Liberty, Lee M. (Department of Geosciences, Boise State University, Boise, Idaho) | Clair, James St (Department of Geosciences, Boise State University, Boise, Idaho) | Gribler, Gabriel (Department of Geosciences, Boise State University, Boise, Idaho)
A seismic land streamer campaign reveals complex faulting and folding within late Quaternary Bonneville lake sediments and alluvial fan deposits beneath the downtown Salt Lake City urban corridor. From more than 15,000 shot gathers along 22 city streets, 35 km of two meter spaced seismic data provide detailed character of late Quaternary stratigraphy and tectonics within a step over region of the Wasatch fault system. We use first arrival tomography to obtain Vp distributions to 20–30 m depth, Rayleigh wave inversions to provide Vs profiles to about 30 m depth, and reflection imaging to 200–300 m depth to map the distribution of faults, fold, and lithologic boundaries. From these data, we provide 1) an updated city-wide Vs30 high frequency site response map, 2) stratigraphic mapping of transgressive and regressive paleolake Bonneville deposits, 3) distributions of tectonically induced lateral spread and colluvium deposits, 4) water table depths and zones of both confined and unconfined groundwater systems, and 5) distributions of active faults related to the Wasatch fault system. We find that complex near surface conditions highlighted in both Vp and Vs tomograms directly relate to changing hydrostratigraphy and active faulting. Complex near surface conditions can diminish reflection data quality. Lower Vp/Vs ratios in the upper 10 m and the presence of higher mode surface waves result in poorer reflection imaging capabilities at greater depths.
Presentation Date: Wednesday, October 17, 2018
Start Time: 1:50:00 PM
Location: 204A (Anaheim Convention Center)
Presentation Type: Oral
Although methane leakage from oil and gas wells has received significant attention in the last thirty years, emission estimates still range between 1-9% of production. In more recent years methane leakage has been under scrutiny by industry, governments and the public. Methane leakage can be characterized as short, medium and long-term. Long-term methane leakage usually relates to wellbore integrity issues and only recently has it been suggested that it can occur through the formation near the wellbore from damage while drilling or pressure cycling, and that conventional cementing may not prevent it. The severity of long-term methane leakage from wells is currently unknown. Thus, this research is investigating long-term leakage with special attention paid to the effect of pressure cycling from hydraulic fracturing on cement and near wellbore rock integrity. An apparatus has been designed that is capable of testing cement under various cyclic pressure conditions: the numerous hydraulic fracturing stages and the inevitable shutdowns and start-ups during production. It is capable of measuring permeability changes along the length of the cement in order to determine when and where damage occurs during pressure cycling. Cement and microannular degradation will be assessed through observed changes in permeability, computerized tomographic (CT) evaluation and visual inspection. Knowing the main cause of leakage allows for specific remediation and/or solutions to prevent leakage without guesswork.
During the last thirty years, methane leakage from hydrocarbon wells has received significant attention from industry, government and the public. Recent studies (Boothroyd et al. 2015; Caulton et al. 2014; Karion et al. 2013; Miller et al. 2013; Rivard et al. 2014; Osborn et al. 2011) have increased not only public awareness but also concern because methane is a powerful greenhouse gas (Myhre et al. 2013). In a typical well steel casing is installed and the annular space between this casing and the drilled rock is filled with cement (Figure 1). Ideally, this cement provides a hydraulic seal in the casing- rock annulus. If this cement becomes damaged it can allow fugitive methane emissions (King and King 2013). Current emission estimates from surface facilities, cemented annuli and the surrounding rock are thought to be somewhere between 1 and 9% of the actually produced gas (Howarth et al. 2011; Kirchgessner et al. 1997; Pétron et al. 2012; Ritter et al. 2013; Tollefson 2013). Methane leakage can be viewed as short-, medium- and long-term. Proper cement system design and good operational practices can easily mitigate short-term leakage that is often the result of wrong cement weights.
Rickett, James (ChevronTexaco Exploration and Production Technology Company, San Ramon, CA) | Mosher, Chuck (ChevronTexaco Exploration and Production Technology Company, San Ramon, CA) | Martin, Harry (ChevronTexaco Exploration and Production Technology Company, San Ramon, CA)
We introduce the procedures of beam-source synthesis and beam-source migration for wave-equation based imaging methods and test the method with Gabor-Daubechies and local-cosine beamlet migration. Plane-source synthesis and migration are treated as a special case of approximation to the beam-source synthesis and migration. Beam-source migration has both space and direction localization of illumination and is very flexible for target-oriented migration using wave-theory based methods. On the other hand, plane-source migration can increase the computation efficiency of depth migration significantly, up to 5-10 times for the SEG-EAGE salt model and Marmousi model.
Guitton, Moritz M. (3DGeo Development Inc.) | Sean, Sean (3DGeo Development Inc.) | Bevc, Dimitri (3DGeo Development Inc.) | Alexander, Antoine M. (3DGeo Development Inc.) | Biondi, Biondo (Stanford University)
Imaging a salt body in the deep Gulf of Mexico that is characterized by rapid changes in topography and smallscale rugosity of its top surface demonstrates limitations in 3-D Kirchhoff depth migration. Common azimuth wavefield-continuation ("wave-equation" for short) migration sharpens the top salt image and reveals details unseen in the Kirchhoff image. This allows us to pick the salt body more accurately and to improve the image of the subsalt target with the corrected velocity model.