Freelance Gephysical Consultants Ltd



  • Vibroseis Parameter Testing

We could help to assess the seismic survey by helping the operating company to select the appropriate type of sweep design, either linear upsweep or downsweep, logarithmic, varisweep, range of frequencies, taper, length of the sweep, number of sweeps and how to maintain the signal to nose ratio either changing the number of sweeps or the length of the sweep when etc. Most of our field consultants carry Pelton Software with Vibra SIG, PSS and sweep design routines loaded in their Notebooks. They also have available some other proprietary software to deal with sweep design.

 

Let us show you what we could do to assist you in your upcoming Vibroseis survey and select source array, peak force and drive level.

The responsibilities of our QC personnel - It our opinion that real time quality control supervision is beneficial for the following reasons: Safeguarding Health, Safety & Environment Ensuring optimum data quality Ensuring objectives are achieved Ensuring commercial value Maintaining standards of Client Company Providing feedback Ensuring optimum data quality. All seismic contractors these days have a commitment to quality, if only because such a commitment is a commercial necessity. However, there will always be a difference in emphasis between the contractor (and perhaps the contractor's field personnel especially) and the client company when interpreting contractual specifications. It is not realistic to expect that the main priority of a contractor's unsupervised field party will in all cases be to acquire optimum, as opposed to merely adequate, quality data. It is our responsibility to ensure that optimum quality data is acquired, consistent with field conditions Ensuring objectives are achieved... Increasingly sophisticated acquisition and positioning equipment and techniques have meant that seismic crews tend to be predominately composed of systems operators rather than geophysicists and surveyors.

The drive level, frequency bandwidth, sweep length, sweep type, whether it be linear upsweep or downsweep, log sweep, varisweeo. Our people will determine what is the best to be injected to the ground to obtain the sub-surface geological targets requested by our clients. Minimizing the cross talk noise and the source generated noise, hamonics and sub harmonic distortion or unwanted noise inside the seismic data. We will make sure your objectives and target are met.

If possible, we will try not to select a linear upsweep, due to it is a waste of money for the Oil Companies, having so many different type of sweeps available in the business, also we will check the DSD SEG-D extended QC files from the VE464 and also the files from the Pelton Vibpro, using our own proprietary software and also some existing in the market.

We can also help to increase production by reducing the vibroseis cycle time and make more efficient productivity.

Slip sweep operations

After assessing other phase encoding techniques developed during this period, we concluded that the slip sweep method offers the most technical advantages in terms of simplicity and flexibility of operations. In normal acquisition mode the time-frequency space domain is not efficiently used by the source signal. There is space left between the parallelograms of useful data defined by record length, sweep length and frequency range. The slip sweep technique takes advantage of this space to boost acquisition productivity. Depending on sweep parameters and moving time, one or more vibrator fleets can be added.

We are specialist in high density channel crews using Distance Separated Simultaneous Slip Sweep, DS4, DS3, ISS, Flip Flop and all the new vibroseis technology available including the latest Force III from Seismic Source, VE464 with the Sercel Guidance System, VLI and Tablet PC plus the DSD network and Pelton VibPpro. Furthermore with the use of the TDMA " Time Domain Multiple Access. Using the Seismic Source Force III vibroseis electronics, the crews are able to perform Radio Similarity on a fleet with 30 vibrators. Contact me for a free Excel sheet with macros to read and display data from VE432 and VE464 "aps & vaps".

WE PROVIDE CUSTOM MADE SWEEPS TO MEET OUR CLIENTS TARGETS


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