Land data acquisition techniques have undergone rapid advancement in recent years, resulting in smarter and more productive operations that deliver better signal quality.
At the heart of this progression lies significant improvements in the way that vibroseis is carried out. Recent developments in mechanical vibrators, digital recorders and correlator stackers, along with the advent of real-time satellite positioning of vibrator fleets, means that more advanced vibroseis strategies can be deployed at far higher levels of consistency and productivity during field operations.
Indeed, these technical advancements means operators can now oversee the highly-efficient management of multiple sources – often as many as 50 vibrators together at the same time – producing more than 30,000 VPs in a single day. These approaches can result in the creation of highly detailed and informative datasets, helping geophysicists to more accurately predict where oil and gas might be trapped.
So, let us look more specifically at where advances have taken place. In terms of vibrators, machines have become far more intelligent – both in the way they position themselves from point-to-point and in how they transmit signals into the ground. Auto-guidance systems enable these gigantic machines to travel to the next source point in a timely manner, lowering the baseplate without delay. This route optimisation and speed of set up, replicated many times across a day, can deliver productivity enhancements of up to ten per cent.
Indeed, delivering more effective vibrator navigation systems is an area of continued development. At present, vibrator drivers are given a set of source points that they are expected to complete during their shift, and they are free to choose the best route to achieve that aim. However, real-time GPS-based navigation systems, similar to road traffic apps such as Waze, are being developed to further improve route optimisation efficiency. This could one day lead to more automated vibroseis, perhaps even resulting in driverless vibrators and fully autonomous source creation.
If vibrators provide the brawn for land data acquisition, then vibrator electronics undoubtedly act as the brains – performing a variety of critical functions such as accurately controlling the amplitude and phase of the vibrator ground force. In recent years, vibrator electronics have become highly optimized to benefit from the latest developments in integration, radio transmission and servo-control.
Advanced digital control systems can now deliver and control signals with much higher accuracy and speed, allowing users to implement vibroseis quicker than ever before. These solutions use fully auto-adaptive servomechanisms, enabling advanced land data acquisition techniques such as pseudo-random sweeps, multiple simultaneous sources, cascaded sweeps and custom sweeps. An even higher level of flexibility can be achieved through dedicated sweeps by programming a different sweep per vibrator in a given fleet.
Improved signal quality
There have also been some giant leaps forward in terms of signal data quality, particularly with the development of some smart methodologies around lower frequencies and distortions. A powerful new technology – known as SmartLF – uses a reliable model to analyse the various sources of low-frequency distortion. Based on this more sophisticated model, the servo control can predict the low-frequency distortion: the servo valve input signal is modified accordingly, and the generation of harmonics can be avoided. The software is embedded in the vibrator electronics itself, without the need for modifications to the vibrators or additional mechanical components. It is, therefore, easy to implement and use during seismic operations, resulting in improved signal data quality.
These are just some of the advances seen with land data acquisition in recent years, and more are being developed by the day. For a more detailed analysis of how digital technologies are delivering faster, smarter and more productive vibroseis, download our new whitepaper entitled Source Management in the Modern Era.