Credit: Dome Energy
The oilfield industry over the past several years has been making vast leaps in drilling efficiency. These gains are not only tallied through advances in casing, drill string or cutting technologies but also through the unsung technologies that have been recently employed and of them, 3D seismic imaging has seen the greatest returns on investment.
Until very recently, the motto of the drilling industry was: Ready. Fire. Aim. There was no room for lost time. Through rather crude geologic surveys (at least compared to modern techniques), drilling companies went into formations somewhat blind. Without full knowledge of reservoir characteristics, drilling was far more financially risky and a mortally dangerous endeavor. Further, even if oil or natural gas was able to flow from the reservoir, lack of information related to the exact hydrocarbon payout ran the risk of the well not being able to cover the the costs associated with the drilling operations.
This economic limit is where 3D seismic imaging has proved with worth. With full knowledge of the depths, pressures and reservoir payouts, drillers can now conduct their operations with more precision, safety and economic efficiency.
The Way It Was
Until 3D technology became for cost-effective for exploration & production and drilling companies, most opted for 2D imaging technology.
Otherwise known as reflection seismic, this technology resembled sonar and ultrasound technologies. By inducing acoustic waves into the geologic subsurface, geologists would be able to listen to the echoes returning from the stratigraphic boundaries and form a picture of the formation. These acoustic waves would typically be generated by underground explosive charges or by thumping the ground with a large mallet mounted on a specially designed vehicle known as a vibroseis truck.
The reverberations felt in the subsurface would be reflected back to the surface and would be “collected” using a special microphone known as a geophone. This data would be collect onto a magnetic tape and then transmuted into readable data via computers. As elementary as this process was, it was far more informative that going off of purely surface-oriented geological surveys. Though it was effective in proving subsurface reservoirs, its shortcoming was a lack of an articulate understanding of subsurface characteristics.
The Way It Is Now
Now companies like Dome Energy are cost-effectively implementing 3D seismic imaging to prove the economics of a rather financially risky drilling process. 3D seismic imaging has shares similar technological hallmarks to that of 2D imagining but the differences between the two are undeniable.
The technology employs acoustics imaging but rather than one source of vibration, 3D seismic imaging involves creating a perimeter where multiple acoustic receivers, rather than microphones, are established. These areas for the receivers are known as patches. By capturing seismic shots that lie between two patches geologists and drilling companies obtain uniform reflection information from a subsurface area. By changing the locations of each patch and repeating the vibration and recording process, companies accumulate overlapping subsurface readings which build a very articulate three dimensional picture.
3D seismic imaging doesn’t eliminate 100% of the exploration and drilling risk, it definitely improves success rates and productive wells. The technology allows explorers and drillers with more pinpoint accuracy that goes to should deliver better production and a slightly longer well life. More importantly, 3D seismic imaging eliminates the possibility of drilling dry holes in the pool development process.