Unleashing the power of nodal seismic sensors – a geologist's perspective.

by STRYDE
Jul 17, 2023 11:28:46 AM

 

 

For geologists like Carolina Mejia Hernandez, high-resolution and dense seismic data plays a vital role by providing the necessary information to map subsurface characteristics, analyse rock properties, and make informed decisions regarding exploration drilling and reservoir optimisation. 

Drawing from her extensive 15-year expertise in analysing subterranean formations across Latin America, Carolina Mejia Hernandez possesses a deep understanding of the prevalent hurdles encountered by geologists in mapping and interpreting onshore seismic data. In this article, Carolina delves into her personal encounters, shedding light on what she envisions as the pivotal factor that will revolutionise geologists' capacity to expedite subsurface mapping and achieve greater precision in well placement and production optimisation decision-making.

 

What do geologists care most about when it comes to onshore seismic data?

“Geologists need to be able to accurately place wells to get the most out of the natural resources they have been tasked with pinpointing. However, if there are artifacts in the seismic data it can cause several issues that can impact the interpretation and analysis of seismic images. 

“In general, most geologists care about the quality of the data they are working with to avoid companies drilling a dry hole, missing the target, or damaging the reservoir which is costly and time-wasting.

“Having a clear seismic image will enable their interpretation to be more accurate and getting access to this data early in the exploration program is also very beneficial to geologists as it provides sufficient time to accurately analyse and interpret the subsurface to define the prospects.”

 

What common challenges do geologists face when it comes to interpreting onshore seismic data?

Artifacts in seismic data

“Artifacts in seismic data is a common issue geologists experience, in my experience, these typically include:

  • False features: Artifacts can introduce false seismic reflections or anomalies that do not correspond to actual subsurface geological structures. These false features can mislead interpretation and lead to incorrect conclusions about the subsurface.
  • Distortion of seismic events: Artifacts can cause distortions in seismic events, such as stretching, smearing, or truncation. This can make it challenging to accurately identify and interpret seismic reflections, making it difficult to determine the true shape, continuity, or position of subsurface formations.
  • Poor signal-to-noise ratio: Some artifacts can introduce additional noise into the seismic data, reducing the signal-to-noise ratio. This can make it harder to identify and distinguish subtle geological features or weak reflections from noise, resulting in a loss of data quality and resolution.
  • Loss of amplitude fidelity: Artifacts may lead to amplitude variations that are unrelated to the actual subsurface reflectivity. This can impact the quantitative interpretation of seismic amplitudes and the estimation of rock properties such as porosity, fluid saturation, or lithology.
  • Migration-related issues: Migration is a common processing step used to improve the positioning accuracy of seismic reflections. However, artifacts can interfere with the migration process and result in poor imaging of subsurface structures. This can lead to imaging artifacts such as false images, mispositioned events, or incomplete migration.

Incomplete or sparse data

“Geologists and data interpreters can also often find incomplete sections in the seismic data, areas where crews have not been able to access, or where a community hasn’t allowed an acquisition team in to survey an area for various reasons such as concerns with land disruption. As a result of this, we are commonly forced to extrapolate data interpretations within these areas, significantly increasing the risk of the exploration programs, by missing key information. Using miniature, lightweight and non-intrusive nodal technology like STRYDE’s enables acquisition teams to easily can access these areas due to its portability and ability to minimise land disruption. 

“With STRYDE Nodes™ also being low-cost, it means companies can afford to increase the density of the receiver spread, helping to increase seismic coverage and resolution to avoid issues associated with incomplete or sparse datasets.  

Low-resolution seismic data

“When high-density seismic data is not acquired it makes the data difficult to analyse the rock physics of the reservoir; thus, geologists usually require another seismic shot or a VSP (Vertical Seismic Profile) to be completed to match the velocity model which can be timely and expensive”

image2

Do you think geologists can benefit from data acquired by wireless seismic sensor technology? 

“Geologists are always looking to have access to high-definition seismic data to aid the exploration or reservoir characterisation part of a project, and high-density data is key to this. 

“But because the technique of acquiring high-density seismic data requires a higher channel count of seismic sensors to be deployed in an array or grid pattern across a survey area, using traditional cabled geophones or bulky and expensive nodal devices to acquire high-density datasets is not always viable from a cost or logistical perspective. So yes, I do think geologists will benefit greatly from nodal technology in this respect, but it needs to be low-cost, small, and lightweight to be commercially viable.  

“Because the spacing between the sensors is reduced on a high-density survey, it results in a higher density of data points. As the goal is to obtain a more detailed and accurate representation of the subsurface, increasing the density of sensors offers several advantages:

  • Improved resolution: The closer spacing of sensors allows for a more finely detailed image of the subsurface. This can help identify small-scale geological features, reservoir compartments, or fault zones that might be missed in lower-density surveys.
  • Enhanced imaging: High-density data provides better imaging of subsurface structures, enabling geologists to interpret seismic reflections with greater precision. This leads to improved geological models and more accurate predictions about subsurface reservoirs.
  • Noise reduction: High-density surveys help mitigate the effects of ambient noise by averaging out random noise sources. The increased number of data points provides a more robust signal-to-noise ratio, leading to cleaner seismic records and easier interpretation.
  • Amplitude fidelity: With more densely sampled data, seismic amplitudes can be preserved more accurately. This is particularly important for reservoir characterisation, where accurate amplitudes are essential for estimating hydrocarbon reserves and fluid properties.

 

How do you think the STRYDE system will help address or overcome common challenges that geologists face?

Due to the nodes reduced size and weight, seismic crews can now access areas by foot where the topography was previously too challenging, such as dense forests, mountains, or marshlands. It also means that less/or no vehicles are required to transport the equipment into and around the survey area, meaning there is less damage done to the land and it is much less intrusive than a conventional survey would be if cabled technology or bigger and bulkier nodal devices were used – helping with access rights and permitting. This leads to more coverage in the dataset, making the images easier to interpret.

“Due to the reduced price-point of the node, it allows companies to easily afford higher channel counts of seismic sensors, giving the opportunity to increase the survey density to gain better resolution at the reservoir level.

 

What common subsurface challenges have you witnessed in Latin America that can be attributed to the location or environment?

“In Latin America, we have several landscapes, two of the most common include very rocky mountains, where temperatures can be very extreme (like The Andes), and dense forest environments such as the “Amazon” rainforest, and “Foreland basins”. 

“Both landscapes present challenges for the acquisition and processing of seismic data due to the extreme topography and temperatures- making it a tough environment to cover and for crews to work in. This often results in sparse data which impacts the ability to interpret the data effectively, risking expensive mistakes in decision making.”

 

What excites you about the STRYDE system?

”I fell in love with STRYDE’s technology from the first time I saw the node and learned about how it has impacted land seismic acquisition for so many different companies operating in different environments, terrain, and for such a variety of different applications, ranging from oil and gas to animal tracking and geothermal energy exploration.

“For me, it has been an honour to work alongside my colleague, Victor Villamizar to bring such a game-changing technology to our home country of Colombia and across Latin America. 

“From a geologist’s perspective, I truly believe this technology is the key to overcoming the subsurface data resolution challenges that exploration teams have been facing for decades and I am excited to help companies experience the benefits of the system in their upcoming onshore exploration programs.”

Learn more about STRYDE's low-cost land seismic acquisition technology

Find out more about STRYDE's technology