Predicting seal risk and charge capacity using chimney processing: Three Gulf of Mexico case histories

Abstract

This paper describes how seismically derived 3D chimney volumes or "cubes" can be used to assess seal risk in exploration wells in the shelf and upper slope of the Gulf of Mexico. For this evaluation four examples of hydrocarbon accumulations with effective seals, one example of a breached seal, and one untested prospect are evaluated. From these examples, we have developed criteria to quantify the seal risk and charge capacity by differentiating different types of chimneys and other information. Such criteria can then be applied to predict seal integrity on un-drilled prospects. The emphasis will be on how chimney cube interpretation can be used in an integrated workflow to constrain uncertainty on both seal and charge for hydrocarbon exploration and rank prospects. For the intact seals, three of the examples studied had minor chimneys above the accumulation and clear evidence of chimneys providing vertical migration into the reservoir interval. These traps were also characterized by relatively low relief and inferred low strain rates. One of the intact seals was adjacent to a zone of vertical chimneys related to salt movement. However the reservoirs themselves were outside this disturbed zone and were characterized by moderate to low relief and low strain. In contrast, the trap which represented a breached accumulation was adjacent to a major chimney which vented hydrocarbons to the surface. It was also characterized by high structural relief and was within the disturbed zone, inferring higher strain rates. The prospect evaluated was also adjacent to a zone of vertical chimney development. However, the reservoir objectives for this prospect were outside the disturbed zone inferring lower strain rates. The trap also had moderate relief and is interpreted as a moderate to low risk for seal failure.

Evaluating hydrocarbon trap integrity during fault reactivation using geomechanical three-dimensional modeling: An example from the Timor Sea, Australia

“…Recent works by Ligtenberg and Thomsen (2003), Heggland (2005), Ligtenberg (2005), Walraven et al (2005a), and Roberts et al (2006) showed that 3-D seismic data are highly successful at detecting hydrocarbon migration pathways to or from a reservoir as well as possible expulsion sites and as such can be used to investigate the fluid transport properties of faults. Results of up-fault leakage will most likely affect the bulk proprieties of a rock body (Judd et al, 1992) in the fault zone or within adjacent discharge sites; it will then produce anomalies such as acoustic turbidity zones capturing gas chimneys, shallow seismic anomalies, and bright spots related to gas pockets (Kaluza and Doyle, 1996;Heggland, 2002;Aminzadeh et al, 2004;Walraven et al, 2005b;Cartwright et al, 2007;Halliday et al, 2008).…”

Interpretation of a gas chimney in the Polish Carpathian Foredeep based on integrated seismic and geochemical data

“…In petroliferous basins, gas chimneys provide clues for a better understanding of spatial and temporal linkages between various storeys of the petroleum system (Meldahl et al ., ; Løseth et al ., ). As summarized by Ligtenberg (), they can provide information as to the type of fluid activity in source rocks (Ligtenberg & Thomsen, ), top‐seal integrity analysis (Heggland, ; Walraven et al ., ; Cartwright et al ., ), and whether the potential target is charged or leaking (Heggland et al ., ).…”

Detection of fluid migration pathways in seismic data: implications for fault seal analysis

“…Leakage from potential reservoirs, which may provide better insight in the lateral and top seal quality (Walraven et al , 2004).…”

“…Gas chimneys and fluids migrating along faults and reaching potential reservoir formations, thereby providing information about whether a prospect is charged or not (Heggland et al , 2000, 2001). Leakage from potential reservoirs, which may provide better insight in the lateral and top seal quality (Walraven et al , 2004). Leakage from these potential reservoirs to shallower levels and charging shallow sands, thus indicating the presence of shallow gas drilling hazards (e.g.…”