Articles

We’re up against the budget and the clock... suggestions?

There is never enough time, never enough resource, and never enough data. These are the challenges you face every day. But you still need to make informed decisions on the prospects in your area, and with the lease clock ticking

…perhaps the term ‘challenge’ is an understatement..

As we all know renewing or relinquishing the block and meeting your contractual obligations has wide ranging ramifications.

Have you adequately identified and evaluated all the prospects in the area? You could renew/extend the lease and carry out further technical work at additional cost. But do you have the budget? The alternative might be to relinquish the acreage to a competitor, who subsequently has a discovery.

Neither scenario is appealing, but without good quality data it’s a high stakes decision nobody wants to get wrong. What you need is quality data, affordable and at speed.

There is a new option…

Salt, again!
...is there nothing we can do?

In a salt province even the latest seismic acquisition and processing technology still demands an element of second sight to quantify the success of an imaging exercise.

The result? Data that doesn’t always instil the confidence you look for when determining firm target locations.

Does this scenario sound familiar?

You know there is petroleum potential in the area but imaging around and beneath the salt is proving problematic. The seismic wavefield is distorted and illumination is irregular - every survey design option is a less than comfortable compromise.

Reconnaissance and legacy seismic data fails to provide sufficient information to properly define the extent of salt, requiring more input before finalising the design of an efficient, effective 3D seismic survey.

You need a better model of the salt, to develop a more accurate velocity model and better define the prospect to de-risk the next stage of development.

That new answer is Gravity Gradiometry...

Advantages of offline effects
Full Tensor Gravity Gradiometry as a regional prospect generating tool

Full tensor Gravity Gradiometry Imaging (GGI) is becoming more commonplace in exploration strategies, where the benefits of high resolution, multi-component data is proving invaluable for discerning both deep and shallow structures. In general, survey acquisition footprints are relatively tight (i.e. 200m x 1km) since the system has been primarily deployed in settings where a more focussed assessment is required.

This datasheet demonstrates how the signals measured by a gradiometer are also suited to wide line spacing acquisition, more akin to a regional style exploration approach. This is primarily because GGI technology using a Full Tensor Gravity Gradiometer (FTGeX) has off-line, sideways, detection capabilities that provide an enhanced interpolation solution between acquisition lines.

Case Study
– Resolving the K-2 salt structure in the Gulf of Mexico

An integrated approach using prestack depth imaging and Full Tensor Gravity Gradiometry

While potential field techniques have long been applied in regional studies and for mineral exploration, the recently-commercialized full tensor gradiometry (FTG) system possesses the resolution and sensitivity required in detailed mapping for oil and gas exploration, even for deep objectives. Used in combination with prestack depth-imaging, this provides a potent mapping capability especially in areas of structural complexity. We illustrate this with a subsalt case study from the Gulf of Mexico where an integrated approach using wave-equation depth-imaging and FTG inversion succeeds in resolving the base of salt in an area where Kirchhoff depth-imaging alone fails.