Measured Swabbing Pressures and Implications for Shallow Gas Blow-Out

Kortekaas, Stella; Peuchen, Joek

doi:10.4043/19280-ms

Cited by 8 publications

(5 citation statements)

References 5 publications

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“…Evans, 2011). Major oil companies have recently been faced with important engineering problems related to the presence of free gas in marine sediments (Kortekaas & Peuchen, 2008). Research into gas-charged sediments has also gained renewed interest in close relation to environmental issues and geological hazard assessment associated with gas release in marine sediments.…”

Section: Introductionmentioning

confidence: 99%

Mechanical behaviour of gas-charged marine plastic sediments

Sultan¹,

Gennaro²,

Puech³

2012

Géotechnique

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Understanding how free gas modifies the mechanical behaviour of marine plastic sediments remains a challenging issue. Special triaxial tests were carried out on natural sediments recovered from the Gulf of Guinea. Special attention was devoted to the laboratory preparation procedure, involving saturation of natural marine sediment samples with carbonated water and generation of free gas following undrained unloading. Experimental data show that soil destructuration and damage generated by gas expansion and exsolution are at the origin of (a) the increase in the isotropic compressibility and decrease in the preconsolidation pressure, and (b) the decrease in the peak undrained strength and abrupt increase of the pore pressure during undrained shearing. The experimental data also show that flooding of gas bubbles and dissolution of free gas do not imply a complete strength recovery of natural sediments.

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Section: Introductionmentioning

confidence: 99%

Mechanical behaviour of gas-charged marine plastic sediments

Sultan¹,

Gennaro²,

Puech³

2012

Géotechnique

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“…Conversely, the industry deliberately avoids drilling through chimney features as well as any high amplitudes in the shallow sedimentary section out of concern for natural gas or shallow water flows (Flemings & Scientists, 2005;Kortekaas & Peuchen, 2008;McConnell, 2000;McConnell et al, 2012;Smith et al, 2005). Therefore, the P gh may be higher than 0.16 because shallow gas anomalies can occur beneath or coexist with the high-saturation gas hydrate occurrences and strong amplitudes could be caused by gas hydrate accumulations (Boswell et al, 2016).…”

Section: Geochemistry Geophysics Geosystemsmentioning

confidence: 99%

The Volume of Gas Hydrate‐Bound Gas in the Northern Gulf of Mexico

Majumdar

Cook

2018

Geochem Geophys Geosyst

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The northern Gulf of Mexico is known to host gas hydrate in submarine sediments. Estimating the amount of gas hydrate for both carbon cycle and resource interest has been ongoing for more than three decades. A large range of estimates (from 0.2 to 680 trillion cubic meters (TCM)) for hydrate‐bound natural gas at standard temperature and pressure exists. We bring a new perspective to resource estimates by using ~800 publicly available petroleum industry well logs assessed for natural gas hydrate. Our resulting probabilistic range of the gas hydrate‐bound natural gas in the northern Gulf of Mexico ranges from 37 TCM (10th percentile estimate) to 78 TCM (90th percentile estimate) of gas hydrate‐bound natural gas, with a mean estimate of 56 TCM. This suggests that the gas hydrate resource density of the northern Gulf of Mexico is 4 times lower than that previously estimated by the Bureau of Ocean Energy Management. Our results also indicate that over half of the gas hydrate in the area is strategically hosted in sand reservoirs, which is significantly higher than that previously estimated.

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“…This means that initial in-situ pore pressure may be inferred from a vertical column of seawater and static pore fluid in the formation. The driving part of the equation includes considerations for swabbing, surging, hydraulic resistance to flow and change of mud density caused by, for example, inclusion of drill cuttings (Kortekaas and Peuchen, 2008;Crespo et al, 2010). excess pore pressures or overpressures, may arise because of natural mechanisms or may be induced by on-site activities.…”

Section: Reasons For Excess Pore Pressuresmentioning

confidence: 99%

Prediction of Formation Pore Pressures for Tophole Well Integrity

Peuchen

Klein

2011

All Days

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Knowledge about formation pore pressures is important for planning and control of offshore well drilling operations. Particularly, a combination of unconsolidated clay/shale sediments and in-situ pore pressures exceeding hydrostatic values can create a distinctly adverse setting for tophole well integrity. If unanticipated, well completion may fail.Pore pressure prediction for the tophole section generally relies on use of multiple methods, as no single technology is available. Actual measurement of in-situ pore pressure is necessary. Pore Pressure Dissipation Testing PPDT with a push-in piezoprobe or piezocone penetrometer is currently the most efficient and accurate method for actual measurement of formation pore pressure in unconsolidated sediments. The method can be used in a pre-well site survey, during pre-setting a tophole well section or combined with well installation itself.Capabilities and limitations are highlighted for predicting and accurately measuring formation pore pressures in shallow unconsolidated clay/shale sediments. Use is made of a unique database containing more than 160 PPDT piezoprobe measurements. The database probably covers a majority of piezoprobe measurements ever completed for offshore tophole sections. It includes (1) hydrostatic pressure profiles, (2) excess pore pressures due to natural phenomena and (3) excess pore pressures due to formation damage caused by earlier well drilling. Depth coverage is up to 400 m below seafloor.Achievable accuracy for measurement of pore pressure is typically estimated at about 50 kPa (= 5 m water column) or 5% of penetration pore pressure, whichever is the greater. Difficulties are noted for establishing formation pore pressures where (1) clay/shale sediments have been affected by formation damage caused by earlier drilling and (2) clay/shale sediments include shallow gas zones. Opportunities for improvement are discussed.

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Measured Swabbing Pressures and Implications for Shallow Gas Blow-Out

Cited by 8 publications

References 5 publications

Mechanical behaviour of gas-charged marine plastic sediments

Mechanical behaviour of gas-charged marine plastic sediments

The Volume of Gas Hydrate‐Bound Gas in the Northern Gulf of Mexico

Prediction of Formation Pore Pressures for Tophole Well Integrity

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