Dealing with Shallow-Water Flow in the Deepwater Gulf of Mexico

Abstract

This paper presents our perspective of the shallow-water flow (SWF) problemin the Deepwater Gulf of Mexico (GOM). The nature of the problem, includingareal extent and overpressuring mechanisms, is discussed. Methods for sandprediction and shallow sediment and flow characterization are reviewed. Theseinclude seismic techniques, the use of geotechnical wells, regional trends, various MWD methods, and cements and settable spots. Finally, examples of flowincidents with pertinent drilling issues, including well failures andabandonment, are described. Total trouble costs due to shallow-water flow for all GOM operators probablyruns into the several hundred million dollars. Though the problem remains aconcern, advances in our knowledge and understanding make it a problem that ismanageable and not the "show stopper" once feared. Introduction SWF may occur while drilling shallow over-pressured formations at deepwatersites. It is a high profile problem in the GOM, though it does occur elsewhere(Ref. 1) and will likely be encountered in other deepwater regions (Fig. 1). Drilling shallow over-pressured sands may cause large and long lastinguncontrolled flows, well damage and foundation failure, formation compaction, damaged casing, and re-entry and control problems. Most spectacularly, eruptions from over-pressured sands may result in seafloor craters, mounds andcracks (Figs. 2 and 3). Eaton2, 3 has described the significant problems causedby SWF in the Ursa area. A recent inspection of 106 wells (Ref. 4) indicatedthat $175 MM has been spent on SWF and prevention and remediation on thosewells. Total industry costs due to SWF likely exceed several $100 MM. The problem is compounded by the difficulty in seismically imaging thesesands (Refs. 5 and 6). This stems from the relatively low sand/shale contrastin acoustic impedance. The impact of this problem on well site selection andwell design is significant, and makes drilling in SWF areas particularlychallenging.

Petrophysical and consolidation behavior of mass transport deposits from the northern Gulf of Mexico, IODP Expedition 308

“…The integration of seismic, petrophysical, and consolidation data suggests that for shear strains observed in the Ursa region, preferential, bed-scale fabrics are not developed within MTDs. hydrocarbon reservoirs at depth, and because of drilling problems associated with flow of unconsolidated sands from the shallow subsurface to the seafloor (Pelletier et al, 1999;Ostermeier et al, 2000). These studies have benefited from the existence of high resolution seismic data (exploration and hazard) and industry and geotechnical wells.…”

Physical properties of sediments from Keathley Canyon and Atwater Valley, JIP Gulf of Mexico gas hydrate drilling program

“…The deep subsurface sediments in the Gulf of Mexico (e.g., Seldon and Flemings, 2005) have been of particular interest due to economic hydrocarbon reserves in the region. In the deepwater Gulf of Mexico, shallow subsurface studies have focused on geohazards and shallow gas accumulations (e.g., Ostermeier et al, 2000). Studies of seeps have characterized leaking gas and gas hydrate within the hydrate stability zone (e.g., MacDonald et al, 2002).…”

In-Situ Sampling and Characterization of Naturally Occurring Marine Methane Hydrate Using the D/V JOIDES Resolution

“…The piezoprobe has been tested and proven (e.g., Ostermeier et al, 2000;Whittle et al, 2001) on numerous geotechnical cruises that measured pressure and temperature, but it had not been adapted for ODP until Leg 204. To adapt it on the JOIDES Resolution for testing and use with the APC/XCB bottom-hole assembly (BHA) required modifications prior to the leg.…”