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PETROMAKS2-Stort program petroleum

Improved prediction of stress and pore-pressure changes in the overburden for infill drilling

Alternative title: Forbedrede spennings- og poretrykksberegninger i takbergarter for supplerende boring for økt utvinning

Awarded: NOK 11.3 mill.

Project Manager:

Project Number:

294369

Project Period:

2019 - 2024

Partner countries:

Infill drilling means to drill more wells into oil and gas producing reservoirs for increased recovery. However, drilling into already producing reservoirs is often a major challenge. The production of a petroleum reservoir implies strains in the subsurface, not only of the reservoir itself, but also deformations, stress and pore pressure changes in the overlaying rocks (overburden). These overburden alterations often result in challenging infill drilling conditions posing severe risk for the wells, equipment and environment. In some cases, infill drilling may not even be possible due to severe alterations in the subsurface. However, these issues may be avoided with better planning and tools. Accurate predictions of stress and pore-pressure changes are therefore essential for safe and efficient drilling. The monitoring of the overburden changes is often done with repeated seismic. By comparing seismic data from different stages of the production one may translate this into information needed for successful infill drilling. However, a prerequisite for this interpretation is that adequate tools are available. The industry needs to understand the link between the altered geomechanics and the repeated (4D) seismic signals. This is possible with active development of rock physics data and models, which link these disciplines. In the first part of the project, we have conducted a series of geomechanical simulations where different reservoir geometries, layering, faults and rock properties are varied. These data are coupled to SINTEF's Shale Rock Physics database, developed in a previous KPN project, to predict changes in the seismic fingerprints. This demonstrates that two-way travel time shifts, obtained from repeated seismic surveys, may be quantified in terms of changes in of the horizontal and vertical stresses (strains). In the coming period we intend to analyse 4D seismic data from North Sea and Norwegian Sea, and compare these with time-shifts obtained from geomechanical simulation data coupled to nonlinear velocity models (strain dependent anisotropic velocity models).

Infill drilling means to drill more wells into oil and gas producing reservoirs for increased recovery. However, drilling into already producing reservoirs is often a major challenge. The production of a petroleum reservoir implies strains in the subsurface, not only of the reservoir itself, but also deformations, stress and pore pressure changes in the overlaying rocks (overburden). These overburden alterations often result in challenging infill drilling conditions posing severe risk for the wells, equipment and environment. In some cases, infill drilling may not even be possible due to severe alterations in the subsurface. However, these issues may be avoided with better planning and tools. Accurate predictions of stress and pore-pressure changes are therefore essential for safe and efficient drilling. The monitoring of the overburden changes is often done with repeated seismic. By comparing seismic data from different stages of the production one may translate this into information needed for successful infill drilling. However, a prerequisite for this interpretation is that adequate tools are available. In this project we will provide a toolbox (Rock Physics Toolbox) containing experimental data, models, and guidelines from which the industry can pick suitable tools for optimizing their infill drilling. This will result in improved efficiency, lower costs and improved safety for drilling operations in producing fields. This research will also strengthen the position of SINTEF's Formation Physics Laboratory, being one of the very few laboratories in the world providing advanced and integrated testing and modelling of shales and other tight rocks for the petroleum sector. The tools of this project are also relevant for improved monitoring of CO2 storage.

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Funding scheme:

PETROMAKS2-Stort program petroleum