- Home
- A-Z Publications
- Petroleum Geoscience
- Previous Issues
- Volume 12, Issue 3, 2006
Petroleum Geoscience - Volume 12, Issue 3, 2006
Volume 12, Issue 3, 2006
-
-
Structural and sedimentological analysis of an early Late Rotliegendes graben based on 3D seismic and well log data, German North Sea
Authors Christoph Börmann, Reinhard Gast and Frank GörischThe geophysical and geological interpretation of a 3D survey, which was acquired in 2001, and four wells in the study area have revealed the structural framework on the West Schleswig Block, consisting of horsts and graben. The structural development of the area from Early to Late Rotliegendes times has been reconstructed and a multiphase history of depositional infill and associated fault patterns can be demonstrated. Well-log correlation provided a wider view of the regional structural styles and the stratigraphic setting of the study area. The Altmark, Havel & Elbe Sub-group lithologies of Rotliegendes times were analysed by sequence stratigraphic methods, concluding that depositional facies is linked to the tectonic movements of the Altmark pulses. Finally, the development of the palaeomorphology and its associated sedimentary facies types throughout time and space showed a sequence starting with dry desert environments and ending with perennial saline lake conditions. The interdisciplinary analysis led to the conclusion that 3D seismic and well information in the German sector of the Southern North Sea identified an early Late Rotliegendes graben filled with reservoir-prone sandstones equivalent to the German onshore.
-
-
-
Elasticity/saturation relationships using flow simulation from an outcrop analogue for 4D seismic modelling
Authors Olivier Kirstetter, Patrick Corbett, Jim Somerville and Colin MacBethThree production scenarios have been simulated for three displacement mechanisms using three lithofacies models built at two scales (fine and coarse) from a 2D outcrop analogue. Analysis of the flow simulation results and the associated seismic modelling investigate the dependence of the time-lapse response on the lithofacies model and the vertical grid block size. Elastic attribute quantification from coarse-grid models requires a decision on the type of fluid saturation distribution (uniform or patchy) within the coarse-grid blocks. Here, empirical relations for scaling up the fluid bulk modulus are developed which, when inserted into standard Gassmann calculations, permit calibration of the response for the coarse-grid block model from the finer-scale model. At the coarse scale, fluid saturation changes during water injection and pressure depletion can be represented adequately by these relations but, for gas injection, it appears necessary to refer back to the fine-scale models. For the case of gas injection they cannot be generalized readily for each different lithofacies model and are thus observed to be outcrop dependent.
-
-
-
Stratigraphy, structure and petroleum potential of the Lady Franklin and Maniitsoq Basins, offshore southern West Greenland
More LessThe Lady Franklin Basin, which contains a thick succession of Cretaceous and Cenozoic sediments, constitutes the western part of the southern West Greenland offshore area. In the Davis Strait and Labrador Sea region rifting was initiated in the earliest Cretaceous and a number of basins formed. In time these basins deepened, although subsidence was interrupted by two main phases of uplift and erosion that took place in middle and late Cretaceous time, resulting in two hiatuses in the succession. Sediments with source or reservoir potential were deposited in the basins. Source rocks are known to occur in the marine Cretaceous successions of onshore northern Canada and central West Greenland and also offshore eastern Canada, and can therefore be expected to occur in the Lady Franklin and Maniitsoq basins.
In the Lady Franklin area Paleocene volcanism associated with further tectonism caused the eruption of flood basalts and hyaloclastites on top of the Cretaceous mudstone and sandstone succession. A Lower Palaeogene sediment succession, which may contain both source and reservoir rocks, was then deposited on top of the basalts, as seen in the nearby Canadian Hekja O-71 well. Around the Ypresian to Lutetian transition a regression took place. The regression gave rise to an unconformity and a hiatus spanning a few million years throughout the entire West Greenland shelf. New deposition followed and, after a long period, major compression set in and a regression occurred across the whole shelf in Late Oligocene time. Erosion set in and was deep on the southern shelf, resulting in a hiatus spanning about 39 Ma. To the north the hiatus is only about 19 Ma.
