A Simulation Framework for Multi-Scenario Production Forecasts in the North Kuwait Jurassic Complex

Ghorayeb, Kassem (Schlumberger) | Aziz, Rafi Mohammad (Kuwait Oil Company) | Penney, Rick (Schlumberger) | Dashti, Qasem (Kuwait Oil Company)

OnePetro 

Abstract
The North Kuwait Jurassic Complex (NKJC) consists of six fields with four potential reservoirs in the Jurassic age naturally fractured carbonate formation. Current understanding of the complex, has led to 12 subdivisions of the area and potentially 48 separate compartments (segments) in the complex. These subdivisions are defined by fault boundaries supported by a combination of variations in fluid composition, initial pressures and free water levels estimated from capillary pressure and log saturation data.

Multi-scenario production forecasts based on integrated full field modeling were needed in the process of building a Field Development Plan (FDP) for the NKJC. An integrated Asset Modeling (IAM) framework is adopted where multiple separate reservoir models (up to 48 models) are coupled through global constraints in order to meet gas delivery targets. The solution uses a black oil delumping technique to obtain compositional wellstreams while running black oil simulation models. The adopted simulation framework provides us with all the benefits of a compositional full field simulation model while topping-up with two advantages i.e. computational speed and flexibility.

We discuss the impact of the IAM solution on the selection of the optimal development scenario given that these fields are in the early stages of production via an early production facility on line in 2008. Coupling of all fields/segments allows optimization over the entire production system rather than optimizing each field individually. This reduces the number of wells required to meet targets at any one time under any reservoir realization, while also staying within the surface network constraints.

Background
The North Kuwait Jurassic Complex (NKJC) consists of six fields with four potential reservoirs (Najmah/Sargelu, Upper Marrat, Middle Marrat and Lower Marrat) in naturally fractured carbonate formations (Figure 1). The fields have been subdivided into 12 major areas based upon fault boundaries, supported by a combination of variations in fluid composition, initial pressures and free water level estimates. With the four producing formations, there are potentially 48 separate compartments (segments) in the complex. The reservoirs contain multiple fluid types at near critical conditions (Ghorayeb et al., 2008).

Compositions vary across the complex - fluid samples from some reservoirs exhibit a dew point pressure behavior (near-critical gas-condensate) while other reservoirs exhibit a bubble point pressure behavior (near-critical volatile oil). Consequently, some reservoirs in the NKJC need to be modeled as gas-condensate reservoirs and some others as volatile oil reservoirs.