Seismic reflection profiles, exploratory well, and outcrop data are used to determine the stratigraphy and tectonic subsidence and uplift history of the western Musandam peninsula. Five major regional megasequences have been recognized: (1) Permian to Late Cretaceous rifted margin sequence, (2) Late Cretaceous Aruma foreland basin sequence that evolved in response to the obduction of the Semail Ophiolite, (3) early–mid‐Cenozoic Pabdeh foreland basin sequence that formed due to orogenic loading associated with the early continent–continent collision of the Arabian and Eurasian plates in the Zagros mountains of central Iran, (4) a sequence above the mid‐Miocene unconformity that marks the final stage of continent–continent collision, and (5) a sequence above the late Pliocene unconformity interpreted as tilting due to the latest stage of continent–continent collision. In addition, seismic and outcrop data captured multiple west‐verging and east‐dipping thrust faults associated with the deformation of the Hagab thrust, which causes repetition of the Permian–Mesozoic shelf sequence and the early–mid Cenozoic foreland basin sequence. The tectonic subsidence and uplift derived from backstripping can be explained by a model in which the margin developed by uniform depth extension with an initial age of rifting of 260 Ma and a final age of rifting of 185 Ma. Moreover, the tectonic subsidence indicates two compressional events that commenced at ~94 Ma and ~25 Ma, respectively. These events are attributed to the obduction of the Semail Ophiolite and the culmination of the Musandam peninsula, respectively.

This paper presents results of polymer flooding application to Kalamkas oilfield with high watercut and low recovery factor (RF). The high layered vertical heterogeneity in permeability and unfavorable oil-water viscosity ratio in reservoir conditions (>20) of the field predetermined the need for chemical methods to enhanced oil recovery (EOR), such as polymer flooding. Polymer flooding pilot has been conducted since 2014. The analysis is based on current and cumulative production data plus Production Logging Testing (PLT) and Injection Logging Testing (ILT) interpretations. There is an improvement of vertical sweep efficiency in injection wells and blocking of washed water zones in production wells. The results of the EOR pilot show a decrease in watercut and an increase in the recovery factor. Our calculations conducted on hard data from the oilfield confirm that a specially designed polymer flooding technology for Kalamkas brownfield development is plausible and commercial.

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Middle East brown fields are penetrated by, more or less, around 1000 wells with long-production history. Attempts to incorporate all these wells create huge challenge caused by uncertainty related to well data discrepancy. The discrepancy in acquisition methods, tools, vintages are few factors to name that are root causes resulting in different depth values. Therefore, varying depth makes difficult to build structure of 3D reservoir model without non-geological anomalies such as distorted, collapsed, non-orthogonal cells. Methodology is to introduce uncertainty to all data feeding the structure modelling process. Following data is used with their ranges of uncertainties: interval velocity, seismic time maps, thickness maps, geological markers and well surveys. These ranges have to be identified quantitatively as they will give us flexibility to integrate data in the model within justifiable windows. Initially, the maps are allowed to change and try to integrate all data without well survey modifications. If, even after number of iterations, data is still not consistent resulting non-geological anomalies, then it is good to try allowing survey to change, but cautiously. Following application of this workflow, the data started to come in agreement and resulted in smooth, geologically reasonable subsurface structures. Horizontal wells targeting multiple thin carbonates are the most challenging to place them correctly. These wells require a lot of iterations or manual intervention to incorporate in the model, sometimes by adding number of pseudo-wells. Figure 1 shows even those examples can result in geological markers, of both vertical and deviated sections, match structure surfaces where horizontal trajectory at right penetrated layers. Worth to mention that the integration of almost ~1000 wells required zero pseudo-wells that helps to avoid introducing unrealistic noise to the data. Successful implementation of this project made this giant field one of the first brownfields that incorporated all data in consistent manner without using pseudo-wells. This structure model will maximize the value from ADNOC's existing data resources to reduce uncertainties during subsequent property and dynamic modelling stages plus while drilling future wells. Average estimates show that proper integration of all data can bring minimum $18 million in value.

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