Effective stress law for the permeability of a limestone

Bouteca, M.J., Sarda, J.P. and Schneider, F. (1996) Subsidence Induced by the Production of Fluids. Revue de l'Institut francais du petrole, 51, 3, 349-379 Abstract - Subsidence Delay: Field Observations and Analysis - The objective of this paper is to describe the subsidence-depletion delay from field observations with the aim to explain its cause and constrain its modelling. The nonlinearity in the surface subsidence response to the reservoir depletion can be seen as a shift between the start of the depletion and the (delayed) start of the subsidence. We have analysed data of eight hydrocarbon fields to quantify the subsidence-depletion delay effect and the corresponding time-delay. The time-delays appeared to be in the range of 1. 6 to 13 years. The fields were categorised according to their depth, age and rock type. To explain the field observations, the data was tested against four categories of mechanisms: - pore pressure diffusion effects; - reservoir compaction behaviour; - deformation of the over- under- and side-burden. The relative importance of these mechanisms was assessed from an analysis of the field data. Some mechanisms could be rejected based on theoretical grounds and others appeared to be irrelevant. It is concluded that pore pressure diffusion always contributes to a delay effect but that its effect is too low to explain the field observations. For the shallow reservoirs, natural over-compaction has the potential to cause the observed subsidence-depletion delay. In general, the other reservoir compaction related mechanisms (such as creep, an intrinsic rate effect and an elastic-plastic transition) could also be the main cause of the subsidence-depletion delay effect.

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Subsidence Delay: Field Observations and Analysis

Numerical modeling of stress effects on solute transport in fractured rocks

Since the early 1970s, basin and petroleum system modeling (BPSM ) has evolved from a simple tool, used mainly to predict regional source rock thermal maturity, to become a critical component in the worldwide exploration programs of many national and international oil companies for both conventional and unconventional resources. The selection of one-dimensional 1-D, 2-D or 3-D BPSM depends on available input data and project objectives. Organic richness and rock properties must be reconstructed to original values prior to burial. For example, in geohistory analysis each unit is decompacted to original thickness and corrected for paleobathymetry and eustasy. Boundary conditions for thermal evolution include heat flow and sediment-water interface temperature corrected for water depth through time. Default petroleum generation kinetics available in most software should be used only when suitable samples of the source rock organofacies are unavailable. Kinetic parameters are best measured using representative, thermally immature equivalents of the effective source rock. 3-D poroelastic and poroplastic rock stress modeling are significant advances over the 1-D Terzaghi method employed by most software. Calibration should start with the available pressure data, followed by thermal calibration (e. g., corrected borehole temperatures or vitrinite reflectance) and calibration to other measurements (e. g., petroleum composition). The dynamic petroleum system concept has proven to be a more reliable tool for exploration than static play fairway maps used in the past, partly because BPSM accounts for the timing of trap formation relative to generation-migration-accumulation. Tectonic activity and other processes can result in remigration or destruction of accumulations and more than one critical moment on the petroleum system event chart. Organoporosity within the kerogen and solid bitumen accounts for much of the petroleum in unconventional mudstone reservoirs, and secondary cracking of oil to gas is particularly important. Hybrid unconventional systems, which juxtapose ductile organic-rich and brittle, more permeable organic-lean intervals are typically the best producers.

Basin and Petroleum System Modeling

https://repository.tudelft.nl/islandora/object/uuid%3A82131e93-4977-4d28-93aa-c45637efabda/datastream/OBJ/download

T.H. Hanssen

Papers

Compaction-Induced Porosity/Permeability Reduction in Sandstone Reservoirs: Data and Model for Elasticity-Dominated Deformation

Compaction-Induced Porosity/Permeability Reduction In Sandstone Reservoirs