First Break - Volume 31, Issue 7, 2013

In a pilot project, very low frequency (VLF) measurements were performed using a prototype unmanned airborne system (UAS) at a test area near Neuchâtel, Switzerland. The VLF system operates over an extended frequency range of 1–250 kHz and consists of a three-component magnetic field sensor and a data logger, both deployed on an unmanned helicopter. Various developments had to be done prior to the first flight. The devices went through a weight reduction process, the noise influence of the aircraft on the devices had to be investigated, and an appropriate suspension had to be developed. This first experiment was conducted on a test site with anomalies due to man-made objects: a buried pipeline and a power cable with known orientation and location. The performance of the system in comparison with ground-based VLF data was investigated. First results demonstrate the feasibility of airborne VLF measurements with a UAS to detect buried pipelines and power cables.

Jaromir Jansky, Vladimir Plicka and Leo Eisner model the feasibility and potential advantages for hydraulic fracture mapping of using both surface and downhole microseismic data.

Unconventional resource plays have now reached mainstream in terms of the amount of commercial exploration and production activity within these fields. In this paper we introduce a no-compromise advanced workflow for imaging and prestack inversion of 3D seismic data for unconventional resource plays. The imaging portion of the workflow includes a calibrated tomography that simultaneously solves for vertical velocity and TI anisotropy, ensuring accurate well ties during prestack depth migration. The prestack inversion portion of the workflow includes both azimuthal traveltime and amplitude inversion schemes. The resulting seismic attributes are well suited to help predict future well performance in planning the development of these fields.

The Glenlivet gas discovery made by DONG E&P and partners (Faroe Petroleum and First Oil) in 2009 is one of the most recent discoveries in the offshore West of Shetland region. The exploration target was an amplitude-supported stratigraphic prospect, and the discovery well 214/30a-2 proved the pre-drill model by finding gas-bearing Late Palaeocene sandstones of excellent quality in the Vaila Formation. The exploration success challenged the exploration history of the Faroe-Shetland Basin, where a number of amplitude-driven stratigraphic prospects led to exploration failures in the 1990s. The prospect was identified by means of high quality 3D seismic data and improved petrophysical and seismic understanding combined with regional mapping of the Vaila Formation sandstones. A detailed sedimentological and biostratigraphic understanding of the Palaeocene succession, in conjunction with the above, helped to de-risk the prospect and led to successful drilling.

Ted Urbancic and Adam Baig describe how engineering objectives of hydraulic fractures can be identified and validated through source characterization of microseismicity recorded as part of the stimulation programme.

Grzegorz Kwiatek, Marco Bohnhoff, Patricia Martínez-Garzón, Fatih Bulut and Georg Dresen discuss well-established waveform processing techniques to investigate physical processes during stimulation of geothermal reservoirs and show that double-difference relocation and spectral ratio methods significantly improve the precision of hypocentre locations and source parameters.

Mike Mueller discusses the essential elements of today’s successful microseismic monitoring surveys used in hydraulic fracturing operations during shale oil and gas resource exploitation, and looks ahead to the major challenge of uncertainty estimation and how it can be met.

Volker Oye, A. Braathen and Ulrich Polom show from their injection tests that microseismic monitoring planned for the proposed CO 2 storage site at Longyearbyen, Norway should be feasible.