Quantitative Characterization of Carbonate Pore Systems by Mercury- Injection Method and Image Analysis in a Homogeneous Reservoir.

摘要

The quantity of direct interest in the flow through porousmedia is not the properties of the matrix (e.g. grain sizedistribution) but rather the properties of the pore (e.g. poresize distribution). The determination of representativecapillary pressures is of vital important for the mapping of thereservoir fluid distribution. Mercury porosimetry or mercuryinjection-capillary pressure curves are commonly used tomeasure the distribution of pores and pore throat sizes. Poreaperture size estimated from mercury injection tests has beenused to categorize the rock by pore type, evaluate seals fortraps and to explain the locations of stratigraphichydrocarbon accumulations.In image analysis, the OM (Optical Microscopy) imagesprovide macroporosity information, whereas the ESEM(Environmental Scanning Electronic Microscopy) imagesyield information on microporosity. Comparison of totalporosity determined from plugs indicates that macroporosityand microporosity values based on image analysis match theplug data, confirming the validity of the method. Thecombination of macroporosity and microporosity data yieldspore size distribution and pore shape information that canexplain the distribution of physical properties, in particularpermeability. Permeability can mainly controlled by themacropore shape in high-permeability samples, and by theamount of intrinsic microporosity in the lowpermeability samples.In this investigation three pore and port geometric systemshave been recognized, 1) Type-1 system that belongs to muddominated bioclastic peloidal packstone, at the top ofreservoir, with good porosity and fair permeability showslarge and smooth pores and ports as bimodal, 2) Type-2system presented in mud dominated bioclastic peloidalpackstone / grainstone with fair porosity and low permeabilityshows moderate to small pores and ports and 3) Type-3 system that has been seen in ploidal bioclastic grainstone andmud dominated planctonic foraminiferal packstone, packstone/wackestone and wackestone with low porosity and lowpermeability shows small pores and ports as matrix porosity.