation grades and varying Representative Elementary Volumes (REVs). These conclusions have important consequences for upscaling diagenesis effects on reservoirs, and the interpretation of geochemical modelling results of diagenetic processes. The same approach can be applied on other type of cements and host-rocks, and could be improved by integrating other petrophysical analyses (e.g. petroacoustic, NMR).

Diagenetic processes in the Brent Group (Middle Jurassic) reservoirs of the North Sea: an overview

1992 ◽  
Vol 61 (1) ◽  
pp. 263-287 ◽  
Author(s):  
Knut Bjørlykke ◽  
Tor Nedkvitne ◽  
Mogens Ramm ◽  
Girish C. Saigal
Keyword(s):  
North Sea ◽  
Middle Jurassic ◽  
The North ◽  
Diagenetic Processes ◽  
The North Sea

Prediction of Archie’s cementation factor from porosity and permeability through specific surface

Geophysics ◽  
2008 ◽  
Vol 73 (2) ◽  
pp. E81-E87 ◽  
Author(s):  
Casper Olsen ◽  
Thanong Hongdul ◽  
Ida Lykke Fabricius
Keyword(s):  
Physical Properties ◽  
Specific Surface ◽  
North Sea ◽  
Published Data ◽  
Simple Relationship ◽  
Porosity And Permeability ◽  
Bulk Volume ◽  
Cementation Factor ◽  
The Relationship

Based on Archie’s cementation factor as measured on North Sea chalk and on published data, we explore how the cementation factor depends on other physical properties of the chalk. A relationship between cementation factor and specific surface with respect to bulk volume is obtained for chalk. This leads to how Archie’s cementation factor may be predicted from porosity and permeability for chalk as well as for sandstone. A common relationship between cementation factor and specific surface with respect to bulk volume calculated from porosity and permeability is obtained. As an alternative, the [Formula: see text]-factor in Archie’s equation is related to specific surface with respect to bulk volume, but the relationship is less clear than the simple relationship between cementation factor and specific surface.

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