Влияние литолого-фациальных зон на эффективность пароциклических обработок (на примере пермокарбоновой залежи сверхвязкой нефти Усинского месторождения Республики Коми)

Abstract

The influence of lithologic facies zones on the development of the Permian-Carboniferous reservoir of the Usinskoye oil field was evaluated. To meet the objective, reservoir porosity and permeability of each lithologic facies zone were addressed, the facial zoning influence on the rate of oil extraction in the Permian-Carboniferous reservoir of the Usinskoye oil field was analyzed, and the performance was evaluated after cyclic steam injection. The research deals with the Permian-Carboniferous reservoir of the Usinskoye oil field in the Komi Republic. In accordance with a developed format, a database of core analysis results and a base on cyclic steam simulation efficiency for the period of 5 years were collected. To determine the belonging of facies, we used the classification system for carbonate rocks suggested by Robert J. Dunham with the additions proposed by A.F. Embry and J.E. Klovan (based on the prevalence of structure components in limestone, the grouting agent type, as well as their interrelation in the rock). Based on the material composition of the rock and on the structural parameter, the following three main facies zones were identified: shallow-water carbonates (internal ramp zone), organogenic buildup (middle ramp zone), shallow-water offshore plain (middle ramp zone, external ramp zone in part). In addition, among the facies, it is possible to single out a moderately deep-water offshore plain (external ramp zone). In accordance with the research results, curves of the displacement coefficient distribution related to porosity were obtained and guidelines on determining the priority drilling sites within the area were given. As per the core analysis results, in the eastern part of the field, a zone of organogenic buildups was clearly determined; such buildups were formed mainly in the middle and late Carboniferous Period and Early Permian period. In the north-western part of the field, the existence of an internal ramp with shallow-water carbonate facies was assumed. The location of the priority drilling wells was chosen with regard to the fact that each cluster of development drilling wells is to penetrate facies of organogenic buildups having the best reservoir properties and oil displacement efficiency.