New approach to appraise non-structural Tyumen formation traps in the absence of high quality of data

Abstract

Background. On the one hand, the focus of exploration works changes to the more difficult reserves side, which were basically accumulated in the non-structural traps of Achimov and Tyumen formations. On the other hand, there are two important questions. The first is how the volume of reserves should be estimated correctly and the second is which volume of reserves is enough for economic successfully development. Aim. The main aim is to create a new actual approach of non-structural traps appraisal is considered in the absence of high quality of seismic data which allows identify such types of traps, which allows identify such types of traps. Materials and methods. Presented at the article algorithm enables estimate resources of non-lithological traps as exemplified in Tyumen formation, which was formed during depositional changes from continental to transitional depositional environments. The algorithm consists of some steps. The first step is collection on numbers, sizes and areas potential sand bodies based on different seismic attributes from analogies data. On the next step the coefficient which shows what numbers of geological bodies can be found on the unit of area was defined. Based on these data the probability distribution function which shows what part of studied area could be covered by potential bodies was made. After these steps, the integral resource base without regard to geological chance of success (gCoS) can be estimated. In order to account for geological risks the numbers of potential traps (including also non-structural traps), which were formed by meandering rives, tidal channels and point-bars, have to be defined. As a result, the discrete mathematical distribution of expected numbers of traps was made based on analogies data. If the oil infl ow was obtained from wells which have already drilled on the studied area part of resource base transfer to reserves (without including gCoS). Results. Discussed method was applied for “blind-test” on the new studied block with 3D seismic data. The obtained results of potential sand bodies fraction is correspond to the initial distribution from analogy fields. The method can be used for resource base potential on any block where there are lithological traps, which are controlled by mainly the facies conditions instead of structural plan, and also the 3D seismic data is absent. Conclusions. The appliance of discussed method which based on the available statistical data helps improve the quality estimation of change resource base range and allows to map the new prospective areas containing reserves and resources. One more important thing is this method allows to resolve the problem of base potential estimation and as a result to put a price on asset and risk capital values needed to explore the potential areas by drilling before the key outlays in the exploration program will be invested.