In the context of global warming, CO2 capture is one of the explored solutions for greenhouse gas emission mitigation. Its injection in oil fields is one of the EOR schemes adapted to the Middle East carbonate reservoirs. A very high ultimate oil recovery is expected with such a process. A proper design to develop full field EOR CO2 is yet to be found and may be fulfilled through the implementation of one or several pilots. This study of EOR CO2 pilot implementation required a geosciences, reservoir and surface integrated work in order to place it in some robust and promising locations. A static and dynamic synthesis was performed to understand and better capture the structural context of the field and its level of production maturity. The major risks were taken into account for the selection thanks to a complete synthesis of the available data from the core scale to the surface facilities. An adequate methodology was developed to narrow down the possible locations from the field extent (several hundred km2) to only a few squared kilometers of interest. The field was divided in 6 km2 squares (called "locators") for which a two step selection process was applied. In the first step, the geological typology of the reservoirs and their dynamic statuses at the locator level were defined. Then the risks associated to CO2 injection were assessed. At the end of this step, the selected locators were the less risky ones, representating each geological typology. In the second step, the locators were studied more thoroughly with the evaluation of the level of knowledge illustrating the amount and quality of data available; a geological variability study on permeability was also performed on each area. Finally the surface constraints were incorporated to prevent any incompatibilities with the current or future facilities. This second step provided another sub-selection of locators amongst the ones kept at the end of step 1. Overall, the methodology applied allowed to screen the whole field and its reservoirs, and to identify some promising pilot locations representative of the geology, for a given dynamic status, combining high level of knowledge and low risks related to CO2 injection.

An updated geological and dynamic model for a giant Middle East carbonate reservoir was constructed and history matched with the objective of creating an alternative model which is capable of replicating the reservoir production mechanisms and improving predictability, allowing optimizing the field development plan and water injection strategy. Giant Middle East carbonate fields often have long production history and exhibit high reservoir heterogeneity. It is always challenging to get a robust history matched model aligned with geological concepts and dynamic behavior understanding. The objective of this paper is to present an improved and integrated reservoir characterization, modeling and history matching procedure for a giant Lower Cretaceous carbonate reservoir in the Middle East. The applied workflow integrates all available geological data (stratigraphy, depositional facies, and diagenesis), petrophysical data (RCA and minipermeameter data, Petrophysical Group definition, cut-off definition) and the extensive database of dynamic data (long production history, well test, RST, open-hole log saturation over more than 40 years of development drilling, and MICP). The process was initiated with the reservoir review by means of a fully integrated study that allowed having better understanding of the reservoir behavior and production mechanisms. The key heterogeneities (high permeability and intra-dense layers) which control the flow behavior were identified during this process. Geological trend maps were generated to control the distribution of high permeability and intra-dense in the model. Well test data, open-hole logs from development wells and time-lapse saturation logs from observation wells were used to calibrate the trend and permeability log data. A phenomenological model was constructed to test the main factors impacting the production mechanism as identified during the reservoir review. Multiple iterations were performed between the static and dynamic models in a way that allowed a quick and efficient work that is consistent with all disciplines assumptions. Such continuous loop between the dynamic and geological models, with focus on the geological heterogeneities driving the dynamic reservoir behavior, has led to a more robust model capable of replicate the production mechanisms, which represents a major improvement compared to previous model in term of predictability.

Well pattern design is difficult due to the very large number of possible solutions, the complexity of constraints deriving from drilling and completion, the nonlinear nature of fluid flow in porous media, the difficulty in ascertaining reservoir properties and, for mature reservoirs, development history. What matters the most is case dependent. This task is therefore traditionally conducted through manual processes with little or no help of computers, leading often to exceedingly conservative or simplistic designs whatever the reservoir heterogeneities. The increase in computational power and algorithmic advances are opening the door to a new "Generative Design" approach, already used by other industries (car, aerospace). It consists in exploring a larger number of computer generated design possibilities more quickly and efficiently than what human can do by combining: i- "technical and experience" rules to automatically build a large number of "designs candidate", ii- workflows that qualify the performance of the designs, iii- selection criteria to identify the best design(s). An innovative Generative Well Pattern Design Workflow named GWPD-WISH was benchmarked against traditional "manual" designs to leverage three reservoir development planning opportunities applicable to a giant mature middle eastern carbonate field already developed by hundreds of wells for which a reliable model was available: Locate 2×15 in-fill producers to be drilled from 2 freely chosen platform locations Locate 2×15 in-fill producers to be drilled from 2 pre-determined platform locations Select 16 multi-string water injector wells for re-drill to improve recovery through better control of local reservoir pressure balance The study was conducted using a large operational compositional model considering complex constraints in a limited time. The workflow proved able to identify substantially better patterns than the traditional approach for each of the three opportunities at the costs of only few hundreds of simulations. Pattern improvement was measured in term of reserves per incremental well and plateau duration extension. It corresponds to an opportunity for reducing drilling expenditures on a rolling basis by 30% or more.