To drill successfully for oil and natural gas, you need to have a good idea of what’s beneath the surface. Seismic data is used by oil and natural gas exploration and development companies to identify portions of geological formations that have the potential to hold hydrocarbons. Seismic data is used in conjunction with well logging data, well core comparisons, geological mapping and surface outcrops to create a detailed map of the Earth’s subsurface at various depths. Two-dimensional (2D) and three-dimensional (3D) seismic are crucial tools in the toolkit that exploration and development teams use to drill new wells with confidence, achieving a high rate of technical success and commercial viability.
Seismic data is used by oil and natural gas exploration and development companies to map and interpret potential reservoirs
2D seismic data is measured in linear kilometres and after processing provides a sectional illustration of geological formations on a straight line directly below the line on which the data was acquired. 2D seismic can extend over a large distance of up to several kilometres in length. Exploration companies typically use 2D seismic to get a sense of the regional geology of an area they think is prospective for oil and natural gas.
3D seismic data is measured in square kilometres and after processing provides map-like overhead views as well as three-dimensional visualizations of the subsurface geology. 3D seismic data is shot in grids, generating a three-dimensional image of the subsurface. 3D seismic data enables a more precise definition of geologically complex targets, and facilitates precise placement of oil and natural gas wells. 3D seismic data is particularly important for horizontal drilling, unconventional plays (such as shale gas and tight sands) and complex conventional drilling.
Seismic waves used to record seismic data are Sound Waves
Seismic waves used to record seismic data are sound waves. Acquiring new seismic data, at its most basic, comprises scouting and mapping the area of interest, preparing the ground so personnel and low impact equipment can travel safely and placing lines of receivers on the ground to record the sound waves generated by an energy source. In acquiring seismic data, an acoustical energy wave radiates from an energy source at or near the surface of the Earth to the subsurface. These seismic waves reflect off the various geological beds or strata in the Earth’s subsurface and sophisticated sensors and instruments at the surface record the reflected waves and convert them to digital form. The data is subsequently processed and an image of the subsurface formations is created, providing explorationists with valuable data on the potential of a particular area to yield oil or natural gas reserves, and assists in the selection of drilling locations.
The energy source can either be a dynamite charge or a hydraulic Vibroseis unit that physically shakes the ground. The majority of Pulse’s recent participation surveys have been located in the Deep Basin and Foothills areas. Due to the difficult terrain and access in these areas, Pulse uses dynamite as the energy source rather than using vibration-induced seismic. Dynamite requires narrower cut-lines, making it environmentally friendlier, provides a superior geophysical signal, especially when surveying deeper targets, and enables heli-assist operations in environmentally challenging areas. Vibroseis is commonly used in areas that are accessible to large equipment such as open fields and areas that restrict the use of dynamite.
The key to seismic quality is the “fold.” High-fold data is acquired by recording a tighter grid of receiver points on the surface, picking up more of the subtle changes in sound frequency and interval necessary for precise geological mapping and seismic modelling. High-fold seismic also collects data from the full range of prospective geological zones, from shallow through deep. Low-fold seismic, which is a result of sparser receiver intervals, is analogous to a grainy image at shallower targets. Pulse focuses on acquiring high-fold data wherever possible.
Wireless Geophones simplify acquisition logistics and reduce operating costs
Pulse also utilizes three-component geophones, which measure both the reflected compressional (vertical) and shear (horizontal) sound waves, which provide additional data to analyze. Seismic technology improved recently with the development of wireless geophones which simplify acquisition logistics and reduce operating costs.