In early Middle Miocene time the tectonic regime in the Davis Strait area changed. Subsidence and deposition resumed offshore West Greenland. These events may have created conditions for generation of hydrocarbons in the potential source-rock sequences in the Cretaceous succession. Therefore, although hydrocarbon exploration has been limited in this region and had little success, it is thought that conditions are favourable for the discovery of significant oil and gas accumulations.
-
-
-
Fracture intensity vs. mechanical stratigraphy in platform top carbonates: the Aquitanian of the Asmari Formation, Khaviz Anticline, Zagros, SW Iran
Authors O. P. Wennberg, T. Svånå, M. Azizzadeh, A. M. M. Aqrawi, P. Brockbank, K. B. Lyslo and S. OgilvieOutcrop analogue studies can significantly improve the understanding of fracture distribution and their impact on fluid flow in hydrocarbon reservoirs. In particular, the outcrops may reveal details on the relationships between mechanical stratigraphy and fracture characteristics. This has been investigated in an integrated sedimentological-structural geological study in the Aquitanian sequence of the Asmari Formation on the NE limb of the Khaviz Anticline in the Zagros foothills in SW Iran. The Aquitanian sequence was deposited in a platform top setting and is characterized by well-defined bedding planes and relatively thin layers (<4 m) with rapid changes in textures from laminated peritidal mudstones to bioclast and ooid grainstones. Fractures in the studied area dominantly strike parallel to the fold axis, have a high angle to bedding and are stratabound. In the literature it is often reported that fracture spacing or the inverse fracture intensity (FI) is controlled by the mechanical layer thickness (MLT). However, in the present study area a rather poor correlation between FI and MLT was observed. Instead, the Dunham texture appears to be more important for the FI. Mud-supported textures (mudstone and wackestone) have higher FI than grain-supported (packstone and grainstone) ones. The degree of dolomitization does not appear to have any significant effect on FI within each texture class. A strong relationship between FI and MLT is observed generally in cases where there has been one single phase of extension and when interbed contacts are weak, e.g. interbedded competent limestones and incompetent shales. However, in the present study area a rather complex deformation history exists and well-developed shales between fractured carbonate layeres are lacking. It is suggested that in such cases the MLT is of minor importance for the FI, which is controlled by the texture.
-
-
-
The Aquitaine Basin
Authors Jean-Jacques Biteau, Alain Le Marrec, Michel Le Vot and Jean-Marie MassetThe Aquitaine Basin is located in the southwest of France, between the Gironde Arch in the north and the Pyrenean Mountain Chain in the south. It is a triangular-shaped domain, extending over 35 000 km2. From north to south, six main geological provinces can be identified: (1) the Medoc Platform located south of the Gironde Arch; (2) the Parentis sub-basin; (3) the Landes Saddle; (4) the North Aquitaine Platform; (5) the foreland of the Pyrenees (also known as the Adour, Arzacq and Comminges sub-basins); and (6) the Pyrenean fold-and-thrust belt. Only the Parentis sub-basin, the foreland of the Pyrenean Chain and a minor part of the fold-and-thrust belt itself are proven hydrocarbon provinces.
The Aquitaine Basin, in turn, is subdivided into four sub-basins – the Parentis, Adour–Arzacq, Tarbes and Comminges areas. The lozenge shape of these depocentres is related to the Hercynian tectonic framework of the Palaeozoic basement, reactivated during Early Cretaceous rifting. This rift phase aborted at the end of the Albian (prior to the development of an oceanic crust) in response to the beginning of the subduction of the Iberian plate under the European plate. During the Upper Cretaceous, continued subduction led to the creation of northwards-migrating flexural basins. In the Eocene, a paroxysmal phase of compression was responsible for the uplift of the Pyrenean Mountain Chain and for the thin-skinned deformation of the foreland basin. The resulting structuration is limited to the south by the internal core of the chain and to the north by the leading edge of the fold-and-thrust belt, where the Lacq and Meillon gas fields are located.
