First Break - Volume 30, Issue 10, 2012

In his recent study ‘Global Oil Production is Surging: Implications for Prices, Geopolitics, and the Environment’ published by the Belfer Centre of Science and International Affairs, Harvard University, Leonardo Maugeri has challenged conventional thinking on worldwide oil resources and rate of depletion. In this edited version of the Executive Summary, he argues that oil production capacity is surging in the US and several other countries at such a rapid rate that global oil output capacity is likely to grow by nearly 20% by 2020 which could prompt a plunge or even a collapse in oil prices.

Zhengzheng Zhou, Milos Cvetkovic, Bing Xu and Philip Fontana provide a case study to show that processing techniques can realize broadband marine seismic results from conventional streamer acquisition data without the need for the emerging built-for-purpose broadband streamer technology.

Patrice Guillaume, Jean-Philippe Montel, Steve Hollingworth, Xiaoming Zhang, Anthony Prescott, Mathieu Reinier, Richard Jupp, Gilles Lambaré, Owen Pape and Alexandre Cavalié describe the application of multi-layer global tomography to improve the velocity inversion workflow in the modelling and imaging of seismic data.

Jaime A. Stein discusses newly developed multi-dimensional high resolution algorithms that can benefit seismic data processing.

Yan Shixin, Oz Yilmaz, Wang Xishuang, Zhang Yan, Fan Mingtao, Dong Shitai, Xie Wendao and Lin Gang describe the processing steps required to optimize the imaging of large-offset data acquired in the Yumen oil field northwest China and the benefits compared with a conventional 2D seismic survey approach.

Xinxiang Li, Rodney Couzens, Jeff P. Grossman and Ken Lazorko present with a supporting case study a QC procedure for the simultaneous processing of multi-vintage time-lapse datasets which can improve the repeatability of the time-lapse data.

T.E. Galikeev, A.P. Zhukov and V.S. Kozyrev present interactive statics technology (IST) as a method to refine the statics solution in seismic data processing, notable for not being dependent upon the exact velocity model, the velocity field, or the first breaks.

Reactive transport modelling can be applied to dolomitization to test interpretations of the diagenetic process and to help predict the lateral extent of dolomite reservoirs. Here we report applications to four different cases of dolomitization. The first case simulates the compaction-driven flow model of a drowned palaeohigh and demonstrates that the main limiting constraint is the ratio between the volume of basinal fluids and the rock volume in the palaeohigh. In the second case, hydrothermal dolomitization was simulated in a shallow burial setting above deep-seated rift faults, and shows the importance fault geometry may have in constraining the geometry of the dolomitized body. In the third and fourth cases, two synsedimentary dolomitization processes, thermal convection and mesohaline reflux, were tested in modelling an isolated carbonate platform. Thermal convection produced a dolomitized wedge in the bank margin area, and reflux model simulation shows that some dolomitization can also be produced by mesohaline seawater influx from the top of the platform. In all cases, the simulations suggest that the hydrogeological system is the most important driver for dolomitization, and the final geometry of dolomite bodies is greatly affected by the permeability and the presence of fractures.

Detection of shallow gas, and mitigation of this hazard while drilling, is the most significant and critical aspect of geohazard site surveys. Case studies show that the interpretation of shallow gas from seismic data, although well understood, is by no means unambiguous. In spite of the developments in acquisition and processing techniques over the last 20 years, which have improved the quality and interpretability of high resolution seismic data, the industry standard is still limited to the acquisition of 2D datasets. This paper compares the suitability of 2D and 3D exploration seismic data with high resolution seismic (HRS) data, and shows the advantages of better vertical and horizontal resolution that can be achieved with the use of HRS 3D data. Conventional 2D exploration seismic data are inadequate to identify shallow gas because of limited vertical resolution. In shallow water, the highest quality 3D exploration seismic data will not suffice either, because of the high angles of incidence for shallow reflection events. In deep water, 3D exploration data may be used for geohazard evaluation provided the dataset is of sufficient quality, but the best dataset for identification of shallow gas would always be an HRS 3D dataset.

Today reservoir monitoring is being used for increased oil recovery in about 75% of the fields operated by Statoil. The Snorre Field is a good example of how time-lapse seismic surveys help understanding and drive reservoir management. Even after more than 14 years of time-lapse seismic surveys, interpreting the 4D results is challenging due to the complexity of the reservoir and the drainage strategy. The time interval between seismic surveys is much larger than the water and gas injection cycles, and these variations in production operations between surveys make it difficult to reconstruct the reservoir history, including the inversion of the time-lapse data to estimate pressure and saturation changes. Using time-lapse seismic surveying as a tool to improve the static and dynamic models is important, but understanding the meaning of the 4D signal together with the uncertainties is critical. Here we describe how the asset works with the 4D data and show how time-lapse seismic data are used qualitatively.