SPONTANEOUS IMBIBITION IN 2 DIFFERENT CHALK FACIES

An evaluation is made of the imbibition potential of two different cha lk facies from outcrops in England and Denmark. Both chalk facies have low permeability, moderate to high porosity, and comparable low insol uble residues (< 5%), but different texture, depositional origin and d iagenetic history. Spontaneous imbibition experiments were carried out on plugs with low initial water saturation and North Sea dead oil. Di stinctly different production rates and production plateaus were obser ved for the two chalk facies. Careful investigations of the rock frame work and pore system of the sample material form the basis for a theor etical description of wettability alteration and possible imbibition p rocesses in the two chalks. The theoretical descriptions are used to r ationalize the results from the spontaneous imbibition experiments. Th e results suggest that by knowing lithology, depositional history and degree of diagenetic alteration a relative potential of spontaneous im bibition in different chalk facies may be elucidated.