2015-248

Mechanical and physical behavior of high-porosity chalks exposed to chemical perturabation

Author: 

;;;;

;;;;;;;;
Title:Mechanical and physical behavior of high-porosity chalks exposed to chemical perturabation

Category:

Articles (Tidsskriftartikler)
Authors:Megawati, M.
Madland, M.V.
Hiorth, A.
Research group:Økt utvinning (Improved Oil Recovery)
Distribution restriction:Open
Published by:Elsevier, www.elsevier.com/locate/petrol;
;
Additional information:
Journal of Petroleum Science and Engineering 2015; Volume 133; s. 313-327;Published by: Elsevier, www.elsevier.com/locate/petrol;;

Abstract:
Extensive study on the effect of dissolution–precipitation on mechanical ;behavior of various high-porosity outcrop chalks (Liége, Aalborg, Kansas, ;Stevns Klint, and Mons) flooded with simplified aqueous;chemistry at 130 °C under isotropic stress beyond the yield is performed. ;Chemical effects induced by;injection of 0.219 M MgCl2 solutions into impure chalks (Liége, Aalborg, ;Kansas) lead to an immediate;enhancement on the macroscopic creep with more than a factor of 2 larger than ;that of exposed to;0.657 M NaCl solutions. In pure chalks (Stevns Klint and Mons) however, the ;creep response is characterized by a time lag, where creep initially diminishes ;before a tertiary-like creep develops. Systematic;correlation between calcite dissolution and the resulting creep strain is ;consistently demonstrated by all;the different chalk types.;The chemical effects are described as precipitation of Mg-bearing minerals and ;dissolution processes,;which involve both the carbonate and non-carbonate phases. SEM-EDS, XRD, and ;BET (N2) analyses;indicate newly formed Mg-bearing minerals primarily present as Magnesite, which ;precipitated in the;pore space. Enhanced dissolution is shown by continuous production of Ca2 þ ;measured in the core;effluent. The time for the dissolution to overcome intergranular friction ;accounts for the delay in the;creep acceleration in pure chalks (Stevns Klint and Mons). For impure chalks ;(Liége, Aalborg, Kansas);chemical alterations on the non-carbonate phases outweigh the intergranular ;friction. This additional;effect accounts for the immediate impact in the creep deformation.;The chemical effects are also demonstrated by marked reduction in the ;permeability. The porosity–;permeability relationship measured at the end of creep test is shifted down ;from the initial correlation,;indicating a dramatic increase in the chalk specific surface area;;;;;;;;;;;;;

tags: 

<< Back

International Research Institute of Stavanger
Mailing address:
Visiting address:
P.O. Box 8046, N-4068 Stavanger, Norway
Prof. Olav Hanssensvei 15, 4021 Stavanger


Phone:
Fax:

+47 51 87 50 00
+47 51 87 52 00

General email address: firmapost@iris.no
International Research Institute of Stavanger
Mailing address:
Visiting address:
P.O. Box 8046, N-4068 Stavanger, Norway
Prof. Olav Hanssensvei 15, 4021 Stavanger


Phone:
Fax:

+47 51 87 50 00
+47 51 87 52 00

General email address: firmapost@iris.no