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3 Sequence Stratigraphy and Correlation
3.1 Some Principles of Sequence Stratigraphy and Correlation
The primary objective of this study was a more thorough and detailed analysis of the facies and
microfacies (sequence stratigraphy) present in the M-1 and a more refined correlation of the relevant units
between wells. While log analysis is able to accurately resolve vertical lithology profiles and depths of the
fluid contacts for each, a sequence stratigraphy framework and the consequent improved correlation is
required for mapping the reservoir structure, planning production rates, and predicting reservoir behavior.
3.1.1 Some Principles of Sequence Stratigraphic Analysis and Correlation
The transfer point of a base level cycle is the preferred position of chronostratigraphic contrast in genetic
stratigraphic analysis. The transfer point is the limit position of the irreversible change when
accommodation was added to the top or vice versa. The transfer point (surface) is discontinuous in some
areas and continuous in others. The location of the transfer surface and the lithologies of the section are
determined by the accommodation space and the sediment supply.
According to (Cross, 2000), base level development and the accomodation/supply ratio, A/S, determine
the different stratigraphic profiles and base level cycles that are generated within different depositional
environments (Figure 1).
The main lithologic category for the study area is a sequence of sandstone-mudstone-coal. Based on the
regional depositional environment, previous work, and detailed core and well logging analysis, we
conclude that the M-1 target interval was deposited in a tidal delta environment. From a sequence
stratigraphy point of view, The M-1 represents a complete medium-scale cycle of base level rising and
falling.
Figure .3-1 Medium-short term cycle identification in different sedimentary environments (after cross,
2000).
3.1.2 Sequence Stratigraphic Framework
We chose the GR, RESS, RESD and SP logging curves for stratigraphic classification and correlation.
We generated 48 cross sections (Figure 3-2) over the area and here show 4 of them in Figures 3-4, 3-5, 36, and 3-7. The transfer point of base level is defined based on logging curves, marker beds, sedimentary
cycles, and bed thickness. A chronostratigraphic framework (Figure 3-3) which was separated by short
term base level was established. In this framework, one long-term semi-cycle, two medium-term semi-
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cycles and seven short-term semi-cycles were identified.
Figure 3-2 Map of wells for which cross
sections were generated
Figure .3-3 Synthesis Column Map of
The target layer is related to the bottom of the rising periods of a medium-term base level cycle. The
target layer was divided into 3 short cycles: S1, S2 and S3. S3 and S2 are related to the rising periods of a
medium-term base level cycle , while S1 is related to the falling periods. S2 is divided into S2-1 and S2-2
S3 is divided into S3-1, S3-2 and S3-3.
Figure .3-4 Stratigraphic Correlation of DORINE_41-DORINE_18
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Figure .3-5 Stratigraphic Correlation of DORINE_07-DORINE_27
Figure .3-6 Stratigraphic Correlation of FANNY_18B_16-DORINE_45_ST1
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