MEO Australia: Ibu Horst 3D seismic survey identifies significant prospectivity

By Demas Simbolon

Australia-listed MEO Australia Limited provides the following update on the status of its comprehensive seismic data acquisition program in the Seruway PSC, offshore North Sumatra, Indonesia.

The Ibu Horst 3D ?fast track? cube was delivered in-house in April.

The data has enabled identification of substantial carbonate build-ups on the horst. Following integration of this data with historical well results including proven hydrocarbons, a number of prospects have been identified which, together with the discovered resources at Gurame and Kuala Langsa, have formed an integral part of the Seruway farm-out.

Delivery of the final processed volume, expected in August will enable MEO to develop a comprehensive prospects and leads inventory.

MEO?s CEO and MD J?rgen Hendrich commented on the announcement:

?MEO has made a substantial investment in high quality seismic acquisition and processing in most of our project areas in the last year.

We are very encouraged by the preliminary interpretation that reinforces the exploration concepts and strategies we have for these high potential opportunities.

It is apparent that the acquisition of seismic data will result in a significant upgrading of the value of MEO?s portfolio.

We look forward to completing this process ahead of realizing the value of these opportunities.?

Further details regarding the various surveys, their locations and current status are included in the attached ?Seismic Program Update ? Supplementary Information?.

Current status
The Ibu Horst 3D final 3D cube is due to be received later this month. Interpretation of the fast track cube has identified a significant number of appraisal as well as exploration targets. Strong amplitude anomalies in the shallow section are evident and thought to indicate the presence of gas. Deeper structures with carbonate build-ups are also present. The seismic section above illustrates both these features, with the deep structure offering the potential for an up-dip appraisal of the ONS B-1 discovery well.

Quality of data
Seismic reflection data is acquired using a variety of related methods with the goal of imaging the upper part of the earth?s crust. Images may be acquired as profiles (2D seismic) or covering an area (3D seismic), thereby providing a 3-dimensional image of the subsurface (not unlike a giant CT scan!). For example, MEO?s recent 3D surveys were acquired at sea using custom built seismic vessels, typically towing 6-8 streamers of 6000m in length for the recording of sound reflections emitted from an array of airguns, which are towed immediately behind the vessel.

The quality of a seismic dataset depends on many factors, both during acquisition and processing of the final image. During acquisition, the sea state and other operational issues can play a role, but probably more depends upon the survey design itself and the degree to which the subsurface is sampled by the seismic experiment. Greater cost usually results in greater quality.

Quality itself, in the context of seismic data, means the degree to which the image accurately represents the subsurface. Typically, we strive to achieve images with:
1) low random noise;
2) no coherent noise (false events);
3) high resolution (in all spatial dimensions); and
4) accurate positioning.

Ultimately the quality of an image is judged on its ability to reveal identifiable geological features and possibly even hydrocarbons directly.

Processing
Seismic data processing is complex, computer intensive and ultimately time consuming process, in which geophysicists use numerical algorithms to assemble the best possible image from the recorded dataset. Standard processing of modern 3D datasets typically revolves around the main imaging step, known as Pre-stack Time Migration (PSTM). Often a crude image is produced on the seismic vessel itself during acquisition for QC purposes, or possibly finished onshore and delivered as a ?fast-track volume? for use while the more sophisticated processing is done.

In situations where the geology is highly structured and imaging is difficult, the data may be reprocessed using specialist techniques, for example Pre-stack Depth Migration (PSDM). Further improvements in data quality may result from combining multiple seismic surveys, shot in different directions to allow complementary imaging under obstacles (Multi-Azimuth, or MAz surveying). It is common for seismic datasets to be ?reprocessed? multiple times as new processing techniques become available.

Editing by Reiner Simanjuntak