MEASUREMENT AND USE OF FORMATION FLUID, SATURATE, AND AROMATIC CONTENT, WITH WIRELINE FORMATION TESTERS

摘要

The measurement of the composition of a formation fluid can provide great insight for petrophysical, geochemical, and phase behavior interpretation. Laboratory analyses of bottomhole samples have historically provided much of this required compositional data. The delay in providing this critical information for decision making can range from weeks to months. By the time evaluation occurs, the opportunity to collect additional samples is lost, and any ambiguities regarding the sampled fluids may not be resolved. Providing formation fluid characterization in situ and in real time by means of wireline formation testers can enhance formation characterization and sampling programs. However, direct single station fluid compositional analysis measurements by wireline formation testers have historically been limited to gas components C1-C5 and bulk oil C6+. Although some multistation extrapolation can provide information regarding asphaltene content, no direct assay of bulk oil C6+ into measured components has been available. New measurement technology based on a multivariate optical computing technique has provided evidence of saturate and aromatics content. The bulk residual of a single-phase oil with respect to the directly measured gas, saturates, and aromatic fraction represents the non-polar resins and asphaltene fraction of the oil. A comparison of tool response to laboratory values for eight formation fluids validates the measurements of gas/oil ratio (GOR), C1, saturates, and aromatics concentration. The bulk difference with measured density corresponds well with resin and asphaltene content. Because of the high associated aromatic character of fluids in and near tar mat zones, the measurement of aromatic content can be useful for pinpointing the locations of such zones.