Land seismic acquisition is the technique used to record images of the earth’s subsurface.
The data gathered from land seismic acquisition can become very valuable in a variety of projects including mapping areas of weakness in bedrock and sedimentary structures, exploration for sources of energy and even for archaeologists on a mission to uncover the past.
The process of land seismic acquisition is complex and involves the use of specialized equipment that help to generate controlled seismic or sound waves which are reflected back by subsurface layers and recorded by sensors at the surface.
At STRYDE, we have created the world’s smallest land seismic sensor, this wireless node allows companies who are seeking to understand the subsurface to do so in a more cost effective manner, and faster than ever before - without compromising the quality of the subsurface data acquired.
To ensure land seismic surveys are delivered efficiently, STRYDE has developed 3 separate node management systems which have scalable node charging and harvesting units, data management servers and cleaning apparatus to accommodate a wide range of survey sizes. These systems are designed to rapidly rotate large quantities of nodes, with minimal operator requirements.
Now that we have a bit of background surrounding land seismic acquisition, it's time to delve further into the process behind it.
The first step of the process is to start developing the survey layout and design. This will involve determining the number and locations of geophones or sensors, and the location where the seismic energy or source will be generated. There are multiple ways the energy can be generated, including the use of explosive charges, thumpers or vibrator trucks. Important at this stage is to determine any restrictions to access like infrastructure, environmentally sensitive areas or complex terrains.
Once the survey has been designed, it's time to set the equipment up on the surface and deploy the geophones or sensors at the agreed locations. For onshore seismic data acquisition this involves laying the equipment at regular intervals (2D inline spacing) and within closely-spaced lines (crossline) for 3D seismic. The seismic energy is then generated and the reflections are recorded. This process is then repeated multiple times at varying locations in order to create a dense data set that builds a more granular image of the subsurface.
After the data is collected, it is then processed and analysed using seismic data processing solutions. This can be a very complex and time-consuming process, as it requires compensating for terrain and near surface effects (statics), removing noise and distortion from the data and then using advanced algorithms to generate an image of the subsurface. The outcome is either a 2D line or 3D model of the subsurface which can be used to locate potential energy sources or reservoirs, optimal injection locations for carbon storage and much more.
It's no secret that onshore seismic acquisition can face a number of challenges, from demand for human and capital resources to complex logistics and environmental footprint. But what are the most common challenges currently faced, and how can they be overcome?
Accessing the area in which land seismic acquisition takes place can prove hard or impossible due to the terrain, vegetation or other physical or environmental barriers. This can restrict the ability to set up equipment or acquire data in certain areas.
Solution: By using portable, wireless equipment that can be easily transported and set up in remote locations, it’s easier to reach hard to access areas. The STRYDE Node™ is the lightest on the market by a factor of four, weighing a mere 150g, allowing 1 crew member to comfortably carry 90 nodes in a custom-made ergonomic deployment backpack, allowing seismic sensors to be deployed solely on foot, reducing the need for vehicles and line clearance. This capability is important when considering the need to reduce the environmental impact on sensitive areas or close proximity to urban areas or infrastructure.
2. Permitting and regulations
As with any form of unconventional land operations, there are a variety of regulations and permits or permissions surrounding land seismic acquisition that need to be acquired before a survey can commence. These will vary depending on the chosen location, and are specifically challenging to acquire in agricultural, urban or environmentally sensitive regions.
Solution: Demonstrating how you intend to reduce environmental disruption is key to fast-tracking and securing permits to operate from local regulatory agencies and organisations. The use of unobtrusive seismic equipment that can be rapidly deployed and retrieved are key components to minimising land disruption, for the likes of farmers, and are proven to help with this process. Lightweight nodes that can be deployed by foot and utilisation of electronic source vehicles should be considered as alternative technology for seismic acquisition.
3. Surface noise
Having excess surface noise can interfere with the quality of the seismic data,such noise may be caused by factors such as animals, wind or traffic and by the seismic source itself.
Solution: Our land seismic acquisition technology - The STRYDE Node - has been designed to deal with a noise density of up to 22ng/sqrt(Hz) @ 16dB making it less sensitive to surface noise. The small, light weight nodes can be easily buried reducing further the impact of noise generated by wind (as an example). The ability to increase the density of sensors on the surface also helps with attenuating the noise during the processing sequence.
In order to de-risk investment decisions, geoscientists need high-resolution seismic data to make informed decisions. To acquire high-definition images of the subsurface, more receiver and source points are required to increase the density of the data, and cost is often a limiting factor when it comes to deploying large quantities of seismic sensors for high-density seismic acquisition.
Solution: Combining low-cost, wireless seismic receiver technology like STRYDE Nodes™ with greater efficiencies of deploying and retrieving nodal seismic equipment with smaller crews allows companies to comfortably afford higher channel counts and therefore increase the density of the seismic image acquired to make smarter, more informed decisions.
By understanding these challenges and implementing the relevant solution, you will be able to carry out land seismic acquisition that is cost-effective, efficient and safe. If you’re still interested in finding out more about the challenges associated with seismic acquisition then you can read more here.
