Special Core Analysis of Low Reservoir Quality Chalk

This experimental work investigates Low Reservoir Quality Chalk (LRQC) reservoir properties using outcrop samples from six zones. The thesis is part of Joint Chalk Research Programme, Phase 7 (JCR 7), a large interdisciplinary consortium that focus on chalk research. The work have two main parts: Part A measures porosity, permeability and study flow, oil storage- and oil recovery potential for LRQC; Part B evaluates the use of a new method to measure relative permeability and capillary pressure using spontaneous imbibition with controlled boundary conditions. Porosity and permeability are two important properties that define the quality of a reservoir. Porosity was measured, with gas or brine, for 24 core plugs and ranges between φ=14.2-26.0%. Absolute permeability, measured with constant rate injection of brine, gas or oil, ranges between K=0.002-0.820 mD. Permeability varied with injected fluid, and gas porosity and permeability were on average higher than measured with brine. Local heterogeneities within core plugs identified with CT imaging significantly influenced the measured reservoir properties. Oil recovery potential and multiphase flow properties were measured on 12 LRQC core plugs. The initial water saturation, established using constant differential pressure during oil injection in cores initially 100% water saturated, varied between S_iw=32.9-38.1%. Oil recovery during forced or spontaneous imbibition was on average 36.5% OOIP. Relative permeability and capillary pressure for five LRQC core plugs were determined experimentally based on a methodology using spontaneous imbibition. A special boundary condition and theory proposed by (Haugen et al., 2014) was applied for the first time to LRQC core plugs to estimate relative permeability and capillary pressure. Relative permeability to water ranged between k_r,w=0.055-0.366, whereas capillary pressure ranged between P_c,f = 8.4-47.3 kPa