The oil industry, especially the offshore oil industry, lives with risk, but runs on luck. Good risk reduction coupled with luck opens new oilfields. Every well that is drilled has an uncertain outcome, even though risk mitigation and reduction are a part of every decision. This is especially true of exploration.
The development and commercialization of electromagnetic technology is now altering the relationship between risk, luck, and success by reducing the uncertainty factor for drillable prospects. It does this by identifying qualities of the industry’s most elusive essential - the hydrocarbon charge within the reservoir.
Electromagnetics is the most recent tool in the industry’s bag of remote sensing tricks: gravity, magnetic, and seismic surveying. Surveyors measure the lateral and vertical resistance of reservoir rocks and their enclosed fluids to induced EM-flow. EM-flow is induced using two methods:
• By emitting EM radiation from a towed source (controlled source electromagnetics)
• By stressing the oil/water interface with a tuned acoustic shock wave (induced electrokinetics).
Oil and gas are found when reservoir, seal, trap, and hydrocarbon charge come together with the penetration of a drill bit. The presence of these four elements and the application of the fifth element encompass the risks geoscientist face daily. Gravity, magnetic, seismic, and EM surveying and interpretation are techniques tasked with determining the relationship between these elements.
Gravity, magnetic, and EM are field effects. The first two are used for regional investigations to understand the deep structure of a new basin. Seismic fills in the gaps and helps locate the specific controls on hydrocarbon movement: faults, diapiric structures, sedimentation patterns through time, as well as pinchouts, unconformities, and other sedimentation controls.
EM surveying helps complete the data set by inducing a local field effect. The resistive beds respond with a signal that can be overlaid on the seismic dataset to check the correlation of structure and resistive rock/fluids. It is not perfect and must be used in conjunction with other standard methods. Its purpose is to constrain the envelope of possibilities with firm data. Proof of concept still requires drilling.
Most exciting of all is that this technology is early in its lifecycle. Improvements are coming to both tools and interpretation, not to mention the untapped combination of attributes (similar to seismic attributes) that will quickly guide interpreters to the most prospective anomalies. It is similar to seismic surveying many years ago, before 3D surveys illuminated the subsurface. Finding oil and gas is not any easier, but dry hole risk will take a significant drop.•
TECHNOLOGY360º viz
Actuality Systems Inc. unveiled Perspecta 1.9 Spatial 3D system, its 360º 3D spatial visualization workstation. The new system has an embedded graphics system, faster graphics rendering, and increased-brightness than its earlier model.
The Perspecta 360º spatial visualization workstation has an embedded graphics system, faster graphics rendering, and increased-brightness.
Spatial 3D image data can come from a variety of sources, including oil and gas exploration software, which use the OpenGL API. It includes core-rendering-electronics to calculate and project complex geometric, volumetric, and merged data. Key elements include an AMD Athlon 64 chipset, an Nvidia GeForce 6800 Ultra graphical processing unit, dual gigabit Ethernet ports, and a proprietary voxel router, which drives three 1 Gb/sec links to an embedded optical subsystem.
New modules
Roxar added two modules to its IRAP RMS software suite. A well correlation module, RMSwellstrat, reduces the time iterating between model and interpretation, according to the company, and allows interpreters to handle complex geology and well geometries in a 3D environment. Users can view well trajectories, log data seismic, faults, maps, and reservoir data.
The fault seal analysis module, RMSfaultseal, can analyze fault zone properties within the reservoir modeling workflow and export results for simulation. The software comes with multiple algorithms for fault zone permeabilities and transmissibilities.
EXPLORATIONCombo seismic/CSEM
TGS-Nopec Geophysical Co. in collaboration with Offshore Hydrocarbon Mapping (OHM) began a multi-client controlled source electromagnetic (CSEM) survey in the Norwegian Barents Sea.
The survey is based on TGS-NOPEC’s multi-client 2D and 3D-seismic database in the area, and is the first one conducted under a project-by-project collaboration agreement between the two companies.
A combination of seismic and CSEM techniques focuses exploration on the most prospective targets. Receivers are positioned along the CSEM tow lines (red).
While seismic can define the shape of hydrocarbon traps, it cannot directly detect the presence of hydrocarbons. OHM’s CSEM method can identify highly resistive subsurface bodies like hydrocarbon bearing reservoirs. The two techniques in combination focus exploration efforts on the most prospective targets.
The companies will have final processed data and analysis available this summer.
Falkland Island survey
Falkland Oil and Gas Ltd. with partner Hardman Resources Ltd. began shooting an 8,000 km 2D seismic program over prospects identified in its recently completed 9,450 km survey. Geophysical Services Inc. of Calgary is shooting the survey using theGSI Admiral vessel.
Indonesian survey
Serica Energy Corp. completed a 2D seismic survey over its Biliton block in the Java Sea, between the islands of Java and Kalimantan. The company shot 2,300 km of 2D seismic along with gravity and magnetic data. The survey was an infill program to gather data over several large structures. Processing and interpretation will take six months.