Four main petroleum provinces have been exploited since the Second World War: (1) the oil-prone Parentis sub-basin and (2) salt ridges surrounding the Arzacq and Tarbes sub-basins; and (3) the gas-prone southern Arzacq sub-basin (including the external Pyrenean fold-and-thrust belt and the proximal foreland sub-basin) and (4) Comminges sub-basin. Two major distinct vertically drained petroleum systems (PS) can be identified: the Upper Kimmeridgian–Barremian is the main PS, based on Type II shaly-carbonate source rocks; and the Lias PS based on Type II–III source rocks. The latter is restricted to the Comminges and Tarbes sub-basins. Reservoirs consist of fractured and diagenetically modified carbonates, and clastics. Shaly-marly deposits of regional extent associated with transgressive systems provide the main seals.
Formation of petroleum traps results from a complex polyphase geodynamic evolution. They are developed mainly along Palaeozoic inherited palaeostructures. Oil and gas migration took place from Albian times up to the present, depending on the respective structural position and histories of the traps. These petroleum provinces of the Aquitaine Basin have been exploited since 1939 and a total of 11.5×1012 SCF of gas and 470×106 BBL oil recoverable reserves have been proven to date (the total amount is in the order of 2.5×109 BOE).
-
-
-
Productivity evaluation of hydraulically fractured gas-condensate reservoirs
Authors Shi-Yi Zheng, Murat Zhiyenkulov and TongChun YiThis study describes an application of a compositional single well simulator to analyse well tests in gas-condensate reservoirs. An important aspect of this application for gas-condensate well tests is accurate fluid property prediction during the multi-phase flow regime, which occurs in the near-well region. The simulator can also be used to understand the impact of liquid drop-out and fracture flow on well productivity.
Hydraulic fracturing improves the economics of wells drilled in tight reservoirs. However, the operation involves a significant amount of expenditure. In recent years this technique has also been used to stimulate gas-condensate reservoirs by creating a flow conduit through the condensate banking near the well. Thus, it is crucial to keep a fracture as small as possible. In practice it has been proved that a short, wide fracture can provide much higher production than the traditionally pursued narrow, long fracture.
The workflow in this study contains compositional simulation of a single well in a tight gas-condensate reservoir, which is used to generate transient pressure data for well test analysis and interpretation to predict multi-phase flow behaviour, and to analyse productivity impairment due to condensation. Simulation models were then further modified to study the impact of various hydraulic fractures on the well productivity index (PI), which is defined as the ratio of production rate (constant) divided by the pressure drop across the reservoir. PIs for fractured cases are compared with respect to the non-fractured base case. Streamline simulation of the fractured gas-condensate reservoir was also included in the study to allow visualization of the flow profile in and around the hydraulic fracture.
-
Volumes & issues
-
Volume 30 (2024)
-
Volume 29 (2023)
-
Volume 28 (2022)
-
Volume 27 (2021)
-
Volume 26 (2020)
-
Volume 25 (2019)
-
Volume 24 (2018)
-
Volume 23 (2017)
-
Volume 22 (2016)
-
Volume 21 (2015)
-
Volume 20 (2014)
-
Volume 19 (2013)
-
Volume 18 (2012)
-
Volume 17 (2011)
-
Volume 16 (2010)
-
Volume 15 (2009)
-
Volume 14 (2008)
-
Volume 13 (2007)
-
Volume 12 (2006)
-
Volume 11 (2005)
-
Volume 10 (2004)
-
Volume 9 (2003)
-
Volume 8 (2002)
-
Volume 7 (2001)
-
Volume 6 (2000)
-
Volume 5 (1999)
-
Volume 4 (1998)
-
Volume 3 (1997)
-
Volume 2 (1996)
-
Volume 1 (1995)