Strength and Biot's coefficient for high-porosity oil- or water-saturated chalk

Katrine Alling Andreassen

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In the petroleum industry it is relevant to know the Biot coefficient for establishing the effective stresses present in both the overburden and for the reservoir interval. When depleting a reservoir it is important to estimate the settlement through the strain imposed by the effective stress. Also considerations for the size of the drilling window and the magnitude of the lateral stress involve the Biot coefficient. Additionally, the fluid effect of oil-saturated chalk behaving much stronger than water-saturated chalk affects geomechanical considerations related to e.g. water injection into a reservoir.
The Biot coefficient states the degree of cementation or how the pore pressure contributes to the strain resulting from an external load for a porous material. It is here calculated from dynamic measurements and correlated with the strength of outcrop chalk characterized by the onset of pore collapse during hydrostatic loading. The hypothesis is that the Biot coefficient and the theory of poroelasticity may cover the fluid effect by including the increased fluid bulk modulus from oil to water. A high number of test results for both oil- and water-saturated high-porosity outcrop chalk show correlation between the Biot coefficient and the strength.
Original languageEnglish
Publication date2014
Number of pages5
Publication statusPublished - 2014
Event48th US Rock Mechanics / Geomechanics Symposium - Minneapolis, United States
Duration: 1 Jun 20144 Jun 2014
Conference number: 48


Conference48th US Rock Mechanics / Geomechanics Symposium
Country/TerritoryUnited States


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