Deep Water Reservoir Characterization and Its Challenges in Field Development Drilling Campaign, Kutei Basin, Indonesia - A Case Study

Abstract

Prediction of the presence, distribution and quality of deep water reservoir requires integration of all subsurface disciplines (Geology, Sedimentlology, Geophysics, Petrophysics, Operational Geology and Reservoir Engineering). Complex environments of deposition and reservoir architectures must be understood by integrating all disciplines to ensure optimal resource development and hydrocarbon recovery. The case study is located in Kutei Basin, East Kalimantan, Indonesia. The subsurface description is challenging because the field is a system of individual hydraulically discrete reservoir ЉsegmentsЉ not all of which have been penetrated. Several subsurface challenges have been identified using all subsurface data (seismic, core and log) in order to optimizing the development drilling campaign and for developing the production strategy.Seismic attributes are used to delimit the segment boundaries and thickness, determining the impact of seismic tuning has been particularly important in understanding reservoir geometry uncertainties. The extensive series of 3D seismic processing attribute extractions, seismic interpretations and supportive studies have been utilized to design a drilling sequence, well placement and formation evaluation plan that will reduce uncertainty/risk in the drilling campaign process.All exploration wells encountered gas within Pliocene deep water turbiditic sandstones characterized by staked, very thin to moderately thick bedded sandstone bodies separated by thick to very thick intervals of shale and siltstones. Those sediments are product of submarine canyon fill. Generally, the sandstones have good to excellent reservoir properties (porosity 0.22-0.30 with permeability Ͼ100 mD).The other challenge is that the reservoirs consist of thinly bedded sandstone-siltstone and shale, where the conventional log analysis can underestimate hydrocarbon pore thickness and volume in such beds. It will impact static and dynamic modeling for gas in place calculation. Hence, thin beds analysis should be performed to obtain reliable interpretation by using proper logging tool and method.The results of characterizing and mitigating the risks have been applied in the planning and execution of development wells during drilling campaign of the case study and is considered successful finding good quality sandstone reservoirs. Development of deepwater gas fields in Indonesia is in its early stages. The depositional environment is challenging due to the number of separate reservoir systems included in a single development. Limited well control requires heavy reliance on seismic interpretation of two different data sets.