Laboratory tests on core samples generally serve as one of the most important source of input data to oil and gas simulation studies. The reliability of results core data directly depends on quality of the tests carried out and how well the samples used are representative of the reservoir. The quality of cores or samples is of foremost importance, as among other sources of input data to reservoir modeling and simulation core tests are the only direct means of determining reservoir properties. The data obtained from core tests are generally unique, well founded and can be repeated by other specialists elsewhere.
This article focuses on the quality of cores used in laboratory tests, while pointing out the need for samples used to be consolidated, most especially in flow experiments in order to obtain reliable data. Possible mishaps affecting experimental results from unconsolidated cores or low quality samples, like those drilled with liquid nitrogen are discussed. We present the results of laboratory tests, showing how the quality of core samples can affect experimental results. Examples of capillary pressure curves, obtained from cores samples, disintegrated in a centrifugal experiments are shown. A criterion for assessing the quality of the results of such studies is presented.
To improve upon data quality of laboratory tests on core samples, reservoir rock type and possible rock-fluid interaction must be taken into account. Results presented show the much impact such interactions can have of on rock flow properties. Core preservation by bottom hole sealing or well-site preservation to prevent alteration of reservoir and fluids characteristics also plays a key role in obtaining reliable data in laboratory tests. Samples from preserved cores are shown to yield more reliable experimental results.
