Abstract
The Cheleken area holds a series of hydrocarbon accumulations along a transpressional ridge (Apsheron trend). Seismic data is key to understand each field's structural setting and complexity especially in the inter-well space. Previous data interpretations could not overcome limitations and ambiguities of data quality leading to a range of possible interpretations. This study presents how integration of well data and structural style concepts into the seismic workflow results in a structural model matching all data and field characteristics.
Interpretation of band limited thus low-resolution seismic data in context of a complex structural setting across a thick deltaic succession is challenging. In order to avoid over-interpretation and non-systematic patterns all available information was integrated into the interpretation process. From preliminary identification of the master fault and stress regime, a classical Riedel shear system was recognized. Prevailing fault plane geometries at each deformation stage were defined and applied to guide fault delineation at larger scale. Linking interpreted faults to corresponding well markers, identified by layer doubling or missing sections, required considerable effort due to the high number of deviated wells, but strongly reduced ambiguities.
The central part of the Lam field forms a positive flower structure across the productive Red Series. A strike slip system with helicoidal fault geometry is the prevailing structural style. Such fault system originates from a single master fault at large depth. Transpressional deformation led to the formation of Riedel faults that root in the main fault. Ongoing deformation resulted in the additional formation of P- faults connecting the Riedel faults at larger depth only. At the same time, Riedel faults steepen while propagating upward, but die out at the top of the Red Series. This resulted in structural highs developed as updomings between the en-echelon patterns of the Riedel faults. These show reverse offsets on the flanks but typically only minor throw when passing the central sections of the updomings. A second, relatively younger set of normal faults was identified which did not match the strike slip system interpretation. These faults crosscut the older faults in the shallow succession and indicate a recent extensional regime.
Exceptional situations require exceptional effort across multiple disciplines to arrive at a common understanding for hydrocarbon fields. Success keys were to find the balance between data driven and model driven results and to allow for a certain degree of simplification. The latter was substantial in the construction of a model that captures the main field characteristics but avoids unnecessary detail in terms of structure and subsequently hydrocarbon distribution.
