First Break - Volume 31, Issue 10, 2013

We believe this edited for print presentation given by Matthias Bichsel, projects and technology director, Royal Dutch Shell, for the Executive Session on the ‘Global Gas Challenge’ at the EAGE Conference in London in June deserves the attention of the wider specialist audience that makes up the readership of First Break. It is an admirably objective assessment of the technological and other issues facing oil companies, governments and local communities worldwide considering an energy future involving unconventional gas resources, embraced by North America but much more controversial elsewhere.

John Brittan, Jianyong Bai, Helen Delome, Chao Wang and David Yingst look at latest developments in full-wave inversion (FWI), tracing its development into a commercial technology used on exploration projects throughout the world.

Baskoro Arif Kurniawan, Ehsan Zabihi Naeini and Dinara Kazyyeva show how spectral decomposition based inversion on the Brenda Field can be used to get an idea of how the reservoir varies laterally and also to predict the decompositional environment of the reservoir and give a better understanding of the spatial continuity of the sand reservoir using timefrequency decomposition.

Daniel Fischer, Nils Sørenes, Emanuel Teichmann, Hanna Blekastad, Anita S. Moen, Ivar H. Sollie1 and Patrick Smith show the value created by time-lapse seismic processing on the Heidrun field and how Statoil has used the technique to cut the timeframe on its 4D seismic.

Jaime A. Stein, Kevin Hellman, Scott Boyer and Tom Charlton explore new ways to derive a 3D velocity model with a data field used in conjunction with the velocity and epsilon field to produce images that are more accurate and to true depth.

The estimation of the volume of pores available for fluids is of prime importance when evaluating the potential of a site for the geological storage of CO2. Acoustic impedance (AI) cube, inverted from seismic amplitude, are used to guide the geostatistical simulations of porosity. The use of an AI cube inverted by a deterministic approach generates a bias in the simulated porosity of the Saint-Flavien reservoir, Québec, Canada. The poor vertical resolution of the seismic data generates a low-pass filtered distribution of AI, where extreme values evaluated at well logs cannot be recovered. Stochastic seismic inversion (SSI) allows better recovering the whole bandwidth of AI distribution by optimally combining AI information from the observed seismic amplitude and AI well logs. AI cubes obtained by SSI better reproduce the distribution of porosity observed on well logs. This methodology is of prime importance in the Saint-Flavien context, as the average porosity is extremely low, and only a fraction of the reservoir exhibits higher porosity where CO2 injection would be possible. Zones of low AI and high porosity, recognized on well cuttings as having high clay content in the Saint-Flavien region, are only identified when using high-frequency AI cubes obtained by SSI.

We discuss a new method of marine electromagnetic sounding in shallow water using a horizontal electric dipole as a source of current and a vertical electric dipole as a receiver. The measurements are performed in the time domain at short transmitter-receiver offsets. The locality, sensitivity, resolution and detection depth of the proposed method were studied using a number of simple three-dimensional model examples. A new approach to determining the electrical characteristics of a hydrocarbon reservoir based on seismic ‘skeleton’ fixing the boundaries of the geological formations was demonstrated on the Luva Discovery electrical model. The new method enables surveying in depths of water in the range of 25 to 100 m using a towed source and a vertical four-electrode gradient receiver.

Our study is conducted with the aim to find OBC survey designs meeting technical and business objectives among infinite selections that OBC technique inherently provides. We perform productivity analysis on a total of 2604 survey designs, and only designs meeting established geophysical requirements are selected. We show that current equipment availability along with several geometry options enables a variety of survey designs and geometries which consequently lead to improvements in survey productivity. The use of two dual source-vessel operations, 1) Distanced Separated Simultaneous Shooting (DS3); and (2) Dual Source-Vessel Flip-Flop Shooting (DSVFFS), for OBC surveys can significantly reduce acquisition time. Additionally, we show technical challenges of dual source-vessel operations resulting from the relationship between OBC survey designs and resultant interference noise wave fields not generally associated with other acquisition technique