Importance of accounting macro heterogeneity of productive strata to improve efficiency of water alternating gas injection process

The paper focuses on improvement of reliability of geological information used in the water alternating gas injection projects for productive strata in the course of scavenger oilfield development. Spotlight is on the study of macro heterogeneities revealed by interpretation of drilling and seismic survey data. One of the critical objectives of this research is updating of interwell correlation according to the analysis of seismic wavefield recorded in the interval of productive strata occurrence. The paper describes a casestudy of the revised concept on the structure of BV10 stratum in the Nizhnevartovsk oil and gas area of the West Siberian oil and gas province. As a result, instead of the current concept on the parallel bedding of the test sedimentation, the progradation structure of the latter is assumed, which eliminates the use of wouldbe lithological screens in delineation of oil reservoirs. The disregard of the progradation structure in oilfield development would have an adverse influence on the oil recovery efficiency. The integrated interpretation of drilling and seismic survey data reveals screening fractures which make an impact on oil displacement efficiency. It is necessary to take such fractures into account in water alternating gas injection. Inclusion of sufficient vertical discriminability of well information and lateral discriminability of seismic survey data in the analysis allows predicting the change in petrophysical parameters in interwell space. The authors exemplify interpolation of well data with regard to wavefield properties. The information on macro heterogeneities of reservoir properties helps improve the water alternating gas injection performance and, accordingly, enhance the sweep efficiency. The paper presents also the physical framework for the adjustment of fluid flow in reservoirs using the seismic survey data.