| Popis: |
A giant Middle East Carbonate Field is producing since 47 years with more than 700 borehole penetrations. The reservoir is 400ft thick of Lower Cretaceous shallow water carbonates with large intra-shelf basin. The reservoir has complex internal architecture due to the formation and in fill of the Basin. Although connected to a large aquifer, with production the reservoir pressure declined by almost a 1000 psi within 10 years. Peripheral injection started to restore the reservoir energy and sustain production. Injected water in the periphery naturally went into the most permeable layers causing uneven sweep both aerially and vertically. Especially in the progrades with sequence of porous/dense intervals and typical permeability range between 0.1-10 md, oil production could not be sustained with peripheral injection, resulting in dedicated pattern injection schemes. The reservoir unit, subject of this paper, is geologically complex due ro-grading and oblique clinoforms intervened by dense subunits, overlain with high permeable unit. The unit was developed in the last 5 years using gas-injection line-drive in the northern flank (permeability less than 2 md) and inverted 9-spot WAG patterns. Production from the area has not reached the target rate based on simulation. In addition, some injectors are suffering from low injectivity and based on pressure response compartmentalization is an issue. This study integrates newly acquired data through additional wells, 3D seismic reprocessing, updated stratigraphy studies, better understanding of the porous/dense correlation, updated static model and dynamic performance data (well testing, transient surveys, saturation logging, production logging, etc…). Main conclusions of the study include: Lack of connectivity is largely attributed to completing wells in different clinoforms.Producers and injectors do not have uniform profile across the horizontal section.Injected gas in the WAG is not contained and has percolated to the upper unit. As result of integrating the static and dynamic data, the newly developed model will be utilized to optimize well trajectories, reduce pattern size and study the merits of continuing the WAG injection scheme. |
