Productivity of Fractured Gas Condensate Wells - A Case Study of the Smorbukk Field
- Antonin Settari (Simtech Consulting Services Ltd.) | R.C. Bachman (Simtech Consulting Services Ltd.) | K.A. Hovem (Statoil) | S.G. Paulsen (Statoil)
- Document ID
- Society of Petroleum Engineers
- SPE Reservoir Engineering
- Publication Date
- November 1996
- Document Type
- Journal Paper
- 236 - 244
- 1996. Society of Petroleum Engineers
- 4.6 Natural Gas, 5.2.1 Phase Behavior and PVT Measurements, 5.4.3 Gas Cycling, 2.5.1 Fracture design and containment, 5.1.1 Exploration, Development, Structural Geology, 5.8.8 Gas-condensate reservoirs, 1.2.3 Rock properties, 4.1.2 Separation and Treating, 3.2.3 Hydraulic Fracturing Design, Implementation and Optimisation, 5.3.2 Multiphase Flow, 3 Production and Well Operations, 5.1.5 Geologic Modeling, 2.4.3 Sand/Solids Control, 2.5.2 Fracturing Materials (Fluids, Proppant), 5.6.4 Drillstem/Well Testing, 2.2.2 Perforating, 5.1 Reservoir Characterisation, 5.1.2 Faults and Fracture Characterisation
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This paper describes a systematic study of the effect of condensate blockage on the productivity index (PI) of hydraulically fractured wells in a complex, highly heterogeneous reservoir containing rich gas condensate. The study was performed for the Smorbukk field offshore Norway with sophisticated simulation models. The techniques used are general, and the study findings apply as guidelines in general to fractured gas-condensate wells. Proppant fracturing is capable of restoring most of the productivity lost owing to liquid buildup. The effectiveness depends primarily on the reservoir heterogeneity, fracture length and conductivity. The relative benefits of fracturing decrease in highly heterogeneous formations.
It is well known that the productivity of gas-condensate wells can be severely reduced as a result of accumulation of liquid around the well during depletion. This phenomenon has been described for unfractured wells, and an approximate analytical method for estimating the PI reduction has been developed by Fussell. For engineering analysis of projects involving pressure depletion, it is necessary to be able to represent this phenomenon in numerical models. One method of calculating the reduction in well PI in a compositional simulator was described by Flores. However, until recently it was not possible to estimate the effect for fractured wells because of the complexity of the problem. Carlson and Myer have presented a study of the effect of condensate on a low-permeability fractured well. Their study concluded that fracturing is effective, but it considered only a homogeneous reservoir and relatively lean gas (2% liquid dropout). This study presents results of a detailed investigation of the problem in the Smorbukk North Sea field. Smorbukk is a complex multizone reservoir characterized by extreme reservoir heterogeneity varying between the zones and across the field, with rich condensate fluid of varying properties (up to 24% liquid dropout).
With the aid of detailed coupled fracture and reservoir numerical models, production histories of two typical wells (from Ile and Tilje horizons) were simulated under a variety of scenarios. Idealized as well as realistic (simulated) propped fracture geometries were used in wells with two types of fluid and different relative permeability characteristics. The questions addressed included the effect of heterogeneity, fracture length and conductivity, partial perforation, relative permeability characteristics, and strategies for stimulating infill wells after initial depletion. The results are now being used in field development planning and in full-field compositional modeling.
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