Water/Chalk (or Collapsible Soil) Interaction: Part II. Results of Tests Performed In Laboratory On Lixhe Chalk to Calibrate Water/Chalk Models

Abstract

hi. SPE/lSRM 47587 Water/chalk (or collapsible soil) interaction: Part Il. Results of tests performed in laboratory on Lixhe chalk to calibrate water/chalk models Ch. Schroed&, University of Lkge, A-P. Bois SPE, SIMECSOL, V. Maury SPE, ELF-EP and G. Halle, Elf Petroleum Norge m! 1*. q-of POtrO&IM Engi'wers, Inc. This paper was prepared for pmsentatkm al ttw SPEflSRM Eur.xk '9S held in Trc+xlheim, Nmway, 3-10 July t99B This paper was selected for paemlafion w an SPE Program Committee following review of lnfornmti~ccolah?ed in an abstract submitted by the aulhor(s). Conlenls of the paper, as pmsew6d, have not been mviewad by the society ot Petroleum Engineers and are subject to WTdhI~th. WthO@) 7h0 fIWtWid,~S pf9S-811tWf dW6 ITOt IVB3SSWIV Wfkd any P@fim d the SociMy d Petroleum Engineers, ifs officers, or nwmbsrs. Papers presented at SPE meetings am subject to rwbikation review ty Editorial Committees of Ihe Society of Petroleum Engineers, Electrcfdc reproduction. distribution, or stomgs of any part of this paper for commercial purposes without the witkin ccfwent of the society of Petroleum Engineers is prohibited. Pwmission to reprod.ica In prtnt IS restricted to an abstract oi not more lhan 300 e Olustmtlons may net be copied. The abstract must wmlmn .YXWp!cuaus 8c4amwledgnmnt d w4'18Mand ty~cm me paper was presented. Write Librarian, SF%, P.O. 60X 8SS8S6, Riiardsm, 7X 750S34836, U. S.A., iaX 01-972-952-9435 AbstractEkof~k, Valhall and other North Sea reservoirs are made of water sensitive rocks such as pure high porosity chalk. Production of these fields implying water-flooding leads in several cases to compaction and subsidence. In order to perform reliable predictions of compaction and subsidence when water-flooding such reservoirs, it is necessary to take into account not only the deformations that come from depletion in the compressible reservoir rocks but also to inciude additional deformations induced by water saturation (WS) increase.These additional deformations may eventually be determined by performing water-injection (WI) tests in laboratory.This paper presents additional tests that have been performed in laboratory in order to understand the mechanical behavior of chalk at the water-front.It shows the existence of a degree of WS above which chalks mechanically behaves as if it is fully saturated, while chalk with a lower WS looks stronger than if the degree is higher). Greater the WS is, smaHer the consolidation pressure P co .

On the collapse behaviour of oil reservoir chalk

“…5(a)) and 0.8 MPa and dry sample ( These results are in accordance with well established results showing a higher yield stress observed on chalk full of oil as compared to chalk full of water (Schroeder et al, 1998;Delage et al, 1996). They are also compatible with the water weakening effect.…”

“…Since the early eighties, the effect of the nature of the pore fluids, of their mutual interaction and of their interaction with the rock skeleton were examined to better interpret the origin of compaction (Newman, 1983;Monjoie et al, 1985;Piau & Maury, 1994;Schroeder et al, 1998;Risnes et al, 2003). It was proposed to adopt a coupled hydro-mechanical framework taken from the mechanics of unsaturated soils (containing water and air as a non wetting fluid) and to adapt it to reservoir chalks (containing water and oil as a non wetting fluid) Collin et al, 2002;De Gennaro et al, 2003).…”

On the collapse behaviour of oil reservoir chalk

“…with lower degrees of saturation in water (S rw ). These results are in accordance with wellestablished results showing a higher yield stress observed on chalk full of oil as compared with chalk full of water Schroeder et al, 1998). They are also compatible with the water weakening effect.…”

“…Since the early 1980s, the effects of the nature of the pore fluids, of their mutual interaction and of their interaction with the rock skeleton were examined to better interpret the origin of chalk compaction (Newman, 1983;Monjoie et al, 1985;Piau & Maury, 1994;Schroeder et al, 1998;Lord et al, 2002;Risnes et al, 2003). It was proposed to adopt a coupled hydromechanical framework taken from the mechanics of unsaturated soils (containing water and air as a non-wetting fluid) and to adapt it to reservoir chalks (containing water and oil as a non-wetting fluid) Collin et al, 2002;De Gennaro et al, 2003).…”

Mechanical Behaviour of a Porous Chalk and Water/Chalk Interaction. Part I: Experimental Study

“…The previous laboratory investigations have clearly shown a strong sensitivity of chalky rocks to water content (Halleux et al, 1990;Brignoli et al, 1994;Risnes and Garspestad, 1998;Risnes and Kaarigstad, 1996;Monjoie et al, 1995;Schroeder, 1995;Schroeder et al, 1998).…”