Geophysical surveying
AssigneeOHM Limited
InventorsPeter Harris, Joel Walls
Life of this patent
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Abstract
Joint processing of seismic and controlled source electromagnetic (CSEM) surface data is performed by using a common rock physics model which relates reservoir properties (such as porosity, lithology, saturation, and shaliness) to surface seismic AVO (or AVA) data. This allows one to determine how perturbations in the reservoir properties affect surface data. This can be carried out by systematically changing the reservoir properties and examining the effect on the synthetic data. This allows the hydrocarbon type of a reservoir to be established, e.g. oil or gas, as well as the saturation level of the hydrocarbon in the reservoir, which is useful for determining whether the reservoir has a non-commercial, low hydrocarbon saturation or a commercial, high hydrocarbon saturation.
Claims20
A method of characterising a hydrocarbon reservoir contained in a region of interest, comprising:
- obtaining a set of measured CSEM data of the region of interest;
- obtaining a set of measured seismic data of the region of interest;
- defining an earth model of the region of interest by setting values of a plurality of earth model parameters;
- defining a rock physics model with a plurality of interdependent relations linking rock property parameters of the region of interest, including porosity, elasticity moduli water saturation level and hydrocarbon saturation level, with elastic and electrical parameters of the region of interest, including P-wave velocity, S-wave velocity and electrical conductivity,
- setting values for the rock property parameters;
- computing a set of synthetic CSEM data of the region of interest with said values of the rock property parameters and using survey equipment parameters for a CSEM transmitter and CSEM receivers matched to those used when collecting said measured CSEM data;
- computing a set of synthetic seismic data of the region of interest with said values of the rock property parameters and using survey equipment parameters for a seismic transmitter and seismic receivers matched to those used when collecting said measured seismic data;
- and
- perturbing the values of at least a subset of the rock property parameters in order to find a fit of the synthetic CSEM and seismic data to the measured CSEM and seismic data respectively, thereby to determine the hydrocarbon saturation level of the hydrocarbon reservoir.
A method of planning a survey of a region of interest that is known to, or may possibly, include one or more reservoirs, which may or may not be hydrocarbon bearing, the method comprising:
- defining an earth model of the region of interest by setting values for a plurality of earth model parameters;
- defining a rock physics model with a plurality of interdependent relations linking rock property parameters of the region of interest, including porosity, elasticity moduli, water saturation level and hydrocarbon saturation level, with elastic and electrical parameters of the region of interest, including P-wave velocity, S-wave velocity and electrical conductivity;
- defining a set of survey equipment parameters defining CSEM and seismic transmitter and receiver properties;
- setting at least two different values of at least one of the rock property parameters to postulate different possible scenarios for a potential reservoir;
- setting singular values for the other rock property parameters and the survey equipment parameters;
- computing sets of synthetic CSEM and seismic data of the region of interest with said values;
- and
- establishing whether the different possible scenarios are distinguishable in the synthetic CSEM and seismic data, and if yes, using those survey equipment parameters to define a future survey.
Dependencies are inferred from the claim text.