Отправлено: 18.10.12 03:44. Заголовок: WETTABILITY ALTERATION DURING AGING: THE APPLICATION OF NMR TO MONITOR FLUID

SCA2005-10 1/12
WETTABILITY ALTERATION DURING AGING: THE APPLICATION OF NMR TO MONITOR FLUID REDISTRIBUTION
S.H. Al-Mahrooqi, C.A. Grattoni, A. H. Muggeridge and X.D. Jing
Petroleum Development of Oman (PDO), Muscat, Sultanate of Oman
Department of Earth Science and Engineering, Imperial College London, SW7 2AZ
Currently with Shell Representative Office Oman and JVR Centre for
Carbonate Studies, Sultan Qaboos University

This paper was prepared for presentation at the International Symposium of the Society of Core Analysts held in Toronto, Canada, 21-25 August 2005

ABSTRACT
The changes occurring during aging of reservoir core samples in crude oil, which aims to
restore the reservoir wettability, are complex. The dynamic mechanisms involved are still
not entirely clear. Understanding the dynamics of wettability restoration in the laboratory
will improve our ability to reproduce reservoir conditions before performing core tests
and help to ensure that laboratory data are representative of the reservoir.
This paper investigates the changes of fluid distribution occurring at the pore-scale during
wettability restoration using a combination of NMR T2
relaxation data and electrical
impedance measurements. Sandstone core plugs were aged in crude oil at various
conditions. One sample was aged at atmospheric pressure and a temperature of 35 to 50°
C, for more than 100 days while two other plugs were first aged at ambient conditions for
80 days and then at 85° C and 1.38 MPa for 50 more days. NMR relaxation and electrical
measurements were performed on all the plugs at regular time intervals during aging. In
addition, the Amott-Harvey wettability index was measured on clean and aged cores.
The T2 distributions as a function of aging time clearly show changes in oil/water
configuration at the pore scale. We infer that this can only be due to wettability changes
resulting from interactions between the crude oil and the rock surface. Both NMR data
and electrical measurements show that wettability alteration can occur before the 40 days
traditionally used in the majority of studies, even at room temperature and pressure.
These experiments demonstrate the ability of NMR to identify wettability changes and,
under certain conditions, to infer the fluid distributions at pore level.