Methodological assessment of uncertainty in forecasting hydrocarbon reserves of the North Varieganskoye field (Western Siberia)

Relevance. The assessment of uncertainties for the calculation of hydrocarbon reserves is a timely topic. The quality of hydrocarbon reserves is declining as old oil fields are depleted. Rates of discovery are in decline since most of the territories prospectively rich in hydrocarbon resources have already been explored. Newly discovered fields are classified as small and medium in terms of the amount of hydrocarbon reserves and difficult in terms of the quality of reserves. Purpose of the research is to determine important reservoir properties that have the greatest impact on the variability of the initial hydrocarbon reserves using sensitivity analysis and conducting a probabilistic hydrocarbon reserves assessment by the Monte Carlo method. Methods of research. The probabilistic hydrocarbon reserves assessment was carried out by the Monte Carlo method with the corresponding frequency curves of the probability distribution of volumetric parameters, which were performed using the Oracle Crystal Ball application. The sensitivity analysis of volumetric parameters that have the greatest impact on the amount of the initial hydrocarbons reserves was performed using the Oracle Crystal Ball application as well. Results and their application. An assessment of uncertainties and risks is necessary both for newly discovered fields in order to negate the risk of drilling unproductive wells and mature fields for a targeted program of geological and technological measures (GTM). Conclusions. The formation of bedded sand bodies of the Vasyugan (SE11, SE12, SE13) and Tyumen (SE2) suites took place in various sedimentation conditions, which could not but affect the quality of the reservoir of the studied formations. The analysis of the sensitivity of parameters has shown that different parameters affect the amount of hydrocarbon reserves in places SE11, SE12, SE13 and place SE2 .