Perm Journal of Petroleum and Mining Engineering (Sep 2016)
Study of geological and technological model of complex reservoirs of Samotlor field oil and gas deposits
Abstract
The achievement of project indicators of complex reservoirs` development through integrated management of oil and gas reserves` recovery requires the use of models that adequately reflect the geological structure of the medium, which determines the filtration flows direction during waterflooding. Their reliability increases based on the analysis of lithofacies features of productive part of the cut and enclosing sediments formation, reservoir features prediction in the inter-well space. It is known that the heterogeneity of macro level (sand content, segmentation) plays a crucial role in the formation of primary directions of reservoir fluid`s filtration flows. Microinhomogeneity (anisotropy, lateral variability in the permeability) has an impact on the nature of mass transfer processes, the target fluid`s displacement indicators and the phase permeability changing. Analyzing the the productive section of the AV11–2 reservoir, which is the most lithologically volatile in the Samotlor field, a special attention was given to textural characteristics (monolithicity and segmentation) of collectors. As a result, based on the ratio of two basic parameters Hef и αps, formation reservoirs were classified into three main classes: with massive texture, with thin-layered structure and with mixed texture. As a result of detailed studies of the geological and physical characteristic`s features of structure and, taking into account the results of facies analysis for each of layers, criteria referring to a particular type were formed. It was found that the productive strata gof the roup AB are characterized by a very complex facies formation environment, which occurred mainly in the coastal-marine conditions, in the areas of semi-enclosed sea gulfs and lagoons, deltaic subtraction of paleorivers. This affected both the nature of the various deposits types` distribution and their structure, and resulted in a significant heterogeneity of reservoir properties. The research results allowed to allocate within the considered layers zones with different facies. It was found that the most effective barrier waterflooding is in the avandelta area. The influence of reservoir facies affiliation on the effectiveness of the barrier flooding associated with distribution characteristics of interlayers with different permeability and of reservoir segmentation degree was explained. The recommendations for optimizing the barrier waterflooding techniques depending on the facial characteristics of the area were developed.
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