Energy companies face a difficult dilemma as the need for new sources of energy is ever-increasing to keep up with the world's demand for energy while the risk and cost of drilling projects have skyrocketed.
Seismic data is a critical tool for companies to get a detailed understanding of the risks and potential success and profitability that an area may bring - before any large and expensive drilling operations take place.
There are many benefits of using STRYDE Nodes™ for seismic acquisition in the energy sector including:
Quick and easy access to high-density seismic at a reduced cost
Minimises risk and environmental footprint
Allows you to make informed decisions faster through accelerated seismic acquisition and data processing
Unlock seismic projects that were previously uneconomic
Before discussing new forms of land seismic acquisition, it's important to understand and compare the risks of traditional methods. Dynamite blasting, vibes and thumper trucks are techniques used for seismic acquisition, which can cause significant damage to the environment. These methods rely heavily on the use of loud and powerful equipment to generate strong sounds and vibrations which impact the nearby wildlife, soil, subsurface and vegetation. Combined with bulky, obtrusive cable receiver systems this made traditional methods unattractive to some land owners and regulators.
However, the advancement in light-weight technology has now allowed for more eco-friendly methods to be used to acquire seismic data. Nodal technology is key in making land seismic more environmentally friendly by:
Reducing the need for excessive line clearing or preparation to allow for vehicle and equipment access
Replacing heavy support vehicles with light weight, low impact ones
Increasing the ability to reduce the amount of high impact source activity by deploying denser, low impact receiver grids to achieve better subsurface imaging
Avoiding multiple passes of the survey area by removing the need for constant line checking or replacement of damaged or stolen cable equipment
In addition, a significant benefit of land seismic acquisition is that it can help to reduce the number of exploratory wells that need to be drilled. By providing a detailed subsurface model of an area, you can identify areas of potential energy developments or optimise well locations during production. This eliminates the need to drill in areas that may prove unsuccessful - reducing unnecessary drilling costs and damage to the ecosystem.
Nodal technology, also referred to as wireless sensors, is revolutionising land seismic acquisition by allowing for faster and more cost-effective data collection. Traditional methods of land seismic acquisition often rely upon cabled geophones which can prove costly and time-consuming to manage.
One of the main advantages of nodal technology is its ability to increase the density of sensor coverage due to its wireless functions, which allow nodes to be placed close to one another in a dense layout. This helps to generate a more detailed and accurate image of the subsurface.
Each STRYDE node contains a piezoelectric sensor that has the ability to conduct autonomous recording for up to 28 days of 24/7 recording or 45 days of 12-hour recording. This makes it the smallest, lightest and most affordable autonomous node in the world.
Improved subsurface imaging:
Use of low-cost wireless technology allows for the creation of detailed imaging of subsurfaces that can be used to identify the exact location of energy and subsurface risk, especially when high-density techniques are applied to the survey design.
At STRYDE, we pride ourselves on enabling fast and efficient methods of land seismic acquisition. Whether that be in relation to the sensor technology itself or our node management systems, acquiring seismic on large and complex areas of land at pace, is one of the main benefits companies can experience using STRYDE.
Not only can companies significantly reduce OPEX and CAPEX costs associated with purchasing or leasing the seismic receiver equipment, but the efficiencies and cost reduction opportunities on the seismic crew enables seismic contractors to be more competitive than ever before, and for the end-users of the data to acquire the data they need at a much lower cost.
Reduced environmental impact:
When compared to other methods of subsurface exploration, miniature wireless technology like the STRYDE Nodes(™) are proven to reduce environmental impact by minimising the need for line clearing, transportation vehicles and camp emissions due to the portability of the node and the ability to manage and transport them with less people, on foot.
Minimised exposure to HSE risks:
Traditional land seismic acquisition methods can be costly and expose workers to significant health, safety and environmental risks. However, the advancement in technology and new land seismic solutions such as the STRYDE node can help to minimise the exposure to potential HSE risks by having less crew in the field, less driving and minimal line clearing.
Reduced project cycle times:
Using STRYDE nodes to rapidly acquire and process land seismic data is allowing operators to accelerate decision making on project investment or quickly select and plan well locations to determine project economics. This reduced time sale is allowing operates to focus scarce financial and human resources on the the most efficient projects.
To better understand land seismic acquisition and the equipment used throughout the process, we’ve broken down some of the most frequently asked questions surrounding the topic.
Accelerometers measure acceleration, which in the case of the STRYDE nodes is through the piezoelectric sensors. Contrastingly, geophones measure velocity.
The frequency and phase response of the STRYDE sensor is flat between 1-125Hz/ and the sensitivity is 3.6V/g. The STRYDE nodes can record lower and higher frequencies which can be recovered, if required, in the data processing process.
Seismic deliverables are output from STRYDE systems in SEGD rev3 format allowing multiple information to be recorded on seismic headers. Software utilities are provided for ad hoc conversion to SEGY format, if required.
Starting from a battery that has been completely drained, it takes 4 hours to recharge. Each battery cell is designed to last the entire lifetime of the node - the cells that make up the battery have been designed to withstand frequent charging without significant loss of capacity.