... Abstract According to many experimental investigations of porous chalk an elastoplastic model with two yield surfaces is proposed. The physical meaning of the parameters of the model and the method used for their determination are explained. Some laboratory tests are then simulated in order...

... Abstract Ekofisk, Valhall and other North Sea reservoirs are made of water sensitive rocks such as pure high porosity chalk. Production of these fields implying water-flooding leads in several cases to compaction and subsidence. In order to perform reliable predictions of compaction...

... Abstract The problem of strain hardening has been approached by preparing series of similar cylindrical chalk samples front outcrop material. The samples in each series could then be given a certain degree of deformation beyond the elastic limit. Afterwards the samples could be tested...

... Abstract Ekofisk, Valhall and other North Sea reservoirs are made of water sensitive rocks such as pure high porosity chalk (Andersen 1). Production of these fields may imply water- flooding which has two important consequences. On one hand water-flooding seems to fracture the reservoirs...

... water flooding began in 1987. Over the past decade numerous, long term laboratory studies of reservoir chalks were undertaken to understand the effects of water flooding on chalk strength and to provide input data for reservoir simulators and geomechanics codes used to predict reservoir compaction...

... Abstract This paper is based on a series of residual water analyses performed on Ekofisk Field chalk samples. The main objective of this work was to critically evaluate the importance of capillary suction as a cohesive mechanism in chalk. . Capillary suction models have been proposed...

... Abstract A parametric study of compressional and shear wave velocity was conducted on Ekofisk reservoir chalk to gain more insight in the acoustic response of the chalk to changes in temperature, stress state and fluid saturations. The information from the study is used to interpret seismic...

... Abstract Oil saturated specimens of Stevns outcrop chalk were tested in a standard Hoek cell. The test programme included uniaxial strain and waterflooding. The waterflooding test results lead to the conclusion that above the yield stress level the Stevns chalk compacts due to waterflooding...

... Abstract For North Sea chalk fields, finite element models are used to evaluate the reservoir compaction and the associated seafloor subsidence. The present paper addresses aspects of the calibration of the stress strain laws to be used for the chalk and the overburden. Results of laboratory...

... Abstract A scanning electron microscope study of textures in several companion pairs of uncompacted and experimentally compacted Ekofisk chalk samples has documented two principal mechanisms of chalk matrix compaction. The dominant mechanism — which we have quantified through processing...

... Abstract Numerical modelling of the behaviour of the fractured chalk in the Ekofisk reservoir was performed using the distinct element code UDEC-BB. The non-linear fracture behaviour was modelled by the Barton-Bandis model, while the pore collapse of the rock matrix was modelled by NGI's cap...

... Abstract In order to study the behaviour of chalk, four chalks were tested under different loading conditions. We present, in this paper, the behaviour of these chalks under hydrostatic, oedometric, deviatoric, proportional and torsional tests. It appears that the behaviour of chalk can...

... Abstract A laboratory study on weak high porosity outcrop chalk has been performed in order to see how mechanical strength is affected when the material is strained beyond the elastic limit. Both tensile and compressive strength and Young's modulus are considerably reduced, although...

... small pores such as chalks and shaley sandstones. Laboratory investigations have been carried out on an impure chalk in order to determine its mechanical properties and constitutive behaviour under different environment conditions; the variations of the moduli resulting from a set of experiments...

... contributes to mitigate compaction and subsidence of highly compactable reservoirs. This last function is however severely put in question by the mechanical behaviour of North Sea chalk fields submitted to massive water-injection. From experimental results common to most labs we develop several models...

... Abstract Three aspects of reservoir compaction/subsidence simulation for Ekofisk are addressed: (i) stress paths in the reservoir during depletion, (ii) impact of porosity heterogeneities in reservoir chalk on scaling laboratory compaction data to field behavior, and (iii) methods for treating...