METHODOLOGY FOR DETERMINING THE DISTRIBUTION OF WETTABILITY FROM LABORATORY AND WELL LOG MEASUREMENTS FOR A MICROCRYSTALLINE/MICROFOSSILIFEROUS CARBONATE FIELD

摘要

Knowledge of the wettability characteristics of reservoirs can be an important parameter to evaluate and manage waterfloods and Enhanced Oil Recovery projects. This paper will present methods and initial results from a study that obtained wettability data in the laboratory and compared it to the apparent wettability obtained from conventional well logs in extensively flooded zones of high porosity, low permeability microcrystalline/microfossiliferous carbonate reservoirs. A data base of laboratory spontaneous imbibition measurements was obtained from extracted reservoir core plugs. These plugs had been extracted with mild solvents to a wettability state believed similar to that occurring in the reservoir. Wettabilities of the plugs were determined by either an Amott Water Index or a Spontaneous Imbibition Index (ratio of measured spontaneous imbibition to highly water wet imbibition). Apparent wettabilities for the reservoir were obtained from water saturations measured by conventional well logs and saturations based upon capitlary pressure correlations. Comparisons of the wettability determined in the laboratory with the apparent wettability from well logs showed similarities. Apparent wettability appeared to vary within different formations and with the porosity of the reservoir rock. The moderate to strongly water-wet character of this reservoir rock provided a probable basis for the success of a waterflood in the highly fractured reservoirs of the field and may point the direction for additional Enhanced Oil Recovery.