An example study using conventional 3D seismic data to delineate shallow gas drilling hazards from the West Delta Deep Marine Concession, offshore Nile Delta, Egypt

Abstract

This paper details a study that was completed at the end of 1999 to investigate the suitability of using existing, high quality, conventionally processed 3D seismic data (hereafter 3D data) to replace specifically commissioned 2D seismic site survey data (hereafter 2D site data). For this study, three wells from an existing dataset of six in the West Delta Deep Marine Concession, offshore Egypt (WDDM) were investigated. A prescriptive workflow was developed using the 3D data and the results compared to those obtained from a conventional previously commissioned 2D digital site survey dataset. For this dataset from WDDM, the results obtained from the 3D data and the 2D data were similar, the main difference being that more numerous, smaller probable hazards were prognosed by the 3D data. After undertaking this investigation and following an independent review of the results, a recommendation was made to operate the 2000 WDDM drilling campaign using hazard prognosis from the conventional 3D data, i.e. not to acquire well-specific, new digital site surveys. This recommendation was followed and five exploration wells were drilled in 2000 with no specific, digital site survey data being acquired. No safety, operational or environmental implications were encountered as a result of this replacement and significant operational savings accrued to the operating partnership.

Intra- to post-Messinian deep-water gas piping in the Levant Basin, SE Mediterranean

“…2). These features are usually screened for within 1 s two-way travel-time (or~750 m) below the seafloor, as was reported in deep-water off Brazil (Sharp and Badalini, 2013) and in the adjacent Nile Delta (Sharp and Samuel, 2004). This situation certainly is applicable for the current study, in which wells drilled to explore and exploit hydrocarbons must penetrate the overburden successions before reaching target horizons and reservoirs (e.g.…”

“…The resurgence in hydrocarbon exploration activities in the region necessitate better understanding of the distribution and evolution of subsurface fluid flow features. This is particularly crucial in overburden successions where they may pose geohazards to hydrocarbon exploration and production (Judd and Hovland, 1992;Sharp and Samuel, 2004;Andreassen et al, 2007).…”

Morphological Controls on Submarine Slab Failures

“…These are underlain by two evaporite facies marking the dessication, and lago-marine sediments from a lacustrine event preceding the refilling of the Mediterranean (Lonke et al 2006). The Rosetta canyon is also a conduit for sediment transfer processes, which explains the frequency of turbidite deposits in this area of the fan (Sharp and Samuel 2004).…”

“…52.1) (Mascle et al 2003). The present-day state of the fan originates from the late Miocene (Sharp and Samuel 2004). Evaporite deposits from the Mediterranean desiccation have been covered by clastic sedimentation from the Nile, interrupted by episodes of erosion and landsliding over a least the last 250,000 years ).…”

Review of progress in evaluating gas hydrate drilling hazards

“…Overpressured gas sands can lead to the uncontrolled flow of gas into the well that can lead to a blow-out situation with risks to people, drilling operations, and the environment (Bryant and Roemer, 1983;Lukkien, 1985;Sills and Wheeler, 1992;BOEMRE, 2006;Flores et al, 2007;Judd and Hovland, 2007;and Kortekaas and Peuchen, 2008). The typical approach in assessing shallow gas hazards is through the identification and avoidance of "bright spot", high amplitude anomalies in seismic data consistent with zones of low acoustic velocity that indicate the presence of free gas (Luheshi et al, 1996;Orren et al, 1996;Salisbury et al, 1996;Hilterman, 2001;García-García et al, 2004;Sharp and Samuel, 2004;Orange et al, 2005). Disperse accumulations of gas bubbles at low saturation are also common (MacKay et al, 1994;Lu and McMechan, 2004) and, while not usually perceived as a threat to drilling safety, can add costs to the drilling program.…”