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Use of X-Ray computed tomography to quantify the petrophysical properties of volcanic rocks: a case study from Tenerife, Canary Islands

Use of X-Ray computed tomography to quantify the petrophysical properties of volcanic rocks: a case study from Tenerife, Canary Islands
Use of X-Ray computed tomography to quantify the petrophysical properties of volcanic rocks: a case study from Tenerife, Canary Islands
Basaltic lava flows and ignimbrite units around Puerto de Santiago, SW Tenerife, were investigated as potential analogues for hydrocarbon-bearing volcanic reservoir rocks. Conventional helium porosity and air permeability measurements together with the results of a micro-focus X-ray computed tomography study were integrated with field observations on flow morphology and the continuity of defined internal lava flow zones.

Individual lava flows typically comprise distinct tops, cores and bases, with lava piles showing repeated cycles of these three internal zones. Reservoir quality is best in the flow tops (mean ? = 23.14%, k = 5.622mD) where vesicular porosity dominates. Flow cores are relatively tight with primary porosity mainly controlled by cooling joints, fractures and intercrystalline microporosity (mean ? = 2.40%, k = 0.001mD). Flow bases show variable reservoir potential due to the presence of breccia and/or vesiculation (mean ? = 11.77%, k = 0.001mD). By contrast, ignimbrites show the highest porosities but have low permeabilities (mean ? = 35.64%, k = 0.0056mD). In all cases, the primary porosity and permeability may have been modified to create additional secondary porosity and permeability as a result of fracturing and mineral dissolution during burial or weathering, although porosity may also be occluded through the precipitation of secondary minerals or the alteration of primary minerals.

The new porosity data presented demonstrates that pyroclastics and basaltic lava flow tops have the best reservoir properties, with the flow tops having sufficient porosity and permeability to transmit fluids and gas. In contrast, flow cores are relatively tight (impermeable), and would act as seals to potential hydrocarbon accumulations when fractures and cooling joints are absent. The reservoir potential can be high where vesicles and fractures are present (i.e. in lava flow tops), although there is uncertainty whether flow tops could be connected to each other vertically to form a potentially exploitable hydrocarbon reservoir. Although in some areas such volcanic rocks can be primary targets for hydrocarbon exploration (e.g. onshore China), in many others they are considered to be a secondary target, adding incremental resources to hydrocarbons produced from more conventional sandstone and carbonate reservoirs.
Tenerife, volcanic reservoir rocks, reservoir quality, lava flows, porosity permeability, micro-focus X-ray tomography
0141-6421
79-94
Couves, C.
43c45b63-cac9-4b3a-b1bf-664699394051
Roberts, S.
f095c7ab-a37b-4064-8a41-ae4820832856
Racey, A.
97c507de-97c8-4c6d-9e30-56e0cdd5cb1e
Troth, I.
d3427de4-ce8d-45e9-9993-7a77b265a978
Best, A.
cad03726-10f8-4f90-a3ba-5031665234c9
Couves, C.
43c45b63-cac9-4b3a-b1bf-664699394051
Roberts, S.
f095c7ab-a37b-4064-8a41-ae4820832856
Racey, A.
97c507de-97c8-4c6d-9e30-56e0cdd5cb1e
Troth, I.
d3427de4-ce8d-45e9-9993-7a77b265a978
Best, A.
cad03726-10f8-4f90-a3ba-5031665234c9

Couves, C., Roberts, S., Racey, A., Troth, I. and Best, A. (2016) Use of X-Ray computed tomography to quantify the petrophysical properties of volcanic rocks: a case study from Tenerife, Canary Islands. Journal of Petroleum Geology, 39 (1), 79-94. (doi:10.1111/jpg.12629).

Record type: Article

Abstract

Basaltic lava flows and ignimbrite units around Puerto de Santiago, SW Tenerife, were investigated as potential analogues for hydrocarbon-bearing volcanic reservoir rocks. Conventional helium porosity and air permeability measurements together with the results of a micro-focus X-ray computed tomography study were integrated with field observations on flow morphology and the continuity of defined internal lava flow zones.

Individual lava flows typically comprise distinct tops, cores and bases, with lava piles showing repeated cycles of these three internal zones. Reservoir quality is best in the flow tops (mean ? = 23.14%, k = 5.622mD) where vesicular porosity dominates. Flow cores are relatively tight with primary porosity mainly controlled by cooling joints, fractures and intercrystalline microporosity (mean ? = 2.40%, k = 0.001mD). Flow bases show variable reservoir potential due to the presence of breccia and/or vesiculation (mean ? = 11.77%, k = 0.001mD). By contrast, ignimbrites show the highest porosities but have low permeabilities (mean ? = 35.64%, k = 0.0056mD). In all cases, the primary porosity and permeability may have been modified to create additional secondary porosity and permeability as a result of fracturing and mineral dissolution during burial or weathering, although porosity may also be occluded through the precipitation of secondary minerals or the alteration of primary minerals.

The new porosity data presented demonstrates that pyroclastics and basaltic lava flow tops have the best reservoir properties, with the flow tops having sufficient porosity and permeability to transmit fluids and gas. In contrast, flow cores are relatively tight (impermeable), and would act as seals to potential hydrocarbon accumulations when fractures and cooling joints are absent. The reservoir potential can be high where vesicles and fractures are present (i.e. in lava flow tops), although there is uncertainty whether flow tops could be connected to each other vertically to form a potentially exploitable hydrocarbon reservoir. Although in some areas such volcanic rocks can be primary targets for hydrocarbon exploration (e.g. onshore China), in many others they are considered to be a secondary target, adding incremental resources to hydrocarbons produced from more conventional sandstone and carbonate reservoirs.

Full text not available from this repository.

More information

Published date: January 2016
Keywords: Tenerife, volcanic reservoir rocks, reservoir quality, lava flows, porosity permeability, micro-focus X-ray tomography
Organisations: Geochemistry, Marine Geoscience

Identifiers

Local EPrints ID: 385039
URI: https://eprints.soton.ac.uk/id/eprint/385039
ISSN: 0141-6421
PURE UUID: accaf413-a498-4120-8b1e-c4fd2d090b8e
ORCID for S. Roberts: ORCID iD orcid.org/0000-0003-4755-6703

Catalogue record

Date deposited: 14 Dec 2015 11:04
Last modified: 15 Aug 2019 00:57

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