Introduction 7
1. Literature review 8
1.1 SAGD process features 8
1.2 Studying of heterogeneity influence on steam chamber distribution 9
1.2.1 Vertical barrier 9
1.2.2 Vertical permeability 10
1.2.3 Studying of the problem with a numerical solution 11
2. General information of the field 13
3. The geological and geophysical study of an A deposit 15
4. Geological structure and oil and gas production 17
4.1 Stratigraphy and lithology 17
4.2 Tectonics 20
4.3 Geological structure of the A deposit 21
5. Geological and geophysical characteristics of the A deposit 22
6. Modelling of a reservoir according to its depositional environment 24
6.1 Depositional environment of the reservoir 24
6.2 Stages of sand reservoir formation 27
6.3 Origin of tight interlayers 29
6.4 Layering according to mouth bar theory 30
7. Effect of tight sandstones on SAGD reservoir development 32
Conclusion 35
References 36
Due to the depletion of traditional energy resources heavy oil is becoming increasingly important in the world economy, [1]. More specifically in Russia, where light oil fields are more than half developed, and at the same time - existing and potential refiners in most cases do not have direct access to resources. Meanwhile, according to experts, the world's reserves of heavy oil are more than 810 billion tons. Geological reserves of high-viscosity and heavy oil in Russia reach 6-7 billion tons (40-50 billion barrels), but their use and extraction require the use of certain expensive technologies. Few Russian companies are willing to invest in heavy field development and heavy oil refining, even though there is significant government support.
Since there are many geological heterogeneities in the reservoir, there is a problem that the steam is distributed unevenly, and it is difficult to predict steam chamber evolution.
The purpose of the work was to evaluate the influence of heterogeneities on SAGD development.
Since heterogeneities influence to sweep efficiency and thus final recovery of each specific pair of wells, the scope of the work is the determination of origin and presence of the heterogeneities, its special distribution and how much they can influence on production.
One of the important aspects of understanding of the geological situation is a depositional environment which can help to understand many circumstances. It includes a level of heterogeneity, major direction of homogeneity and opposite of property distribution. At the first step bedding from different levels of the reservoir was identified. Grain size, electro facies distribution contributed to the final decision of identifying of a deltaic depositional environment. According to it, the layering of a geological model was constructed. In this work, layering and distribution of heterogeneity were one of the important features.
Different production parameters of SAGD method were analyzed in order to detect and evaluate the influence of the heterogeneity. It was shown that this heterogeneity is influencing to production with the SAGD method especially when it is located between a pair of wells. Moreover, it was proved that closer to production well the barrier less it influences to cumulative production comparing with the homogeneous situation.
That is why it is important to take into account the distribution of such features and purpose proper development strategy which takes into consideration the horizontal well profiles in the already drilled reservoir. An understanding of such features can help to more accurately predict a steam chamber evolution and thus, production rates and total recovery.
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